PARTIALLY SOLVED

SOLVED
UNSOLVED
2021-07-07 21:03:42 +01:00 · 2021-07-07 21:02:31 +01:00 · 2021-07-07 20:58:36 +01:00 · 2021-07-07 20:57:20 +01:00 · 2021-07-07 19:49:15 +00:00 · 2021-07-05 18:57:05 +02:00
136 changed files with 6857 additions and 2055 deletions
--- a/.all-contributorsrc
+++ b/.all-contributorsrc
@ -0,0 +1,922 @@
+{
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+    {
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+    {
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+    {
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+  "projectName": "rustlings",
+  "projectOwner": "rust-lang",
+  "repoType": "github",
+  "repoHost": "https://github.com",
+  "skipCi": true
+}
--- a/.clog.toml
+++ b/.clog.toml
@ -0,0 +1,4 @@
+[clog]
+
+repository = "https://github.com/rust-lang/rustlings"
+changelog = "CHANGELOG.md"
--- a/.editorconfig
+++ b/.editorconfig
@ -0,0 +1,7 @@
+root = true
+
+[*.rs]
+end_of_line = lf
+insert_final_newfile = true
+indent_style = space
+indent_size = 4
--- a/.gitignore
+++ b/.gitignore
@ -1,5 +1,9 @@
 *.swp
 target/
 **/*.rs.bk
-Cargo.lock
 .DS_Store
+*.pdb
+exercises/clippy/Cargo.toml
+exercises/clippy/Cargo.lock
+.idea
+.vscode
--- a/.gitpod.yml
+++ b/.gitpod.yml
@ -0,0 +1,7 @@
+tasks:
+  - init: /workspace/rustlings/install.sh
+    command: /workspace/.cargo/bin/rustlings watch
+
+vscode:
+  extensions:
+    - rust-lang.rust@0.7.8:CvNqMTgDdt3UXt+6BCDTVg==
--- a/.replit
+++ b/.replit
@ -0,0 +1,2 @@
+language = "rust"
+run = "[ -x ~/.cargo/bin/rustlings ] && ~/.cargo/bin/rustlings watch || ./install.sh"
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@ -0,0 +1,396 @@
+<a name="4.4.0"></a>
+## 4.4.0 (2021-04-24)
+
+
+#### Bug Fixes
+
+*   Fix spelling error in main.rs ([91ee27f2](https://github.com/rust-lang/rustlings/commit/91ee27f22bd3797a9db57e5fd430801c170c5db8))
+*   typo in default out text ([644c49f1](https://github.com/rust-lang/rustlings/commit/644c49f1e04cbb24e95872b3a52b07d692ae3bc8))
+* **collections:**  Naming exercises for vectors and hashmap ([bef39b12](https://github.com/rust-lang/rustlings/commit/bef39b125961310b34b34871e480a82e82af4678))
+* **from_str:**
+  *  Correct typos ([5f7c89f8](https://github.com/rust-lang/rustlings/commit/5f7c89f85db1f33da01911eaa479c3a2d4721678))
+  *  test for error instead of unwrap/should_panic ([15e71535](https://github.com/rust-lang/rustlings/commit/15e71535f37cfaed36e22eb778728d186e2104ab))
+  *   use trait objects for from_str ([c3e7b831](https://github.com/rust-lang/rustlings/commit/c3e7b831786c9172ed8bd5d150f3c432f242fba9))
+* **functions3:**  improve function argument type (#687) ([a6509cc4](https://github.com/rust-lang/rustlings/commit/a6509cc4d545d8825f01ddf7ee37823b372154dd))
+* **hashmap2:**  Update incorrect assertion (#660) ([72aaa15e](https://github.com/rust-lang/rustlings/commit/72aaa15e6ab4b72b3422f1c6356396e20a2a2bb8))
+* **info:**  Fix typo (#635) ([cddc1e86](https://github.com/rust-lang/rustlings/commit/cddc1e86e7ec744ee644cc774a4887b1a0ded3e8))
+* **iterators2:**  Moved errors out of tests. ([baf4ba17](https://github.com/rust-lang/rustlings/commit/baf4ba175ba6eb92989e3dd54ecbec4bedc9a863), closes [#359](https://github.com/rust-lang/rustlings/issues/359))
+* **iterators3:**  Enabled iterators3.rs to run without commented out tests. ([c6712dfc](https://github.com/rust-lang/rustlings/commit/c6712dfccd1a093e590ad22bbc4f49edc417dac0))
+* **main:**  Let find_exercise work with borrows ([347f30bd](https://github.com/rust-lang/rustlings/commit/347f30bd867343c5ace1097e085a1f7e356553f7))
+* **move_semantics4:**
+  *  Remove redundant "instead" (#640) ([cc266d7d](https://github.com/rust-lang/rustlings/commit/cc266d7d80b91e79df3f61984f231b7f1587218e))
+  *  Small readbility improvement (#617) ([10965920](https://github.com/rust-lang/rustlings/commit/10965920fbdf8a1efc85bed869e55a1787006404))
+* **option2:**  Rename uninformative variables (#675) ([b4de6594](https://github.com/rust-lang/rustlings/commit/b4de6594380636817d13c2677ec6f472a964cf43))
+* **quiz3:**  Force an answer to Q2 (#672) ([0d894e6f](https://github.com/rust-lang/rustlings/commit/0d894e6ff739943901e1ae8c904582e5c2f843bd))
+* **structs:**  Add 5.3 to structs/README (#652) ([6bd791f2](https://github.com/rust-lang/rustlings/commit/6bd791f2f44aa7f0ad926df767f6b1fa8f12a9a9))
+* **structs2:**  correct grammar in hint (#663) ([ebdb66c7](https://github.com/rust-lang/rustlings/commit/ebdb66c7bfb6d687a14cc511a559a222e6fc5de4))
+* **structs3:**
+  * reword heading comment (#664) ([9f3e8c2d](https://github.com/rust-lang/rustlings/commit/9f3e8c2dde645e5264c2d2200e68842b5f47bfa3))
+  *   add check to prevent naive implementation of is_international ([05a753fe](https://github.com/rust-lang/rustlings/commit/05a753fe6333d36dbee5f68c21dec04eacdc75df))
+* **threads1:**  line number correction ([7857b0a6](https://github.com/rust-lang/rustlings/commit/7857b0a689b0847f48d8c14cbd1865e3b812d5ca))
+* **try_from_into:**  use trait objects ([2e93a588](https://github.com/rust-lang/rustlings/commit/2e93a588e0abe8badb7eafafb9e7d073c2be5df8))
+
+#### Features
+
+*   Replace clap with argh ([7928122f](https://github.com/rust-lang/rustlings/commit/7928122fcef9ca7834d988b1ec8ca0687478beeb))
+*   Replace emojis when NO_EMOJI env variable present ([8d62a996](https://github.com/rust-lang/rustlings/commit/8d62a9963708dbecd9312e8bcc4b47049c72d155))
+*   Added iterators5.rs exercise. ([b29ea17e](https://github.com/rust-lang/rustlings/commit/b29ea17ea94d1862114af2cf5ced0e09c197dc35))
+* **arc1:**  Add more details to description and hint (#710) ([81be4044](https://github.com/rust-lang/rustlings/commit/81be40448777fa338ebced3b0bfc1b32d6370313))
+* **cli:**  Improve the list command with options, and then some ([8bbe4ff1](https://github.com/rust-lang/rustlings/commit/8bbe4ff1385c5c169c90cd3ff9253f9a91daaf8e))
+* **list:**
+  *  updated progress percentage ([1c6f7e4b](https://github.com/rust-lang/rustlings/commit/1c6f7e4b7b9b3bd36f4da2bb2b69c549cc8bd913))
+  *  added progress info ([c0e3daac](https://github.com/rust-lang/rustlings/commit/c0e3daacaf6850811df5bc57fa43e0f249d5cfa4))
+
+
+
+<a name="4.3.0"></a>
+## 4.3.0 (2020-12-29)
+
+#### Features
+
+*   Rewrite default out text ([44d39112](https://github.com/rust-lang/rustlings/commit/44d39112ff122b29c9793fe52e605df1612c6490))
+*   match exercise order to book chapters (#541) ([033bf119](https://github.com/rust-lang/rustlings/commit/033bf1198fc8bfce1b570e49da7cde010aa552e3))
+*   Crab? (#586) ([fa9f522b](https://github.com/rust-lang/rustlings/commit/fa9f522b7f043d7ef73a39f003a9272dfe72c4f4))
+*   add "rustlings list" command ([838f9f30](https://github.com/rust-lang/rustlings/commit/838f9f30083d0b23fd67503dcf0fbeca498e6647))
+* **try_from_into:**  remove duplicate annotation ([04f1d079](https://github.com/rust-lang/rustlings/commit/04f1d079aa42a2f49af694bc92c67d731d31a53f))
+
+#### Bug Fixes
+
+*   update structs README ([bcf14cf6](https://github.com/rust-lang/rustlings/commit/bcf14cf677adb3a38a3ac3ca53f3c69f61153025))
+*   added missing exercises to info.toml ([90cfb6ff](https://github.com/rust-lang/rustlings/commit/90cfb6ff28377531bfc34acb70547bdb13374f6b))
+*   gives a bit more context to magic number ([30644c9a](https://github.com/rust-lang/rustlings/commit/30644c9a062b825c0ea89435dc59f0cad86b110e))
+* **functions2:**  Change signature to trigger precise error message: (#605) ([0ef95947](https://github.com/rust-lang/rustlings/commit/0ef95947cc30482e63a7045be6cc2fb6f6dcb4cc))
+* **structs1:**  Adjust wording (#573) ([9334783d](https://github.com/rust-lang/rustlings/commit/9334783da31d821cc59174fbe8320df95828926c))
+* **try_from_into:**
+  *  type error ([4f4cfcf3](https://github.com/rust-lang/rustlings/commit/4f4cfcf3c36c8718c7c170c9c3a6935e6ef0618c))
+  *  Update description (#584) ([96347df9](https://github.com/rust-lang/rustlings/commit/96347df9df294f01153b29d9ad4ba361f665c755))
+* **vec1:**  Have test compare every element in a and v ([9b6c6293](https://github.com/rust-lang/rustlings/commit/9b6c629397b24b944f484f5b2bbd8144266b5695))
+
+<a name="4.2.0"></a>
+## 4.2.0 (2020-11-07)
+
+#### Features
+
+*   Add HashMap exercises ([633c00cf](https://github.com/rust-lang/rustlings/commit/633c00cf8071e1e82959a3010452a32f34f29fc9))
+*   Add Vec exercises ([0c12fa31](https://github.com/rust-lang/rustlings/commit/0c12fa31c57c03c6287458a0a8aca7afd057baf6))
+* **primitive_types6:**  Add a test (#548) ([2b1fb2b7](https://github.com/rust-lang/rustlings/commit/2b1fb2b739bf9ad8d6b7b12af25fee173011bfc4))
+* **try_from_into:**  Add tests (#571) ([95ccd926](https://github.com/rust-lang/rustlings/commit/95ccd92616ae79ba287cce221101e0bbe4f68cdc))
+
+#### Bug Fixes
+
+*   log error output when inotify limit is exceeded ([d61b4e5a](https://github.com/rust-lang/rustlings/commit/d61b4e5a13b44d72d004082f523fa1b6b24c1aca))
+*   more unique temp_file ([5643ef05](https://github.com/rust-lang/rustlings/commit/5643ef05bc81e4a840e9456f4406a769abbe1392))
+* **installation:**  Update the MinRustVersion ([21bfb2d4](https://github.com/rust-lang/rustlings/commit/21bfb2d4777429c87d8d3b5fbf0ce66006dcd034))
+* **iterators2:**  Update description (#578) ([197d3a3d](https://github.com/rust-lang/rustlings/commit/197d3a3d8961b2465579218a6749b2b2cefa8ddd))
+* **primitive_types6:**
+  *  remove 'unused doc comment' warning ([472d8592](https://github.com/rust-lang/rustlings/commit/472d8592d65c8275332a20dfc269e7ac0d41bc88))
+  *  missing comma in test ([4fb230da](https://github.com/rust-lang/rustlings/commit/4fb230daf1251444fcf29e085cee222a91f8a37e))
+* **quiz3:**  Second test is for odd numbers, not even. (#553) ([18e0bfef](https://github.com/rust-lang/rustlings/commit/18e0bfef1de53071e353ba1ec5837002ff7290e6))
+
+<a name="4.1.0"></a>
+## 4.1.0 (2020-10-05)
+
+#### Bug Fixes
+
+*   Update rustlings version in Cargo.lock ([1cc40bc9](https://github.com/rust-lang/rustlings/commit/1cc40bc9ce95c23d56f6d91fa1c4deb646231fef))
+* **arc1:**  index mod should equal thread count ([b4062ef6](https://github.com/rust-lang/rustlings/commit/b4062ef6993e80dac107c4093ea85166ad3ee0fa))
+* **enums3:**  Update Message::ChangeColor to take a tuple. (#457) ([4b6540c7](https://github.com/rust-lang/rustlings/commit/4b6540c71adabad647de8a09e57295e7c7c7d794))
+* **exercises:**  adding question mark to quiz2 ([101072ab](https://github.com/rust-lang/rustlings/commit/101072ab9f8c80b40b8b88cb06cbe38aca2481c5))
+* **generics3:**  clarify grade change ([47f7672c](https://github.com/rust-lang/rustlings/commit/47f7672c0307732056e7426e81d351f0dd7e22e5))
+* **structs3:**  Small adjustment of variable name ([114b54cb](https://github.com/rust-lang/rustlings/commit/114b54cbdb977234b39e5f180d937c14c78bb8b2))
+* **using_as:**  Add test so that proper type is returned. (#512) ([3286c5ec](https://github.com/rust-lang/rustlings/commit/3286c5ec19ea5fb7ded81d047da5f8594108a490))
+
+#### Features
+
+*   Added iterators1.rs exercise ([9642f5a3](https://github.com/rust-lang/rustlings/commit/9642f5a3f686270a4f8f6ba969919ddbbc4f7fdd))
+*   Add ability to run rustlings on repl.it (#471) ([8f7b5bd0](https://github.com/rust-lang/rustlings/commit/8f7b5bd00eb83542b959830ef55192d2d76db90a))
+*   Add gitpod support (#473) ([4821a8be](https://github.com/rust-lang/rustlings/commit/4821a8be94af4f669042a06ab917934cfacd032f))
+*   Remind the user of the hint option (#425) ([816b1f5e](https://github.com/rust-lang/rustlings/commit/816b1f5e85d6cc6e72673813a85d0ada2a8f84af))
+*   Remind the user of the hint option (#425) ([9f61db5d](https://github.com/rust-lang/rustlings/commit/9f61db5dbe38538cf06571fcdd5f806e7901e83a))
+* **cli:**  Added 'cls' command to 'watch' mode (#474) ([4f2468e1](https://github.com/rust-lang/rustlings/commit/4f2468e14f574a93a2e9b688367b5752ed96ae7b))
+* **try_from_into:**  Add insufficient length test (#469) ([523d18b8](https://github.com/rust-lang/rustlings/commit/523d18b873a319f7c09262f44bd40e2fab1830e5))
+
+<a name="4.0.0"></a>
+## 4.0.0 (2020-07-08)
+
+#### Breaking Changes
+
+*   Add a --nocapture option to display test harnesses' outputs ([8ad5f9bf](https://github.com/rust-lang/rustlings/commit/8ad5f9bf531a4848b1104b7b389a20171624c82f))
+*   Rename test to quiz, fixes #244 ([010a0456](https://github.com/rust-lang/rustlings/commit/010a04569282149cea7f7a76fc4d7f4c9f0f08dd))
+
+#### Features
+
+*   Add traits README ([173bb141](https://github.com/rust-lang/rustlings/commit/173bb14140c5530cbdb59e53ace3991a99d804af))
+*   Add box1.rs exercise ([7479a473](https://github.com/rust-lang/rustlings/commit/7479a4737bdcac347322ad0883ca528c8675e720))
+*   Rewrite try_from_into (#393) ([763aa6e3](https://github.com/rust-lang/rustlings/commit/763aa6e378a586caae2d8d63755a85eeba227933))
+*   Add if2 exercise ([1da84b5f](https://github.com/rust-lang/rustlings/commit/1da84b5f7c489f65bd683c244f13c7d1ee812df0))
+*   Added exercise structs3.rs ([b66e2e09](https://github.com/rust-lang/rustlings/commit/b66e2e09622243e086a0f1258dd27e1a2d61c891))
+*   Add exercise variables6 covering const (#352) ([5999acd2](https://github.com/rust-lang/rustlings/commit/5999acd24a4f203292be36e0fd18d385887ec481))
+
+#### Bug Fixes
+
+*   Change then to than ([ddd98ad7](https://github.com/rust-lang/rustlings/commit/ddd98ad75d3668fbb10eff74374148aa5ed2344d))
+*   rename quiz1 to tests1 in info (#420) ([0dd1c6ca](https://github.com/rust-lang/rustlings/commit/0dd1c6ca6b389789e0972aa955fe17aa15c95f29))
+*   fix quiz naming inconsistency (#421) ([5563adbb](https://github.com/rust-lang/rustlings/commit/5563adbb890587fc48fbbc9c4028642687f1e85b))
+*   confine the user further in variable exercises ([06ef4cc6](https://github.com/rust-lang/rustlings/commit/06ef4cc654e75d22a526812919ee49b8956280bf))
+*   update iterator and macro text for typos and clarity ([95900828](https://github.com/rust-lang/rustlings/commit/959008284834bece0196a01e17ac69a7e3590116))
+*   update generics2       closes #362 ([964c974a](https://github.com/rust-lang/rustlings/commit/964c974a0274199d755073b917c2bc5da0c9b4f1))
+*   confusing comment in conversions/try_from_into.rs ([c9e4f2cf](https://github.com/rust-lang/rustlings/commit/c9e4f2cfb4c48d0b7451263cfb43b9426438122d))
+* **arc1:**  Passively introduce attributes (#429) ([113cdae2](https://github.com/rust-lang/rustlings/commit/113cdae2d4e4c55905e8056ad326ede7fd7de356))
+* **box1:**  fix comment typo (#426) ([bb2ca251](https://github.com/rust-lang/rustlings/commit/bb2ca251106b27a7272d9a30872904dd1376654c))
+* **errorsn:**  Try harder to confine the user. (#388) ([2b20c8a0](https://github.com/rust-lang/rustlings/commit/2b20c8a0f5774d07c58d110d75879f33fc6273b5))
+* **from_into.rs:**  typo ([a901499e](https://github.com/rust-lang/rustlings/commit/a901499ededd3ce1995164700514fe4e9a0373ea))
+* **generics2:**  Guide students to the answer (#430) ([e6bd8021](https://github.com/rust-lang/rustlings/commit/e6bd8021d9a7dd06feebc30c9d5f953901d7b419))
+* **installation:**
+  *  Provide a backup git reference when tag can't be curl ([9e4fb100](https://github.com/rust-lang/rustlings/commit/9e4fb1009f1c9e3433915c03e22c2af422e5c5fe))
+  *  Check if python is available while checking for git,rustc and cargo ([9cfb617d](https://github.com/rust-lang/rustlings/commit/9cfb617d5b0451b4b51644a1298965390cda9884))
+* **option1:**
+  *  Don't add only zeros to the numbers array ([cce6a442](https://github.com/rust-lang/rustlings/commit/cce6a4427718724a9096800754cd3abeca6a1580))
+  *  Add cast to usize, as it is confusing in the context of an exercise about Option ([f6cffc7e](https://github.com/rust-lang/rustlings/commit/f6cffc7e487b42f15a6f958e49704c93a8d4465b))
+* **option2:**  Add TODO to comments (#400) ([10967bce](https://github.com/rust-lang/rustlings/commit/10967bce57682812dc0891a9f9757da1a9d87404))
+* **options1:**  Add hint about Array Initialization (#389) ([9f75554f](https://github.com/rust-lang/rustlings/commit/9f75554f2a30295996f03f0160b98c0458305502))
+* **test2:**  name of type String and &str (#394) ([d6c0a688](https://github.com/rust-lang/rustlings/commit/d6c0a688e6a96f93ad60d540d4b326f342fc0d45))
+* **variables6:**  minor typo (#419) ([524e17df](https://github.com/rust-lang/rustlings/commit/524e17df10db95f7b90a0f75cc8997182a8a4094))
+
+<a name="3.0.0"></a>
+## 3.0.0 (2020-04-11)
+
+#### Breaking Changes
+
+* make "compile" exercises print output (#278) ([3b6d5c](https://github.com/fmoko/rustlings/commit/3b6d5c3aaa27a242a832799eb66e96897d26fde3))
+
+#### Bug Fixes
+
+* **primitive_types:** revert primitive_types4 (#296) ([b3a3351e](https://github.com/rust-lang/rustlings/commit/b3a3351e8e6a0bdee07077d7b0382953821649ae))
+* **run:**  compile clippy exercise files (#295) ([3ab084a4](https://github.com/rust-lang/rustlings/commit/3ab084a421c0f140ae83bf1fc3f47b39342e7373))
+* **conversions:**
+  * add additional test to meet exercise rules (#284) ([bc22ec3](https://github.com/fmoko/rustlings/commit/bc22ec382f843347333ef1301fc1bad773657f38))
+  * remove duplicate not done comment (#292) ([dab90f](https://github.com/fmoko/rustlings/commit/dab90f7b91a6000fe874e3d664f244048e5fa342))
+* don't hardcode documentation version for traits (#288) ([30e6af](https://github.com/fmoko/rustlings/commit/30e6af60690c326fb5d3a9b7335f35c69c09137d))
+
+#### Features
+
+*   add Option2 exercise (#290) ([86b5c08b](https://github.com/rust-lang/rustlings/commit/86b5c08b9bea1576127a7c5f599f5752072c087d))
+*   add excercise for option (#282) ([135e5d47](https://github.com/rust-lang/rustlings/commit/135e5d47a7c395aece6f6022117fb20c82f2d3d4))
+*   add new exercises for generics (#280) ([76be5e4e](https://github.com/rust-lang/rustlings/commit/76be5e4e991160f5fd9093f03ee2ba260e8f7229))
+* **ci:**  add buildkite config ([b049fa2c](https://github.com/rust-lang/rustlings/commit/b049fa2c84dba0f0c8906ac44e28fd45fba51a71))
+
+<a name="2.2.1"></a>
+### 2.2.1 (2020-02-27)
+
+#### Bug Fixes
