release: 4.4.0

Merge pull request #725 from Zerotask/add-hint-corresponding-readme
chore(watch): add hint for the exercises README.md
2025-12-26 00:11:49 +02:00 · 2021-04-24 11:57:00 +02:00 · 2021-04-24 11:46:25 +02:00 · 2021-04-24 11:45:56 +02:00 · 2021-04-24 11:45:37 +02:00 · 2021-04-23 20:28:55 +02:00
58 changed files with 2381 additions and 1370 deletions
--- a/.all-contributorsrc
+++ b/.all-contributorsrc
@@ -591,6 +591,253 @@
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--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,92 @@
+<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)

--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -26,12 +26,12 @@ isn't really that complicated since the bulk of the work is done by `rustc`.
 <a name="addex"></a>
 ### Adding an exercise

-First step is to add the exercise! Call it `exercises/yourTopic/yourTopicN.rs`, make sure to
+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 you want to make sure it runs when using `rustlings`. All exercises are stored in `info.toml`, under the `exercises` array. They're ordered by the order they're ran when using `rustlings verify`.
+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`.

-You want to make sure where in the file you add your exercise. If you're not sure, add it at the bottom and ask in your pull request. To add an exercise, edit the file like this:
+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]]
--- a/Cargo.lock
+++ b/Cargo.lock
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,11 +1,11 @@
 [package]
 name = "rustlings"
-version = "4.1.0"
+version = "4.4.0"
 authors = ["Marisa <mokou@posteo.de>", "Carol (Nichols || Goulding) <carol.nichols@gmail.com>"]
 edition = "2018"

 [dependencies]
-clap = "2.32.0"
+argh = "0.1.4"
 indicatif = "0.10.3"
 console = "0.7.7"
 notify = "4.0.15"
--- a/README.md
+++ b/README.md
@@ -1,9 +1,8 @@
-![crab pet](https://i.imgur.com/LbZJgmm.gif)
 <!-- ALL-CONTRIBUTORS-BADGE:START - Do not remove or modify this section -->
-[![All Contributors](https://img.shields.io/badge/all_contributors-63-orange.svg?style=flat-square)](#contributors-)
+[![All Contributors](https://img.shields.io/badge/all_contributors-90-orange.svg?style=flat-square)](#contributors-)
 <!-- ALL-CONTRIBUTORS-BADGE:END -->

-# rustlings 🦀❤️ [![Build status](https://badge.buildkite.com/7af93d81dc522c67a1ec8e33ff5705861b1cb36360b774807f.svg)](https://buildkite.com/mokou/rustlings)
+# 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!

@@ -25,9 +24,9 @@ You will need to have Rust installed. You can get it by visiting https://rustup.
 Just run:

 ```bash
-curl -L https://git.io/rustlings | bash
+curl -L https://git.io/install-rustlings | bash
 # Or if you want it to be installed to a different path:
-curl -L https://git.io/rustlings | bash -s mypath/
+curl -L https://git.io/install-rustlings | bash -s mypath/
 ```

 This will install Rustlings and give you access to the `rustlings` command. Run it to get started!
@@ -43,11 +42,13 @@ Set-ExecutionPolicy RemoteSigned
 Then, you can run:

 ```ps
-Start-BitsTransfer -Source https://git.io/rustlings-win -Destination $env:TMP/install_rustlings.ps1; Unblock-File $env:TMP/install_rustlings.ps1; Invoke-Expression $env:TMP/install_rustlings.ps1
+Start-BitsTransfer -Source https://git.io/JTL5v -Destination $env:TMP/install_rustlings.ps1; Unblock-File $env:TMP/install_rustlings.ps1; Invoke-Expression $env:TMP/install_rustlings.ps1
 ```

 To install Rustlings. Same as on MacOS/Linux, you will have access to the `rustlings` command after it.

+When you get a permission denied message then you have to exclude the directory where you placed the rustlings in your virus-scanner
+
 ## Browser:

 [Run on Repl.it](https://repl.it/github/rust-lang/rustlings)
@@ -61,7 +62,7 @@ Basically: Clone the repository, checkout to the latest tag, run `cargo install`
 ```bash
 git clone https://github.com/rust-lang/rustlings
 cd rustlings
-git checkout tags/4.1.0 # or whatever the latest version is (find out at https://github.com/rust-lang/rustlings/releases/latest)
+git checkout tags/4.4.0 # or whatever the latest version is (find out at https://github.com/rust-lang/rustlings/releases/latest)
 cargo install --force --path .
 ```

@@ -103,6 +104,11 @@ exercise:
 rustlings hint myExercise1
 ```

+To check your progress, you can run the following command:
+```bash
+rustlings list
+```
+
 ## Testing yourself

 After every couple of sections, there will be a quiz that'll test your knowledge on a bunch of sections at once. These quizzes are found in `exercises/quizN.rs`.
@@ -111,13 +117,24 @@ After every couple of sections, there will be a quiz that'll test your knowledge

 Once you've completed Rustlings, put your new knowledge to good use! Continue practicing your Rust skills by building your own projects, contributing to Rustlings, or finding other open-source projects to contribute to.

-If you'd like to uninstall Rustlings, you can do so by invoking cargo and removing the rustlings directory:
+## Uninstalling Rustlings

-```bash
-cargo uninstall rustlings
-rm -r rustlings/ # or on Windows: rmdir /s rustlings
+If you want to remove Rustlings from your system, there's two steps. First, you'll need to remove the exercises folder that the install script created
+for you:
+
+``` bash
+rm -rf rustlings # or your custom folder name, if you chose and or renamed it
 ```

+Second, since Rustlings got installed via `cargo install`, it's only reasonable to assume that you can also remove it using Cargo, and
+exactly that is the case. Run `cargo uninstall` to remove the `rustlings` binary:
+
+``` bash
+cargo uninstall rustlings
+```
+
+Now you should be done!
+
 ## Completion

