Merge pull request #106 from rustlings/new

rustlings v2

75 files changed, 541 insertions, 586 deletions

diff --git a/.gitignore b/.gitignore
index d6c1194..61e30e2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,5 @@
 *.swp
 target/
+**/*.rs.bk
+Cargo.lock
+.DS_Store
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index 684b265..0000000
--- a/.travis.yml
+++ /dev/null
@@ -1,19 +0,0 @@
-language: rust
-
-branches:
-  only:
-  - master
-
-cache:
-  cargo: true
-
-script:
-  - cargo run --bin generate_readme
-  - git config user.name "Carol (Nichols || Goulding)"
-  - git config user.email "carol.nichols@gmail.com"
-  - git commit -am "Regenerate README" && git remote add upstream "https://$GH_TOKEN@github.com/carols10cents/rustlings.git" && git push -q upstream HEAD:master > /dev/null 2>&1 || true
-
-notifications:
-  email:
-    on_success: never
-
diff --git a/Cargo.toml b/Cargo.toml
index d82b8a1..e6a2a16 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,9 +1,12 @@
 [package]
 name = "rustlings"
 version = "0.1.0"
-authors = ["Carol (Nichols || Goulding) <carol.nichols@gmail.com>"]
+authors = ["olivia <819880950@qq.com>", "Carol (Nichols || Goulding) <carol.nichols@gmail.com"]
+edition = "2018"
 