+
+*   Re-add cloning the repo to install scripts ([3d9b03c5](https://github.com/rust-lang/rustlings/commit/3d9b03c52b8dc51b140757f6fd25ad87b5782ef5))
+
+#### Features
+
+*   Add clippy lints (#269) ([1e2fd9c9](https://github.com/rust-lang/rustlings/commit/1e2fd9c92f8cd6e389525ca1a999fca4c90b5921))
+
+<a name="2.2.0"></a>
+## 2.2.0 (2020-02-25)
+
+
+#### Bug Fixes
+
+*   Update deps to version compatable with aarch64-pc-windows (#263) ([19a93428](https://github.com/rust-lang/rustlings/commit/19a93428b3c73d994292671f829bdc8e5b7b3401))
+* **docs:**
+  * Added a necessary step to Windows installation process (#242) ([3906efcd](https://github.com/rust-lang/rustlings/commit/3906efcd52a004047b460ed548037093de3f523f))
+  * Fixed mangled sentence from book; edited for clarity (#266) ([ade52ff](https://github.com/rust-lang/rustlings/commit/ade52ffb739987287ddd5705944c8777705faed9))
+  * Updated iterators readme to account for iterators4 exercise (#273) ([bec8e3a](https://github.com/rust-lang/rustlings/commit/bec8e3a644cbd88db1c73ea5f1d8a364f4a34016))
+* **installation:**  make fatal errors more obvious (#272) ([17d0951e](https://github.com/rust-lang/rustlings/commit/17d0951e66fda8e11b204d5c4c41a0d5e22e78f7))
+* **iterators2:**
+  *  Remove reference to missing iterators2.rs (#245) ([419f7797](https://github.com/rust-lang/rustlings/commit/419f7797f294e4ce6a2b883199731b5bde77d262))
+* **as_ref_mut:** Enable a test and improve per clippy's suggestion (#256) ([dfdf809](https://github.com/rust-lang/rustlings/commit/dfdf8093ebbd4145864995627b812780de52f902))
+* **tests1:**
+  * Change test command ([fe10e06c](https://github.com/rust-lang/rustlings/commit/fe10e06c3733ddb4a21e90d09bf79bfe618e97ce)
+  * Correct test command in tests1.rs comment (#263) ([39fa7ae](https://github.com/rust-lang/rustlings/commit/39fa7ae8b70ad468da49b06f11b2383135a63bcf))
+
+#### Features
+
+*   Add variables5.rs exercise (#264) ([0c73609e](https://github.com/rust-lang/rustlings/commit/0c73609e6f2311295e95d6f96f8c747cfc4cba03))
+*   Show a completion message when watching (#253) ([d25ee55a](https://github.com/rust-lang/rustlings/commit/d25ee55a3205882d35782e370af855051b39c58c))
+*   Add type conversion and parsing exercises (#249) ([0c85dc11](https://github.com/rust-lang/rustlings/commit/0c85dc1193978b5165491b99cc4922caf8d14a65))
+*   Created consistent money unit (#258) ([fd57f8f](https://github.com/rust-lang/rustlings/commit/fd57f8f2c1da2af8ddbebbccec214e6f40f4dbab))
+*   Enable test for exercise test4 (#276) ([8b971ff](https://github.com/rust-lang/rustlings/commit/8b971ffab6079a706ac925f5917f987932b55c07))
+*   Added traits exercises (#274 but specifically #216, which originally added
+    this :heart:) ([b559cdd](https://github.com/rust-lang/rustlings/commit/b559cdd73f32c0d0cfc1feda39f82b3e3583df17))
+
+
+<a name="2.1.0"></a>
+## 2.1.0 (2019-11-27)
+
+#### Bug Fixes
+
+* add line numbers in several exercises and hints ([b565c4d3](https://github.com/rust-lang/rustlings/commit/b565c4d3e74e8e110bef201a082fa1302722a7c3))
+* **arc1:**  Fix some words in the comment ([c42c3b21](https://github.com/rust-lang/rustlings/commit/c42c3b2101df9164c8cd7bb344def921e5ba3e61))
+* **enums:**  Add link to chapter on pattern syntax (#242) ([615ce327](https://github.com/rust-lang/rustlings/commit/615ce3279800c56d89f19d218ccb7ef576624feb))
+* **primitive_types4:**
+  *  update outdated hint ([4c5189df](https://github.com/rust-lang/rustlings/commit/4c5189df2bdd9a231f6b2611919ba5aa14da0d3f))
+  *  update outdated comment ([ded2c034](https://github.com/rust-lang/rustlings/commit/ded2c034ba93fa1e3c2c2ea16b83abc1a57265e8))
+* **strings2:**  update line number in hint ([a09f684f](https://github.com/rust-lang/rustlings/commit/a09f684f05c58d239a6fc59ec5f81c2533e8b820))
+* **variables1:**  Correct wrong word in comment ([fda5a470](https://github.com/rust-lang/rustlings/commit/fda5a47069e0954f16a04e8e50945e03becb71a5))
+
+#### Features
+
+* **watch:**  show hint while watching ([8143d57b](https://github.com/rust-lang/rustlings/commit/8143d57b4e88c51341dd4a18a14c536042cc009c))
+
+<a name="2.0.0"></a>
+## 2.0.0 (2019-11-12)
+
+#### Bug Fixes
+
+* **default:**  Clarify the installation procedure ([c371b853](https://github.com/rust-lang/rustlings/commit/c371b853afa08947ddeebec0edd074b171eeaae0))
+* **info:**  Fix trailing newlines for hints ([795b6e34](https://github.com/rust-lang/rustlings/commit/795b6e348094a898e9227a14f6232f7bb94c8d31))
+* **run:**  make `run` never prompt ([4b265465](https://github.com/rust-lang/rustlings/commit/4b26546589f7d2b50455429482cf1f386ceae8b3))
+
+#### Breaking Changes
+
+*   Refactor hint system ([9bdb0a12](https://github.com/rust-lang/rustlings/commit/9bdb0a12e45a8e9f9f6a4bd4a9c172c5376c7f60))
+*   improve `watch` execution mode ([2cdd6129](https://github.com/rust-lang/rustlings/commit/2cdd61294f0d9a53775ee24ad76435bec8a21e60))
+*   Index exercises by name ([627cdc07](https://github.com/rust-lang/rustlings/commit/627cdc07d07dfe6a740e885e0ddf6900e7ec336b))
+* **run:**  makes `run` never prompt ([4b265465](https://github.com/rust-lang/rustlings/commit/4b26546589f7d2b50455429482cf1f386ceae8b3))
+
+#### Features
+
+* **cli:**  check for rustc before doing anything ([36a033b8](https://github.com/rust-lang/rustlings/commit/36a033b87a6549c1e5639c908bf7381c84f4f425))
+* **hint:**  Add test for hint ([ce9fa6eb](https://github.com/rust-lang/rustlings/commit/ce9fa6ebbfdc3e7585d488d9409797285708316f))
+
+<a name="1.5.1"></a>
+### 1.5.1 (2019-11-11)
+
+#### Bug Fixes
+
+* **errors3:**  Update hint ([dcfb427b](https://github.com/rust-lang/rustlings/commit/dcfb427b09585f0193f0a294443fdf99f11c64cb), closes [#185](https://github.com/rust-lang/rustlings/issues/185))
+* **if1:**  Remove `return` reference ([ad03d180](https://github.com/rust-lang/rustlings/commit/ad03d180c9311c0093e56a3531eec1a9a70cdb45))
+* **strings:**  Move Strings before Structs ([6dcecb38](https://github.com/rust-lang/rustlings/commit/6dcecb38a4435593beb87c8e12d6314143631482), closes [#204](https://github.com/rust-lang/rustlings/issues/204))
+* **structs1:**  Remove misleading comment ([f72e5a8f](https://github.com/rust-lang/rustlings/commit/f72e5a8f05568dde04eaeac10b9a69872f21cb37))
+* **threads:**  Move Threads behind SLT ([fbe91a67](https://github.com/rust-lang/rustlings/commit/fbe91a67a482bfe64cbcdd58d06ba830a0f39da3), closes [#205](https://github.com/rust-lang/rustlings/issues/205))
+* **watch:** clear screen before each `verify()`  ([3aff590](https://github.com/rust-lang/rustlings/commit/3aff59085586c24196a547c2693adbdcf4432648))
+
+<a name="1.5.0"></a>
+## 1.5.0 (2019-11-09)
+
+#### Bug Fixes
+
+* **test1:** Rewrite logic ([79a56942](https://github.com/rust-lang/rustlings/commit/79a569422c8309cfc9e4aed25bf4ab3b3859996b))
+* **installation:**  Fix rustlings installation check ([7a252c47](https://github.com/rust-lang/rustlings/commit/7a252c475551486efb52f949b8af55803b700bc6))
+* **iterators:**  Rename iterator3.rs ([433d2115](https://github.com/rust-lang/rustlings/commit/433d2115bc1c04b6d34a335a18c9a8f3e2672bc6))
+* **iterators2:**  Remove syntax resulting in misleading error message ([4cde8664](https://github.com/rust-lang/rustlings/commit/4cde86643e12db162a66e62f23b78962986046ac))
+* **option1:**
+  *  Fix arguments passed to assert! macro (#222) ([4c2cf6da](https://github.com/rust-lang/rustlings/commit/4c2cf6da755efe02725e05ecc3a303304c10a6da))
+  *  Fix arguments passed to assert! macro ([ead4f7af](https://github.com/rust-lang/rustlings/commit/ead4f7af9e10e53418efdde5c359159347282afd))
+  *  Add test for prematurely passing exercise ([a750e4a1](https://github.com/rust-lang/rustlings/commit/a750e4a1a3006227292bb17d57d78ce84da6bfc6))
+* **primitive_types4:**  Fail on a slice covering the wrong area ([5b1e673c](https://github.com/rust-lang/rustlings/commit/5b1e673cec1658afc4ebbbc800213847804facf5))
+* **readme:**  http to https ([70946b85](https://github.com/rust-lang/rustlings/commit/70946b85e536e80e70ed9505cb650ca0a3a1fbb5))
+* **test1:**
+  *  Swap assertion parameter order ([4086d463](https://github.com/rust-lang/rustlings/commit/4086d463a981e81d97781851d17db2ced290f446))
+  *  renamed function name to snake case closes #180 ([89d5186c](https://github.com/rust-lang/rustlings/commit/89d5186c0dae8135ecabf90ee8bb35949bc2d29b))
+
+#### Features
+
+*   Add enums exercises ([dc150321](https://github.com/rust-lang/rustlings/commit/dc15032112fc485226a573a18139e5ce928b1755))
+*   Added exercise for struct update syntax ([1c4c8764](https://github.com/rust-lang/rustlings/commit/1c4c8764ed118740cd4cee73272ddc6cceb9d959))
+* **iterators2:**  adds iterators2 exercise including config ([9288fccf](https://github.com/rust-lang/rustlings/commit/9288fccf07a2c5043b76d0fd6491e4cf72d76031))
+
+<a name="1.4.1"></a>
+### 1.4.1 (2019-08-13)
+
+
+#### Bug Fixes
+
+* **iterators2:**  Remove syntax resulting in misleading error message ([4cde8664](https://github.com/rust-lang/rustlings/commit/4cde86643e12db162a66e62f23b78962986046ac))
+* **option1:**  Add test for prematurely passing exercise ([a750e4a1](https://github.com/rust-lang/rustlings/commit/a750e4a1a3006227292bb17d57d78ce84da6bfc6))
+* **test1:**  Swap assertion parameter order ([4086d463](https://github.com/rust-lang/rustlings/commit/4086d463a981e81d97781851d17db2ced290f446))
+
+
+
+<a name="1.4.0"></a>
+## 1.4.0 (2019-07-13)
+
+#### Bug Fixes
+
+* **installation:**  Fix rustlings installation check ([7a252c47](https://github.com/rust-lang/rustlings/commit/7a252c475551486efb52f949b8af55803b700bc6))
+* **iterators:**  Rename iterator3.rs ([433d2115](https://github.com/rust-lang/rustlings/commit/433d2115bc1c04b6d34a335a18c9a8f3e2672bc6))
+* **readme:**  http to https ([70946b85](https://github.com/rust-lang/rustlings/commit/70946b85e536e80e70ed9505cb650ca0a3a1fbb5))
+* **test1:**  renamed function name to snake case ([89d5186c](https://github.com/rust-lang/rustlings/commit/89d5186c0dae8135ecabf90ee8bb35949bc2d29b))
+* **cli:** Check if changed exercise file exists before calling verify ([ba85ca3](https://github.com/rust-lang/rustlings/commit/ba85ca32c4cfc61de46851ab89f9c58a28f33c88))
+* **structs1:** Fix the irrefutable let pattern warning ([cc6a141](https://github.com/rust-lang/rustlings/commit/cc6a14104d7c034eadc98297eaaa972d09c50b1f))
+
+#### Features
+
+* **changelog:**  Use clog for changelogs ([34e31232](https://github.com/rust-lang/rustlings/commit/34e31232dfddde284a341c9609b33cd27d9d5724))
+* **iterators2:**  adds iterators2 exercise including config ([9288fccf](https://github.com/rust-lang/rustlings/commit/9288fccf07a2c5043b76d0fd6491e4cf72d76031))
+
+<a name="1.3.0"></a>
+### 1.3.0 (2019-06-05)
+
+#### Features
+
+- Adds a simple exercise for structures (#163, @briankung)
+
+#### Bug Fixes
+
+- Add Result type signature as it is difficult for new comers to understand Generics and Error all at once. (#157, @veggiemonk)
+- Rustfmt and whitespace fixes (#161, @eddyp)
+- errorsn.rs: Separate also the hints from each other to avoid accidental viewing (#162, @eddyp)
+- fixed outdated links (#165, @gushroom)
+- Fix broken link (#164, @HanKruiger)
+- Remove highlighting and syntect (#167, @komaeda)
+
+<a name="1.2.2"></a>
+### 1.2.2 (2019-05-07)
+
+#### Bug Fixes
+
+- Reverted `--nocapture` flag since it was causing tests to pass unconditionally
+
+<a name="1.2.1"></a>
+### 1.2.1 (2019-04-22)
+
+#### Bug Fixes
+
+- Fix the `--nocapture` feature (@komaeda)
+- Provide a nicer error message for when you're in the wrong directory
+
+<a name="1.2.0"></a>
+### 1.2.0 (2019-04-22)
+
+#### Features
+
+- Add errors to exercises that compile without user changes (@yvan-sraka)
+- Use --nocapture when testing, enabling `println!` when running (@komaeda)
+
+<a name="1.1.1"></a>
+### 1.1.1 (2019-04-14)
+
+#### Bug fixes
+
+- Fix permissions on exercise files (@zacanger, #133)
+- Make installation checks more thorough (@komaeda, 1b3469f236bc6979c27f6e1a04e4138a88e55de3)
+- Fix order of true/false in tests for executables (@mgeier, #137)
+- Stop run from panicking when compile fails (@cjpearce, #141)
+- Fix intermittent test failure caused by race condition (@cjpearce, #140)
+- Fix links by deleting book version (@diodfr, #142)
+- Canonicalize paths to fix path matching (@cjpearce, #143)
+
+<a name="1.1.0"></a>
+### 1.1.0 (2019-03-20)
+
+- errors2.rs: update link to Rust book (#124)
+- Start verification at most recently modified file (#120)
+- Watch for file creation events in watch mode (#117)
+- Add standard library types to exercises suite (#119)
+- Give a warning when Rustlings isn't run from the right directory (#123)
+- Verify that rust version is recent enough to install Rustlings (#131)
+
+<a name="1.0.1"></a>
+### 1.0.1 (2019-03-06)
+
+- Adds a way to install Rustlings in one command (`curl -L https://git.io/rustlings | bash`)
+- Makes `rustlings watch` react to create file events (@shaunbennett, #117)
+- Reworks the exercise management to use an external TOML file instead of just listing them in the code
+
+<a name="1.0.0"></a>
+### 1.0.0 (2019-03-06)
+
+Initial release.
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@ -0,0 +1,131 @@
+## Contributing to Rustlings
+
+First off, thanks for taking the time to contribute!! ❤️
+
+### Quick Reference
+
+I want to...
+
+_add an exercise! ➡️ [read this](#addex) and then [open a Pull Request](#prs)_
+
+_update an outdated exercise! ➡️ [open a Pull Request](#prs)_
+
+_report a bug! ➡️ [open an Issue](#issues)_
+
+_fix a bug! ➡️ [open a Pull Request](#prs)_
+
+_implement a new feature! ➡️ [open an Issue to discuss it first, then a Pull Request](#issues)_
+
+<a name="#src"></a>
+### Working on the source code
+
+`rustlings` is basically a glorified `rustc` wrapper. Therefore the source code
+isn't really that complicated since the bulk of the work is done by `rustc`.
+`src/main.rs` contains a simple `clap` CLI that loads from `src/verify.rs` and `src/run.rs`.
+
+<a name="addex"></a>
+### Adding an exercise
+
+The first step is to add the exercise! Name the file `exercises/yourTopic/yourTopicN.rs`, make sure to
+put in some helpful links, and link to sections of the book in `exercises/yourTopic/README.md`.
+
+Next make sure it runs with `rustlings`. The exercise metadata is stored in `info.toml`, under the `exercises` array. The order of the `exercises` array determines the order the exercises are run by `rustlings verify`.
+
+Add the metadata for your exercise in the correct order in the `exercises` array. If you are unsure of the correct ordering, add it at the bottom and ask in your pull request. The exercise metadata should contain the following:
+```diff
+  ...
+ [[exercises]]
+ name = "yourTopicN"
+ path = "exercises/yourTopic/yourTopicN.rs"
+ mode = "compile"
+ hint = """
+ Some kind of useful hint for your exercise."""
+  ...
+```
+
+The `mode` attribute decides whether Rustlings will only compile your exercise, or compile and test it. If you have tests to verify in your exercise, choose `test`, otherwise `compile`.
+
+That's all! Feel free to put up a pull request.
+
+<a name="issues"></a>
+### Issues
+
+You can open an issue [here](https://github.com/rust-lang/rustlings/issues/new).
+If you're reporting a bug, please include the output of the following commands:
+
+- `rustc --version`
+- `rustlings --version`
+- `ls -la`
+- Your OS name and version
+
+<a name="prs"></a>
+### Pull Requests
+
+Opening a pull request is as easy as forking the repository and committing your
+changes. There's a couple of things to watch out for:
+
+#### Write correct commit messages
+
+We follow the [Conventional Commits](https://www.conventionalcommits.org/en/v1.0.0-beta.4/)
+specification, because it makes it easier to generate changelogs automatically.
+This means that you have to format your commit messages in a specific way. Say
+you're working on adding a new exercise called `foobar1.rs`. You could write
+the following commit message:
+
+```
+feat: Add foobar1.rs exercise
+```
+
+If you're just fixing a bug, please use the `fix` type:
+
+```
+fix(verify): Make sure verify doesn't self-destruct
+```
+
+The scope within the brackets is optional, but should be any of these:
+
+- `installation` (for the installation script)
+- `cli` (for general CLI changes)
+- `verify` (for the verification source file)
+- `watch` (for the watch functionality source)
+- `run` (for the run functionality source)
+- `EXERCISENAME` (if you're changing a specific exercise, or set of exercises,
+  substitute them here)
+
+When the commit also happens to close an existing issue, link it in the message
+body:
+
+```
+fix: Update foobar
+
+closes #101029908
+```
+
+If you're doing simple changes, like updating a book link, use `chore`:
+
+```
+chore: Update exercise1.rs book link
+```
+
+If you're updating documentation, use `docs`:
+
+```
+docs: Add more information to Readme
+```
+
+If, and only if, you're absolutely sure you want to make a breaking change
+(please discuss this beforehand!), add an exclamation mark to the type and
+explain the breaking change in the message body:
+
+```
+fix!: Completely change verification
+
+BREAKING CHANGE: This has to be done because lorem ipsum dolor
+```
+
+#### Pull Request Workflow
+
+Once you open a Pull Request, it may be reviewed or labeled (or both) until
+the maintainers accept your change. Then, [bors](https://github.com/bors) will
+run the test suite with your changes and if it's successful, automatically
+merge it in!
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--- a/Cargo.toml
+++ b/Cargo.toml
@ -1,12 +1,23 @@
 [package]
 name = "rustlings"
-version = "1.0.0"
-authors = ["Lynn <819880950@qq.com>", "Carol (Nichols || Goulding) <carol.nichols@gmail.com"]
+version = "4.4.0"
+authors = ["Marisa <mokou@posteo.de>", "Carol (Nichols || Goulding) <carol.nichols@gmail.com>"]
 edition = "2018"