 Rustlings isn't done; there are a couple of sections that are very experimental and don't have proper documentation. These include:
@@ -149,88 +166,124 @@ Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/d
 <!-- markdownlint-disable -->
 <table>
  <tr>
-    <td align="center"><a href="http://carol-nichols.com"><img src="https://avatars2.githubusercontent.com/u/193874?v=4" width="100px;" alt=""/><br /><sub><b>Carol (Nichols &#124;&#124; Goulding)</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=carols10cents" title="Code">💻</a> <a href="#content-carols10cents" title="Content">🖋</a></td>
-    <td align="center"><a href="https://twitter.com/QuietMisdreavus"><img src="https://avatars2.githubusercontent.com/u/5217170?v=4" width="100px;" alt=""/><br /><sub><b>QuietMisdreavus</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=QuietMisdreavus" title="Code">💻</a> <a href="#content-QuietMisdreavus" title="Content">🖋</a></td>
-    <td align="center"><a href="https://github.com/robertlugg"><img src="https://avatars0.githubusercontent.com/u/6054540?v=4" width="100px;" alt=""/><br /><sub><b>Robert M Lugg</b></sub></a><br /><a href="#content-robertlugg" title="Content">🖋</a></td>
-    <td align="center"><a href="https://hynek.me/about/"><img src="https://avatars3.githubusercontent.com/u/41240?v=4" width="100px;" alt=""/><br /><sub><b>Hynek Schlawack</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=hynek" title="Code">💻</a></td>
-    <td align="center"><a href="https://spacekookie.de"><img src="https://avatars0.githubusercontent.com/u/7669898?v=4" width="100px;" alt=""/><br /><sub><b>Katharina Fey</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=spacekookie" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/lukabavdaz"><img src="https://avatars0.githubusercontent.com/u/9624558?v=4" width="100px;" alt=""/><br /><sub><b>lukabavdaz</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=lukabavdaz" title="Code">💻</a> <a href="#content-lukabavdaz" title="Content">🖋</a></td>
-    <td align="center"><a href="http://vestera.as"><img src="https://avatars2.githubusercontent.com/u/4187449?v=4" width="100px;" alt=""/><br /><sub><b>Erik Vesteraas</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=evestera" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/Delet0r"><img src="https://avatars1.githubusercontent.com/u/23195618?v=4" width="100px;" alt=""/><br /><sub><b>delet0r</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=Delet0r" title="Code">💻</a></td>
+    <td align="center"><a href="http://carol-nichols.com"><img src="https://avatars2.githubusercontent.com/u/193874?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Carol (Nichols &#124;&#124; Goulding)</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=carols10cents" title="Code">💻</a> <a href="#content-carols10cents" title="Content">🖋</a></td>
+    <td align="center"><a href="https://twitter.com/QuietMisdreavus"><img src="https://avatars2.githubusercontent.com/u/5217170?v=4?s=100" width="100px;" alt=""/><br /><sub><b>QuietMisdreavus</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=QuietMisdreavus" title="Code">💻</a> <a href="#content-QuietMisdreavus" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/robertlugg"><img src="https://avatars0.githubusercontent.com/u/6054540?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Robert M Lugg</b></sub></a><br /><a href="#content-robertlugg" title="Content">🖋</a></td>
+    <td align="center"><a href="https://hynek.me/about/"><img src="https://avatars3.githubusercontent.com/u/41240?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Hynek Schlawack</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=hynek" title="Code">💻</a></td>
+    <td align="center"><a href="https://spacekookie.de"><img src="https://avatars0.githubusercontent.com/u/7669898?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Katharina Fey</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=spacekookie" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/lukabavdaz"><img src="https://avatars0.githubusercontent.com/u/9624558?v=4?s=100" width="100px;" alt=""/><br /><sub><b>lukabavdaz</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=lukabavdaz" title="Code">💻</a> <a href="#content-lukabavdaz" title="Content">🖋</a></td>
+    <td align="center"><a href="http://vestera.as"><img src="https://avatars2.githubusercontent.com/u/4187449?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Erik Vesteraas</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=evestera" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/Delet0r"><img src="https://avatars1.githubusercontent.com/u/23195618?v=4?s=100" width="100px;" alt=""/><br /><sub><b>delet0r</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=Delet0r" title="Code">💻</a></td>
  </tr>
  <tr>
-    <td align="center"><a href="http://phinary.ca"><img src="https://avatars1.githubusercontent.com/u/10522375?v=4" width="100px;" alt=""/><br /><sub><b>Shaun Bennett</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=shaunbennett" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/abagshaw"><img src="https://avatars2.githubusercontent.com/u/8594541?v=4" width="100px;" alt=""/><br /><sub><b>Andrew Bagshaw</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=abagshaw" title="Code">💻</a></td>
-    <td align="center"><a href="https://ai6ua.net/"><img src="https://avatars2.githubusercontent.com/u/175578?v=4" width="100px;" alt=""/><br /><sub><b>Kyle Isom</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=kisom" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/ColinPitrat"><img src="https://avatars3.githubusercontent.com/u/1541863?v=4" width="100px;" alt=""/><br /><sub><b>Colin Pitrat</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=ColinPitrat" title="Code">💻</a></td>
-    <td align="center"><a href="https://zacanger.com"><img src="https://avatars3.githubusercontent.com/u/12520493?v=4" width="100px;" alt=""/><br /><sub><b>Zac Anger</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=zacanger" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/mgeier"><img src="https://avatars1.githubusercontent.com/u/705404?v=4" width="100px;" alt=""/><br /><sub><b>Matthias Geier</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=mgeier" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/cjpearce"><img src="https://avatars1.githubusercontent.com/u/3453268?v=4" width="100px;" alt=""/><br /><sub><b>Chris Pearce</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=cjpearce" title="Code">💻</a></td>
-    <td align="center"><a href="https://yvan-sraka.github.io"><img src="https://avatars2.githubusercontent.com/u/705213?v=4" width="100px;" alt=""/><br /><sub><b>Yvan Sraka</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=yvan-sraka" title="Code">💻</a></td>
+    <td align="center"><a href="http://phinary.ca"><img src="https://avatars1.githubusercontent.com/u/10522375?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Shaun Bennett</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=shaunbennett" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/abagshaw"><img src="https://avatars2.githubusercontent.com/u/8594541?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Andrew Bagshaw</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=abagshaw" title="Code">💻</a></td>
+    <td align="center"><a href="https://ai6ua.net/"><img src="https://avatars2.githubusercontent.com/u/175578?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Kyle Isom</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=kisom" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/ColinPitrat"><img src="https://avatars3.githubusercontent.com/u/1541863?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Colin Pitrat</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=ColinPitrat" title="Code">💻</a></td>
+    <td align="center"><a href="https://zacanger.com"><img src="https://avatars3.githubusercontent.com/u/12520493?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Zac Anger</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=zacanger" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/mgeier"><img src="https://avatars1.githubusercontent.com/u/705404?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Matthias Geier</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=mgeier" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/cjpearce"><img src="https://avatars1.githubusercontent.com/u/3453268?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Chris Pearce</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=cjpearce" title="Code">💻</a></td>
+    <td align="center"><a href="https://yvan-sraka.github.io"><img src="https://avatars2.githubusercontent.com/u/705213?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Yvan Sraka</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=yvan-sraka" title="Code">💻</a></td>
  </tr>
  <tr>
-    <td align="center"><a href="https://github.com/dendi239"><img src="https://avatars3.githubusercontent.com/u/16478650?v=4" width="100px;" alt=""/><br /><sub><b>Denys Smirnov</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=dendi239" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/eddyp"><img src="https://avatars2.githubusercontent.com/u/123772?v=4" width="100px;" alt=""/><br /><sub><b>eddyp</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=eddyp" title="Code">💻</a></td>
-    <td align="center"><a href="http://about.me/BrianKung"><img src="https://avatars1.githubusercontent.com/u/2836167?v=4" width="100px;" alt=""/><br /><sub><b>Brian Kung</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=briankung" title="Code">💻</a> <a href="#content-briankung" title="Content">🖋</a></td>
-    <td align="center"><a href="https://rcousineau.gitlab.io"><img src="https://avatars3.githubusercontent.com/u/281039?v=4" width="100px;" alt=""/><br /><sub><b>Russell</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=miller-time" title="Code">💻</a></td>
-    <td align="center"><a href="http://danwilhelm.com"><img src="https://avatars3.githubusercontent.com/u/6137185?v=4" width="100px;" alt=""/><br /><sub><b>Dan Wilhelm</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=danwilhelm" title="Documentation">📖</a></td>
-    <td align="center"><a href="https://github.com/Jesse-Cameron"><img src="https://avatars3.githubusercontent.com/u/3723654?v=4" width="100px;" alt=""/><br /><sub><b>Jesse</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=Jesse-Cameron" title="Code">💻</a> <a href="#content-Jesse-Cameron" title="Content">🖋</a></td>
-    <td align="center"><a href="https://github.com/MrFroop"><img src="https://avatars3.githubusercontent.com/u/196700?v=4" width="100px;" alt=""/><br /><sub><b>Fredrik Jambrén</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=MrFroop" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/petemcfarlane"><img src="https://avatars3.githubusercontent.com/u/3472717?v=4" width="100px;" alt=""/><br /><sub><b>Pete McFarlane</b></sub></a><br /><a href="#content-petemcfarlane" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/dendi239"><img src="https://avatars3.githubusercontent.com/u/16478650?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Denys Smirnov</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=dendi239" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/eddyp"><img src="https://avatars2.githubusercontent.com/u/123772?v=4?s=100" width="100px;" alt=""/><br /><sub><b>eddyp</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=eddyp" title="Code">💻</a></td>
+    <td align="center"><a href="http://about.me/BrianKung"><img src="https://avatars1.githubusercontent.com/u/2836167?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Brian Kung</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=briankung" title="Code">💻</a> <a href="#content-briankung" title="Content">🖋</a></td>
+    <td align="center"><a href="https://rcousineau.gitlab.io"><img src="https://avatars3.githubusercontent.com/u/281039?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Russell</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=miller-time" title="Code">💻</a></td>
+    <td align="center"><a href="http://danwilhelm.com"><img src="https://avatars3.githubusercontent.com/u/6137185?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Dan Wilhelm</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=danwilhelm" title="Documentation">📖</a></td>
+    <td align="center"><a href="https://github.com/Jesse-Cameron"><img src="https://avatars3.githubusercontent.com/u/3723654?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Jesse</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=Jesse-Cameron" title="Code">💻</a> <a href="#content-Jesse-Cameron" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/MrFroop"><img src="https://avatars3.githubusercontent.com/u/196700?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Fredrik Jambrén</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=MrFroop" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/petemcfarlane"><img src="https://avatars3.githubusercontent.com/u/3472717?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Pete McFarlane</b></sub></a><br /><a href="#content-petemcfarlane" title="Content">🖋</a></td>
  </tr>
  <tr>
-    <td align="center"><a href="https://github.com/nkanderson"><img src="https://avatars0.githubusercontent.com/u/4128825?v=4" width="100px;" alt=""/><br /><sub><b>nkanderson</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=nkanderson" title="Code">💻</a> <a href="#content-nkanderson" title="Content">🖋</a></td>
-    <td align="center"><a href="https://github.com/ajaxm"><img src="https://avatars0.githubusercontent.com/u/13360138?v=4" width="100px;" alt=""/><br /><sub><b>Ajax M</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=ajaxm" title="Documentation">📖</a></td>
-    <td align="center"><a href="https://dylnuge.com"><img src="https://avatars2.githubusercontent.com/u/118624?v=4" width="100px;" alt=""/><br /><sub><b>Dylan Nugent</b></sub></a><br /><a href="#content-Dylnuge" title="Content">🖋</a></td>
-    <td align="center"><a href="https://github.com/vyaslav"><img src="https://avatars0.githubusercontent.com/u/1385427?v=4" width="100px;" alt=""/><br /><sub><b>vyaslav</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=vyaslav" title="Code">💻</a> <a href="#content-vyaslav" title="Content">🖋</a></td>
-    <td align="center"><a href="https://join.sfxd.org"><img src="https://avatars1.githubusercontent.com/u/17297466?v=4" width="100px;" alt=""/><br /><sub><b>George</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=gdoenlen" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/nyxtom"><img src="https://avatars2.githubusercontent.com/u/222763?v=4" width="100px;" alt=""/><br /><sub><b>Thomas Holloway</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=nyxtom" title="Code">💻</a> <a href="#content-nyxtom" title="Content">🖋</a></td>
-    <td align="center"><a href="https://github.com/workingjubilee"><img src="https://avatars1.githubusercontent.com/u/46493976?v=4" width="100px;" alt=""/><br /><sub><b>Jubilee</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=workingjubilee" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/WofWca"><img src="https://avatars1.githubusercontent.com/u/39462442?v=4" width="100px;" alt=""/><br /><sub><b>WofWca</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=WofWca" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/nkanderson"><img src="https://avatars0.githubusercontent.com/u/4128825?v=4?s=100" width="100px;" alt=""/><br /><sub><b>nkanderson</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=nkanderson" title="Code">💻</a> <a href="#content-nkanderson" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/ajaxm"><img src="https://avatars0.githubusercontent.com/u/13360138?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Ajax M</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=ajaxm" title="Documentation">📖</a></td>
+    <td align="center"><a href="https://dylnuge.com"><img src="https://avatars2.githubusercontent.com/u/118624?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Dylan Nugent</b></sub></a><br /><a href="#content-Dylnuge" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/vyaslav"><img src="https://avatars0.githubusercontent.com/u/1385427?v=4?s=100" width="100px;" alt=""/><br /><sub><b>vyaslav</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=vyaslav" title="Code">💻</a> <a href="#content-vyaslav" title="Content">🖋</a></td>
+    <td align="center"><a href="https://join.sfxd.org"><img src="https://avatars1.githubusercontent.com/u/17297466?v=4?s=100" width="100px;" alt=""/><br /><sub><b>George</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=gdoenlen" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/nyxtom"><img src="https://avatars2.githubusercontent.com/u/222763?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Thomas Holloway</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=nyxtom" title="Code">💻</a> <a href="#content-nyxtom" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/workingjubilee"><img src="https://avatars1.githubusercontent.com/u/46493976?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Jubilee</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=workingjubilee" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/WofWca"><img src="https://avatars1.githubusercontent.com/u/39462442?v=4?s=100" width="100px;" alt=""/><br /><sub><b>WofWca</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=WofWca" title="Code">💻</a></td>
  </tr>
  <tr>
-    <td align="center"><a href="https://github.com/jrvidal"><img src="https://avatars0.githubusercontent.com/u/1636604?v=4" width="100px;" alt=""/><br /><sub><b>Roberto Vidal</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=jrvidal" title="Code">💻</a> <a href="https://github.com/rust-lang/rustlings/commits?author=jrvidal" title="Documentation">📖</a> <a href="#ideas-jrvidal" title="Ideas, Planning, & Feedback">🤔</a> <a href="#maintenance-jrvidal" title="Maintenance">🚧</a></td>
-    <td align="center"><a href="https://github.com/jensim"><img src="https://avatars0.githubusercontent.com/u/3663856?v=4" width="100px;" alt=""/><br /><sub><b>Jens</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=jensim" title="Documentation">📖</a></td>
-    <td align="center"><a href="http://rahatah.me/d"><img src="https://avatars3.githubusercontent.com/u/3174006?v=4" width="100px;" alt=""/><br /><sub><b>Rahat Ahmed</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=rahatarmanahmed" title="Documentation">📖</a></td>
-    <td align="center"><a href="https://github.com/AbdouSeck"><img src="https://avatars2.githubusercontent.com/u/6490055?v=4" width="100px;" alt=""/><br /><sub><b>Abdou Seck</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=AbdouSeck" title="Code">💻</a> <a href="#content-AbdouSeck" title="Content">🖋</a> <a href="https://github.com/rust-lang/rustlings/pulls?q=is%3Apr+reviewed-by%3AAbdouSeck" title="Reviewed Pull Requests">👀</a></td>
-    <td align="center"><a href="https://codehearts.com"><img src="https://avatars0.githubusercontent.com/u/2885412?v=4" width="100px;" alt=""/><br /><sub><b>Katie</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=codehearts" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/Socratides"><img src="https://avatars3.githubusercontent.com/u/27732983?v=4" width="100px;" alt=""/><br /><sub><b>Socrates</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=Socratides" title="Documentation">📖</a></td>
-    <td align="center"><a href="https://github.com/gnodarse"><img src="https://avatars3.githubusercontent.com/u/46761795?v=4" width="100px;" alt=""/><br /><sub><b>gnodarse</b></sub></a><br /><a href="#content-gnodarse" title="Content">🖋</a></td>
-    <td align="center"><a href="https://github.com/harrisonmetz"><img src="https://avatars1.githubusercontent.com/u/7883408?v=4" width="100px;" alt=""/><br /><sub><b>Harrison Metzger</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=harrisonmetz" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/jrvidal"><img src="https://avatars0.githubusercontent.com/u/1636604?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Roberto Vidal</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=jrvidal" title="Code">💻</a> <a href="https://github.com/rust-lang/rustlings/commits?author=jrvidal" title="Documentation">📖</a> <a href="#ideas-jrvidal" title="Ideas, Planning, & Feedback">🤔</a> <a href="#maintenance-jrvidal" title="Maintenance">🚧</a></td>
+    <td align="center"><a href="https://github.com/jensim"><img src="https://avatars0.githubusercontent.com/u/3663856?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Jens</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=jensim" title="Documentation">📖</a></td>
+    <td align="center"><a href="http://rahatah.me/d"><img src="https://avatars3.githubusercontent.com/u/3174006?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Rahat Ahmed</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=rahatarmanahmed" title="Documentation">📖</a></td>