 [dependencies]
-handlebars = "0.32.0"
-serde_json = "1.0.10"
-prlink = { git = "https://github.com/btbytes/prlink" }
+clap = "2.32.0"
+indicatif = "0.9.0"
+console = "0.6.2"
+syntect = "3.0.2"
+notify = "4.0.0"
diff --git a/README-template.hbs b/README-template.hbs
deleted file mode 100644
index 32838d5..0000000
--- a/README-template.hbs
+++ /dev/null
@@ -1,191 +0,0 @@
-<!--
-{{ autogenerated_notice }}
--->
-
-# rustlings
-
-Small exercises to get you used to reading and writing Rust code. Includes practice reading and
-responding to compiler messages!
-
-This repo is very much the smallest thing that could possibly work :)
-
-## To do these exercises
-
-Thanks to [btbytes'](https://twitter.com/btbytes) [prlinks](https://github.com/btbytes/prlink), you
-can now click on the links below to load the exercises in the rust playground!
-
-There are infinite correct answers-- the exercises are sometimes left very open-ended. Scroll down
-in the playground to find comments that have hints.
-
-If you need more help or would like to compare solutions, you can ask in [#rust-beginners on
-irc.mozilla.org](https://chat.mibbit.com/?server=irc.mozilla.org&channel=%23rust-beginners ), the
-[user forum](https://users.rust-lang.org/), or [the subreddit](https://reddit.com/r/rust). If an
-exercise could be improved in any way, please [create an
-issue](https://github.com/carols10cents/rustlings/issues/new) or submit a pull request!
-
-### Variable bindings
-
-[Relevant chapter in The Rust Programming
-Language](https://doc.rust-lang.org/book/second-edition/ch03-01-variables-and-mutability.html)
-
-{{ playground_link "variables/variables1.rs" }}
-{{ playground_link "variables/variables2.rs" }}
-{{ playground_link "variables/variables3.rs" }}
-{{ playground_link "variables/variables4.rs" }}
-
-### Functions
-
-[Relevant chapter in The Rust Programming
-Language](https://doc.rust-lang.org/book/second-edition/ch03-03-how-functions-work.html)
-
-{{ playground_link "functions/functions1.rs" }}
-{{ playground_link "functions/functions2.rs" }}
-{{ playground_link "functions/functions3.rs" }}
-{{ playground_link "functions/functions4.rs" }}
-{{ playground_link "functions/functions5.rs" }}
-
-### Primitive types
-
-[Relevant chapter in The Rust Programming
-Language](https://doc.rust-lang.org/book/second-edition/ch03-02-data-types.html)
-
-{{ playground_link "primitive_types/primitive_types1.rs" }}
-{{ playground_link "primitive_types/primitive_types2.rs" }}
-{{ playground_link "primitive_types/primitive_types3.rs" }}
-{{ playground_link "primitive_types/primitive_types4.rs" }}
-{{ playground_link "primitive_types/primitive_types5.rs" }}
-{{ playground_link "primitive_types/primitive_types6.rs" }}
-
-### Tests
-
-Going out of order from the book to cover tests-- many of the following exercises will ask you to
-make tests pass!
-
-[Relevant chapter in The Rust Programming
-Language](https://doc.rust-lang.org/book/second-edition/ch11-01-writing-tests.html)
-
-{{ playground_link "tests/tests1.rs" }}
-{{ playground_link "tests/tests2.rs" }}
-{{ playground_link "tests/tests3.rs" }}
-{{ playground_link "tests/tests4.rs" }}
-
-### If
-
-[Relevant chapter in The Rust Programming
-Language](https://doc.rust-lang.org/book/second-edition/ch03-05-control-flow.html)
-
-{{ playground_link "if/if1.rs" }}
-
-### Strings
-
-[Relevant chapter in The Rust Programming
-Language](https://doc.rust-lang.org/book/second-edition/ch08-02-strings.html)
-
-{{ playground_link "strings/strings1.rs" }}
-{{ playground_link "strings/strings2.rs" }}
-{{ playground_link "strings/strings3.rs" }}
-
-### Move semantics
-
-These exercises are adapted from [pnkfelix]()'s [Rust
-Tutorial](https://pnkfelix.github.io/rust-examples-icfp2014/) -- thank you Felix!!!
-
-Relevant chapters in the book:
-
-- [Ownership](https://doc.rust-lang.org/book/second-edition/ch04-01-what-is-ownership.html)
-- [References and borrowing](https://doc.rust-lang.org/book/second-edition/ch04-02-references-and-borrowing.html)
-
-Note that the exercises in this section may look similar to each other but they are subtly
-different :)
-
-{{ playground_link "move_semantics/move_semantics1.rs" }}
-{{ playground_link "move_semantics/move_semantics2.rs" }}
-{{ playground_link "move_semantics/move_semantics3.rs" }}
-{{ playground_link "move_semantics/move_semantics4.rs" }}
-
-### Modules
-
-[Relevant chapter in The Rust Programming
-Language](https://doc.rust-lang.org/book/second-edition/ch07-01-mod-and-the-filesystem.html)
-
-{{ playground_link "modules/modules1.rs" }}
-{{ playground_link "modules/modules2.rs" }}
-
-### Macros
-
-Check out:
-
-- [The Macros section of the first edition of the book
-  book](https://doc.rust-lang.org/book/first-edition/macros.html)
-- [The Macros appendix of the second edition of the
-  book](https://doc.rust-lang.org/book/second-edition/appendix-04-macros.html)
-- [The Little Book of Rust Macros](https://danielkeep.github.io/tlborm/book/index.html)
-
-{{ playground_link "macros/macros1.rs" }}
-{{ playground_link "macros/macros2.rs" }}
-{{ playground_link "macros/macros3.rs" }}
-{{ playground_link "macros/macros4.rs" }}
-
-### Error Handling
-
-The [Error
-Handling](https://doc.rust-lang.org/book/second-edition/ch09-02-recoverable-errors-with-result.html)
-and [Generics](https://doc.rust-lang.org/book/second-edition/ch10-01-syntax.html) sections are
-relevant.
-
-{{ playground_link "error_handling/option1.rs" }}
-{{ playground_link "error_handling/result1.rs" }}
-{{ playground_link "error_handling/errors1.rs" }}
-{{ playground_link "error_handling/errors2.rs" }}
-{{ playground_link "error_handling/errors3.rs" }}
-{{ playground_link "error_handling/errorsn.rs" }}
-
-### Standard library types
-
-#### `Arc`
-
-The [Concurrency](https://doc.rust-lang.org/book/second-edition/ch16-03-shared-state.html) section
-is relevant.
-
-{{ playground_link "standard_library_types/arc1.rs" }}
-
-#### Iterators
-
-Do not adjust your monitors-- iterators 1 and 2 are indeed missing. Iterator 3 is a bit challenging
-so we're leaving space for some exercises to lead up to it!
-
-Check out the [Iterators chapter of the
-book](https://doc.rust-lang.org/book/second-edition/ch13-02-iterators.html) and the [Iterator
-docs](https://doc.rust-lang.org/stable/std/iter/trait.Iterator.html).
-
-{{ playground_link "standard_library_types/iterator3.rs" }}
-{{ playground_link "standard_library_types/iterators4.rs" }}
-
-### Threads
-
-See [the Dining Philosophers
-example](https://doc.rust-lang.org/1.4.0/book/dining-philosophers.html) and the
-[Concurrency Chapter](https://doc.rust-lang.org/book/second-edition/ch16-01-threads.html) from the
-book.
-
-{{ playground_link "threads/threads1.rs" }}
-
-### Uncategorized
-
-A few exercises based on things I've encountered or had trouble with getting used to.
-
-{{ playground_link "ex1.rs" }}
-{{ playground_link "ex2.rs" }}
-{{ playground_link "ex3.rs" }}
-{{ playground_link "ex4.rs" }}
-{{ playground_link "ex5.rs" }}
-{{ playground_link "ex6.rs" }}
-
-## To help with this repo/TODO list
-
-* File issues for problems or suggestions!
-* Contribute more exercises! Anything that took you time to get used to, or that you had trouble
-  with, or that deserves practice would be a good exercise!
-* How could the process of doing these exercises work better? This is an open-ended question :) Are
-  the playground links good enough? Are there ways that we could make going to the next exercise
-  easier without forking the playground??
diff --git a/README.md b/README.md
index c6e00e0..762ae6b 100644
--- a/README.md
+++ b/README.md
@@ -1,204 +1,117 @@
-<!--
-This file was autogenerated by the script in src/bin/generate_readme.rs.
-Please edit either the script or the template in README-template.md in
-order to make changes here rather than committing the changes directly.
--->
+![crab pet](http://i.imgur.com/LbZJgmm.gif) 
 