 [dependencies]
-clap = "2.32.0"
-indicatif = "0.9.0"
-console = "0.6.2"
-syntect = "3.0.2"
-notify = "4.0.0"
+argh = "0.1.4"
+indicatif = "0.10.3"
+console = "0.7.7"
+notify = "4.0.15"
+toml = "0.4.10"
+regex = "1.1.6"
+serde = {version = "1.0.10", features = ["derive"]}
+
+[[bin]]
+name = "rustlings"
+path = "src/main.rs"
+
+[dev-dependencies]
+assert_cmd = "0.11.0"
+predicates = "1.0.1"
+glob = "0.3.0"
--- a/README.md
+++ b/README.md
@ -1,121 +1,3 @@
-![crab pet](http://i.imgur.com/LbZJgmm.gif) 
-
-# rustlings 🦀❤️
-
-Greetings and welcome to `rustlings`. This project contains small exercises to get you used to reading and writing Rust code. This includes reading and responding to compiler messages!
-
-_...looking for the old, web-based version of Rustlings? Try [here](https://github.com/rust-lang/rustlings/tree/rustlings-1)_
-
-Alternatively, for a first-time Rust learner, there's several other resources:
-
- [The Book](https://doc.rust-lang.org/book/index.html) - The most comprehensive resource for learning Rust, but a bit theoretical sometimes. You will be using this along with Rustlings!
- [Rust By Example](https://doc.rust-lang.org/rust-by-example/index.html) - Learn Rust by solving little exercises! It's almost like `rustlings`, but online
-
-## Getting Started
-
-To use `rustlings` you need to have [Rust](https://www.rust-lang.org/) installed on your computer. To install Rust, go to [rustup.rs](https://rustup.rs/).
-
-Once Rust is installed, clone the `rustlings` repository and enter the resulting directory:
-
-```bash
-git clone https://github.com/rust-lang/rustlings.git
-cd rustlings
-```
-
-_Note: If you're on MacOS, make sure you've installed Xcode and its developer tools by typing `xcode-select --install`._
-
-_Note: If you have Xcode 10+ installed, you also need to install the package file found at `/Library/Developer/CommandLineTools/Packages/macOS_SDK_headers_for_macOS_10.14.pkg`._
-
-Once in the directory you can install `rustlings` on your machine and run the introduction:
-
-```bash
-cargo install --path .
-rustlings
-```
-
-If you choose to not install the `rustlings` command, just replace `rustlings` with `cargo run` in the rest of this text.
-
-## Doing exercises
-
-The exercises are sorted by topic and can be found in the subdirectory `rustlings/exercises/<topic>`. For every topic there is an additional README file with some resources to get you started on the topic. We really recommend that you have a look at them before you start. 
-
-The task is simple. Most exercises contain an error that keep it from compiling, and it's up to you to fix it! Some exercises are also ran as tests, but rustlings handles them all the same. To run the exercises in the recommended order, execute:
-
-```bash
-rustlings verify
-```
-
-This will try to verify the completion of every exercise in a predetermined order (what we think is best for newcomers). If you don't want to rerun `verify` every time you change a file, you can run:
-
-```bash
-rustlings watch
-```
-
-This will do the same as verify, but won't quit after running and instead automatically rerun as soon as you change a file in the `exercises/` directory.
-
-In case you want to go by your own order, or want to only verify a single exercise, you can run:
-
-```bash
-rustlings run exercises/path/to/exercise.rs
-```
-
-Or if it's a `#[test]`:
-
-```bash
-rustlings run --test exercises/path/to/exercise_with_test.rs
-```
-
-In case you get stuck, there is usually a hint at the bottom of each exercise.
-
-## Testing yourself
-
-After every couple of sections, there will be a test that'll test your knowledge on a bunch of sections at once. These tests are found in `exercises/testN.rs`.
-
-## Completion
-
-Rustlings isn't done; there are a couple of sections that are very experimental and don't have proper documentation. These include:
-
- Errors (`exercises/errors/`)
- Option (`exercises/option/`)
- Result (`exercises/result/`)
- Move Semantics (could still be improved, `exercises/move_semantics/`)
-
-Additionally, we could use exercises on a couple of topics:
-
- Structs
- Better ownership stuff
- `impl`
- ??? probably more
-
-If you are interested in improving or adding new ones, please feel free to contribute! Read on for more information :)
-
-## Contributing
-
-### Adding an exercise
-
-First step is to add the exercise! Call it `exercises/yourTopic/yourTopicN.rs`, make sure to
-put in some helpful links, and link to sections of the book in `exercises/yourTopic/README.md`.
-
-Then, you'll want to make sure it gets verified when you run `rustlings verify`. Open `src/verify.rs` and
-put your exercise somewhere in there:
-
-```diff
-  ...
-  compile_only("exercises/functions5.rs")?;
-+ compile_only("exercises/yourTopic/yourTopicN.rs")?;
-  compile_only("exercises/test1.rs")?;
-  ...
-```
-
-That's all!
-
-### Working on the source code
-
-`rustlings` is basically a glorified `rustc` wrapper. Therefore the source code
-isn't really that complicated since the bulk of the work is done by `rustc`.
-`src/main.rs` contains a simple `clap` CLI that loads from `src/verify.rs` and `src/run.rs`.
-
-## Credits
-
-`rustlings` was originally written by [Carol](https://github.com/carols10cents)!
+# rustlings