+    <td align="center"><a href="https://github.com/AbdouSeck"><img src="https://avatars2.githubusercontent.com/u/6490055?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Abdou Seck</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=AbdouSeck" title="Code">💻</a> <a href="#content-AbdouSeck" title="Content">🖋</a> <a href="https://github.com/rust-lang/rustlings/pulls?q=is%3Apr+reviewed-by%3AAbdouSeck" title="Reviewed Pull Requests">👀</a></td>
+    <td align="center"><a href="https://codehearts.com"><img src="https://avatars0.githubusercontent.com/u/2885412?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Katie</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=codehearts" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/Socratides"><img src="https://avatars3.githubusercontent.com/u/27732983?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Socrates</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=Socratides" title="Documentation">📖</a></td>
+    <td align="center"><a href="https://github.com/gnodarse"><img src="https://avatars3.githubusercontent.com/u/46761795?v=4?s=100" width="100px;" alt=""/><br /><sub><b>gnodarse</b></sub></a><br /><a href="#content-gnodarse" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/harrisonmetz"><img src="https://avatars1.githubusercontent.com/u/7883408?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Harrison Metzger</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=harrisonmetz" title="Code">💻</a></td>
  </tr>
  <tr>
-    <td align="center"><a href="https://github.com/TorbenJ"><img src="https://avatars2.githubusercontent.com/u/9077102?v=4" width="100px;" alt=""/><br /><sub><b>Torben Jonas</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=TorbenJ" title="Code">💻</a> <a href="#content-TorbenJ" title="Content">🖋</a></td>
-    <td align="center"><a href="http://paulbissex.com/"><img src="https://avatars0.githubusercontent.com/u/641?v=4" width="100px;" alt=""/><br /><sub><b>Paul Bissex</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=pbx" title="Documentation">📖</a></td>
-    <td align="center"><a href="https://github.com/sjmann"><img src="https://avatars0.githubusercontent.com/u/6589896?v=4" width="100px;" alt=""/><br /><sub><b>Steven Mann</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=sjmann" title="Code">💻</a> <a href="#content-sjmann" title="Content">🖋</a></td>
-    <td align="center"><a href="https://smmdb.net/"><img src="https://avatars2.githubusercontent.com/u/5855071?v=4" width="100px;" alt=""/><br /><sub><b>Mario Reder</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=Tarnadas" title="Code">💻</a> <a href="#content-Tarnadas" title="Content">🖋</a></td>
-    <td align="center"><a href="https://keybase.io/skim"><img src="https://avatars0.githubusercontent.com/u/47347?v=4" width="100px;" alt=""/><br /><sub><b>skim</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=sl4m" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/sanjaykdragon"><img src="https://avatars1.githubusercontent.com/u/10261698?v=4" width="100px;" alt=""/><br /><sub><b>Sanjay K</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=sanjaykdragon" title="Code">💻</a> <a href="#content-sanjaykdragon" title="Content">🖋</a></td>
-    <td align="center"><a href="http://www.rohanjain.in"><img src="https://avatars1.githubusercontent.com/u/343499?v=4" width="100px;" alt=""/><br /><sub><b>Rohan Jain</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=crodjer" title="Code">💻</a></td>
-    <td align="center"><a href="https://www.saidaspen.se"><img src="https://avatars1.githubusercontent.com/u/7727687?v=4" width="100px;" alt=""/><br /><sub><b>Said Aspen</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=saidaspen" title="Code">💻</a> <a href="#content-saidaspen" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/TorbenJ"><img src="https://avatars2.githubusercontent.com/u/9077102?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Torben Jonas</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=TorbenJ" title="Code">💻</a> <a href="#content-TorbenJ" title="Content">🖋</a></td>
+    <td align="center"><a href="http://paulbissex.com/"><img src="https://avatars0.githubusercontent.com/u/641?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Paul Bissex</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=pbx" title="Documentation">📖</a></td>
+    <td align="center"><a href="https://github.com/sjmann"><img src="https://avatars0.githubusercontent.com/u/6589896?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Steven Mann</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=sjmann" title="Code">💻</a> <a href="#content-sjmann" title="Content">🖋</a></td>
+    <td align="center"><a href="https://smmdb.net/"><img src="https://avatars2.githubusercontent.com/u/5855071?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Mario Reder</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=Tarnadas" title="Code">💻</a> <a href="#content-Tarnadas" title="Content">🖋</a></td>
+    <td align="center"><a href="https://keybase.io/skim"><img src="https://avatars0.githubusercontent.com/u/47347?v=4?s=100" width="100px;" alt=""/><br /><sub><b>skim</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=sl4m" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/sanjaykdragon"><img src="https://avatars1.githubusercontent.com/u/10261698?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Sanjay K</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=sanjaykdragon" title="Code">💻</a> <a href="#content-sanjaykdragon" title="Content">🖋</a></td>
+    <td align="center"><a href="http://www.rohanjain.in"><img src="https://avatars1.githubusercontent.com/u/343499?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Rohan Jain</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=crodjer" title="Code">💻</a></td>
+    <td align="center"><a href="https://www.saidaspen.se"><img src="https://avatars1.githubusercontent.com/u/7727687?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Said Aspen</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=saidaspen" title="Code">💻</a> <a href="#content-saidaspen" title="Content">🖋</a></td>
  </tr>
  <tr>
-    <td align="center"><a href="https://github.com/uce"><img src="https://avatars3.githubusercontent.com/u/1756620?v=4" width="100px;" alt=""/><br /><sub><b>Ufuk Celebi</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=uce" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/lebedevsergey"><img src="https://avatars2.githubusercontent.com/u/7325764?v=4" width="100px;" alt=""/><br /><sub><b>lebedevsergey</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=lebedevsergey" title="Documentation">📖</a></td>
-    <td align="center"><a href="https://github.com/avrong"><img src="https://avatars2.githubusercontent.com/u/6342851?v=4" width="100px;" alt=""/><br /><sub><b>Aleksei Trifonov</b></sub></a><br /><a href="#content-avrong" title="Content">🖋</a></td>
-    <td align="center"><a href="https://drn.ie"><img src="https://avatars2.githubusercontent.com/u/411136?v=4" width="100px;" alt=""/><br /><sub><b>Darren Meehan</b></sub></a><br /><a href="#content-Darrenmeehan" title="Content">🖋</a></td>
-    <td align="center"><a href="https://github.com/jihchi"><img src="https://avatars1.githubusercontent.com/u/87983?v=4" width="100px;" alt=""/><br /><sub><b>Jihchi Lee</b></sub></a><br /><a href="#content-jihchi" title="Content">🖋</a></td>
-    <td align="center"><a href="https://github.com/bertonha"><img src="https://avatars3.githubusercontent.com/u/1225902?v=4" width="100px;" alt=""/><br /><sub><b>Christofer Bertonha</b></sub></a><br /><a href="#content-bertonha" title="Content">🖋</a></td>
-    <td align="center"><a href="https://github.com/apatniv"><img src="https://avatars2.githubusercontent.com/u/22565917?v=4" width="100px;" alt=""/><br /><sub><b>Vivek Bharath Akupatni</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=apatniv" title="Code">💻</a> <a href="https://github.com/rust-lang/rustlings/commits?author=apatniv" title="Tests">⚠️</a></td>
-    <td align="center"><a href="https://github.com/DiD92"><img src="https://avatars3.githubusercontent.com/u/6002416?v=4" width="100px;" alt=""/><br /><sub><b>Dídac Sementé Fernández</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=DiD92" title="Code">💻</a> <a href="#content-DiD92" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/uce"><img src="https://avatars3.githubusercontent.com/u/1756620?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Ufuk Celebi</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=uce" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/lebedevsergey"><img src="https://avatars2.githubusercontent.com/u/7325764?v=4?s=100" width="100px;" alt=""/><br /><sub><b>lebedevsergey</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=lebedevsergey" title="Documentation">📖</a></td>
+    <td align="center"><a href="https://github.com/avrong"><img src="https://avatars2.githubusercontent.com/u/6342851?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Aleksei Trifonov</b></sub></a><br /><a href="#content-avrong" title="Content">🖋</a></td>
+    <td align="center"><a href="https://drn.ie"><img src="https://avatars2.githubusercontent.com/u/411136?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Darren Meehan</b></sub></a><br /><a href="#content-Darrenmeehan" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/jihchi"><img src="https://avatars1.githubusercontent.com/u/87983?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Jihchi Lee</b></sub></a><br /><a href="#content-jihchi" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/bertonha"><img src="https://avatars3.githubusercontent.com/u/1225902?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Christofer Bertonha</b></sub></a><br /><a href="#content-bertonha" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/apatniv"><img src="https://avatars2.githubusercontent.com/u/22565917?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Vivek Bharath Akupatni</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=apatniv" title="Code">💻</a> <a href="https://github.com/rust-lang/rustlings/commits?author=apatniv" title="Tests">⚠️</a></td>
+    <td align="center"><a href="https://github.com/DiD92"><img src="https://avatars3.githubusercontent.com/u/6002416?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Dídac Sementé Fernández</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=DiD92" title="Code">💻</a> <a href="#content-DiD92" title="Content">🖋</a></td>
  </tr>
  <tr>
-    <td align="center"><a href="https://github.com/wrobstory"><img src="https://avatars3.githubusercontent.com/u/2601457?v=4" width="100px;" alt=""/><br /><sub><b>Rob Story</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=wrobstory" title="Code">💻</a></td>
-    <td align="center"><a href="https://github.com/siobhanjacobson"><img src="https://avatars2.githubusercontent.com/u/28983835?v=4" width="100px;" alt=""/><br /><sub><b>Siobhan Jacobson</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=siobhanjacobson" title="Code">💻</a></td>
-    <td align="center"><a href="https://www.linkedin.com/in/evancarroll/"><img src="https://avatars2.githubusercontent.com/u/19922?v=4" width="100px;" alt=""/><br /><sub><b>Evan Carroll</b></sub></a><br /><a href="#content-EvanCarroll" title="Content">🖋</a></td>
-    <td align="center"><a href="http://www.jawaadmahmood.com"><img src="https://avatars3.githubusercontent.com/u/95606?v=4" width="100px;" alt=""/><br /><sub><b>Jawaad Mahmood</b></sub></a><br /><a href="#content-jmahmood" title="Content">🖋</a></td>
-    <td align="center"><a href="https://github.com/GaurangTandon"><img src="https://avatars1.githubusercontent.com/u/6308683?v=4" width="100px;" alt=""/><br /><sub><b>Gaurang Tandon</b></sub></a><br /><a href="#content-GaurangTandon" title="Content">🖋</a></td>
-    <td align="center"><a href="https://github.com/dev-cyprium"><img src="https://avatars1.githubusercontent.com/u/6002628?v=4" width="100px;" alt=""/><br /><sub><b>Stefan Kupresak</b></sub></a><br /><a href="#content-dev-cyprium" title="Content">🖋</a></td>
-    <td align="center"><a href="https://github.com/greg-el"><img src="https://avatars3.githubusercontent.com/u/45019882?v=4" width="100px;" alt=""/><br /><sub><b>Greg Leonard</b></sub></a><br /><a href="#content-greg-el" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/wrobstory"><img src="https://avatars3.githubusercontent.com/u/2601457?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Rob Story</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=wrobstory" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/siobhanjacobson"><img src="https://avatars2.githubusercontent.com/u/28983835?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Siobhan Jacobson</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=siobhanjacobson" title="Code">💻</a></td>
+    <td align="center"><a href="https://www.linkedin.com/in/evancarroll/"><img src="https://avatars2.githubusercontent.com/u/19922?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Evan Carroll</b></sub></a><br /><a href="#content-EvanCarroll" title="Content">🖋</a></td>
+    <td align="center"><a href="http://www.jawaadmahmood.com"><img src="https://avatars3.githubusercontent.com/u/95606?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Jawaad Mahmood</b></sub></a><br /><a href="#content-jmahmood" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/GaurangTandon"><img src="https://avatars1.githubusercontent.com/u/6308683?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Gaurang Tandon</b></sub></a><br /><a href="#content-GaurangTandon" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/dev-cyprium"><img src="https://avatars1.githubusercontent.com/u/6002628?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Stefan Kupresak</b></sub></a><br /><a href="#content-dev-cyprium" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/greg-el"><img src="https://avatars3.githubusercontent.com/u/45019882?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Greg Leonard</b></sub></a><br /><a href="#content-greg-el" title="Content">🖋</a></td>
+    <td align="center"><a href="https://ryanpcmcquen.org"><img src="https://avatars3.githubusercontent.com/u/772937?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Ryan McQuen</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=ryanpcmcquen" title="Code">💻</a></td>
+  </tr>
+  <tr>
+    <td align="center"><a href="https://github.com/AnnikaCodes"><img src="https://avatars3.githubusercontent.com/u/56906084?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Annika</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/pulls?q=is%3Apr+reviewed-by%3AAnnikaCodes" title="Reviewed Pull Requests">👀</a></td>
+    <td align="center"><a href="https://darnuria.eu"><img src="https://avatars1.githubusercontent.com/u/2827553?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Axel Viala</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=darnuria" title="Code">💻</a></td>
+    <td align="center"><a href="https://sazid.github.io"><img src="https://avatars1.githubusercontent.com/u/2370167?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Mohammed Sazid Al Rashid</b></sub></a><br /><a href="#content-sazid" title="Content">🖋</a> <a href="https://github.com/rust-lang/rustlings/commits?author=sazid" title="Code">💻</a></td>
+    <td align="center"><a href="https://codingthemsoftly.com"><img src="https://avatars1.githubusercontent.com/u/17479099?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Caleb Webber</b></sub></a><br /><a href="#maintenance-seeplusplus" title="Maintenance">🚧</a></td>
+    <td align="center"><a href="https://github.com/pcn"><img src="https://avatars2.githubusercontent.com/u/1056756?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Peter N</b></sub></a><br /><a href="#maintenance-pcn" title="Maintenance">🚧</a></td>
+    <td align="center"><a href="https://github.com/seancad"><img src="https://avatars1.githubusercontent.com/u/47405611?v=4?s=100" width="100px;" alt=""/><br /><sub><b>seancad</b></sub></a><br /><a href="#maintenance-seancad" title="Maintenance">🚧</a></td>
+    <td align="center"><a href="http://willhayworth.com"><img src="https://avatars3.githubusercontent.com/u/181174?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Will Hayworth</b></sub></a><br /><a href="#content-wsh" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/chrizel"><img src="https://avatars3.githubusercontent.com/u/20802?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Christian Zeller</b></sub></a><br /><a href="#content-chrizel" title="Content">🖋</a></td>
+  </tr>
+  <tr>
+    <td align="center"><a href="https://github.com/jfchevrette"><img src="https://avatars.githubusercontent.com/u/3001?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Jean-Francois Chevrette</b></sub></a><br /><a href="#content-jfchevrette" title="Content">🖋</a> <a href="https://github.com/rust-lang/rustlings/commits?author=jfchevrette" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/jbaber"><img src="https://avatars.githubusercontent.com/u/1908117?v=4?s=100" width="100px;" alt=""/><br /><sub><b>John Baber-Lucero</b></sub></a><br /><a href="#content-jbaber" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/tal-zvon"><img src="https://avatars.githubusercontent.com/u/3195851?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Tal</b></sub></a><br /><a href="#content-tal-zvon" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/apogeeoak"><img src="https://avatars.githubusercontent.com/u/59737221?v=4?s=100" width="100px;" alt=""/><br /><sub><b>apogeeoak</b></sub></a><br /><a href="#content-apogeeoak" title="Content">🖋</a> <a href="https://github.com/rust-lang/rustlings/commits?author=apogeeoak" title="Code">💻</a></td>
+    <td align="center"><a href="http://www.garfieldtech.com/"><img src="https://avatars.githubusercontent.com/u/254863?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Larry Garfield</b></sub></a><br /><a href="#content-Crell" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/circumspect"><img src="https://avatars.githubusercontent.com/u/40770208?v=4?s=100" width="100px;" alt=""/><br /><sub><b>circumspect</b></sub></a><br /><a href="#content-circumspect" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/cjwyett"><img src="https://avatars.githubusercontent.com/u/34195737?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Cyrus Wyett</b></sub></a><br /><a href="#content-cjwyett" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/cadolphs"><img src="https://avatars.githubusercontent.com/u/13894820?v=4?s=100" width="100px;" alt=""/><br /><sub><b>cadolphs</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=cadolphs" title="Code">💻</a></td>
+  </tr>
+  <tr>
+    <td align="center"><a href="https://www.haveneer.com"><img src="https://avatars.githubusercontent.com/u/26146722?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Pascal H.</b></sub></a><br /><a href="#content-hpwxf" title="Content">🖋</a></td>
+    <td align="center"><a href="https://twitter.com/chapeupreto"><img src="https://avatars.githubusercontent.com/u/834048?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Rod Elias</b></sub></a><br /><a href="#content-chapeupreto" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/blerchy"><img src="https://avatars.githubusercontent.com/u/2555355?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Matt Lebl</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=blerchy" title="Code">💻</a></td>
+    <td align="center"><a href="http://flakolefluk.dev"><img src="https://avatars.githubusercontent.com/u/11986564?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Ignacio Le Fluk</b></sub></a><br /><a href="#content-flakolefluk" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/tlyu"><img src="https://avatars.githubusercontent.com/u/431873?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Taylor Yu</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=tlyu" title="Code">💻</a> <a href="#content-tlyu" title="Content">🖋</a></td>
+    <td align="center"><a href="https://zerotask.github.io"><img src="https://avatars.githubusercontent.com/u/20150243?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Patrick Hintermayer</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=Zerotask" title="Code">💻</a></td>
+    <td align="center"><a href="https://petkopavlovski.com/"><img src="https://avatars.githubusercontent.com/u/32264020?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Pete Pavlovski</b></sub></a><br /><a href="#content-arthas168" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/k12ish"><img src="https://avatars.githubusercontent.com/u/45272873?v=4?s=100" width="100px;" alt=""/><br /><sub><b>k12ish</b></sub></a><br /><a href="#content-k12ish" title="Content">🖋</a></td>
+  </tr>
+  <tr>
+    <td align="center"><a href="https://github.com/hongshaoyang"><img src="https://avatars.githubusercontent.com/u/19281800?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Shao Yang Hong</b></sub></a><br /><a href="#content-hongshaoyang" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/bmacer"><img src="https://avatars.githubusercontent.com/u/13931806?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Brandon Macer</b></sub></a><br /><a href="#content-bmacer" title="Content">🖋</a></td>
  </tr>
 </table>