-# rustlings
+# rustlings 🦀❤️
 
-Small exercises to get you used to reading and writing Rust code. Includes practice reading and
-responding to compiler messages!
+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!
 
-This repo is very much the smallest thing that could possibly work :)
+_...looking for the old, web-based version of Rustlings? Try [here](https://github.com/rustlings/rustlings/tree/rustlings-1)_
 
-## To do these exercises
+Alternatively, for a first-time Rust learner, there's several other resources:
 
-Thanks to [btbytes'](https://twitter.com/btbytes) [prlinks](https://github.com/btbytes/prlink), you
-can now click on the links below to load the exercises in the rust playground!
+- [The Book](https://doc.rust-lang.org/book/index.html) - The most comprehensive resource for learning Rust, but a bit theoretical sometimes. You will be using this along with Rustlings!
+- [Rust By Example](https://doc.rust-lang.org/rust-by-example/index.html) - Learn Rust by solving little exercises! It's almost like `rustlings`, but online
 
-There are infinite correct answers-- the exercises are sometimes left very open-ended. Scroll down
-in the playground to find comments that have hints.
+## Getting Started
 
-### To do these exercises in your local environment and execute them online afterwards:
+To use `rustlings` you need to have [Rust](https://www.rust-lang.org/) installed on your computer. To install Rust, go to [rustup.rs](https://rustup.rs/).
 
-* clone the repo to your local environment: `git clone https://github.com/rustlings/rustlings.git`
-* edit the rustling that you want, per example `variables/variables1.rs`
-* run `cargo run` in the project folder
-* you will notice that your README file was modified and now it has the new content of the file that you edited
-* click in the new URL in the README and you will redirect to the rust playground and the whole file content it will be loaded
-* to execute in the rust playground, just click on `run`
+Once Rust is installed, clone the `rustlings` repository and enter the resulting directory:
 
-### Need help?
+```bash
+git clone https://github.com/rustlings/rustlings.git
+cd rustlings
+```
 
-If you need more help or would like to compare solutions, you can ask in [#rust-beginners on
-irc.mozilla.org](https://chat.mibbit.com/?server=irc.mozilla.org&channel=%23rust-beginners ), the
-[user forum](https://users.rust-lang.org/), or [the subreddit](https://reddit.com/r/rust). If an
-exercise could be improved in any way, please [create an
-issue](https://github.com/carols10cents/rustlings/issues/new) or submit a pull request!
+Once in the directory you can install `rustlings` on your machine and run the introduction:
 
-### Variable bindings
+```bash
+cargo install --path .
+rustlings
+```
 
-[Relevant chapter in The Rust Programming
-Language](https://doc.rust-lang.org/book/second-edition/ch03-01-variables-and-mutability.html)
+If you choose to not install the `rustlings` command, just replace `rustlings` with `cargo run` in the rest of this text.
 