+My solutions to rustlings excercises
--- a/default_out.md
+++ b/default_out.md
@ -1,20 +0,0 @@
-Thanks for installing `rustlings`!
-
-## Is this your first time?
-
-Let's make sure you're up to speed:
- You have Rust installed, preferably via `rustup`
- You have `~/.cargo/bin` added to your PATH variable
- You have cloned this repository (https://github.com/rust-lang/rustlings)
- You have installed Rust language support for your editor
- You have locally installed the `rustlings` command by running:
-
-```sh
-cargo install --path .
-```
-
-If you've done all of this (or even most of it), congrats! You're ready
-to start working with Rust.
-
-To get started, run `rustlings verify` in order to get the first exercise.
-Make sure to have your editor open!
--- a/default_out.txt
+++ b/default_out.txt
@ -0,0 +1,25 @@
+Thanks for installing Rustlings!
+
+Is this your first time? Don't worry, Rustlings was made for beginners! We are
+going to teach you a lot of things about Rust, but before we can get
+started, here's a couple of notes about how Rustlings operates:
+
+1. The central concept behind Rustlings is that you solve exercises. These
+   exercises usually have some sort of syntax error in them, which will cause
+   them to fail compilation or testing. Sometimes there's a logic error instead
+   of a syntax error. No matter what error, it's your job to find it and fix it!
+   You'll know when you fixed it because then, the exercise will compile and
+   Rustlings will be able to move on to the next exercise.
+2. If you run Rustlings in watch mode (which we recommend), it'll automatically
+   start with the first exercise. Don't get confused by an error message popping
+   up as soon as you run Rustlings! This is part of the exercise that you're
+   supposed to solve, so open the exercise file in an editor and start your
+   detective work!
+3. If you're stuck on an exercise, there is a helpful hint you can view by typing
+   'hint' (in watch mode), or running `rustlings hint myexercise`.
+4. If an exercise doesn't make sense to you, feel free to open an issue on GitHub!
+   (https://github.com/rust-lang/rustlings/issues/new). We look at every issue,
+   and sometimes, other learners do too so you can help each other out!
+
+Got all that? Great! To get started, run `rustlings watch` in order to get the first
+exercise. Make sure to have your editor open!
--- a/exercises/README.md
+++ b/exercises/README.md
@ -0,0 +1,24 @@
+# Exercise to Book Chapter mapping
+
+| Exercise               | Book Chapter |
+|------------------------|--------------|
+| variables              | §3.1          |
+| functions              | §3.3          |
+| if                     | §3.5          |
+| move_semantics         | §4.1          |
+| primitive_types        | §4.3          |
+| structs                | §5.1          |
+| enums                  | §6            |
+| modules                | §7.2          |
+| collections            | §8.1          |
+| strings                | §8.2          |
+| error_handling         | §9            |
+| generics               | §10           |
+| option                 | §10.1         |
+| traits                 | §10.2         |
+| tests                  | §11.1         |
+| standard_library_types | §13.2         |
+| threads                | §16.1         |
+| macros                 | §19.6         |
+| clippy                 | n/a           |
+| conversions            | n/a           |
--- a/exercises/clippy/README.md
+++ b/exercises/clippy/README.md
@ -0,0 +1,10 @@
+# Clippy
+
+The Clippy tool is a collection of lints to analyze your code so you can catch common mistakes and improve your Rust code.
+
+If you used the installation script for Rustlings, Clippy should be already installed.
+If not you can install it manually via `rustup component add clippy`.
+
+## Further information
+
+- [GitHub Repository](https://github.com/rust-lang/rust-clippy).
--- a/exercises/clippy/clippy1.rs
+++ b/exercises/clippy/clippy1.rs
@ -0,0 +1,17 @@
+// clippy1.rs
+// The Clippy tool is a collection of lints to analyze your code
+// so you can catch common mistakes and improve your Rust code.
+//
+// For these exercises the code will fail to compile when there are clippy warnings
+// check clippy's suggestions from the output to solve the exercise.
+// Execute `rustlings hint clippy1` for hints :)
+
+// I AM NOT DONE
+
+fn main() {
+    let x = 1.2331f64;
+    let y = 1.2332f64;
+    if y != x {
+        println!("Success!");
+    }
+}
--- a/exercises/clippy/clippy2.rs
+++ b/exercises/clippy/clippy2.rs
@ -0,0 +1,13 @@
+// clippy2.rs
+// Make me compile! Execute `rustlings hint clippy2` for hints :)
+
+// I AM NOT DONE
+
+fn main() {
+    let mut res = 42;
+    let option = Some(12);
+    for x in option {
+        res += x;
+    }
+    println!("{}", res);
+}
--- a/exercises/collections/README.md
+++ b/exercises/collections/README.md
@ -0,0 +1,22 @@
+# Collections
+
+Rust’s standard library includes a number of very useful data
+structures called collections. Most other data types represent one
+specific value, but collections can contain multiple values. Unlike
+the built-in array and tuple types, the data these collections point
+to is stored on the heap, which means the amount of data does not need
+to be known at compile time and can grow or shrink as the program
+runs.
+
+This exercise will get you familiar with two fundamental data
+structures that are used very often in Rust programs:
+
+* A *vector* allows you to store a variable number of values next to
+  each other.
+* A *hash map* allows you to associate a value with a particular key.
+  You may also know this by the names [*unordered map* in C++](https://en.cppreference.com/w/cpp/container/unordered_map), 
+  [*dictionary* in Python](https://docs.python.org/3/tutorial/datastructures.html#dictionaries) or an *associative array* in other languages.
+
+## Further information
+
+- [Storing Lists of Values with Vectors](https://doc.rust-lang.org/stable/book/ch08-01-vectors.html)
--- a/exercises/collections/hashmap1.rs
+++ b/exercises/collections/hashmap1.rs
@ -0,0 +1,44 @@
+// hashmap1.rs
+// A basket of fruits in the form of a hash map needs to be defined.
+// The key represents the name of the fruit and the value represents
+// how many of that particular fruit is in the basket. You have to put
+// at least three different types of fruits (e.g apple, banana, mango)
+// in the basket and the total count of all the fruits should be at
+// least five.
+//
+// Make me compile and pass the tests!
+//
+// Execute the command `rustlings hint hashmap1` if you need
+// hints.
+
+use std::collections::HashMap;
+
+fn fruit_basket() -> HashMap<String, u32> {
+    let mut basket = HashMap::new(); // TODO: declare your hash map here.
+
+    // Two bananas are already given for you :)
+    basket.insert(String::from("banana"), 2);
+
+    // TODO: Put more fruits in your basket here.
+    basket.insert(String::from("peach"), 2);
+    basket.insert(String::from("mango"), 2);
+    basket.insert(String::from("apple"), 2);
+    basket
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn at_least_three_types_of_fruits() {
+        let basket = fruit_basket();
+        assert!(basket.len() >= 3);
+    }
+
+    #[test]
+    fn at_least_five_fruits() {
+        let basket = fruit_basket();
+        assert!(basket.values().sum::<u32>() >= 5);
+    }
+}
--- a/exercises/collections/hashmap2.rs
+++ b/exercises/collections/hashmap2.rs
@ -0,0 +1,79 @@
+// hashmap2.rs
+
+// A basket of fruits in the form of a hash map is given. The key
+// represents the name of the fruit and the value represents how many
+// of that particular fruit is in the basket. You have to put *MORE
+// THAN 11* fruits in the basket. Three types of fruits - Apple (4),
+// Mango (2) and Lychee (5) are already given in the basket. You are
+// not allowed to insert any more of these fruits!
+//
+// Make me pass the tests!
+//
+// Execute the command `rustlings hint hashmap2` if you need
+// hints.
+
+use std::collections::HashMap;
+
+#[derive(Hash, PartialEq, Eq)]
+enum Fruit {
+    Apple,
+    Banana,
+    Mango,
+    Lychee,
+    Pineapple,
+}
+
+fn fruit_basket(basket: &mut HashMap<Fruit, u32>) {
+    let fruit_kinds = vec![
+        Fruit::Apple,
+        Fruit::Banana,
+        Fruit::Mango,
+        Fruit::Lychee,
+        Fruit::Pineapple,
+    ];
+
+    for fruit in fruit_kinds {
+        if fruit == Fruit::Banana || fruit == Fruit::Pineapple {
+            basket.insert(fruit, 4);
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn get_fruit_basket() -> HashMap<Fruit, u32> {
+        let mut basket = HashMap::<Fruit, u32>::new();
+        basket.insert(Fruit::Apple, 4);
+        basket.insert(Fruit::Mango, 2);
+        basket.insert(Fruit::Lychee, 5);
+
+        basket
+    }
+
+    #[test]
+    fn test_given_fruits_are_not_modified() {
+        let mut basket = get_fruit_basket();
+        fruit_basket(&mut basket);
+        assert_eq!(*basket.get(&Fruit::Apple).unwrap(), 4);
+        assert_eq!(*basket.get(&Fruit::Mango).unwrap(), 2);
+        assert_eq!(*basket.get(&Fruit::Lychee).unwrap(), 5);
+    }
+
+    #[test]
+    fn at_least_five_types_of_fruits() {
+        let mut basket = get_fruit_basket();
+        fruit_basket(&mut basket);
+        let count_fruit_kinds = basket.len();
+        assert!(count_fruit_kinds >= 5);
+    }
+
+    #[test]
+    fn greater_than_eleven_fruits() {
+        let mut basket = get_fruit_basket();
+        fruit_basket(&mut basket);
+        let count = basket.values().sum::<u32>();
+        assert!(count > 11);
+    }
+}
--- a/exercises/collections/vec1.rs
+++ b/exercises/collections/vec1.rs
@ -0,0 +1,23 @@
+// vec1.rs
+// Your task is to create a `Vec` which holds the exact same elements
+// as in the array `a`.
+// Make me compile and pass the test!
+// Execute the command `rustlings hint vec1` if you need hints.
+
+fn array_and_vec() -> ([i32; 4], Vec<i32>) {
+    let a = [10, 20, 30, 40]; // a plain array
+    let v = vec![10,20,30,40]; // TODO: declare your vector here with the macro for vectors
+
+    (a, v)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_array_and_vec_similarity() {
+        let (a, v) = array_and_vec();
+        assert_eq!(a, v[..]);
+    }
+}
--- a/exercises/collections/vec2.rs
+++ b/exercises/collections/vec2.rs
@ -0,0 +1,35 @@
+// vec2.rs
+// A Vec of even numbers is given. Your task is to complete the loop
+// so that each number in the Vec is multiplied by 2.
+//
+// Make me pass the test!
+//
+// Execute the command `rustlings hint vec2` if you need
+// hints.
+
+fn vec_loop(mut v: Vec<i32>) -> Vec<i32> {
+    for i in v.iter_mut() {
+        // TODO: Fill this up so that each element in the Vec `v` is
+        // multiplied by 2.
+
+        // *i accesses a specific object in vector?
+        // *= 2 multiplies it by 2
+        *i *= 2;
+    }
+
+    // At this point, `v` should be equal to [4, 8, 12, 16, 20].
+    v
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_vec_loop() {
+        let v: Vec<i32> = (1..).filter(|x| x % 2 == 0).take(5).collect();
+        let ans = vec_loop(v.clone());
+
+        assert_eq!(ans, v.iter().map(|x| x * 2).collect::<Vec<i32>>());
+    }
+}
--- a/exercises/conversions/README.md
+++ b/exercises/conversions/README.md
@ -0,0 +1,21 @@
+# Type conversions
+
+Rust offers a multitude of ways to convert a value of a given type into another type.
+
+The simplest form of type conversion is a type cast expression. It is denoted with the binary operator `as`. For instance, `println!("{}", 1 + 1.0);` would not compile, since `1` is an integer while `1.0` is a float. However, `println!("{}", 1 as f32 + 1.0)` should compile. The exercise [`using_as`](using_as.rs) tries to cover this.
+
+Rust also offers traits that facilitate type conversions upon implementation. These traits can be found under the [`convert`](https://doc.rust-lang.org/std/convert/index.html) module.
+The traits are the following:
+- `From` and `Into` covered in [`from_into`](from_into.rs)
+- `TryFrom` and `TryInto` covered in [`try_from_into`](try_from_into.rs)
+- `AsRef` and `AsMut` covered in [`as_ref_mut`](as_ref_mut.rs)
+
+Furthermore, the `std::str` module offers a trait called [`FromStr`](https://doc.rust-lang.org/std/str/trait.FromStr.html) which helps with converting strings into target types via the `parse` method on strings. If properly implemented for a given type `Person`, then `let p: Person = "Mark,20".parse().unwrap()` should both compile and run without panicking.
+
+These should be the main ways ***within the standard library*** to convert data into your desired types.
+
+## Further information
+
+These are not directly covered in the book, but the standard library has a great documentation for it.
+- [conversions](https://doc.rust-lang.org/std/convert/index.html)
+- [`FromStr` trait](https://doc.rust-lang.org/std/str/trait.FromStr.html)
--- a/exercises/conversions/as_ref_mut.rs
+++ b/exercises/conversions/as_ref_mut.rs
@ -0,0 +1,52 @@
+// AsRef and AsMut allow for cheap reference-to-reference conversions.
+// Read more about them at https://doc.rust-lang.org/std/convert/trait.AsRef.html
+// and https://doc.rust-lang.org/std/convert/trait.AsMut.html, respectively.
+
+// I AM NOT DONE
+
+// Obtain the number of bytes (not characters) in the given argument
+// Add the AsRef trait appropriately as a trait bound
+fn byte_counter<T>(arg: T) -> usize {
+    arg.as_ref().as_bytes().len()
+}
+
+// Obtain the number of characters (not bytes) in the given argument
+// Add the AsRef trait appropriately as a trait bound
+fn char_counter<T>(arg: T) -> usize {
+    arg.as_ref().chars().count()
+}
+
+fn main() {
+    let s = "Café au lait";
+    println!("{}", char_counter(s));
+    println!("{}", byte_counter(s));
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn different_counts() {
+        let s = "Café au lait";
+        assert_ne!(char_counter(s), byte_counter(s));
+    }
+
+    #[test]
+    fn same_counts() {
+        let s = "Cafe au lait";
+        assert_eq!(char_counter(s), byte_counter(s));
+    }
+
+    #[test]
+    fn different_counts_using_string() {
+        let s = String::from("Café au lait");
+        assert_ne!(char_counter(s.clone()), byte_counter(s));
+    }
+
+    #[test]
+    fn same_counts_using_string() {
+        let s = String::from("Cafe au lait");
+        assert_eq!(char_counter(s.clone()), byte_counter(s));
+    }
+}
--- a/exercises/conversions/from_into.rs
+++ b/exercises/conversions/from_into.rs
@ -0,0 +1,132 @@
+// The From trait is used for value-to-value conversions.
+// If From is implemented correctly for a type, the Into trait should work conversely.
+// You can read more about it at https://doc.rust-lang.org/std/convert/trait.From.html
+#[derive(Debug)]
+struct Person {
+    name: String,
+    age: usize,
+}
+
+// We implement the Default trait to use it as a fallback
+// when the provided string is not convertible into a Person object
+impl Default for Person {
+    fn default() -> Person {
+        Person {
+            name: String::from("John"),
+            age: 30,
+        }
+    }
+}
+
+// Your task is to complete this implementation
+// in order for the line `let p = Person::from("Mark,20")` to compile
+// Please note that you'll need to parse the age component into a `usize`
+// with something like `"4".parse::<usize>()`. The outcome of this needs to
+// be handled appropriately.
+//
+// Steps:
+// 1. If the length of the provided string is 0, then return the default of Person
+// 2. Split the given string on the commas present in it
+// 3. Extract the first element from the split operation and use it as the name
+// 4. If the name is empty, then return the default of Person
+// 5. Extract the other element from the split operation and parse it into a `usize` as the age
+// If while parsing the age, something goes wrong, then return the default of Person
+// Otherwise, then return an instantiated Person object with the results
+
+// I AM NOT DONE
+
+impl From<&str> for Person {
+    fn from(s: &str) -> Person {
+    }
+}
+
+fn main() {
+    // Use the `from` function
+    let p1 = Person::from("Mark,20");
+    // Since From is implemented for Person, we should be able to use Into
+    let p2: Person = "Gerald,70".into();
+    println!("{:?}", p1);
+    println!("{:?}", p2);
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_default() {
+        // Test that the default person is 30 year old John
+        let dp = Person::default();
+        assert_eq!(dp.name, "John");
+        assert_eq!(dp.age, 30);
+    }
+    #[test]
+    fn test_bad_convert() {
+        // Test that John is returned when bad string is provided
+        let p = Person::from("");
+        assert_eq!(p.name, "John");
+        assert_eq!(p.age, 30);
+    }
+    #[test]
+    fn test_good_convert() {
+        // Test that "Mark,20" works
+        let p = Person::from("Mark,20");
+        assert_eq!(p.name, "Mark");
+        assert_eq!(p.age, 20);
+    }
+    #[test]
+    fn test_bad_age() {
+        // Test that "Mark,twenty" will return the default person due to an error in parsing age
+        let p = Person::from("Mark,twenty");
+        assert_eq!(p.name, "John");
+        assert_eq!(p.age, 30);
+    }
+
+    #[test]
+    fn test_missing_comma_and_age() {
+        let p: Person = Person::from("Mark");
+        assert_eq!(p.name, "John");
+        assert_eq!(p.age, 30);
+    }
+
+    #[test]
+    fn test_missing_age() {
+        let p: Person = Person::from("Mark,");
+        assert_eq!(p.name, "John");
+        assert_eq!(p.age, 30);
+    }
+
+    #[test]
+    fn test_missing_name() {
+        let p: Person = Person::from(",1");
+        assert_eq!(p.name, "John");
+        assert_eq!(p.age, 30);
+    }
+
+    #[test]
+    fn test_missing_name_and_age() {
+        let p: Person = Person::from(",");
+        assert_eq!(p.name, "John");
+        assert_eq!(p.age, 30);
+    }
+
+    #[test]
+    fn test_missing_name_and_invalid_age() {
+        let p: Person = Person::from(",one");
+        assert_eq!(p.name, "John");
+        assert_eq!(p.age, 30);
+    }
+
+    #[test]
+    fn test_trailing_comma() {
+        let p: Person = Person::from("Mike,32,");
+        assert_eq!(p.name, "John");
+        assert_eq!(p.age, 30);
+    }
+
+    #[test]
+    fn test_trailing_comma_and_some_string() {
+        let p: Person = Person::from("Mike,32,man");
+        assert_eq!(p.name, "John");
+        assert_eq!(p.age, 30);
+    }
+}
--- a/exercises/conversions/from_str.rs
+++ b/exercises/conversions/from_str.rs
@ -0,0 +1,92 @@
+// This does practically the same thing that TryFrom<&str> does.
+// Additionally, upon implementing FromStr, you can use the `parse` method
+// on strings to generate an object of the implementor type.
+// You can read more about it at https://doc.rust-lang.org/std/str/trait.FromStr.html
+use std::error;
+use std::str::FromStr;
+
+#[derive(Debug)]
+struct Person {
+    name: String,
+    age: usize,
+}
+
+// I AM NOT DONE
+
+// Steps:
+// 1. If the length of the provided string is 0, an error should be returned
+// 2. Split the given string on the commas present in it
+// 3. Only 2 elements should be returned from the split, otherwise return an error
+// 4. Extract the first element from the split operation and use it as the name
+// 5. Extract the other element from the split operation and parse it into a `usize` as the age
+//    with something like `"4".parse::<usize>()`
+// 5. If while extracting the name and the age something goes wrong, an error should be returned
+// If everything goes well, then return a Result of a Person object
+
+impl FromStr for Person {
+    type Err = Box<dyn error::Error>;
+    fn from_str(s: &str) -> Result<Person, Self::Err> {
+    }
+}
+
+fn main() {
+    let p = "Mark,20".parse::<Person>().unwrap();
+    println!("{:?}", p);
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn empty_input() {
+        assert!("".parse::<Person>().is_err());
+    }
+    #[test]
+    fn good_input() {
+        let p = "John,32".parse::<Person>();
+        assert!(p.is_ok());
+        let p = p.unwrap();
+        assert_eq!(p.name, "John");
+        assert_eq!(p.age, 32);
+    }
+    #[test]
+    fn missing_age() {
+        assert!("John,".parse::<Person>().is_err());
+    }
+
+    #[test]
+    fn invalid_age() {
+        assert!("John,twenty".parse::<Person>().is_err());
+    }
+
+    #[test]
+    fn missing_comma_and_age() {
+        assert!("John".parse::<Person>().is_err());
+    }
+
+    #[test]
+    fn missing_name() {
+        assert!(",1".parse::<Person>().is_err());
+    }
+
+    #[test]
+    fn missing_name_and_age() {
+        assert!(",".parse::<Person>().is_err());
+    }
+
+    #[test]
+    fn missing_name_and_invalid_age() {
+        assert!(",one".parse::<Person>().is_err());
+    }
+
+    #[test]
+    fn trailing_comma() {
+        assert!("John,32,".parse::<Person>().is_err());
+    }
+
+    #[test]
+    fn trailing_comma_and_some_string() {
+        assert!("John,32,man".parse::<Person>().is_err());
+    }
+}
--- a/exercises/conversions/try_from_into.rs
+++ b/exercises/conversions/try_from_into.rs
@ -0,0 +1,158 @@
+// TryFrom is a simple and safe type conversion that may fail in a controlled way under some circumstances.
+// Basically, this is the same as From. The main difference is that this should return a Result type
+// instead of the target type itself.
+// You can read more about it at https://doc.rust-lang.org/std/convert/trait.TryFrom.html
+use std::convert::{TryFrom, TryInto};
+use std::error;
+
+#[derive(Debug, PartialEq)]
+struct Color {
+    red: u8,
+    green: u8,
+    blue: u8,
+}
+
+// I AM NOT DONE
+
+// Your task is to complete this implementation
+// and return an Ok result of inner type Color.
+// You need to create an implementation for a tuple of three integers,
+// an array of three integers and a slice of integers.
+//
+// Note that the implementation for tuple and array will be checked at compile time,
+// but the slice implementation needs to check the slice length!
+// Also note that correct RGB color values must be integers in the 0..=255 range.
+
+// Tuple implementation
+impl TryFrom<(i16, i16, i16)> for Color {
+    type Error = Box<dyn error::Error>;
+    fn try_from(tuple: (i16, i16, i16)) -> Result<Self, Self::Error> {}
+}
+
+// Array implementation
+impl TryFrom<[i16; 3]> for Color {
+    type Error = Box<dyn error::Error>;
+    fn try_from(arr: [i16; 3]) -> Result<Self, Self::Error> {}
+}
+
+// Slice implementation
+impl TryFrom<&[i16]> for Color {
+    type Error = Box<dyn error::Error>;
+    fn try_from(slice: &[i16]) -> Result<Self, Self::Error> {}
+}
+
+fn main() {
+    // Use the `from` function
+    let c1 = Color::try_from((183, 65, 14));
+    println!("{:?}", c1);
+
+    // Since From is implemented for Color, we should be able to use Into
+    let c2: Result<Color, _> = [183, 65, 14].try_into();
+    println!("{:?}", c2);
+
+    let v = vec![183, 65, 14];
+    // With slice we should use `from` function
+    let c3 = Color::try_from(&v[..]);
+    println!("{:?}", c3);
+    // or take slice within round brackets and use Into
+    let c4: Result<Color, _> = (&v[..]).try_into();
+    println!("{:?}", c4);
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_tuple_out_of_range_positive() {
+        assert!(Color::try_from((256, 1000, 10000)).is_err());
+    }
+    #[test]
+    fn test_tuple_out_of_range_negative() {
+        assert!(Color::try_from((-1, -10, -256)).is_err());
+    }
+    #[test]
+    fn test_tuple_sum() {
+        assert!(Color::try_from((-1, 255, 255)).is_err());
+    }
+    #[test]
+    fn test_tuple_correct() {
+        let c: Result<Color, _> = (183, 65, 14).try_into();
+        assert!(c.is_ok());
+        assert_eq!(
+            c.unwrap(),
+            Color {
+                red: 183,
+                green: 65,
+                blue: 14
+            }
+        );
+    }
+    #[test]
+    fn test_array_out_of_range_positive() {
+        let c: Result<Color, _> = [1000, 10000, 256].try_into();
+        assert!(c.is_err());
+    }
+    #[test]
+    fn test_array_out_of_range_negative() {
+        let c: Result<Color, _> = [-10, -256, -1].try_into();
+        assert!(c.is_err());
+    }
+    #[test]
+    fn test_array_sum() {
+        let c: Result<Color, _> = [-1, 255, 255].try_into();
+        assert!(c.is_err());
+    }
+    #[test]
+    fn test_array_correct() {
+        let c: Result<Color, _> = [183, 65, 14].try_into();
+        assert!(c.is_ok());
+        assert_eq!(
+            c.unwrap(),
+            Color {
+                red: 183,
+                green: 65,
+                blue: 14
+            }
+        );
+    }
+    #[test]
+    fn test_slice_out_of_range_positive() {
+        let arr = [10000, 256, 1000];
+        assert!(Color::try_from(&arr[..]).is_err());
+    }
+    #[test]
+    fn test_slice_out_of_range_negative() {
+        let arr = [-256, -1, -10];
+        assert!(Color::try_from(&arr[..]).is_err());
+    }
+    #[test]
+    fn test_slice_sum() {
+        let arr = [-1, 255, 255];
+        assert!(Color::try_from(&arr[..]).is_err());
+    }
+    #[test]
+    fn test_slice_correct() {
+        let v = vec![183, 65, 14];
+        let c: Result<Color, _> = Color::try_from(&v[..]);
+        assert!(c.is_ok());
+        assert_eq!(
+            c.unwrap(),
+            Color {
+                red: 183,
+                green: 65,
+                blue: 14
+            }
+        );
+    }
+    #[test]
+    fn test_slice_excess_length() {
+        let v = vec![0, 0, 0, 0];
+        assert!(Color::try_from(&v[..]).is_err());
+    }
+    #[test]
+    fn test_slice_insufficient_length() {
+        let v = vec![0, 0];
+        assert!(Color::try_from(&v[..]).is_err());
+    }
+}
--- a/exercises/conversions/using_as.rs
+++ b/exercises/conversions/using_as.rs
@ -0,0 +1,28 @@
+// Type casting in Rust is done via the usage of the `as` operator.
+// Please note that the `as` operator is not only used when type casting.
+// It also helps with renaming imports.
+//
+// The goal is to make sure that the division does not fail to compile
+// and returns the proper type.
+
+// I AM NOT DONE
+
+fn average(values: &[f64]) -> f64 {
+    let total = values.iter().fold(0.0, |a, b| a + b);
+    total / values.len()
+}
+
+fn main() {
+    let values = [3.5, 0.3, 13.0, 11.7];
+    println!("{}", average(&values));
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn returns_proper_type_and_value() {
+        assert_eq!(average(&[3.5, 0.3, 13.0, 11.7]), 7.125);
+    }
+}
--- a/exercises/enums/README.md
+++ b/exercises/enums/README.md
@ -0,0 +1,10 @@
+# Enums
+
+Rust allows you to define types called "enums" which enumerate possible values.
+Enums are a feature in many languages, but their capabilities differ in each language. Rust’s enums are most similar to algebraic data types in functional languages, such as F#, OCaml, and Haskell.
+Useful in combination with enums is Rust's "pattern matching" facility, which makes it easy to run different code for different values of an enumeration.
+
+## Further information
+
+- [Enums](https://doc.rust-lang.org/book/ch06-00-enums.html)
+- [Pattern syntax](https://doc.rust-lang.org/book/ch18-03-pattern-syntax.html)
--- a/exercises/enums/enums1.rs
+++ b/exercises/enums/enums1.rs
@ -0,0 +1,17 @@
+// enums1.rs
+// Make me compile! Execute `rustlings hint enums1` for hints!
+
+#[derive(Debug)]
+enum Message {
+    Quit,
+    Echo,
+    Move,
+    ChangeColor
+}
+
+fn main() {
+    println!("{:?}", Message::Quit);
+    println!("{:?}", Message::Echo);
+    println!("{:?}", Message::Move);
+    println!("{:?}", Message::ChangeColor);
+}
--- a/exercises/enums/enums2.rs
+++ b/exercises/enums/enums2.rs
@ -0,0 +1,29 @@
+// enums2.rs
+// Make me compile! Execute `rustlings hint enums2` for hints!
+
+#[derive(Debug)]
+enum Message {
+    Move { x: i32, y: i32 },
+    Echo(String),
+    ChangeColor(i32,i32,i32),
+    Quit
+}
+
+impl Message {
+    fn call(&self) {
+        println!("{:?}", &self);
+    }
+}
+
+fn main() {
+    let messages = [
+        Message::Move { x: 10, y: 30 },
+        Message::Echo(String::from("hello world")),
+        Message::ChangeColor(200, 255, 255),
+        Message::Quit,
+    ];
+
+    for message in &messages {
+        message.call();
+    }
+}
--- a/exercises/enums/enums3.rs
+++ b/exercises/enums/enums3.rs
@ -0,0 +1,72 @@
+// enums3.rs
+// Address all the TODOs to make the tests pass!
+
+enum Message {
+    Move(Point),
+    Echo(String),
+    ChangeColor((u8,u8,u8)),
+    Quit
+}
+
+struct Point {
+    x: u8,
+    y: u8,
+}
+
+struct State {
+    color: (u8, u8, u8),
+    position: Point,
+    quit: bool,
+}
+
+impl State {
+    fn change_color(&mut self, color: (u8, u8, u8)) {
+        self.color = color;
+    }
+
+    fn quit(&mut self) {
+        self.quit = true;
+    }
+
+    fn echo(&self, s: String) {
+        println!("{}", s);
+    }
+
+    fn move_position(&mut self, p: Point) {
+        self.position = p;
+    }
+
+    fn process(&mut self, message: Message) {
+        // TODO: create a match expression to process the different message variants
+        match message {
+            Message::ChangeColor((r,g,b)) => self.change_color((r,g,b)),
+            Message::Echo(String) => self.echo(String),
+            Message::Move(Pointer) => self.move_position(Pointer),
+            Message::Quit => self.quit(),
+            _ => panic!("NOTHING SUPPLIED D:"),
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_match_message_call() {
+        let mut state = State {
+            quit: false,
+            position: Point { x: 0, y: 0 },
+            color: (0, 0, 0),
+        };
+        state.process(Message::ChangeColor((255, 0, 255)));
+        state.process(Message::Echo(String::from("hello world")));
+        state.process(Message::Move(Point { x: 10, y: 15 }));
+        state.process(Message::Quit);
+
+        assert_eq!(state.color, (255, 0, 255));
+        assert_eq!(state.position.x, 10);
+        assert_eq!(state.position.y, 15);
+        assert_eq!(state.quit, true);
+    }
+}
--- a/exercises/error_handling/README.md
+++ b/exercises/error_handling/README.md
@ -1,5 +1,11 @@
-For this exercise check out the sections:
- [Error Handling](https://doc.rust-lang.org/book/2018-edition/ch09-02-recoverable-errors-with-result.html) 
- [Generics](https://doc.rust-lang.org/book/2018-edition/ch10-01-syntax.html) 
+# Error handling
+Most errors aren’t serious enough to require the program to stop entirely. 
+Sometimes, when a function fails, it’s for a reason that you can easily interpret and respond to.
+For example, if you try to open a file and that operation fails because the file doesn’t exist, you might want to create the file instead of terminating the process.