-<!-- markdownlint-enable -->
+<!-- markdownlint-restore -->
 <!-- prettier-ignore-end -->
+
 <!-- ALL-CONTRIBUTORS-LIST:END -->

 This project follows the [all-contributors](https://github.com/all-contributors/all-contributors) specification. Contributions of any kind welcome!
--- a/buildkite.yml
+++ b/buildkite.yml
@@ -1,5 +0,0 @@
-steps:
-  - label: "Test with stable"
-    command: rustup run stable cargo test
-  - label: "Test with beta"
-    command: rustup run beta cargo test
--- a/default_out.txt
+++ b/default_out.txt
@@ -1,19 +1,25 @@
 Thanks for installing Rustlings!

-Is this your first time?
+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:

-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 an
-  installation script or manually executing:
+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!

-cargo install --force --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 watch` in order to get the first exercise.
-Make sure to have your editor open!
+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
@@ -1,8 +1,10 @@
-### Clippy
+# 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`.

-For more information about Clippy lints, please see [their documentation page](https://rust-lang.github.io/rust-clippy/master/).
+## Further information
+
+- [GitHub Repository](https://github.com/rust-lang/rust-clippy).
--- 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.
+
+// I AM NOT DONE
+
+use std::collections::HashMap;
+
+fn fruit_basket() -> HashMap<String, u32> {
+    let mut basket = // 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
+}
+
+#[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 +1,81 @@
+// 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.
+
+// I AM NOT DONE
+
+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 {
+        // TODO: Put new fruits if not already present. Note that you
+        // are not allowed to put any type of fruit that's already
+        // present!
+    }
+}
+
+#[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 +1,25 @@
+// 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.
+
+// I AM NOT DONE
+
+fn array_and_vec() -> ([i32; 4], Vec<i32>) {
+    let a = [10, 20, 30, 40]; // a plain array
+    let v = // 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 +1,33 @@
+// 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.
+
+// I AM NOT DONE
+
+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.
+    }
+
+    // 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
@@ -1,5 +1,4 @@
-### Type conversions
-
+# Type conversions

 Rust offers a multitude of ways to convert a value of a given type into another type.

@@ -15,6 +14,8 @@ Furthermore, the `std::str` module offers a trait called [`FromStr`](https://doc

 These should be the main ways ***within the standard library*** to convert data into your desired types.

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

-These are not directly covered in the book, but the standard library has great documentation for [conversions here](https://doc.rust-lang.org/std/convert/index.html). The `FromStr` trait is also covered [here](https://doc.rust-lang.org/std/str/trait.FromStr.html).
+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/from_into.rs
+++ b/exercises/conversions/from_into.rs
@@ -115,4 +115,18 @@ mod tests {
        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
@@ -2,6 +2,7 @@
 // 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)]
@@ -11,17 +12,19 @@ struct Person {
 }

 // I AM NOT DONE
+
 // Steps:
-// 1. If the length of the provided string is 0, then return an error
+// 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. Extract the first element from the split operation and use it as the name
-// 4. If the name is empty, then return an error
+// 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>()`.
-// If while parsing the age, something goes wrong, then return an error
-// Otherwise, then return a Result of a Person object
+//    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 = String;
+    type Err = Box<dyn error::Error>;
    fn from_str(s: &str) -> Result<Person, Self::Err> {
    }
 }
@@ -48,38 +51,42 @@ mod tests {
        assert_eq!(p.age, 32);
    }
    #[test]
-    #[should_panic]
    fn missing_age() {
-        "John,".parse::<Person>().unwrap();
+        assert!("John,".parse::<Person>().is_err());
    }

    #[test]
-    #[should_panic]
    fn invalid_age() {
-        "John,twenty".parse::<Person>().unwrap();
+        assert!("John,twenty".parse::<Person>().is_err());
    }

    #[test]
-    #[should_panic]
    fn missing_comma_and_age() {
-        "John".parse::<Person>().unwrap();
+        assert!("John".parse::<Person>().is_err());
    }

    #[test]
-    #[should_panic]
    fn missing_name() {
-        ",1".parse::<Person>().unwrap();
+        assert!(",1".parse::<Person>().is_err());
    }

    #[test]
-    #[should_panic]
    fn missing_name_and_age() {
-        ",".parse::<Person>().unwrap();
+        assert!(",".parse::<Person>().is_err());
    }

    #[test]
-    #[should_panic]
    fn missing_name_and_invalid_age() {
-        ",one".parse::<Person>().unwrap();
+        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
@@ -3,8 +3,9 @@
 // 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)]
+#[derive(Debug, PartialEq)]
 struct Color {
    red: u8,
    green: u8,
@@ -15,32 +16,29 @@ struct Color {

 // Your task is to complete this implementation
 // and return an Ok result of inner type Color.
-// You need create implementation for a tuple of three integer,
-// an array of three integer and slice of integer.
+// You need to create an implementation for a tuple of three integers,
+// an array of three integers and a slice of integers.
 //
-// Note, that implementation for tuple and array will be checked at compile-time,
-// but slice implementation need check slice length!
-// Also note, that chunk of correct rgb color must be integer in range 0..=255.
+// 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 = String;
-    fn try_from(tuple: (i16, i16, i16)) -> Result<Self, Self::Error> {
-    }
+    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 = String;
-    fn try_from(arr: [i16; 3]) -> Result<Self, Self::Error> {
-    }
+    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 = String;
-    fn try_from(slice: &[i16]) -> Result<Self, Self::Error> {
-    }
+    type Error = Box<dyn error::Error>;
+    fn try_from(slice: &[i16]) -> Result<Self, Self::Error> {}
 }

 fn main() {
@@ -66,71 +64,95 @@ mod tests {
    use super::*;

    #[test]
-    #[should_panic]
    fn test_tuple_out_of_range_positive() {
-        let _ = Color::try_from((256, 1000, 10000)).unwrap();
+        assert!(Color::try_from((256, 1000, 10000)).is_err());
    }
    #[test]
-    #[should_panic]
    fn test_tuple_out_of_range_negative() {
-        let _ = Color::try_from((-1, -10, -256)).unwrap();
+        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: Color = (183, 65, 14).try_into().unwrap();
-        assert_eq!(c.red, 183);
-        assert_eq!(c.green, 65);
-        assert_eq!(c.blue, 14);
+        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]
-    #[should_panic]
    fn test_array_out_of_range_positive() {
-        let _: Color = [1000, 10000, 256].try_into().unwrap();
+        let c: Result<Color, _> = [1000, 10000, 256].try_into();
+        assert!(c.is_err());
    }
    #[test]
-    #[should_panic]
    fn test_array_out_of_range_negative() {
-        let _: Color = [-10, -256, -1].try_into().unwrap();
+        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: Color = [183, 65, 14].try_into().unwrap();
-        assert_eq!(c.red, 183);
-        assert_eq!(c.green, 65);
-        assert_eq!(c.blue, 14);
+        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]
-    #[should_panic]
    fn test_slice_out_of_range_positive() {
        let arr = [10000, 256, 1000];
-        let _ = Color::try_from(&arr[..]).unwrap();
+        assert!(Color::try_from(&arr[..]).is_err());
    }
    #[test]
-    #[should_panic]
    fn test_slice_out_of_range_negative() {
        let arr = [-256, -1, -10];
-        let _ = Color::try_from(&arr[..]).unwrap();
+        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 = Color::try_from(&v[..]).unwrap();
-        assert_eq!(c.red, 183);
-        assert_eq!(c.green, 65);
-        assert_eq!(c.blue, 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]
-    #[should_panic]
    fn test_slice_excess_length() {
        let v = vec![0, 0, 0, 0];
-        let _ = Color::try_from(&v[..]).unwrap();
+        assert!(Color::try_from(&v[..]).is_err());
    }
    #[test]
-    #[should_panic]
    fn test_slice_insufficient_length() {
        let v = vec![0, 0];
-        let _ = Color::try_from(&v[..]).unwrap();
+        assert!(Color::try_from(&v[..]).is_err());
    }
 }
--- a/exercises/enums/README.md
+++ b/exercises/enums/README.md
@@ -1,10 +1,10 @@
-### Enums
+# 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.

-#### Book Sections
+## 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/error_handling/README.md
+++ b/exercises/error_handling/README.md
@@ -1,5 +1,11 @@
-For this exercise check out the sections:
+# 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.
+
+## 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)
-
-of the Rust Book.
+- [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/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/book/ch03-03-how-functions-work.html)
--- a/exercises/functions/functions2.rs
+++ b/exercises/functions/functions2.rs
@@ -7,7 +7,7 @@ fn main() {
    call_me(3);
 }

-fn call_me(num) {
+fn call_me(num:) {
    for i in 0..num {
        println!("Ring! Call number {}", i + 1);
    }
--- a/exercises/functions/functions3.rs
+++ b/exercises/functions/functions3.rs
@@ -7,7 +7,7 @@ fn main() {
    call_me();
 }

-fn call_me(num: i32) {
+fn call_me(num: u32) {
    for i in 0..num {
        println!("Ring! Call number {}", i + 1);
    }
--- a/exercises/generics/README.md
+++ b/exercises/generics/README.md
@@ -1,7 +1,11 @@
-### Generics
+# Generics

-In this section you'll learn about saving yourself many lines of code with 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.

-### Book Sections
+## Further information

- [Generic Data Types](https://doc.rust-lang.org/stable/book/ch10-01-syntax.html)
+- [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/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/book/ch03-05-control-flow.html#if-expressions)
--- 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
 macros. Instead, we'll show you how to use and create them.

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

 - [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/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/book/ch07-02-defining-modules-to-control-scope-and-privacy.html)
--- a/exercises/move_semantics/README.md
+++ b/exercises/move_semantics/README.md
@@ -1,8 +1,8 @@
-### 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.

--- a/exercises/move_semantics/move_semantics4.rs
+++ b/exercises/move_semantics/move_semantics4.rs
@@ -1,6 +1,6 @@
 // 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
+// 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!

@@ -18,7 +18,7 @@ fn main() {
    println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);
 }

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

--- a/exercises/option/README.md
+++ b/exercises/option/README.md
@@ -1,8 +1,17 @@
-### Option
+# Option

-#### Book Sections
+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

-To learn about Option<T>, check out these links:
+## 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/)
--- a/exercises/option/option2.rs
+++ b/exercises/option/option2.rs
@@ -4,22 +4,22 @@
 // I AM NOT DONE

 fn main() {
-    let optional_value = Some(String::from("rustlings"));
+    let optional_word = Some(String::from("rustlings"));
    // TODO: Make this an if let statement whose value is "Some" type
-    value = optional_value {
-        println!("the value of optional value is: {}", value);
+    word = optional_word {
+        println!("The word is: {}", word);
    } else {
-        println!("The optional value doesn't contain anything!");
+        println!("The optional word doesn't contain anything");
    }

-    let mut optional_values_vec: Vec<Option<i8>> = Vec::new();
+    let mut optional_integers_vec: Vec<Option<i8>> = Vec::new();
    for x in 1..10 {
-        optional_values_vec.push(Some(x));
+        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
-    value = optional_values_vec.pop() {
-        println!("current value: {}", value);
+    integer = optional_integers_vec.pop() {
+        println!("current value: {}", integer);
    }
 }
--- a/exercises/primitive_types/README.md
+++ b/exercises/primitive_types/README.md
@@ -1,9 +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_types6.rs
+++ b/exercises/primitive_types/primitive_types6.rs
@@ -1,11 +1,16 @@
 // 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.
+// You can put the expression for the second element where ??? is so that the test passes.
 // Execute `rustlings hint primitive_types6` for hints!

 // I AM NOT DONE

-fn main() {
+#[test]
+fn indexing_tuple() {
    let numbers = (1, 2, 3);
-    println!("The second number is {}", ???);
+    // Replace below ??? with the tuple indexing syntax.
+    let second = ???;
+
+    assert_eq!(2, second,
+        "This is not the 2nd number in the tuple!")
 }
--- a/exercises/quiz3.rs
+++ b/exercises/quiz3.rs
@@ -24,6 +24,7 @@ mod tests {

    #[test]
    fn returns_twice_of_negative_numbers() {
-        // TODO write an assert for `times_two(-4)`
+        // TODO replace unimplemented!() with an assert for `times_two(-4)`
+        unimplemented!()
    }
 }
--- a/exercises/standard_library_types/README.md
+++ b/exercises/standard_library_types/README.md
@@ -1,5 +1,10 @@
-For the Box exercise check out the chapter [Using Box to Point to Data on the Heap](https://doc.rust-lang.org/book/ch15-01-box.html).
+# Standard library types

-For the Arc exercise check out the chapter [Shared-State Concurrency](https://doc.rust-lang.org/book/ch16-03-shared-state.html) of the Rust Book.
+This section will teach you about Box, Shared-State Concurrency and Iterators.