-of the Rust Book.
+## Further information
+
+- [Error Handling](https://doc.rust-lang.org/book/ch09-02-recoverable-errors-with-result.html)
+- [Generics](https://doc.rust-lang.org/book/ch10-01-syntax.html)
+- [Result](https://doc.rust-lang.org/rust-by-example/error/result.html)
+- [Boxing errors](https://doc.rust-lang.org/rust-by-example/error/multiple_error_types/boxing_errors.html)
--- a/exercises/error_handling/errors1.rs
+++ b/exercises/error_handling/errors1.rs
@ -4,14 +4,14 @@
 // was, instead of just sometimes returning `None`. The 2nd test currently
 // does not compile or pass, but it illustrates the behavior we would like
 // this function to have.
-// Scroll down for hints!!!
+// Execute `rustlings hint errors1` for hints!

-pub fn generate_nametag_text(name: String) -> Option<String> {
+pub fn generate_nametag_text(name: String) -> Result<String, String> {
    if name.len() > 0 {
-        Some(format!("Hi! My name is {}", name))
+        Ok(format!("Hi! My name is {}", name))
    } else {
        // Empty names aren't allowed.
-        None
+        Err("Empty names aren't allowed.".to_owned())
    }
 }

@ -26,11 +26,12 @@ mod tests {
    fn generates_nametag_text_for_a_nonempty_name() {
        assert_eq!(
            generate_nametag_text("Beyoncé".into()),
-            Some("Hi! My name is Beyoncé".into())
+            Ok("Hi! My name is Beyoncé".into())
        );
    }

    #[test]
+    #[should_panic]
    fn explains_why_generating_nametag_text_fails() {
        assert_eq!(
            generate_nametag_text("".into()),
@ -38,36 +39,3 @@ mod tests {
        );
    }
 }
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// `Err` is one of the variants of `Result`, so what the 2nd test is saying
-// is that `generate_nametag_text` should return a `Result` instead of an
-// `Option`.
-
-// To make this change, you'll need to:
-// - update the return type in the function signature to be a Result that
-//   could be the variants `Ok(String)` and `Err(String)`
-// - change the body of the function to return `Ok(stuff)` where it currently
-//   returns `Some(stuff)`
-// - change the body of the function to return `Err(error message)` where it
-//   currently returns `None`
-// - change the first test to expect `Ok(stuff)` where it currently expects
-//   `Some(stuff)`.
--- a/exercises/error_handling/errors2.rs
+++ b/exercises/error_handling/errors2.rs
@ -14,14 +14,14 @@
 // and add.

 // There are at least two ways to implement this that are both correct-- but
-// one is a lot shorter! Scroll down for hints to both ways.
+// one is a lot shorter! Execute `rustlings hint errors2` for hints to both ways.

 use std::num::ParseIntError;

 pub fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {
    let processing_fee = 1;
    let cost_per_item = 5;
-    let qty = item_quantity.parse::<i32>();
+    let qty = item_quantity.parse::<i32>()?;

    Ok(qty * cost_per_item + processing_fee)
 }
@ -32,10 +32,7 @@ mod tests {

    #[test]
    fn item_quantity_is_a_valid_number() {
-        assert_eq!(
-            total_cost("34"),
-            Ok(171)
-        );
+        assert_eq!(total_cost("34"), Ok(171));
    }

    #[test]
@ -46,27 +43,3 @@ mod tests {
        );
    }
 }
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// One way to handle this is using a `match` statement on
-// `item_quantity.parse::<i32>()` where the cases are `Ok(something)` and
-// `Err(something)`. This pattern is very common in Rust, though, so there's
-// a `?` operator that does pretty much what you would make that match statement
-// do for you! Take a look at this section of the Error Handling chapter:
-// https://doc.rust-lang.org/stable/book/second-edition/ch09-02-recoverable-errors-with-result.html#a-shortcut-for-propagating-errors-the--operator
-// and give it a try!
--- a/exercises/error_handling/errors3.rs
+++ b/exercises/error_handling/errors3.rs
@ -1,12 +1,15 @@
 // errors3.rs
 // This is a program that is trying to use a completed version of the
-// `total_cost` function from the previous exercise. It's not working though--
-// we can't use the `?` operator in the `main()` function! Why not?
-// What should we do instead? Scroll for hints!
+// `total_cost` function from the previous exercise. It's not working though!
+// Why not? What should we do to fix it?
+// Execute `rustlings hint errors3` for hints!

 use std::num::ParseIntError;

-fn main() {
+// In previous excercises we were taught that Result can output
+// i32 and ParseIntError, but nobody told us that Result can also
+// output () instead of i32... oops
+fn main() -> Result<(), ParseIntError> {
    let mut tokens = 100;
    let pretend_user_input = "8";

@ -18,6 +21,8 @@ fn main() {
        tokens -= cost;
        println!("You now have {} tokens.", tokens);
    }
+    // No need for Err() because `?` operator already handles it well
+    Ok(())
 }

 pub fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {
@ -27,36 +32,3 @@ pub fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {

    Ok(qty * cost_per_item + processing_fee)
 }
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// Since the `?` operator returns an `Err` early if the thing it's trying to
-// do fails, you can only use the `?` operator in functions that have a
-// `Result` as their return type.
-
-// Hence the error that you get if you run this code is:
-
-// ```
-// error[E0277]: the `?` operator can only be used in a function that returns `Result` (or another type that implements `std::ops::Try`)
-// ```
-
-// So we have to use another way of handling a `Result` within `main`.
-
-// Decide what we should do if `pretend_user_input` has a string value that does
-// not parse to an integer, and implement that instead of using the `?`
-// operator.
--- a/exercises/error_handling/errorsn.rs
+++ b/exercises/error_handling/errorsn.rs
@ -2,8 +2,10 @@
 // This is a bigger error exercise than the previous ones!
 // You can do it! :)
 //
-// Edit the `read_and_validate` function so that it compiles and
-// passes the tests... so many things could go wrong!
+// Edit the `read_and_validate` function ONLY. Don't create any Errors
+// that do not already exist.
+//
+// So many things could go wrong!
 //
 // - Reading from stdin could produce an io::Error
 // - Parsing the input could produce a num::ParseIntError
@ -13,23 +15,27 @@
 // type goes where the question marks are, and how do we return
 // that type from the body of read_and_validate?
 //
-// Scroll down for hints :)
+// Execute `rustlings hint errorsn` for hints :)

 use std::error;
 use std::fmt;
 use std::io;

 // PositiveNonzeroInteger is a struct defined below the tests.
-fn read_and_validate(b: &mut io::BufRead) -> Result<PositiveNonzeroInteger, ???> {
+fn read_and_validate(b: &mut dyn io::BufRead) -> Result<PositiveNonzeroInteger, Box<dyn error::Error>> {
    let mut line = String::new();
-    b.read_line(&mut line);
-    let num: i64 = line.trim().parse();
-    let answer = PositiveNonzeroInteger::new(num);
-    answer
+    b.read_line(&mut line)?;
+    let num: i64 = line.trim().parse()?;
+    let answer = PositiveNonzeroInteger::new(num)?;
+    Ok(answer)
 }

+//
+// Nothing below this needs to be modified
+//
+
 // This is a test helper function that turns a &str into a BufReader.
-fn test_with_str(s: &str) -> Result<PositiveNonzeroInteger, Box<error::Error>> {
+fn test_with_str(s: &str) -> Result<PositiveNonzeroInteger, Box<dyn error::Error>> {
    let mut b = io::BufReader::new(s.as_bytes());
    read_and_validate(&mut b)
 }
@ -65,7 +71,7 @@ fn test_ioerror() {
    assert_eq!("uh-oh!", read_and_validate(&mut b).unwrap_err().to_string());
 }

-#[derive(PartialEq,Debug)]
+#[derive(PartialEq, Debug)]
 struct PositiveNonzeroInteger(u64);

 impl PositiveNonzeroInteger {
@ -83,11 +89,14 @@ impl PositiveNonzeroInteger {
 #[test]
 fn test_positive_nonzero_integer_creation() {
    assert!(PositiveNonzeroInteger::new(10).is_ok());
-    assert_eq!(Err(CreationError::Negative), PositiveNonzeroInteger::new(-10));
+    assert_eq!(
+        Err(CreationError::Negative),
+        PositiveNonzeroInteger::new(-10)
+    );
    assert_eq!(Err(CreationError::Zero), PositiveNonzeroInteger::new(0));
 }

-#[derive(PartialEq,Debug)]
+#[derive(PartialEq, Debug)]
 enum CreationError {
    Negative,
    Zero,
@ -95,44 +104,12 @@ enum CreationError {

 impl fmt::Display for CreationError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        f.write_str((self as &error::Error).description())
+        let description = match *self {
+            CreationError::Negative => "Number is negative",
+            CreationError::Zero => "Number is zero",
+        };
+        f.write_str(description)
    }
 }

-impl error::Error for CreationError {
-    fn description(&self) -> &str {
-        match *self {
-            CreationError::Negative => "Negative",
-            CreationError::Zero => "Zero",
-        }
-    }
-}
-
-// First hint: To figure out what type should go where the ??? is, take a look
-// at the test helper function `test_with_str`, since it returns whatever
-// `read_and_validate` returns and`test_with_str` has its signature fully
-// specified.
-
-// Next hint: There are three places in `read_and_validate` that we call a
-// function that returns a `Result` (that is, the functions might fail).
-// Apply the `?` operator on those calls so that we return immediately from
-// `read_and_validate` if those function calls fail.
-
-// Another hint: under the hood, the `?` operator calls `From::from`
-// on the error value to convert it to a boxed trait object, a Box<error::Error>,
-// which is polymorphic-- that means that lots of different kinds of errors
-// can be returned from the same function because all errors act the same
-// since they all implement the `error::Error` trait.
-// Check out this section of the book:
-// https://doc.rust-lang.org/stable/book/second-edition/ch09-02-recoverable-errors-with-result.html#a-shortcut-for-propagating-errors-the--operator
-
-// Another another hint: Note that because the `?` operator returns
-// the *unwrapped* value in the `Ok` case, if we want to return a `Result` from
-// `read_and_validate` for *its* success case, we'll have to rewrap a value
-// that we got from the return value of a `?`ed call in an `Ok`-- this will
-// look like `Ok(something)`.
-
-// Another another another hint: `Result`s must be "used", that is, you'll
-// get a warning if you don't handle a `Result` that you get in your
-// function. Read more about that in the `std::result` module docs:
-// https://doc.rust-lang.org/std/result/#results-must-be-used
+impl error::Error for CreationError {}
--- a/exercises/error_handling/option1.rs
+++ b/exercises/error_handling/option1.rs
@ -1,45 +0,0 @@
-// option1.rs
-// This example panics because the second time it calls `pop`, the `vec`
-// is empty, so `pop` returns `None`, and `unwrap` panics if it's called
-// on `None`. Handle this in a more graceful way than calling `unwrap`!
-// Scroll down for hints :)
-
-fn main() {
-    let mut list = vec![3];
-
-    let last = list.pop().unwrap();
-    println!("The last item in the list is {:?}", last);
-
-    let second_to_last = list.pop().unwrap();
-    println!("The second-to-last item in the list is {:?}", second_to_last);
-}
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// Try using a `match` statement where the arms are `Some(thing)` and `None`.
-// Or set a default value to print out if you get `None` by using the
-// function `unwrap_or`.
-// Or use an `if let` statement on the result of `pop()` to both destructure
-// a `Some` value and only print out something if we have a value!
--- a/exercises/error_handling/result1.rs
+++ b/exercises/error_handling/result1.rs
@ -1,10 +1,12 @@
 // result1.rs
-// Make this test pass! Scroll down for hints :)
+// Make this test pass! Execute `rustlings hint result1` for hints :)

-#[derive(PartialEq,Debug)]
+// I AM NOT DONE
+
+#[derive(PartialEq, Debug)]
 struct PositiveNonzeroInteger(u64);

-#[derive(PartialEq,Debug)]
+#[derive(PartialEq, Debug)]
 enum CreationError {
    Negative,
    Zero,
@ -19,25 +21,9 @@ impl PositiveNonzeroInteger {
 #[test]
 fn test_creation() {
    assert!(PositiveNonzeroInteger::new(10).is_ok());
-    assert_eq!(Err(CreationError::Negative), PositiveNonzeroInteger::new(-10));
+    assert_eq!(
+        Err(CreationError::Negative),
+        PositiveNonzeroInteger::new(-10)
+    );
    assert_eq!(Err(CreationError::Zero), PositiveNonzeroInteger::new(0));
 }
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// `PositiveNonzeroInteger::new` is always creating a new instance and returning an `Ok` result.
-// It should be doing some checking, returning an `Err` result if those checks fail, and only
-// returning an `Ok` result if those checks determine that everything is... okay :)
--- a/exercises/functions/README.md
+++ b/exercises/functions/README.md
@ -1,7 +1,7 @@
-### Functions
+# Functions

 Here, you'll learn how to write functions and how Rust's compiler can trace things way back.

-#### Book Sections
+## Further information

- [How Functions Work](https://doc.rust-lang.org/stable/book/ch03-03-how-functions-work.html)
+- [How Functions Work](https://doc.rust-lang.org/book/ch03-03-how-functions-work.html)
--- a/exercises/functions/functions1.rs
+++ b/exercises/functions/functions1.rs
@ -1,44 +1,9 @@
 // functions1.rs
-// Make me compile! Scroll down for hints :)
+// Make me compile! Execute `rustlings hint functions1` for hints :)

 fn main() {
    call_me();
 }
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// This main function is calling a function that it expects to exist, but the
-// function doesn't exist. It expects this function to have the name `call_me`.
-// It expects this function to not take any arguments and not return a value.
-// Sounds a lot like `main`, doesn't it?
+fn call_me() {
+    println!("Called!");
+}
--- a/exercises/functions/functions2.rs
+++ b/exercises/functions/functions2.rs
@ -1,42 +1,12 @@
 // functions2.rs
-// Make me compile! Scroll down for hints :)
+// Make me compile! Execute `rustlings hint functions2` for hints :)

 fn main() {
-    call_me(3);
+    call_me(7);
 }

-fn call_me(num) {
+fn call_me(num:i32) {
    for i in 0..num {
        println!("Ring! Call number {}", i + 1);
    }
 }
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// Rust requires that all parts of a function's signature have type annotations,
-// but `call_me` is missing the type annotation of `num`.
--- a/exercises/functions/functions3.rs
+++ b/exercises/functions/functions3.rs
@ -1,42 +1,12 @@
 // functions3.rs
-// Make me compile! Scroll down for hints :)
+// Make me compile! Execute `rustlings hint functions3` for hints :)

 fn main() {
-    call_me();
+    call_me(6);
 }

-fn call_me(num: i32) {
+fn call_me(num: u32) {
    for i in 0..num {
        println!("Ring! Call number {}", i + 1);
    }
 }
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// This time, the function *declaration* is okay, but there's something wrong
-// with the place where we're calling the function.
--- a/exercises/functions/functions4.rs
+++ b/exercises/functions/functions4.rs
@ -1,15 +1,15 @@
 // functions4.rs
-// Make me compile! Scroll down for hints :)
+// Make me compile! Execute `rustlings hint functions4` for hints :)

 // This store is having a sale where if the price is an even number, you get
-// 10 (money unit) off, but if it's an odd number, it's 3 (money unit) less.
+// 10 Rustbucks off, but if it's an odd number, it's 3 Rustbucks off.

 fn main() {
    let original_price = 51;
    println!("Your sale price is {}", sale_price(original_price));
 }

-fn sale_price(price: i32) -> {
+fn sale_price(price: i32) -> i32 {
    if is_even(price) {
        price - 10
    } else {
@ -20,25 +20,3 @@ fn sale_price(price: i32) -> {
 fn is_even(num: i32) -> bool {
    num % 2 == 0
 }
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// The error message points to line 12 and says it expects a type after the
-// `->`. This is where the function's return type should be-- take a look at
-// the `is_even` function for an example!
--- a/exercises/functions/functions5.rs
+++ b/exercises/functions/functions5.rs
@ -1,47 +1,17 @@
 // functions5.rs
-// Make me compile! Scroll down for hints :)
+// Make me compile! Execute `rustlings hint functions5` for hints :)

 fn main() {
    let answer = square(3);
    println!("The answer is {}", answer);
 }

+// without ; the expression is a return statement
+// it can be either both num * num or 
+// return num * num; 
+// but it cannot be
+// return num * num OR num * num;
+
 fn square(num: i32) -> i32 {
-    num * num;
+    num * num
 }
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// This is a really common error that can be fixed by removing one character.
-// It happens because Rust distinguishes between expressions and statements: expressions return
-// a value based on its operand, and statements simply return a () type which behaves just like `void` in C/C++ language. 
-// We want to return a value of `i32` type from the `square` function, but it is returning a `()` type...
-// They are not the same. There are two solutions:
-// 1. Add a `return` ahead of `num * num;`
-// 2. remove `;`, make it to be `num * num`
--- a/exercises/generics/README.md
+++ b/exercises/generics/README.md
@ -0,0 +1,11 @@
+# Generics
+
+Generics is the topic of generalizing types and functionalities to broader cases.
+This is extremely useful for reducing code duplication in many ways, but can call for rather involving syntax.
+Namely, being generic requires taking great care to specify over which types a generic type is actually considered valid.
+The simplest and most common use of generics is for type parameters.
+
+## Further information
+
+- [Generic Data Types](https://doc.rust-lang.org/stable/book/ch10-01-syntax.html)
+- [Bounds](https://doc.rust-lang.org/rust-by-example/generics/bounds.html)
--- a/exercises/generics/generics1.rs
+++ b/exercises/generics/generics1.rs
@ -0,0 +1,7 @@
+// This shopping list program isn't compiling!
+// Use your knowledge of generics to fix it.
+
+fn main() {
+    let mut shopping_list: Vec<&str> = Vec::new();
+    shopping_list.push("milk");
+}
--- a/exercises/generics/generics2.rs
+++ b/exercises/generics/generics2.rs
@ -0,0 +1,27 @@
+// This powerful wrapper provides the ability to store a positive integer value.
+// Rewrite it using generics so that it supports wrapping ANY type.
+
+struct Wrapper<T> {
+    value: T,
+}
+// <T> must be both for impl and Wrapper
+impl<T> Wrapper<T> {
+    pub fn new(value: T) -> Self {
+        Wrapper { value }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn store_u32_in_wrapper() {
+        assert_eq!(Wrapper::new(42).value, 42);
+    }
+
+    #[test]
+    fn store_str_in_wrapper() {
+        assert_eq!(Wrapper::new("Foo").value, "Foo");
+    }
+}
--- a/exercises/generics/generics3.rs
+++ b/exercises/generics/generics3.rs
@ -0,0 +1,58 @@
+// An imaginary magical school has a new report card generation system written in Rust!
+// Currently the system only supports creating report cards where the student's grade
+// is represented numerically (e.g. 1.0 -> 5.5).
+// However, the school also issues alphabetical grades (A+ -> F-) and needs
+// to be able to print both types of report card!
+
+// Make the necessary code changes in the struct ReportCard and the impl block
+// to support alphabetical report cards. Change the Grade in the second test to "A+"
+// to show that your changes allow alphabetical grades.
+
+// Execute 'rustlings hint generics3' for hints!
+
+pub struct ReportCard<T> {
+    pub grade: T,
+    pub student_name: String,
+    pub student_age: u8,
+}
+
+// <T> must implement std::fmt::Display or no format!() macro
+// for you
+impl<T: std::fmt::Display> ReportCard<T> {
+    pub fn print(&self) -> String {
+        format!("{} ({}) - achieved a grade of {}",
+            &self.student_name, &self.student_age, &self.grade)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn generate_numeric_report_card() {
+        let report_card = ReportCard {
+            grade: 2.1,
+            student_name: "Tom Wriggle".to_string(),
+            student_age: 12,
+        };
+        assert_eq!(
+            report_card.print(),
+            "Tom Wriggle (12) - achieved a grade of 2.1"
+        );
+    }
+
+    #[test]
+    fn generate_alphabetic_report_card() {
+        // TODO: Make sure to change the grade here after you finish the exercise.
+        let report_card = ReportCard {
+            grade: "A+".to_string(),
+            student_name: "Gary Plotter".to_string(),
+            student_age: 11,
+        };
+        assert_eq!(
+            report_card.print(),
+            "Gary Plotter (11) - achieved a grade of A+"
+        );
+    }
+}
--- a/exercises/if/README.md
+++ b/exercises/if/README.md
@ -1,7 +1,7 @@
-### If
+# If

 `if`, the most basic type of control flow, is what you'll learn here.