-For the Iterator exercise check out the chapters [Iterator](https://doc.rust-lang.org/book/ch13-02-iterators.html) of the Rust Book and the [Iterator documentation](https://doc.rust-lang.org/stable/std/iter/).
+## 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
@@ -1,7 +1,21 @@
 // arc1.rs
+// 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
-// TODO comment is and create an initial binding for `child_numbers`
-// somewhere. Try not to create any copies of the `numbers` Vec!
+// 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
@@ -16,6 +30,7 @@ fn main() {
    let mut joinhandles = Vec::new();

    for offset in 0..8 {
+        let child_numbers = // TODO
        joinhandles.push(thread::spawn(move || {
            let mut i = offset;
            let mut sum = 0;
--- a/exercises/standard_library_types/iterators2.rs
+++ b/exercises/standard_library_types/iterators2.rs
@@ -1,28 +1,41 @@
 // iterators2.rs
-// In this module, you'll learn some of unique advantages that iterators can offer.
-// Step 1. Complete the `capitalize_first` function to pass the first two cases.
-// Step 2. Apply the `capitalize_first` function to a vector of strings.
-//         Ensure that it returns a vector of strings as well.
-// Step 3. Apply the `capitalize_first` function again to a list.
-//         Try to ensure it returns a single string.
+// 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) => first.collect::<String>() + c.as_str(),
+        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::*;

-    // Step 1.
-    // Tests that verify your `capitalize_first` function implementation
    #[test]
    fn test_success() {
        assert_eq!(capitalize_first("hello"), "Hello");
@@ -33,18 +46,15 @@ mod tests {
        assert_eq!(capitalize_first(""), "");
    }

-    // Step 2.
    #[test]
    fn test_iterate_string_vec() {
        let words = vec!["hello", "world"];
-        let capitalized_words: Vec<String> = // TODO
-        assert_eq!(capitalized_words, ["Hello", "World"]);
+        assert_eq!(capitalize_words_vector(&words), ["Hello", "World"]);
    }

    #[test]
    fn test_iterate_into_string() {
        let words = vec!["hello", " ", "world"];
-        let capitalized_words = // TODO
-        assert_eq!(capitalized_words, "Hello World");
+        assert_eq!(capitalize_words_string(&words), "Hello World");
    }
 }
--- a/exercises/standard_library_types/iterators3.rs
+++ b/exercises/standard_library_types/iterators3.rs
@@ -1,11 +1,10 @@
 // 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. Uncomment the last two tests and get them to pass by filling in
-//    values for `x` using `division_results`.
+// 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!
-// Have fun :-)

 // I AM NOT DONE

@@ -21,16 +20,28 @@ pub struct NotDivisibleError {
    divisor: i32,
 }

-// This function should calculate `a` divided by `b` if `a` is
-// evenly divisible by b.
-// Otherwise, it should return a suitable error.
+// 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::*;

-    // Tests that verify your `divide` function implementation
    #[test]
    fn test_success() {
        assert_eq!(divide(81, 9), Ok(9));
@@ -57,22 +68,16 @@ mod tests {
        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])");
+    fn test_result_with_list() {
+        assert_eq!(format!("{:?}", result_with_list()), "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)]");
+    fn test_list_of_results() {
+        assert_eq!(
+            format!("{:?}", list_of_results()),
+            "[Ok(1), Ok(11), Ok(1426), Ok(3)]"
+        );
    }
-    */
 }
--- 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/book/ch08-02-strings.html)
--- a/exercises/structs/README.md
+++ b/exercises/structs/README.md
@@ -1,7 +1,8 @@
-### Structs
+# Structs

-Rust has three struct types: a classic c struct, a tuple struct, and a unit struct.
+Rust has three struct types: a classic C struct, a tuple struct, and a unit struct.

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

- [Structures](https://doc.rust-lang.org/rust-by-example/custom_types/structs.html)
+- [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/structs3.rs
+++ b/exercises/structs/structs3.rs
@@ -1,7 +1,8 @@
 // structs3.rs
-// Structs contain more than simply some data, they 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`
+// 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`

 // I AM NOT DONE

@@ -57,6 +58,16 @@ mod tests {
        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");
--- 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/book/ch11-01-writing-tests.html)
--- a/exercises/tests/tests3.rs
+++ b/exercises/tests/tests3.rs
@@ -20,7 +20,7 @@ mod tests {
    }

    #[test]
-    fn is_false_when_even() {
+    fn is_false_when_odd() {
        assert!();
    }
 }
--- a/exercises/threads/README.md
+++ b/exercises/threads/README.md
@@ -1 +1,9 @@
-For this exercise check out the [Dining Philosophers example](https://doc.rust-lang.org/1.4.0/book/dining-philosophers.html) and the chapter [Concurrency](https://doc.rust-lang.org/book/ch16-01-threads.html) of the Rust Book.
+# Threads
+
+In most current operating systems, an executed program’s code is run in a process, and the operating system manages multiple processes at once.
+Within your program, you can also have independent parts that run simultaneously. The features that run these independent parts are called threads.
+
+## Further information
+
+- [Dining Philosophers example](https://doc.rust-lang.org/1.4.0/book/dining-philosophers.html)
+- [Using Threads to Run Code Simultaneously](https://doc.rust-lang.org/book/ch16-01-threads.html)
--- a/exercises/threads/threads1.rs
+++ b/exercises/threads/threads1.rs
@@ -1,7 +1,8 @@
 // threads1.rs
 // Make this compile! Execute `rustlings hint threads1` for hints :)
-// The idea is the thread spawned on line 21 is completing jobs while the main thread is
-// monitoring progress until 10 jobs are completed. If you see 6 lines
+// The idea is the thread spawned on line 22 is completing jobs while the main thread is
+// monitoring progress until 10 jobs are completed. Because of the difference between the
+// spawned threads' sleep time, and the waiting threads sleep time, when you see 6 lines
 // of "waiting..." and the program ends without timing out when running,
 // you've got it :)

--- a/exercises/traits/README.md
+++ b/exercises/traits/README.md
@@ -1,4 +1,4 @@
-### Traits
+# Traits

 A trait is a collection of methods.

@@ -7,14 +7,13 @@ Data types can implement traits. To do so, the methods making up the trait are d
 In this way, traits are somewhat similar to Java interfaces and C++ abstract classes.

 Some additional common Rust traits include:
-
-+ `Clone` (the `clone` method),
-+ `Display` (which allows formatted display via `{}`), and
-+ `Debug` (which allows formatted display via `{:?}`).
+- `Clone` (the `clone` method)
+- `Display` (which allows formatted display via `{}`)
+- `Debug` (which allows formatted display via `{:?}`)

 Because traits indicate shared behavior between data types, they are useful when writing generics.


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

 - [Traits](https://doc.rust-lang.org/book/ch10-02-traits.html)
--- a/exercises/variables/README.md
+++ b/exercises/variables/README.md
@@ -1,7 +1,9 @@
-### Variables
+# Variables

-Here you'll learn about simple variables.
+In Rust, variables are immutable by default.
+When a variable is immutable, once a value is bound to a name, you can’t change that value.
+You can make them mutable by adding mut in front of the variable name.

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

 - [Variables and Mutability](https://doc.rust-lang.org/book/ch03-01-variables-and-mutability.html)
--- a/info.toml
+++ b/info.toml
--- a/install.ps1
+++ b/install.ps1
@@ -53,7 +53,7 @@ function vercomp($v1, $v2) {
 }

 $rustVersion = $(rustc --version).Split(" ")[1]
-$minRustVersion = "1.31"
+$minRustVersion = "1.39"
 if ((vercomp $rustVersion $minRustVersion) -eq 2) {
    Write-Host "WARNING: Rust version is too old: $rustVersion - needs at least $minRustVersion"
    Write-Host "Please update Rust with 'rustup update'"
--- a/install.sh
+++ b/install.sh
@@ -87,7 +87,7 @@ function vercomp() {
 }

 RustVersion=$(rustc --version | cut -d " " -f 2)
-MinRustVersion=1.31
+MinRustVersion=1.39
 vercomp $RustVersion $MinRustVersion
 if [ $? -eq 2 ]
 then
--- a/src/exercise.rs
+++ b/src/exercise.rs
@@ -1,5 +1,6 @@
 use regex::Regex;
 use serde::Deserialize;
+use std::env;
 use std::fmt::{self, Display, Formatter};
 use std::fs::{self, remove_file, File};
 use std::io::Read;
@@ -11,14 +12,19 @@ const I_AM_DONE_REGEX: &str = r"(?m)^\s*///?\s*I\s+AM\s+NOT\s+DONE";
 const CONTEXT: usize = 2;
 const CLIPPY_CARGO_TOML_PATH: &str = "./exercises/clippy/Cargo.toml";

-// Get a temporary file name that is hopefully unique to this process
+// Get a temporary file name that is hopefully unique
 #[inline]
 fn temp_file() -> String {
-    format!("./temp_{}", process::id())
+    let thread_id: String = format!("{:?}", std::thread::current().id())
+        .chars()
+        .filter(|c| c.is_alphanumeric())
+        .collect();
+
+    format!("./temp_{}_{}", process::id(), thread_id)
 }

 // The mode of the exercise.
-#[derive(Deserialize, Copy, Clone)]
+#[derive(Deserialize, Copy, Clone, Debug)]
 #[serde(rename_all = "lowercase")]
 pub enum Mode {
    // Indicates that the exercise should be compiled as a binary
@@ -36,7 +42,7 @@ pub struct ExerciseList {

 // A representation of a rustlings exercise.
 // This is deserialized from the accompanying info.toml file
-#[derive(Deserialize)]
+#[derive(Deserialize, Debug)]
 pub struct Exercise {
    // Name of the exercise
    pub name: String,
@@ -121,8 +127,12 @@ name = "{}"
 path = "{}.rs""#,
                    self.name, self.name, self.name
                );
-                fs::write(CLIPPY_CARGO_TOML_PATH, cargo_toml)
-                    .expect("Failed to write 📎 Clippy 📎 Cargo.toml file.");
+                let cargo_toml_error_msg = if env::var("NO_EMOJI").is_ok() {
+                    "Failed to write Clippy Cargo.toml file."
+                } else {
+                    "Failed to write 📎 Clippy 📎 Cargo.toml file."
+                };
+                fs::write(CLIPPY_CARGO_TOML_PATH, cargo_toml).expect(cargo_toml_error_msg);
                // To support the ability to run the clipy exercises, build
                // an executable, in addition to running clippy. With a
                // compilation failure, this would silently fail. But we expect
@@ -227,6 +237,16 @@ path = "{}.rs""#,

        State::Pending(context)
    }
+
+    // Check that the exercise looks to be solved using self.state()
+    // This is not the best way to check since
+    // the user can just remove the "I AM NOT DONE" string from the file
+    // without actually having solved anything.
+    // The only other way to truly check this would to compile and run
+    // the exercise; which would be both costly and counterintuitive
+    pub fn looks_done(&self) -> bool {
+        self.state() == State::Done
+    }
 }

 impl Display for Exercise {
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,13 +1,13 @@
 use crate::exercise::{Exercise, ExerciseList};
 use crate::run::run;
 use crate::verify::verify;
-use clap::{crate_version, App, Arg, SubCommand};
+use argh::FromArgs;
 use console::Emoji;
 use notify::DebouncedEvent;
 use notify::{RecommendedWatcher, RecursiveMode, Watcher};
 use std::ffi::OsStr;
 use std::fs;
-use std::io;
+use std::io::{self, prelude::*};
 use std::path::Path;
 use std::process::{Command, Stdio};
 use std::sync::mpsc::channel;
@@ -22,41 +22,91 @@ mod exercise;
 mod run;
 mod verify;

-fn main() {
-    let matches = App::new("rustlings")
-        .version(crate_version!())
-        .author("Olivia Hugger, Carol Nichols")
-        .about("Rustlings is a collection of small exercises to get you used to writing and reading Rust code")
-        .arg(
-            Arg::with_name("nocapture")
-                .long("nocapture")
-                .help("Show outputs from the test exercises")
-        )
-        .subcommand(
-            SubCommand::with_name("verify")
-                .alias("v")
-                .about("Verifies all exercises according to the recommended order")
-        )
-        .subcommand(
-            SubCommand::with_name("watch")
-                .alias("w")
-                .about("Reruns `verify` when files were edited")
-        )
-        .subcommand(
-            SubCommand::with_name("run")
-                .alias("r")
-                .about("Runs/Tests a single exercise")
-                .arg(Arg::with_name("name").required(true).index(1)),
-        )
-        .subcommand(
-            SubCommand::with_name("hint")
-                .alias("h")
-                .about("Returns a hint for the current exercise")
-                .arg(Arg::with_name("name").required(true).index(1)),
-        )
-        .get_matches();
+// In sync with crate version
+const VERSION: &str = "4.4.0";