-#### Book Sections
+## Further information

- [Control Flow - if expressions](https://doc.rust-lang.org/stable/book/ch03-05-control-flow.html#if-expressions)
+- [Control Flow - if expressions](https://doc.rust-lang.org/book/ch03-05-control-flow.html#if-expressions)
--- a/exercises/if/if1.rs
+++ b/exercises/if/if1.rs
@ -1,12 +1,16 @@
 // if1.rs

-pub fn bigger(a: i32, b:i32) -> i32 {
    // Complete this function to return the bigger number!
    // Do not use:
-    // - return
    // - another function call
    // - additional variables
-    // Scroll down for hints.
+    // Execute `rustlings hint if1` for hints
+pub fn bigger(a: i32, b: i32) -> i32 {
+    if a > b {
+        a
+    } else {
+        b
+    }
 }

 // Don't mind this for now :)
@ -24,36 +28,3 @@ mod tests {
        assert_eq!(42, bigger(32, 42));
    }
 }
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// It's possible to do this in one line if you would like!
-// Some similar examples from other languages:
-// - In C(++) this would be: `a > b ? a : b`
-// - In Python this would be:  `a if a > b else b`
-// Remember in Rust that:
-// - the `if` condition does not need to be surrounded by parentheses
-// - `if`/`else` conditionals are expressions
-// - Each condition is followed by a `{}` block.
--- a/exercises/if/if2.rs
+++ b/exercises/if/if2.rs
@ -0,0 +1,37 @@
+// if2.rs
+
+// Step 1: Make me compile!
+// Step 2: Get the bar_for_fuzz and default_to_baz tests passing!
+// Execute the command `rustlings hint if2` if you want a hint :)
+
+
+pub fn fizz_if_foo(fizzish: &str) -> &str {
+    if fizzish == "fizz" {
+        "foo"
+    } else if fizzish == "fuzz" {
+        "bar"
+    } else {
+        "baz"
+    }
+}
+
+// No test changes needed!
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn foo_for_fizz() {
+        assert_eq!(fizz_if_foo("fizz"), "foo")
+    }
+
+    #[test]
+    fn bar_for_fuzz() {
+        assert_eq!(fizz_if_foo("fuzz"), "bar")
+    }
+
+    #[test]
+    fn default_to_baz() {
+        assert_eq!(fizz_if_foo("literally anything"), "baz")
+    }
+}
--- a/exercises/macros/README.md
+++ b/exercises/macros/README.md
@ -1,10 +1,10 @@
-### Macros
+# Macros

 Rust's macro system is very powerful, but also kind of difficult to wrap your
 head around. We're not going to teach you how to write your own fully-featured
-modules, instead we'll show you how to use and create them.
+macros. Instead, we'll show you how to use and create them.

-#### Book Sections
+## Further information

- [Macros](https://doc.rust-lang.org/stable/book/ch19-06-macros.html)
+- [Macros](https://doc.rust-lang.org/book/ch19-06-macros.html)
 - [The Little Book of Rust Macros](https://danielkeep.github.io/tlborm/book/index.html)
--- a/exercises/macros/macros1.rs
+++ b/exercises/macros/macros1.rs
@ -1,5 +1,7 @@
 // macros1.rs
-// Make me compile! Scroll down for hints :)
+// Make me compile! Execute `rustlings hint macros1` for hints :)
+
+// I AM NOT DONE

 macro_rules! my_macro {
    () => {
@ -10,55 +12,3 @@ macro_rules! my_macro {
 fn main() {
    my_macro();
 }
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// When you call a macro, you need to add something special compared to a
-// regular function call. If you're stuck, take a look at what's inside
-// `my_macro`.
--- a/exercises/macros/macros2.rs
+++ b/exercises/macros/macros2.rs
@ -1,5 +1,7 @@
 // macros2.rs
-// Make me compile! Scroll down for hints :)
+// Make me compile! Execute `rustlings hint macros2` for hints :)
+
+// I AM NOT DONE

 fn main() {
    my_macro!();
@ -10,64 +12,3 @@ macro_rules! my_macro {
        println!("Check out my macro!");
    };
 }
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// Macros don't quite play by the same rules as the rest of Rust, in terms of
-// what's available where.
-
-
-
-
-
-
-
-
-// Unlike other things in Rust, the order of "where you define a macro" versus
-// "where you use it" actually matters.
--- a/exercises/macros/macros3.rs
+++ b/exercises/macros/macros3.rs
@ -1,5 +1,8 @@
 // macros3.rs
-// Make me compile, without taking the macro out of the module! Scroll down for hints :)
+// Make me compile, without taking the macro out of the module!
+// Execute `rustlings hint macros3` for hints :)
+
+// I AM NOT DONE

 mod macros {
    macro_rules! my_macro {
@ -12,64 +15,3 @@ mod macros {
 fn main() {
    my_macro!();
 }
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// In order to use a macro outside of its module, you need to do something
-// special to the module to lift the macro out into its parent.
-
-
-
-
-
-
-
-
-// The same trick also works on "extern crate" statements for crates that have
-// exported macros, if you've seen any of those around.
--- a/exercises/macros/macros4.rs
+++ b/exercises/macros/macros4.rs
@ -1,5 +1,7 @@
 // macros4.rs
-// Make me compile! Scroll down for hints :)
+// Make me compile! Execute `rustlings hint macros4` for hints :)
+
+// I AM NOT DONE

 macro_rules! my_macro {
    () => {
@ -14,64 +16,3 @@ fn main() {
    my_macro!();
    my_macro!(7777);
 }
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// You only need to add a single character to make this compile.
-
-
-
-
-
-
-
-
-
-// The way macros are written, it wants to see something between each
-// "macro arm", so it can separate them.
--- a/exercises/modules/README.md
+++ b/exercises/modules/README.md
@ -1,7 +1,7 @@
-### Modules
+# Modules

 In this section we'll give you an introduction to Rust's module system.

-#### Book Sections
+## Further information

- [The Module System](https://doc.rust-lang.org/stable/book/ch07-02-modules-and-use-to-control-scope-and-privacy.html)
+- [The Module System](https://doc.rust-lang.org/book/ch07-02-defining-modules-to-control-scope-and-privacy.html)
--- a/exercises/modules/modules1.rs
+++ b/exercises/modules/modules1.rs
@ -1,8 +1,12 @@
 // modules1.rs
-// Make me compile! Scroll down for hints :)
+// Make me compile! Execute `rustlings hint modules1` for hints :)
+
+// `mod` defines a module which can contain functions, structs etc.
+// by default, its `fn`s only limited within itself, creating "closed
+// ecosystem". you can make them public with `pub`

 mod sausage_factory {
-    fn make_sausage() {
+    pub fn make_sausage() {
        println!("sausage!");
    }
 }
@ -10,34 +14,3 @@ mod sausage_factory {
 fn main() {
    sausage_factory::make_sausage();
 }
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// Everything is private in Rust by default-- but there's a keyword we can use
-// to make something public! The compiler error should point to the thing that
-// needs to be public.
--- a/exercises/modules/modules2.rs
+++ b/exercises/modules/modules2.rs
@ -1,9 +1,9 @@
 // modules2.rs
-// Make me compile! Scroll down for hints :)
+// Make me compile! Execute `rustlings hint modules2` for hints :)

-mod delicious_snacks { 
-    use self::fruits::PEAR as fruit;
-    use self::veggies::CUCUMBER as veggie;
+mod delicious_snacks {
+    pub use self::fruits::PEAR as fruit;
+    pub use self::veggies::CUCUMBER as veggie;

    mod fruits {
        pub const PEAR: &'static str = "Pear";
@ -17,29 +17,9 @@ mod delicious_snacks {
 }

 fn main() {
-    println!("favorite snacks: {} and {}",
-             delicious_snacks::fruit,
-             delicious_snacks::veggie);
+    println!(
+        "favorite snacks: {} and {}",
+        delicious_snacks::fruit,
+        delicious_snacks::veggie
+    );
 }
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// The delicious_snacks module is trying to present an external
-// interface (the `fruit` and `veggie` constants) that is different than
-// its internal structure (the `fruits` and `veggies` modules and
-// associated constants). It's almost there except for one keyword missing for
-// each constant.
--- a/exercises/move_semantics/README.md
+++ b/exercises/move_semantics/README.md
@ -1,10 +1,10 @@
-### Move Semantics
+# Move Semantics

 These exercises are adapted from [pnkfelix](https://github.com/pnkfelix)'s [Rust Tutorial](https://pnkfelix.github.io/rust-examples-icfp2014/) -- Thank you Felix!!!

-#### Book Sections
+## Further information

 For this section, the book links are especially important.

- [Ownership](https://doc.rust-lang.org/stable/book/ch04-01-what-is-ownership.html)
- [Reference and borrowing](https://doc.rust-lang.org/stable/book/ch04-02-references-and-borrowing.html)
+- [Ownership](https://doc.rust-lang.org/book/ch04-01-what-is-ownership.html)
+- [Reference and borrowing](https://doc.rust-lang.org/book/ch04-02-references-and-borrowing.html)
--- a/exercises/move_semantics/move_semantics1.rs
+++ b/exercises/move_semantics/move_semantics1.rs
@ -1,17 +1,17 @@
 // move_semantics1.rs
-// Make me compile! Scroll down for hints :)
+// Make me compile! Execute `rustlings hint move_semantics1` for hints :)
+

 fn main() {
    let vec0 = Vec::new();

-    let vec1 = fill_vec(vec0);
+    let mut vec1 = fill_vec(vec0);

    println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);

    vec1.push(88);

    println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);
-
 }

 fn fill_vec(vec: Vec<i32>) -> Vec<i32> {
@ -23,21 +23,3 @@ fn fill_vec(vec: Vec<i32>) -> Vec<i32> {

    vec
 }
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// So you've got the "cannot borrow immutable local variable `vec1` as mutable" error on line 11,
-// right? The fix for this is going to be adding one keyword, and the addition is NOT on line 11
-// where the error is.
--- a/exercises/move_semantics/move_semantics2.rs
+++ b/exercises/move_semantics/move_semantics2.rs
@ -1,10 +1,11 @@
 // move_semantics2.rs
-// Make me compile without changing line 10! Scroll down for hints :)
+// Make me compile without changing line 13!
+// Execute `rustlings hint move_semantics2` for hints :)

 fn main() {
    let vec0 = Vec::new();

-    let mut vec1 = fill_vec(vec0);
+    let mut vec1 = fill_vec(&vec0);

    // Do not change the following line!
    println!("{} has length {} content `{:?}`", "vec0", vec0.len(), vec0);
@ -12,11 +13,10 @@ fn main() {
    vec1.push(88);

    println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);
-
 }

-fn fill_vec(vec: Vec<i32>) -> Vec<i32> {
-    let mut vec = vec;
+fn fill_vec(vec: &[i32]) -> Vec<i32> {
+    let mut vec = vec.to_vec();

    vec.push(22);
    vec.push(44);
@ -24,31 +24,3 @@ fn fill_vec(vec: Vec<i32>) -> Vec<i32> {

    vec
 }
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// So `vec0` is being *moved* into the function `fill_vec` when we call it on
-// line 7, which means it gets dropped at the end of `fill_vec`, which means we
-// can't use `vec0` again on line 10 (or anywhere else in `main` after the
-// `fill_vec` call for that matter). We could fix this in a few ways, try them
-// all!
-// 1. Make another, separate version of the data that's in `vec0` and pass that
-// to `fill_vec` instead.
-// 2. Make `fill_vec` borrow its argument instead of taking ownership of it,
-// and then copy the data within the function in order to return an owned
-// `Vec<i32>`
-// 3. Make `fill_vec` *mutably* borrow its argument (which will need to be
-// mutable), modify it directly, then not return anything. Then you can get rid
-// of `vec1` entirely -- note that this will change what gets printed by the
-// first `println!`
--- a/exercises/move_semantics/move_semantics3.rs
+++ b/exercises/move_semantics/move_semantics3.rs
@ -1,46 +1,25 @@
 // move_semantics3.rs
 // Make me compile without adding new lines-- just changing existing lines!
 // (no lines with multiple semicolons necessary!)
-// Scroll down for hints :)
+// Execute `rustlings hint move_semantics3` for hints :)

 fn main() {
    let vec0 = Vec::new();

-    let mut vec1 = fill_vec(vec0);
+    let mut vec1 = fill_vec(&vec0);

    println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);

    vec1.push(88);

    println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);
-
 }

-fn fill_vec(vec: Vec<i32>) -> Vec<i32> {
+fn fill_vec(vec: &[i32]) -> Vec<i32> { 
+    let mut vec = vec.to_vec();
    vec.push(22);
    vec.push(44);
    vec.push(66);

    vec
 }
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// The difference between this one and the previous ones is that the first line
-// of `fn fill_vec` that had `let mut vec = vec;` is no longer there. You can,
-// instead of adding that line back, add `mut` in one place that will change
-// an existing binding to be a mutable binding instead of an immutable one :)
--- a/exercises/move_semantics/move_semantics4.rs
+++ b/exercises/move_semantics/move_semantics4.rs
@ -1,23 +1,25 @@
 // move_semantics4.rs
 // Refactor this code so that instead of having `vec0` and creating the vector
-// in `fn main`, we instead create it within `fn fill_vec` and transfer the
-// freshly created vector from fill_vec to its caller. Scroll for hints!
+// in `fn main`, we create it within `fn fill_vec` and transfer the
+// freshly created vector from fill_vec to its caller.
+// Execute `rustlings hint move_semantics4` for hints!
+

 fn main() {
-    let vec0 = Vec::new();
+   // let vec0 = Vec::new();

-    let mut vec1 = fill_vec(vec0);
+    let mut vec1 = fill_vec();

    println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);

    vec1.push(88);

    println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);
-
 }

-fn fill_vec(vec: Vec<i32>) -> Vec<i32> {
-    let mut vec = vec;
+// `fill_vec()` no longer takes `vec: Vec<i32>` as argument
+fn fill_vec() -> Vec<i32> {
+    let mut vec = Vec::new();

    vec.push(22);
    vec.push(44);
@ -25,24 +27,3 @@ fn fill_vec(vec: Vec<i32>) -> Vec<i32> {

    vec
 }
-
-
-
-
-
-
-
-
-
-
-
-
-// Stop reading whenever you feel like you have enough direction :) Or try
-// doing one step and then fixing the compiler errors that result!
-// So the end goal is to:
-// - get rid of the first line in main that creates the new vector
-// - so then `vec0` doesn't exist, so we can't pass it to `fill_vec`
-// - we don't want to pass anything to `fill_vec`, so its signature should
-//   reflect that it does not take any arguments
-// - since we're not creating a new vec in `main` anymore, we need to create
-//   a new vec in `fill_vec`, similarly to the way we did in `main`
--- a/exercises/option/README.md
+++ b/exercises/option/README.md
@ -0,0 +1,18 @@
+# Option
+
+Type Option represents an optional value: every Option is either Some and contains a value, or None, and does not. 
+Option types are very common in Rust code, as they have a number of uses:
+- Initial values
+- Return values for functions that are not defined over their entire input range (partial functions)
+- Return value for otherwise reporting simple errors, where None is returned on error
+- Optional struct fields
+- Struct fields that can be loaned or "taken"
+- Optional function arguments
+- Nullable pointers
+- Swapping things out of difficult situations
+
+## Further Information
+
+- [Option Enum Format](https://doc.rust-lang.org/stable/book/ch10-01-syntax.html#in-enum-definitions)
+- [Option Module Documentation](https://doc.rust-lang.org/std/option/)
+- [Option Enum Documentation](https://doc.rust-lang.org/std/option/enum.Option.html)
--- a/exercises/option/option1.rs
+++ b/exercises/option/option1.rs
@ -0,0 +1,24 @@
+// option1.rs
+// Make me compile! Execute `rustlings hint option1` for hints
+
+// I AM NOT DONE
+
+// you can modify anything EXCEPT for this function's sig
+fn print_number(maybe_number: Option<u16>) {
+    println!("printing: {}", maybe_number.unwrap());
+}
+
+fn main() {
+    // rustc suggested solutions
+    print_number(Some(13));
+    print_number(Some(99));
+
+    let numbers: [Option<u16>; 5];
+    for iter in 0..5 {
+        let number_to_add: u16 = {
+            ((iter * 1235) + 2) / (4 * 16)
+        };
+
+        numbers[iter as usize] = Some(number_to_add);
+    }
+}
--- a/exercises/option/option2.rs
+++ b/exercises/option/option2.rs
@ -0,0 +1,25 @@
+// option2.rs
+// Make me compile! Execute `rustlings hint option2` for hints
+
+// I AM NOT DONE
+
+fn main() {
+    let optional_word = Some(String::from("rustlings"));
+    // TODO: Make this an if let statement whose value is "Some" type
+    word = optional_word {
+        println!("The word is: {}", word);
+    } else {
+        println!("The optional word doesn't contain anything");
+    }
+
+    let mut optional_integers_vec: Vec<Option<i8>> = Vec::new();
+    for x in 1..10 {
+        optional_integers_vec.push(Some(x));
+    }
+
+    // TODO: make this a while let statement - remember that vector.pop also adds another layer of Option<T>
+    // You can stack `Option<T>`'s into while let and if let
+    integer = optional_integers_vec.pop() {
+        println!("current value: {}", integer);
+    }
+}
--- a/exercises/primitive_types/README.md
+++ b/exercises/primitive_types/README.md
@ -1,8 +1,9 @@
-### Primitive Types
+# Primitive Types

 Rust has a couple of basic types that are directly implemented into the
 compiler. In this section, we'll go through the most important ones.