-    if matches.subcommand_name().is_none() {
+#[derive(FromArgs, PartialEq, Debug)]
+/// Rustlings is a collection of small exercises to get you used to writing and reading Rust code
+struct Args {
+    /// show outputs from the test exercises
+    #[argh(switch)]
+    nocapture: bool,
+    /// show the executable version
+    #[argh(switch, short = 'v')]
+    version: bool,
+    #[argh(subcommand)]
+    nested: Option<Subcommands>,
+}
+
+#[derive(FromArgs, PartialEq, Debug)]
+#[argh(subcommand)]
+enum Subcommands {
+    Verify(VerifyArgs),
+    Watch(WatchArgs),
+    Run(RunArgs),
+    Hint(HintArgs),
+    List(ListArgs),
+}
+
+#[derive(FromArgs, PartialEq, Debug)]
+#[argh(subcommand, name = "verify")]
+/// Verifies all exercises according to the recommended order
+struct VerifyArgs {}
+
+#[derive(FromArgs, PartialEq, Debug)]
+#[argh(subcommand, name = "watch")]
+/// Reruns `verify` when files were edited
+struct WatchArgs {}
+
+#[derive(FromArgs, PartialEq, Debug)]
+#[argh(subcommand, name = "run")]
+/// Runs/Tests a single exercise
+struct RunArgs {
+    #[argh(positional)]
+    /// the name of the exercise
+    name: String,
+}
+
+#[derive(FromArgs, PartialEq, Debug)]
+#[argh(subcommand, name = "hint")]
+/// Returns a hint for the given exercise
+struct HintArgs {
+    #[argh(positional)]
+    /// the name of the exercise
+    name: String,
+}
+
+#[derive(FromArgs, PartialEq, Debug)]
+#[argh(subcommand, name = "list")]
+/// Lists the exercises available in Rustlings
+struct ListArgs {
+    #[argh(switch, short = 'p')]
+    /// show only the paths of the exercises
+    paths: bool,
+    #[argh(switch, short = 'n')]
+    /// show only the names of the exercises
+    names: bool,
+    #[argh(option, short = 'f')]
+    /// provide a string to match exercise names
+    /// comma separated patterns are acceptable
+    filter: Option<String>,
+    #[argh(switch, short = 'u')]
+    /// display only exercises not yet solved
+    unsolved: bool,
+    #[argh(switch, short = 's')]
+    /// display only exercises that have been solved
+    solved: bool,
+}
+
+fn main() {
+    let args: Args = argh::from_env();
+
+    if args.version {
+        println!("v{}", VERSION);
+        std::process::exit(0);
+    }
+
+    if args.nested.is_none() {
        println!();
        println!(r#"       welcome to...                      "#);
        println!(r#"                 _   _ _                  "#);
@@ -86,62 +136,135 @@ fn main() {

    let toml_str = &fs::read_to_string("info.toml").unwrap();
    let exercises = toml::from_str::<ExerciseList>(toml_str).unwrap().exercises;
-    let verbose = matches.is_present("nocapture");
+    let verbose = args.nocapture;

-    if let Some(ref matches) = matches.subcommand_matches("run") {
-        let name = matches.value_of("name").unwrap();
-
-        let matching_exercise = |e: &&Exercise| name == e.name;
-
-        let exercise = exercises.iter().find(matching_exercise).unwrap_or_else(|| {
-            println!("No exercise found for your given name!");
-            std::process::exit(1)
-        });
-
-        run(&exercise, verbose).unwrap_or_else(|_| std::process::exit(1));
-    }
-
-    if let Some(ref matches) = matches.subcommand_matches("hint") {
-        let name = matches.value_of("name").unwrap();
-
-        let exercise = exercises
-            .iter()
-            .find(|e| name == e.name)
-            .unwrap_or_else(|| {
-                println!("No exercise found for your given name!");
-                std::process::exit(1)
-            });
-
-        println!("{}", exercise.hint);
-    }
-
-    if matches.subcommand_matches("verify").is_some() {
-        verify(&exercises, verbose).unwrap_or_else(|_| std::process::exit(1));
-    }
-
-    if matches.subcommand_matches("watch").is_some() && watch(&exercises, verbose).is_ok() {
-        println!(
-            "{emoji} All exercises completed! {emoji}",
-            emoji = Emoji("🎉", "★")
-        );
-        println!();
-        println!("We hope you enjoyed learning about the various aspects of Rust!");
-        println!("If you noticed any issues, please don't hesitate to report them to our repo.");
-        println!("You can also contribute your own exercises to help the greater community!");
-        println!();
-        println!("Before reporting an issue or contributing, please read our guidelines:");
-        println!("https://github.com/rust-lang/rustlings/blob/main/CONTRIBUTING.md");
-    }
-
-    if matches.subcommand_name().is_none() {
+    let command = args.nested.unwrap_or_else(|| {
        let text = fs::read_to_string("default_out.txt").unwrap();
        println!("{}", text);
+        std::process::exit(0);
+    });
+    match command {
+        Subcommands::List(subargs) => {
+            if !subargs.paths && !subargs.names {
+                println!("{:<17}\t{:<46}\t{:<7}", "Name", "Path", "Status");
+            }
+            let mut exercises_done: u16 = 0;
+            let filters = subargs.filter.clone().unwrap_or_default().to_lowercase();
+            exercises.iter().for_each(|e| {
+                let fname = format!("{}", e.path.display());
+                let filter_cond = filters
+                    .split(',')
+                    .filter(|f| !f.trim().is_empty())
+                    .any(|f| e.name.contains(&f) || fname.contains(&f));
+                let status = if e.looks_done() {
+                    exercises_done += 1;
+                    "Done"
+                } else {
+                    "Pending"
+                };
+                let solve_cond = {
+                    (e.looks_done() && subargs.solved)
+                        || (!e.looks_done() && subargs.unsolved)
+                        || (!subargs.solved && !subargs.unsolved)
+                };
+                if solve_cond && (filter_cond || subargs.filter.is_none()) {
+                    let line = if subargs.paths {
+                        format!("{}\n", fname)
+                    } else if subargs.names {
+                        format!("{}\n", e.name)
+                    } else {
+                        format!("{:<17}\t{:<46}\t{:<7}\n", e.name, fname, status)
+                    };
+                    // Somehow using println! leads to the binary panicking
+                    // when its output is piped.
+                    // So, we're handling a Broken Pipe error and exiting with 0 anyway
+                    let stdout = std::io::stdout();
+                    {
+                        let mut handle = stdout.lock();
+                        handle.write_all(line.as_bytes()).unwrap_or_else(|e| {
+                            match e.kind() {
+                                std::io::ErrorKind::BrokenPipe => std::process::exit(0),
+                                _ => std::process::exit(1),
+                            };
+                        });
+                    }
+                }
+            });
+            let percentage_progress = exercises_done as f32 / exercises.len() as f32 * 100.0;
+            println!(
+                "Progress: You completed {} / {} exercises ({:.2} %).",
+                exercises_done,
+                exercises.len(),
+                percentage_progress
+            );
+            std::process::exit(0);
+        }
+
+        Subcommands::Run(subargs) => {
+            let exercise = find_exercise(&subargs.name, &exercises);
+
+            run(&exercise, verbose).unwrap_or_else(|_| std::process::exit(1));
+        }
+
+        Subcommands::Hint(subargs) => {
+            let exercise = find_exercise(&subargs.name, &exercises);
+
+            println!("{}", exercise.hint);
+        }
+
+        Subcommands::Verify(_subargs) => {
+            verify(&exercises, verbose).unwrap_or_else(|_| std::process::exit(1));
+        }
+
+        Subcommands::Watch(_subargs) => {
+            if let Err(e) = watch(&exercises, verbose) {
+                println!(
+                    "Error: Could not watch your progress. Error message was {:?}.",
+                    e
+                );
+                println!("Most likely you've run out of disk space or your 'inotify limit' has been reached.");
+                std::process::exit(1);
+            }
+            println!(
+                "{emoji} All exercises completed! {emoji}",
+                emoji = Emoji("🎉", "★")
+            );
+            println!();
+            println!("+----------------------------------------------------+");
+            println!("|          You made it to the Fe-nish line!          |");
+            println!("+--------------------------  ------------------------+");
+            println!("                          \\/                         ");
+            println!("     ▒▒          ▒▒▒▒▒▒▒▒      ▒▒▒▒▒▒▒▒          ▒▒   ");
+            println!("   ▒▒▒▒  ▒▒    ▒▒        ▒▒  ▒▒        ▒▒    ▒▒  ▒▒▒▒ ");
+            println!("   ▒▒▒▒  ▒▒  ▒▒            ▒▒            ▒▒  ▒▒  ▒▒▒▒ ");
+            println!(" ░░▒▒▒▒░░▒▒  ▒▒            ▒▒            ▒▒  ▒▒░░▒▒▒▒ ");
+            println!("   ▓▓▓▓▓▓▓▓  ▓▓      ▓▓██  ▓▓  ▓▓██      ▓▓  ▓▓▓▓▓▓▓▓ ");
+            println!("     ▒▒▒▒    ▒▒      ████  ▒▒  ████      ▒▒░░  ▒▒▒▒   ");
+            println!("       ▒▒  ▒▒▒▒▒▒        ▒▒▒▒▒▒        ▒▒▒▒▒▒  ▒▒     ");
+            println!("         ▒▒▒▒▒▒▒▒▒▒▓▓▓▓▓▓▒▒▒▒▒▒▒▒▓▓▒▒▓▓▒▒▒▒▒▒▒▒       ");
+            println!("           ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒         ");
+            println!("             ▒▒▒▒▒▒▒▒▒▒██▒▒▒▒▒▒██▒▒▒▒▒▒▒▒▒▒           ");
+            println!("           ▒▒  ▒▒▒▒▒▒▒▒▒▒██████▒▒▒▒▒▒▒▒▒▒  ▒▒         ");
+            println!("         ▒▒    ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒    ▒▒       ");
+            println!("       ▒▒    ▒▒    ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒    ▒▒    ▒▒     ");
+            println!("       ▒▒  ▒▒    ▒▒                  ▒▒    ▒▒  ▒▒     ");
+            println!("           ▒▒  ▒▒                      ▒▒  ▒▒         ");
+            println!();
+            println!("We hope you enjoyed learning about the various aspects of Rust!");
+            println!(
+                "If you noticed any issues, please don't hesitate to report them to our repo."
+            );
+            println!("You can also contribute your own exercises to help the greater community!");
+            println!();
+            println!("Before reporting an issue or contributing, please read our guidelines:");
+            println!("https://github.com/rust-lang/rustlings/blob/main/CONTRIBUTING.md");
+        }
    }
 }

 fn spawn_watch_shell(failed_exercise_hint: &Arc<Mutex<Option<String>>>) {
    let failed_exercise_hint = Arc::clone(failed_exercise_hint);
-    println!("Type 'hint' to get help or 'clear' to clear the screen");
+    println!("Type 'hint' or open the corresponding README.md file to get help or type 'clear' to clear the screen.");
    thread::spawn(move || loop {
        let mut input = String::new();
        match io::stdin().read_line(&mut input) {
@@ -162,6 +285,16 @@ fn spawn_watch_shell(failed_exercise_hint: &Arc<Mutex<Option<String>>>) {
    });
 }