-#### Book Sections
+## Further information

 - [Data Types](https://doc.rust-lang.org/stable/book/ch03-02-data-types.html)
+- [The Slice Type](https://doc.rust-lang.org/stable/book/ch04-03-slices.html)
--- a/exercises/primitive_types/primitive_types1.rs
+++ b/exercises/primitive_types/primitive_types1.rs
@ -10,7 +10,7 @@ fn main() {
        println!("Good morning!");
    }

-    let // Finish the rest of this line like the example! Or make it be false!
+    let is_evening = true; // Finish the rest of this line like the example! Or make it be false!
    if is_evening {
        println!("Good evening!");
    }
--- a/exercises/primitive_types/primitive_types2.rs
+++ b/exercises/primitive_types/primitive_types2.rs
@ -14,7 +14,7 @@ fn main() {
        println!("Neither alphabetic nor numeric!");
    }

-    let // Finish this line like the example! What's your favorite character?
+    let your_character = 'D'; // Finish this line like the example! What's your favorite character?
    // Try a letter, try a number, try a special character, try a character
    // from a different language than your own, try an emoji!
    if your_character.is_alphabetic() {
--- a/exercises/primitive_types/primitive_types3.rs
+++ b/exercises/primitive_types/primitive_types3.rs
@ -1,9 +1,10 @@
 // primitive_types3.rs
-// Create an array with at least 100 elements in it where the ??? is. 
-// Scroll down for hints!
+// Create an array with at least 100 elements in it where the ??? is.
+// Execute `rustlings hint primitive_types3` for hints!
+

 fn main() {
-    let a = ???
+    let a: [i32; 300] = [0; 300]; 

    if a.len() >= 100 {
        println!("Wow, that's a big array!");
@ -11,37 +12,3 @@ fn main() {
        println!("Meh, I eat arrays like that for breakfast.");
    }
 }
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// There's a shorthand to initialize Arrays with a certain size that does not 
-// require you to type in 100 items (but you certainly can if you want!).
-// For example, you can do:
-// let array = ["Are we there yet?"; 10];
-
-// Bonus: what are some other things you could have that would return true
-// for `a.len() >= 100`?
--- a/exercises/primitive_types/primitive_types4.rs
+++ b/exercises/primitive_types/primitive_types4.rs
@ -1,49 +1,12 @@
 // primitive_types4.rs
-// Get a slice out of Array a where the ??? is so that the `if` statement
-// returns true. Scroll down for hints!!
+// Get a slice out of Array a where the ??? is so that the test passes.
+// Execute `rustlings hint primitive_types4` for hints!!

-fn main() {
+#[test]
+fn slice_out_of_array() {
    let a = [1, 2, 3, 4, 5];

-    let nice_slice = ???
+    let nice_slice = &a[1..4];

-    if nice_slice == [2, 3, 4] {
-        println!("Nice slice!");
-    } else {
-        println!("Not quite what I was expecting... I see: {:?}", nice_slice);
-    }
+    assert_eq!([2, 3, 4], nice_slice)
 }
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// Take a look at the Understanding Ownership -> Slices -> Other Slices section of the book:
-// https://doc.rust-lang.org/book/ch04-03-slices.html
-// and use the starting and ending indices of the items in the Array
-// that you want to end up in the slice.
-
-// If you're curious why the right hand of the `==` comparison does not
-// have an ampersand for a reference since the left hand side is a
-// reference, take a look at the Deref coercions section of the book:
-// https://doc.rust-lang.org/book/ch15-02-deref.html
--- a/exercises/primitive_types/primitive_types5.rs
+++ b/exercises/primitive_types/primitive_types5.rs
@ -1,45 +1,10 @@
 // primitive_types5.rs
 // Destructure the `cat` tuple so that the println will work.
-// Scroll down for hints!
+// Execute `rustlings hint primitive_types5` for hints!

 fn main() {
    let cat = ("Furry McFurson", 3.5);
-    let /* your pattern here */ = cat;
+    let (name, age) = cat;

    println!("{} is {} years old.", name, age);
 }
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// Take a look at the Data Types -> The Tuple Type section of the book:
-// https://doc.rust-lang.org/stable/book/ch03-02-data-types.html#the-tuple-type
-// Particularly the part about destructuring (second to last example in the section). 
-// You'll need to make a pattern to bind `name` and `age` to the appropriate parts
-// of the tuple. You can do it!!
--- a/exercises/primitive_types/primitive_types6.rs
+++ b/exercises/primitive_types/primitive_types6.rs
@ -1,45 +1,13 @@
 // primitive_types6.rs
 // Use a tuple index to access the second element of `numbers`.
-// You can put this right into the `println!` where the ??? is.
-// Scroll down for hints!
-
-fn main() {
+// You can put the expression for the second element where ??? is so that the test passes.
+// Execute `rustlings hint primitive_types6` for hints!
+#[test]
+fn indexing_tuple() {
    let numbers = (1, 2, 3);
-    println!("The second number is {}", ???);
+    // Replace below ??? with the tuple indexing syntax.
+    let second = numbers.1;
+
+    assert_eq!(2, second,
+        "This is not the 2nd number in the tuple!")
 }
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// While you could use a destructuring `let` for the tuple here, try 
-// indexing into it instead, as explained in the last example of the 
-// Data Types -> The Tuple Type section of the book:
-// https://doc.rust-lang.org/stable/book/ch03-02-data-types.html#the-tuple-type
-// Now you have another tool in your toolbox!
--- a/exercises/quiz1.rs
+++ b/exercises/quiz1.rs
@ -0,0 +1,29 @@
+// quiz1.rs
+// This is a quiz for the following sections:
+// - Variables
+// - Functions
+
+// Mary is buying apples. One apple usually costs 2 Rustbucks, but if you buy
+// more than 40 at once, each apple only costs 1! Write a function that calculates
+// the price of an order of apples given the order amount. No hints this time!
+
+// Put your function here!
+// fn ..... {
+fn calculate_apple_price(amount: i32) -> i32 {
+    if amount > 40 {
+        1 * amount
+    } else {
+        2 * amount
+    }
+}
+
+
+// Don't modify this function!
+#[test]
+fn verify_test() {
+    let price1 = calculate_apple_price(35);
+    let price2 = calculate_apple_price(65);
+
+    assert_eq!(70, price1);
+    assert_eq!(65, price2);
+}
--- a/exercises/quiz2.rs
+++ b/exercises/quiz2.rs
@ -0,0 +1,28 @@
+// quiz2.rs
+// This is a quiz for the following sections:
+// - Strings
+
+// Ok, here are a bunch of values-- some are `String`s, some are `&str`s. Your
+// task is to call one of these two functions on each value depending on what
+// you think each value is. That is, add either `string_slice` or `string`
+// before the parentheses on each line. If you're right, it will compile!
+
+fn string_slice(arg: &str) {
+    println!("{}", arg);
+}
+fn string(arg: String) {
+    println!("{}", arg);
+}
+
+fn main() {
+    string_slice("blue");
+    string("red".to_string());
+    string(String::from("hi"));
+    string("rust is fun!".to_owned());
+    string("nice weather".into());
+    string(format!("Interpolation {}", "Station"));
+    string_slice(&String::from("abc")[0..1]);
+    string_slice("  hello there ".trim());
+    string("Happy Monday!".to_string().replace("Mon", "Tues"));
+    string("mY sHiFt KeY iS sTiCkY".to_lowercase());
+}
--- a/exercises/quiz3.rs
+++ b/exercises/quiz3.rs
@ -1,12 +1,14 @@
-// test2.rs
-// This is a test for the following sections:
+// quiz3.rs
+// This is a quiz for the following sections:
 // - Tests

-// This test isn't testing our function -- make it do that in such a way that
+// This quiz isn't testing our function -- make it do that in such a way that
 // the test passes. Then write a second test that tests that we get the result
 // we expect to get when we call `times_two` with a negative number.
 // No hints, you can do this :)

+// I AM NOT DONE
+
 pub fn times_two(num: i32) -> i32 {
    num * 2
 }
@ -17,6 +19,12 @@ mod tests {

    #[test]
    fn returns_twice_of_positive_numbers() {
-        assert_eq!(4, 4);
+        assert_eq!(times_two(4), ???);
+    }
+
+    #[test]
+    fn returns_twice_of_negative_numbers() {
+        // TODO replace unimplemented!() with an assert for `times_two(-4)`
+        unimplemented!()
    }
 }
--- a/exercises/quiz4.rs
+++ b/exercises/quiz4.rs
@ -0,0 +1,23 @@
+// quiz4.rs
+// This quiz covers the sections:
+// - Modules
+// - Macros
+
+// Write a macro that passes the quiz! No hints this time, you can do it!
+
+// I AM NOT DONE
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_my_macro_world() {
+        assert_eq!(my_macro!("world!"), "Hello world!");
+    }
+
+    #[test]
+    fn test_my_macro_goodbye() {
+        assert_eq!(my_macro!("goodbye!"), "Hello goodbye!");
+    }
+}
--- a/exercises/standard_library_types/README.md
+++ b/exercises/standard_library_types/README.md
@ -1,5 +1,10 @@
-For the Arc exercise check out the chapter [Shared-State Concurrency](https://doc.rust-lang.org/book/2018-edition/ch16-03-shared-state.html) of the Rust Book.
+# Standard library types

-For the Iterator exercise check out the chapters [Iterator](https://doc.rust-lang.org/book/2018-edition/ch13-02-iterators.html) of the Rust Book and the [Iterator documentation](https://doc.rust-lang.org/stable/std/iter/trait.Iterator.htmlj).
-Do not adjust your monitors-- iterators 1 and 2 are indeed missing. Iterator 3 is a bit challenging so we're leaving space for some exercises to lead up to it!
+This section will teach you about Box, Shared-State Concurrency and Iterators.

+## Further information
+
+- [Using Box to Point to Data on the Heap](https://doc.rust-lang.org/book/ch15-01-box.html)
+- [Shared-State Concurrency](https://doc.rust-lang.org/book/ch16-03-shared-state.html)
+- [Iterator](https://doc.rust-lang.org/book/ch13-02-iterators.html)
+- [Iterator documentation](https://doc.rust-lang.org/stable/std/iter/)
--- a/exercises/standard_library_types/arc1.rs
+++ b/exercises/standard_library_types/arc1.rs
@ -1,9 +1,26 @@
 // arc1.rs
-// Make this code compile by filling in a value for `shared_numbers` where the
-// TODO comment is and creating an initial binding for `child_numbers`
-// somewhere. Try not to create any copies of the `numbers` Vec!
-// Scroll down for hints :)
+// In this exercise, we are given a Vec of u32 called "numbers" with values ranging
+// from 0 to 99 -- [ 0, 1, 2, ..., 98, 99 ]
+// We would like to use this set of numbers within 8 different threads simultaneously.
+// Each thread is going to get the sum of every eighth value, with an offset.
+// The first thread (offset 0), will sum 0, 8, 16, ...
+// The second thread (offset 1), will sum 1, 9, 17, ...
+// The third thread (offset 2), will sum 2, 10, 18, ...
+// ...
+// The eighth thread (offset 7), will sum 7, 15, 23, ...

+// Because we are using threads, our values need to be thread-safe.  Therefore,
+// we are using Arc.  We need to make a change in each of the two TODOs.
+
+
+// Make this code compile by filling in a value for `shared_numbers` where the
+// first TODO comment is, and create an initial binding for `child_numbers`
+// where the second TODO comment is. Try not to create any copies of the `numbers` Vec!
+// Execute `rustlings hint arc1` for hints :)
+
+// I AM NOT DONE
+
+#![forbid(unused_imports)] // Do not change this, (or the next) line.
 use std::sync::Arc;
 use std::thread;

@ -13,13 +30,13 @@ fn main() {
    let mut joinhandles = Vec::new();

    for offset in 0..8 {
-        joinhandles.push(
-        thread::spawn(move || {
+        let child_numbers = // TODO
+        joinhandles.push(thread::spawn(move || {
            let mut i = offset;
            let mut sum = 0;
            while i < child_numbers.len() {
                sum += child_numbers[i];
-                i += 5;
+                i += 8;
            }
            println!("Sum of offset {} is {}", offset, sum);
        }));
@ -28,29 +45,3 @@ fn main() {
        handle.join().unwrap();
    }
 }
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// Make `shared_numbers` be an `Arc` from the numbers vector. Then, in order
-// to avoid creating a copy of `numbers`, you'll need to create `child_numbers`
-// inside the loop but still in the main thread.
-
-// `child_numbers` should be a clone of the Arc of the numbers instead of a
-// thread-local copy of the numbers.
--- a/exercises/standard_library_types/box1.rs
+++ b/exercises/standard_library_types/box1.rs
@ -0,0 +1,56 @@
+// box1.rs
+//
+// At compile time, Rust needs to know how much space a type takes up. This becomes problematic
+// for recursive types, where a value can have as part of itself another value of the same type.
+// To get around the issue, we can use a `Box` - a smart pointer used to store data on the heap,
+// which also allows us to wrap a recursive type.
+//
+// The recursive type we're implementing in this exercise is the `cons list` - a data structure
+// frequently found in functional programming languages. Each item in a cons list contains two
+// elements: the value of the current item and the next item. The last item is a value called `Nil`.
+//
+// Step 1: use a `Box` in the enum definition to make the code compile
+// Step 2: create both empty and non-empty cons lists by replacing `unimplemented!()`
+//
+// Note: the tests should not be changed
+//
+// Execute `rustlings hint box1` for hints :)
+
+// I AM NOT DONE
+
+#[derive(PartialEq, Debug)]
+pub enum List {
+    Cons(i32, List),
+    Nil,
+}
+
+fn main() {
+    println!("This is an empty cons list: {:?}", create_empty_list());
+    println!(
+        "This is a non-empty cons list: {:?}",
+        create_non_empty_list()
+    );
+}
+
+pub fn create_empty_list() -> List {
+    unimplemented!()
+}
+
+pub fn create_non_empty_list() -> List {
+    unimplemented!()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_create_empty_list() {
+        assert_eq!(List::Nil, create_empty_list())
+    }
+
+    #[test]
+    fn test_create_non_empty_list() {
+        assert_ne!(create_empty_list(), create_non_empty_list())
+    }
+}
--- a/exercises/standard_library_types/iterator3.rs
+++ b/exercises/standard_library_types/iterator3.rs
@ -1,147 +0,0 @@
-// iterator3.rs
-// This is a bigger exercise than most of the others! You can do it!
-// Here is your mission, should you choose to accept it:
-// 1. Complete the divide function to get the first four tests to pass
-// 2. Uncomment the last two tests and get them to pass by filling in
-//    values for `x` using `division_results`.
-// Scroll down for a minor hint for part 2, and scroll down further for
-// a major hint.
-// Have fun :-)
-
-#[derive(Debug, PartialEq, Eq)]
-pub enum DivisionError {
-    NotDivisible(NotDivisibleError),
-    DivideByZero,
-}
-
-#[derive(Debug, PartialEq, Eq)]
-pub struct NotDivisibleError {
-    dividend: i32,
-    divisor: i32,
-}
-
-// This function should calculate `a` divided by `b` if `a` is
-// evenly divisible by b.
-// Otherwise, it should return a suitable error.
-pub fn divide(a: i32, b: i32) -> Result<i32, DivisionError> {
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    // Tests that verify your `divide` function implementation
-    #[test]
-    fn test_success() {
-        assert_eq!(divide(81, 9), Ok(9));
-    }
-
-    #[test]
-    fn test_not_divisible() {
-        assert_eq!(
-            divide(81, 6),
-            Err(DivisionError::NotDivisible(NotDivisibleError{
-                dividend: 81,
-                divisor: 6
-            }))
-        );
-    }
-
-    #[test]
-    fn test_divide_by_0() {
-        assert_eq!(divide(81, 0), Err(DivisionError::DivideByZero));
-    }
-
-    #[test]
-    fn test_divide_0_by_something() {
-        assert_eq!(divide(0, 81), Ok(0));
-    }
-
-    // Iterator exercises using your `divide` function
-    /*
-    #[test]
-    fn result_with_list() {
-        let numbers = vec![27, 297, 38502, 81];
-        let division_results = numbers.into_iter().map(|n| divide(n, 27));
-        let x //... Fill in here!
-        assert_eq!(format!("{:?}", x), "Ok([1, 11, 1426, 3])");
-    }
-
-    #[test]
-    fn list_of_results() {
-        let numbers = vec![27, 297, 38502, 81];
-        let division_results = numbers.into_iter().map(|n| divide(n, 27));
-        let x //... Fill in here!
-        assert_eq!(format!("{:?}", x), "[Ok(1), Ok(11), Ok(1426), Ok(3)]");
-    }
-    */
-}
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// Minor hint: In each of the two cases in the match in main, you can create x with either 
-// a 'turbofish' or by hinting the type of x to the compiler. You may try both.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// Major hint: Have a look at the Iter trait and at the explanation of its collect function. 
-// Especially the part about Result is interesting.
--- a/exercises/standard_library_types/iterators1.rs
+++ b/exercises/standard_library_types/iterators1.rs
@ -0,0 +1,24 @@
+// iterators1.rs
+// 
+//  Make me compile by filling in the `???`s
+//
+// When performing operations on elements within a collection, iterators are essential.
+// This module helps you get familiar with the structure of using an iterator and 
+// how to go through elements within an iterable collection.
+// 
+// Execute `rustlings hint iterators1` for hints :D
+
+// I AM NOT DONE
+
+fn main () {
+    let my_fav_fruits = vec!["banana", "custard apple", "avocado", "peach", "raspberry"];
+
+    let mut my_iterable_fav_fruits = ???;   // TODO: Step 1
+
+    assert_eq!(my_iterable_fav_fruits.next(), Some(&"banana"));
+    assert_eq!(my_iterable_fav_fruits.next(), ???);     // TODO: Step 2
+    assert_eq!(my_iterable_fav_fruits.next(), Some(&"avocado"));
+    assert_eq!(my_iterable_fav_fruits.next(), ???);     // TODO: Step 2.1
+    assert_eq!(my_iterable_fav_fruits.next(), Some(&"raspberry"));
+    assert_eq!(my_iterable_fav_fruits.next(), ???);     // TODO: Step 3
+}
--- a/exercises/standard_library_types/iterators2.rs
+++ b/exercises/standard_library_types/iterators2.rs
@ -0,0 +1,60 @@
+// iterators2.rs
+// In this exercise, you'll learn some of the unique advantages that iterators
+// can offer. Follow the steps to complete the exercise.
+// As always, there are hints if you execute `rustlings hint iterators2`!
+
+// I AM NOT DONE
+
+// Step 1.
+// Complete the `capitalize_first` function.
+// "hello" -> "Hello"
+pub fn capitalize_first(input: &str) -> String {
+    let mut c = input.chars();
+    match c.next() {
+        None => String::new(),
+        Some(first) => ???,
+    }
+}
+
+// Step 2.
+// Apply the `capitalize_first` function to a slice of string slices.
+// Return a vector of strings.
+// ["hello", "world"] -> ["Hello", "World"]
+pub fn capitalize_words_vector(words: &[&str]) -> Vec<String> {
+    vec![]
+}
+
+// Step 3.
+// Apply the `capitalize_first` function again to a slice of string slices.
+// Return a single string.
+// ["hello", " ", "world"] -> "Hello World"
+pub fn capitalize_words_string(words: &[&str]) -> String {
+    String::new()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_success() {
+        assert_eq!(capitalize_first("hello"), "Hello");
+    }
+
+    #[test]
+    fn test_empty() {
+        assert_eq!(capitalize_first(""), "");
+    }
+
+    #[test]
+    fn test_iterate_string_vec() {
+        let words = vec!["hello", "world"];
+        assert_eq!(capitalize_words_vector(&words), ["Hello", "World"]);
+    }
+
+    #[test]
+    fn test_iterate_into_string() {
+        let words = vec!["hello", " ", "world"];
+        assert_eq!(capitalize_words_string(&words), "Hello World");
+    }
+}
--- a/exercises/standard_library_types/iterators3.rs
+++ b/exercises/standard_library_types/iterators3.rs
@ -0,0 +1,83 @@
+// iterators3.rs
+// This is a bigger exercise than most of the others! You can do it!
+// Here is your mission, should you choose to accept it:
+// 1. Complete the divide function to get the first four tests to pass.
+// 2. Get the remaining tests to pass by completing the result_with_list and
+//    list_of_results functions.
+// Execute `rustlings hint iterators3` to get some hints!
+
+// I AM NOT DONE
+
+#[derive(Debug, PartialEq, Eq)]
+pub enum DivisionError {
+    NotDivisible(NotDivisibleError),
+    DivideByZero,
+}
+
+#[derive(Debug, PartialEq, Eq)]
+pub struct NotDivisibleError {
+    dividend: i32,
+    divisor: i32,
+}
+
+// Calculate `a` divided by `b` if `a` is evenly divisible by `b`.
+// Otherwise, return a suitable error.
+pub fn divide(a: i32, b: i32) -> Result<i32, DivisionError> {}
+
+// Complete the function and return a value of the correct type so the test passes.
+// Desired output: Ok([1, 11, 1426, 3])
+fn result_with_list() -> () {
+    let numbers = vec![27, 297, 38502, 81];
+    let division_results = numbers.into_iter().map(|n| divide(n, 27));
+}
+
+// Complete the function and return a value of the correct type so the test passes.
+// Desired output: [Ok(1), Ok(11), Ok(1426), Ok(3)]
+fn list_of_results() -> () {
+    let numbers = vec![27, 297, 38502, 81];
+    let division_results = numbers.into_iter().map(|n| divide(n, 27));
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_success() {
+        assert_eq!(divide(81, 9), Ok(9));
+    }
+
+    #[test]
+    fn test_not_divisible() {
+        assert_eq!(
+            divide(81, 6),
+            Err(DivisionError::NotDivisible(NotDivisibleError {
+                dividend: 81,
+                divisor: 6
+            }))
+        );
+    }
+
+    #[test]
+    fn test_divide_by_0() {
+        assert_eq!(divide(81, 0), Err(DivisionError::DivideByZero));
+    }
+
+    #[test]
+    fn test_divide_0_by_something() {
+        assert_eq!(divide(0, 81), Ok(0));
+    }
+
+    #[test]
+    fn test_result_with_list() {
+        assert_eq!(format!("{:?}", result_with_list()), "Ok([1, 11, 1426, 3])");
+    }
+
+    #[test]
+    fn test_list_of_results() {
+        assert_eq!(
+            format!("{:?}", list_of_results()),
+            "[Ok(1), Ok(11), Ok(1426), Ok(3)]"
+        );
+    }
+}
--- a/exercises/standard_library_types/iterators4.rs
+++ b/exercises/standard_library_types/iterators4.rs
@ -1,15 +1,17 @@
 // iterators4.rs

+// I AM NOT DONE
+
 pub fn factorial(num: u64) -> u64 {
-    // Complete this function to return factorial of num
+    // Complete this function to return the factorial of num
    // Do not use:
    // - return
-    // For extra fun don't use:
+    // Try not to use:
    // - imperative style loops (for, while)
    // - additional variables
-    // For the most fun don't use:
+    // For an extra challenge, don't use:
    // - recursion
-    // Scroll down for hints.
+    // Execute `rustlings hint iterators4` for hints.
 }

 #[cfg(test)]
@ -30,32 +32,3 @@ mod tests {
        assert_eq!(24, factorial(4));
    }
 }
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// In an imperative language you might write a for loop to iterate through
-// multiply the values into a mutable variable. Or you might write code more
-// functionally with recursion and a match clause. But you can also use ranges
-// and iterators to solve this in rust.
--- a/exercises/standard_library_types/iterators5.rs
+++ b/exercises/standard_library_types/iterators5.rs
@ -0,0 +1,124 @@
+// iterators5.rs
+
+// Let's define a simple model to track Rustlings exercise progress. Progress
+// will be modelled using a hash map. The name of the exercise is the key and
+// the progress is the value. Two counting functions were created to count the
+// number of exercises with a given progress. These counting functions use
+// imperative style for loops. Recreate this counting functionality using
+// iterators. Only the two iterator methods (count_iterator and
+// count_collection_iterator) need to be modified.
+// Execute `rustlings hint
+// iterators5` for hints.
+//
+// Make the code compile and the tests pass.
+
+// I AM NOT DONE
+
+use std::collections::HashMap;
+
+#[derive(PartialEq, Eq)]
+enum Progress {
+    None,
+    Some,
+    Complete,
+}
+
+fn count_for(map: &HashMap<String, Progress>, value: Progress) -> usize {
+    let mut count = 0;
+    for val in map.values() {
+        if val == &value {
+            count += 1;
+        }
+    }
+    count
+}
+
+fn count_iterator(map: &HashMap<String, Progress>, value: Progress) -> usize {
+    // map is a hashmap with String keys and Progress values.
+    // map = { "variables1": Complete, "from_str": None, ... }
+}
+
+fn count_collection_for(collection: &[HashMap<String, Progress>], value: Progress) -> usize {
+    let mut count = 0;
+    for map in collection {
+        for val in map.values() {
+            if val == &value {
+                count += 1;
+            }
+        }
+    }
+    count
+}
+
+fn count_collection_iterator(collection: &[HashMap<String, Progress>], value: Progress) -> usize {
+    // collection is a slice of hashmaps.
+    // collection = [{ "variables1": Complete, "from_str": None, ... },
+    //     { "variables2": Complete, ... }, ... ]
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn count_complete() {
+        let map = get_map();
+        assert_eq!(3, count_iterator(&map, Progress::Complete));
+    }
+
+    #[test]
+    fn count_equals_for() {
+        let map = get_map();
+        assert_eq!(
+            count_for(&map, Progress::Complete),
+            count_iterator(&map, Progress::Complete)
+        );
+    }
+
+    #[test]
+    fn count_collection_complete() {
+        let collection = get_vec_map();
+        assert_eq!(
+            6,
+            count_collection_iterator(&collection, Progress::Complete)
+        );
+    }
+
+    #[test]
+    fn count_collection_equals_for() {
+        let collection = get_vec_map();
+        assert_eq!(
+            count_collection_for(&collection, Progress::Complete),
+            count_collection_iterator(&collection, Progress::Complete)
+        );
+    }
+
+    fn get_map() -> HashMap<String, Progress> {
+        use Progress::*;
+
+        let mut map = HashMap::new();
+        map.insert(String::from("variables1"), Complete);
+        map.insert(String::from("functions1"), Complete);
+        map.insert(String::from("hashmap1"), Complete);
+        map.insert(String::from("arc1"), Some);
+        map.insert(String::from("as_ref_mut"), None);
+        map.insert(String::from("from_str"), None);
+
+        map
+    }
+
+    fn get_vec_map() -> Vec<HashMap<String, Progress>> {
+        use Progress::*;
+
+        let map = get_map();
+
+        let mut other = HashMap::new();
+        other.insert(String::from("variables2"), Complete);
+        other.insert(String::from("functions2"), Complete);
+        other.insert(String::from("if1"), Complete);
+        other.insert(String::from("from_into"), None);
+        other.insert(String::from("try_from_into"), None);
+
+        vec![map, other]
+    }
+}
--- a/exercises/strings/README.md
+++ b/exercises/strings/README.md
@ -1,9 +1,9 @@
-### Strings
+# Strings

 Rust has two string types, a string slice (`&str`) and an owned string (`String`).
 We're not going to dictate when you should use which one, but we'll show you how
 to identify and create them, as well as use them.

-#### Book Sections
+## Further information

- [Strings](https://doc.rust-lang.org/stable/book/ch08-02-strings.html)
+- [Strings](https://doc.rust-lang.org/book/ch08-02-strings.html)
--- a/exercises/strings/strings1.rs
+++ b/exercises/strings/strings1.rs
@ -1,5 +1,6 @@
 // strings1.rs
-// Make me compile without changing the function signature! Scroll down for hints :)
+// Make me compile without changing the function signature!
+// Execute `rustlings hint strings1` for hints ;)

 fn main() {
    let answer = current_favorite_color();
@ -7,40 +8,7 @@ fn main() {
 }

 fn current_favorite_color() -> String {
-    "blue"
+    // .to_string uses fmt trait
+    // .to_owned works too
+    "blue".to_owned()
 }
-
-
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-
-// The `current_favorite_color` function is currently returning a string slice with the `'static`
-// lifetime. We know this because the data of the string lives in our code itself -- it doesn't
-// come from a file or user input or another program -- so it will live as long as our program
-// lives. But it is still a string slice. There's one way to create a `String` by converting a
-// string slice covered in the Strings chapter of the book, and another way that uses the `From`
-// trait.
--- a/exercises/strings/strings2.rs
+++ b/exercises/strings/strings2.rs
@ -1,5 +1,6 @@
 // strings2.rs
-// Make me compile without changing the function signature! Scroll down for hints :)
+// Make me compile without changing the function signature!
+// Execute `rustlings hint strings2` for hints :)

 fn main() {
    let word = String::from("green"); // Try not changing this line :)
@ -10,35 +11,6 @@ fn main() {
    }
 }

-fn is_a_color_word(attempt: &str) -> bool {
+fn is_a_color_word(attempt: String) -> bool {
    attempt == "green" || attempt == "blue" || attempt == "red"
 }
-
-
-
-
-
-
-
-
-
-
-
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-
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-
-
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-
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-
-// Yes, it would be really easy to fix this by just changing the value bound to `word` to be a
-// string slice instead of a `String`, wouldn't it?? There is a way to add one character to line
-// 6, though, that will coerce the `String` into a string slice.
--- a/exercises/structs/README.md
+++ b/exercises/structs/README.md
@ -0,0 +1,8 @@
+# Structs
+
+Rust has three struct types: a classic C struct, a tuple struct, and a unit struct.
+
+## Further information
+
+- [Structures](https://doc.rust-lang.org/book/ch05-01-defining-structs.html)
+- [Method Syntax](https://doc.rust-lang.org/book/ch05-03-method-syntax.html)
--- a/exercises/structs/structs1.rs
+++ b/exercises/structs/structs1.rs
@ -0,0 +1,46 @@
+// structs1.rs
+// Address all the TODOs to make the tests pass!
+
+struct ColorClassicStruct {
+    name: String,
+    hex: String
+}
+
+struct ColorTupleStruct(String, String);
+
+#[derive(Debug)]
+struct UnitStruct;
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn classic_c_structs() {
+        // TODO: Instantiate a classic c struct!
+        let green = ColorClassicStruct { 
+            name: String::from("green"), 
+            hex: String::from("#00FF00")
+        };
+        assert_eq!(green.name, "green");
+        assert_eq!(green.hex, "#00FF00");
+    }
+
+    #[test]
+    fn tuple_structs() {
+        // TODO: Instantiate a tuple struct!
+        let green = ColorTupleStruct("green".to_string(),"#00FF00".to_string());
+
+        assert_eq!(green.0, "green");
+        assert_eq!(green.1, "#00FF00");
+    }
+
+    #[test]
+    fn unit_structs() {
+        // TODO: Instantiate a unit struct!
+        let unit_struct = UnitStruct;
+        let message = format!("{:?}s are fun!", unit_struct);
+
+        assert_eq!(message, "UnitStructs are fun!");
+    }
+}
--- a/exercises/structs/structs2.rs
+++ b/exercises/structs/structs2.rs
@ -0,0 +1,52 @@
+// structs2.rs
+// Address all the TODOs to make the tests pass!
+
+#[derive(Debug)]
+struct Order {
+    name: String,
+    year: u32,
+    made_by_phone: bool,
+    made_by_mobile: bool,
+    made_by_email: bool,
+    item_number: u32,
+    count: u32,
+}
+
+fn create_order_template() -> Order {
+    Order {
+        name: String::from("Bob"),
+        year: 2019,
+        made_by_phone: false,
+        made_by_mobile: false,
+        made_by_email: true,
+        item_number: 123,
+        count: 0,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn your_order() {
+        let order_template = create_order_template();
+        // TODO: Create your own order using the update syntax and template above!
+        let your_order = Order {
+            name: String::from("Hacker in Rust"),
+            year: 2019,
+            made_by_phone: false,
+            made_by_mobile: false,
+            made_by_email: true,
+            item_number: 123,
+            count: 1,
+        };
+        assert_eq!(your_order.name, "Hacker in Rust");
+        assert_eq!(your_order.year, order_template.year);
+        assert_eq!(your_order.made_by_phone, order_template.made_by_phone);
+        assert_eq!(your_order.made_by_mobile, order_template.made_by_mobile);
+        assert_eq!(your_order.made_by_email, order_template.made_by_email);
+        assert_eq!(your_order.item_number, order_template.item_number);
+        assert_eq!(your_order.count, 1);
+    }
+}
--- a/exercises/structs/structs3.rs
+++ b/exercises/structs/structs3.rs
@ -0,0 +1,89 @@
+// structs3.rs
+// Structs contain data, but can also have logic. In this exercise we have
+// defined the Package struct and we want to test some logic attached to it.
+// Make the code compile and the tests pass!
+// If you have issues execute `rustlings hint structs3`
+
+
+#[derive(Debug)]
+struct Package {
+    sender_country: String,
+    recipient_country: String,
+    weight_in_grams: i32,
+}
+
+impl Package {
+    fn new(sender_country: String, recipient_country: String, weight_in_grams: i32) -> Package {
+        if weight_in_grams <= 0 {
+            panic!("Weight is in negative value.");
+        } else {
+            return Package {
+                sender_country,
+                recipient_country,
+                weight_in_grams,
+            };
+        }
+    }
+
+    fn is_international(&self) -> bool {
+        if self.sender_country != self.recipient_country {
+            true
+        } else {
+            false
+        }
+    }
+
+    fn get_fees(&self, cents_per_gram: i32) -> i32 {
+        if cents_per_gram <= 0 {
+            panic!("We don't pay people, do we?");
+        } else {
+            cents_per_gram * self.weight_in_grams
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    #[should_panic]
+    fn fail_creating_weightless_package() {
+        let sender_country = String::from("Spain");
+        let recipient_country = String::from("Austria");
+
+        Package::new(sender_country, recipient_country, -2210);
+    }
+
+    #[test]
+    fn create_international_package() {
+        let sender_country = String::from("Spain");
+        let recipient_country = String::from("Russia");
+
+        let package = Package::new(sender_country, recipient_country, 1200);
+
+        assert!(package.is_international());
+    }
+
+    #[test]
+    fn create_local_package() {
+        let sender_country = String::from("Canada");
+        let recipient_country = sender_country.clone();
+
+        let package = Package::new(sender_country, recipient_country, 1200);
+
+        assert!(!package.is_international());
+    }
+
+    #[test]
+    fn calculate_transport_fees() {
+        let sender_country = String::from("Spain");
+        let recipient_country = String::from("Spain");
+
+        let cents_per_gram = 3;
+
+        let package = Package::new(sender_country, recipient_country, 1500);
+
+        assert_eq!(package.get_fees(cents_per_gram), 4500);
+    }
+}
--- a/exercises/test1.rs
+++ b/exercises/test1.rs
@ -1,21 +0,0 @@
-// test1.rs
-// This is a test for the following sections:
-// - Variables
-// - Functions
-
-// Mary is buying apples. One apple usually costs 2 dollars, but if you buy
-// more than 40 at once, each apple only costs 1! Write a function that calculates
-// the price of an order of apples given the order amount. No hints this time!
-
-// Put your function here!
-// fn ..... {
-
-// Don't modify this function!
-#[test]
-fn verify_test() {
-    let price1 = calculateprice(55);
-    let price2 = calculateprice(40);
-
-    assert_eq!(price1, 55);
-    assert_eq!(price2, 80);
-}
--- a/exercises/test3.rs
+++ b/exercises/test3.rs
@ -1,24 +0,0 @@
-// strings3.rs
-// This is a test for the following sections:
-// - Strings
-
-// Ok, here are a bunch of values-- some are `Strings`, some are `&strs`. Your
-// task is to call one of these two functions on each value depending on what
-// you think each value is. That is, add either `string_slice` or `string`
-// before the parentheses on each line. If you're right, it will compile!
-
-fn string_slice(arg: &str) { println!("{}", arg); }
-fn string(arg: String) { println!("{}", arg); }
-
-fn main() {
-    ("blue");
-    ("red".to_string());
-    (String::from("hi"));
-    ("rust is fun!".to_owned());
-    ("nice weather".into());
-    (format!("Interpolation {}", "Station"));
-    (&String::from("abc")[0..1]);
-    ("  hello there ".trim());
-    ("Happy Monday!".to_string().replace("Mon", "Tues"));
-    ("mY sHiFt KeY iS sTiCkY".to_lowercase());
-}
--- a/exercises/test4.rs
+++ b/exercises/test4.rs
@ -1,12 +0,0 @@
-// test4.rs
-// This test covers the sections:
-// - Modules
-// - Macros
-
-// Write a macro that passes the test! No hints this time, you can do it!
-
-fn main() {
-    if my_macro!("world!") != "Hello world!" {
-        panic!("Oh no! Wrong output!");
-    }
-}
--- a/exercises/tests/README.md
+++ b/exercises/tests/README.md
@ -1,7 +1,7 @@
-### Tests
+# Tests

 Going out of order from the book to cover tests -- many of the following exercises will ask you to make tests pass!

-#### Book Sections
+## Further information

- [Writing Tests](https://doc.rust-lang.org/stable/book/ch11-01-writing-tests.html)
+- [Writing Tests](https://doc.rust-lang.org/book/ch11-01-writing-tests.html)
--- a/exercises/tests/tests1.rs
+++ b/exercises/tests/tests1.rs
@ -1,10 +1,12 @@
 // tests1.rs
 // Tests are important to ensure that your code does what you think it should do.
 // Tests can be run on this file with the following command:
-// rustlings run --test exercises/tests/tests1.rs
+// rustlings run tests1

 // This test has a problem with it -- make the test compile! Make the test
-// pass! Make the test fail! Scroll down for hints :)
+// pass! Make the test fail! Execute `rustlings hint tests1` for hints :)
+
+// I AM NOT DONE

 #[cfg(test)]
 mod tests {
@ -13,37 +15,3 @@ mod tests {
        assert!();
    }
 }
-
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-// You don't even need to write any code to test -- you can just test values and run that, even
-// though you wouldn't do that in real life :) `assert!` is a macro that needs an argument.
-// Depending on the value of the argument, `assert!` will do nothing (in which case the test will
-// pass) or `assert!` will panic (in which case the test will fail). So try giving different values
-// to `assert!` and see which ones compile, which ones pass, and which ones fail :)
--- a/Show more
+++ b/Show more