+fn find_exercise<'a>(name: &str, exercises: &'a [Exercise]) -> &'a Exercise {
+    exercises
+        .iter()
+        .find(|e| e.name == name)
+        .unwrap_or_else(|| {
+            println!("No exercise found for '{}'!", name);
+            std::process::exit(1)
+        })
+}
+
 fn watch(exercises: &[Exercise], verbose: bool) -> notify::Result<()> {
    /* Clears the terminal with an ANSI escape code.
    Works in UNIX and newer Windows terminals. */
@@ -190,7 +323,13 @@ fn watch(exercises: &[Exercise], verbose: bool) -> notify::Result<()> {
                        let filepath = b.as_path().canonicalize().unwrap();
                        let pending_exercises = exercises
                            .iter()
-                            .skip_while(|e| !filepath.ends_with(&e.path));
+                            .skip_while(|e| !filepath.ends_with(&e.path))
+                            // .filter(|e| filepath.ends_with(&e.path))
+                            .chain(
+                                exercises
+                                    .iter()
+                                    .filter(|e| !e.looks_done() && !filepath.ends_with(&e.path)),
+                            );
                        clear_screen();
                        match verify(pending_exercises, verbose) {
                            Ok(_) => return Ok(()),
--- a/src/ui.rs
+++ b/src/ui.rs
@@ -1,23 +1,33 @@
 macro_rules! warn {
    ($fmt:literal, $ex:expr) => {{
        use console::{style, Emoji};
+        use std::env;
        let formatstr = format!($fmt, $ex);
-        println!(
-            "{} {}",
-            style(Emoji("⚠️ ", "!")).red(),
-            style(formatstr).red()
-        );
+        if env::var("NO_EMOJI").is_ok() {
+            println!("{} {}", style("!").red(), style(formatstr).red());
+        } else {
+            println!(
+                "{} {}",
+                style(Emoji("⚠️ ", "!")).red(),
+                style(formatstr).red()
+            );
+        }
    }};
 }

 macro_rules! success {
    ($fmt:literal, $ex:expr) => {{
        use console::{style, Emoji};
+        use std::env;
        let formatstr = format!($fmt, $ex);
-        println!(
-            "{} {}",
-            style(Emoji("✅", "✓")).green(),
-            style(formatstr).green()
-        );
+        if env::var("NO_EMOJI").is_ok() {
+            println!("{} {}", style("✓").green(), style(formatstr).green());
+        } else {
+            println!(
+                "{} {}",
+                style(Emoji("✅", "✓")).green(),
+                style(formatstr).green()
+            );
+        }
    }};
 }
--- a/src/verify.rs
+++ b/src/verify.rs
@@ -1,6 +1,7 @@
 use crate::exercise::{CompiledExercise, Exercise, Mode, State};
 use console::style;
 use indicatif::ProgressBar;
+use std::env;

 // Verify that the provided container of Exercise objects
 // can be compiled and run without any failures.
@@ -137,14 +138,26 @@ fn prompt_for_completion(exercise: &Exercise, prompt_output: Option<String>) ->
        State::Pending(context) => context,
    };

+    let no_emoji = env::var("NO_EMOJI").is_ok();
+
+    let clippy_success_msg = if no_emoji {
+        "The code is compiling, and Clippy is happy!"
+    } else {
+        "The code is compiling, and 📎 Clippy 📎 is happy!"
+    };
+
    let success_msg = match exercise.mode {
        Mode::Compile => "The code is compiling!",
        Mode::Test => "The code is compiling, and the tests pass!",
-        Mode::Clippy => "The code is compiling, and 📎 Clippy 📎 is happy!",
+        Mode::Clippy => clippy_success_msg,
    };

    println!();
-    println!("🎉 🎉  {} 🎉 🎉", success_msg);
+    if no_emoji {
+        println!("~*~ {} ~*~", success_msg)
+    } else {
+        println!("🎉 🎉  {} 🎉 🎉", success_msg)
+    }
    println!();

    if let Some(output) = prompt_output {
--- a/tests/fixture/state/info.toml
+++ b/tests/fixture/state/info.toml
@@ -9,3 +9,10 @@ name = "pending_test_exercise"
 path = "pending_test_exercise.rs"
 mode = "test"
 hint = """"""
+
+[[exercises]]
+name = "finished_exercise"
+path = "finished_exercise.rs"
+mode = "compile"
+hint = """"""
+
--- a/tests/integration_tests.rs
+++ b/tests/integration_tests.rs
@@ -24,7 +24,7 @@ fn fails_when_in_wrong_dir() {
 fn verify_all_success() {
    Command::cargo_bin("rustlings")
        .unwrap()
-        .arg("v")
+        .arg("verify")
        .current_dir("tests/fixture/success")
        .assert()
        .success();
@@ -34,7 +34,7 @@ fn verify_all_success() {
 fn verify_fails_if_some_fails() {
    Command::cargo_bin("rustlings")
        .unwrap()
-        .arg("v")
+        .arg("verify")
        .current_dir("tests/fixture/failure")
        .assert()
        .code(1);
@@ -44,7 +44,7 @@ fn verify_fails_if_some_fails() {
 fn run_single_compile_success() {
    Command::cargo_bin("rustlings")
        .unwrap()
-        .args(&["r", "compSuccess"])
+        .args(&["run", "compSuccess"])
        .current_dir("tests/fixture/success/")
        .assert()
        .success();
@@ -54,7 +54,7 @@ fn run_single_compile_success() {
 fn run_single_compile_failure() {
    Command::cargo_bin("rustlings")
        .unwrap()
-        .args(&["r", "compFailure"])
+        .args(&["run", "compFailure"])
        .current_dir("tests/fixture/failure/")
        .assert()
        .code(1);
@@ -64,7 +64,7 @@ fn run_single_compile_failure() {
 fn run_single_test_success() {
    Command::cargo_bin("rustlings")
        .unwrap()
-        .args(&["r", "testSuccess"])
+        .args(&["run", "testSuccess"])
        .current_dir("tests/fixture/success/")
        .assert()
        .success();
@@ -74,7 +74,7 @@ fn run_single_test_success() {
 fn run_single_test_failure() {
    Command::cargo_bin("rustlings")
        .unwrap()
-        .args(&["r", "testFailure"])
+        .args(&["run", "testFailure"])
        .current_dir("tests/fixture/failure/")
        .assert()
        .code(1);
@@ -84,7 +84,7 @@ fn run_single_test_failure() {
 fn run_single_test_not_passed() {
    Command::cargo_bin("rustlings")
        .unwrap()
-        .args(&["r", "testNotPassed.rs"])
+        .args(&["run", "testNotPassed.rs"])
        .current_dir("tests/fixture/failure/")
        .assert()
        .code(1);
@@ -94,7 +94,7 @@ fn run_single_test_not_passed() {
 fn run_single_test_no_filename() {
    Command::cargo_bin("rustlings")
        .unwrap()
-        .arg("r")
+        .arg("run")
        .current_dir("tests/fixture/")
        .assert()
        .code(1);
@@ -104,7 +104,7 @@ fn run_single_test_no_filename() {
 fn run_single_test_no_exercise() {
    Command::cargo_bin("rustlings")
        .unwrap()
-        .args(&["r", "compNoExercise.rs"])
+        .args(&["run", "compNoExercise.rs"])
        .current_dir("tests/fixture/failure")
        .assert()
        .code(1);
@@ -114,7 +114,7 @@ fn run_single_test_no_exercise() {
 fn get_hint_for_single_test() {
    Command::cargo_bin("rustlings")
        .unwrap()
-        .args(&["h", "testFailure"])
+        .args(&["hint", "testFailure"])
        .current_dir("tests/fixture/failure")
        .assert()
        .code(0)
@@ -131,10 +131,15 @@ fn all_exercises_require_confirmation() {
            file.read_to_string(&mut s).unwrap();
            s
        };
-        source.matches("// I AM NOT DONE").next().expect(&format!(
-            "There should be an `I AM NOT DONE` annotation in {:?}",
-            path
-        ));
+        source
+            .matches("// I AM NOT DONE")
+            .next()
+            .unwrap_or_else(|| {
+                panic!(
+                    "There should be an `I AM NOT DONE` annotation in {:?}",
+                    path
+                )
+            });
    }
 }

@@ -142,7 +147,7 @@ fn all_exercises_require_confirmation() {
 fn run_compile_exercise_does_not_prompt() {
    Command::cargo_bin("rustlings")
        .unwrap()
-        .args(&["r", "pending_exercise"])
+        .args(&["run", "pending_exercise"])
        .current_dir("tests/fixture/state")
        .assert()
        .code(0)
@@ -153,7 +158,7 @@ fn run_compile_exercise_does_not_prompt() {
 fn run_test_exercise_does_not_prompt() {
    Command::cargo_bin("rustlings")
        .unwrap()
-        .args(&["r", "pending_test_exercise"])
+        .args(&["run", "pending_test_exercise"])
        .current_dir("tests/fixture/state")
        .assert()
        .code(0)
@@ -164,7 +169,7 @@ fn run_test_exercise_does_not_prompt() {
 fn run_single_test_success_with_output() {
    Command::cargo_bin("rustlings")
        .unwrap()
-        .args(&["--nocapture", "r", "testSuccess"])
+        .args(&["--nocapture", "run", "testSuccess"])
        .current_dir("tests/fixture/success/")
        .assert()
        .code(0)
@@ -175,9 +180,63 @@ fn run_single_test_success_with_output() {
 fn run_single_test_success_without_output() {
    Command::cargo_bin("rustlings")
        .unwrap()
-        .args(&["r", "testSuccess"])
+        .args(&["run", "testSuccess"])
        .current_dir("tests/fixture/success/")
        .assert()
        .code(0)
        .stdout(predicates::str::contains("THIS TEST TOO SHALL PAS").not());
 }
+
+#[test]
+fn run_rustlings_list() {
+    Command::cargo_bin("rustlings")
+        .unwrap()
+        .args(&["list"])
+        .current_dir("tests/fixture/success")
+        .assert()
+        .success();
+}
+
+#[test]
+fn run_rustlings_list_no_pending() {
+    Command::cargo_bin("rustlings")
+        .unwrap()
+        .args(&["list"])
+        .current_dir("tests/fixture/success")
+        .assert()
+        .success()
+        .stdout(predicates::str::contains("Pending").not());
+}
+
+#[test]
+fn run_rustlings_list_both_done_and_pending() {
+    Command::cargo_bin("rustlings")
+        .unwrap()
+        .args(&["list"])
+        .current_dir("tests/fixture/state")
+        .assert()
+        .success()
+        .stdout(predicates::str::contains("Done").and(predicates::str::contains("Pending")));
+}
+
+#[test]
+fn run_rustlings_list_without_pending() {
+    Command::cargo_bin("rustlings")
+        .unwrap()
+        .args(&["list", "--solved"])
+        .current_dir("tests/fixture/state")
+        .assert()
+        .success()
+        .stdout(predicates::str::contains("Pending").not());
+}
+
+#[test]
+fn run_rustlings_list_without_done() {
+    Command::cargo_bin("rustlings")
+        .unwrap()
+        .args(&["list", "--unsolved"])
+        .current_dir("tests/fixture/state")
+        .assert()
+        .success()
+        .stdout(predicates::str::contains("Done").not());
+}