-- ["variables1.rs"](https://play.rust-lang.org/?code=%2F%2F+variables1.rs%0A%2F%2F+Make+me+compile%21+Scroll+down+for+hints+%3A%29%0A%0Afn+main%28%29+%7B%0A++++x+%3D+5%3B%0A++++println%21%28%22x+has+the+value+%7B%7D%22%2C+x%29%3B%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+Hint%3A+The+declaration+on+line+5+is+missing+a+keyword+that+is+needed+in+Rust%0A%2F%2F+to+create+a+new+variable+binding.%0A)
-- ["variables2.rs"](https://play.rust-lang.org/?code=%2F%2F+variables2.rs%0A%2F%2F+Make+me+compile%21+Scroll+down+for+hints+%3A%29%0A%0Afn+main%28%29+%7B%0A++++let+x%3B%0A++++if+x+%3D%3D+10+%7B%0A++++++++println%21%28%22Ten%21%22%29%3B%0A++++%7D+else+%7B%0A++++++++println%21%28%22Not+ten%21%22%29%3B%0A++++%7D%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+The+compiler+message+is+saying+that+Rust+cannot+infer+the+type+that+the%0A%2F%2F+variable+binding+%60x%60+has+with+what+is+given+here.%0A%2F%2F+What+happens+if+you+annotate+line+5+with+a+type+annotation%3F%0A%2F%2F+What+if+you+give+x+a+value%3F%0A%2F%2F+What+if+you+do+both%3F%0A%2F%2F+What+type+should+x+be%2C+anyway%3F%0A%2F%2F+What+if+x+is+the+same+type+as+10%3F+What+if+it%27s+a+different+type%3F%0A)
-- ["variables3.rs"](https://play.rust-lang.org/?code=%2F%2F+variables3.rs%0A%2F%2F+Make+me+compile%21+Scroll+down+for+hints+%3A%29%0A%0Afn+main%28%29+%7B%0A++++let+x+%3D+3%3B%0A++++println%21%28%22Number+%7B%7D%22%2C+x%29%3B%0A++++x+%3D+5%3B%0A++++println%21%28%22Number+%7B%7D%22%2C+x%29%3B%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+In+Rust%2C+variable+bindings+are+immutable+by+default.+But+here+we%27re+trying%0A%2F%2F+to+reassign+a+different+value+to+x%21+There%27s+a+keyword+we+can+use+to+make%0A%2F%2F+a+variable+binding+mutable+instead.%0A)
-- ["variables4.rs"](https://play.rust-lang.org/?code=%2F%2F+variables4.rs%0A%2F%2F+Make+me+compile%21+Scroll+down+for+hints+%3A%29%0A%0Afn+main%28%29+%7B%0A++++let+x%3A+i32%3B%0A++++println%21%28%22Number+%7B%7D%22%2C+x%29%3B%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+Oops%21+In+this+exercise%2C+we+have+a+variable+binding+that+we%27ve+created+on%0A%2F%2F+line+5%2C+and+we%27re+trying+to+use+it+on+line+6%2C+but+we+haven%27t+given+it+a%0A%2F%2F+value.+We+can%27t+print+out+something+that+isn%27t+there%3B+try+giving+x+a+value%21%0A%2F%2F+This+is+an+error+that+can+cause+bugs+that%27s+very+easy+to+make+in+any%0A%2F%2F+programming+language+--+thankfully+the+Rust+compiler+has+caught+this+for+us%21%0A)
+## Doing exercises
 
-### Functions
+The exercises are sorted by topic and can be found in the subdirectory `rustlings/exercises/<topic>`. For every topic there is an additional README file with some resources to get you started on the topic. We really recommend that you have a look at them before you start. 
 
-[Relevant chapter in The Rust Programming
-Language](https://doc.rust-lang.org/book/second-edition/ch03-03-how-functions-work.html)
+The task is simple. Most exercises contain an error that keep it from compiling, and it's up to you to fix it! Some exercises are also ran as tests, but rustlings handles them all the same. To run the exercises in the recommended order, execute:
 
-- ["functions1.rs"](https://play.rust-lang.org/?code=%2F%2F+functions1.rs%0A%2F%2F+Make+me+compile%21+Scroll+down+for+hints+%3A%29%0A%0Afn+main%28%29+%7B%0A++++call_me%28%29%3B%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+This+main+function+is+calling+a+function+that+it+expects+to+exist%2C+but+the%0A%2F%2F+function+doesn%27t+exist.+It+expects+this+function+to+have+the+name+%60call_me%60.%0A%2F%2F+It+expects+this+function+to+not+take+any+arguments+and+not+return+a+value.%0A%2F%2F+Sounds+a+lot+like+%60main%60%2C+doesn%27t+it%3F%0A)
-- ["functions2.rs"](https://play.rust-lang.org/?code=%2F%2F+functions2.rs%0A%2F%2F+Make+me+compile%21+Scroll+down+for+hints+%3A%29%0A%0Afn+main%28%29+%7B%0A++++call_me%283%29%3B%0A%7D%0A%0Afn+call_me%28num%29+%7B%0A++++for+i+in+0..num+%7B%0A++++++++println%21%28%22Ring%21+Call+number+%7B%7D%22%2C+i+%2B+1%29%3B%0A++++%7D%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+Rust+requires+that+all+parts+of+a+function%27s+signature+have+type+annotations%2C%0A%2F%2F+but+%60call_me%60+is+missing+the+type+annotation+of+%60num%60.%0A)
-- ["functions3.rs"](https://play.rust-lang.org/?code=%2F%2F+functions3.rs%0A%2F%2F+Make+me+compile%21+Scroll+down+for+hints+%3A%29%0A%0Afn+main%28%29+%7B%0A++++call_me%28%29%3B%0A%7D%0A%0Afn+call_me%28num%3A+i32%29+%7B%0A++++for+i+in+0..num+%7B%0A++++++++println%21%28%22Ring%21+Call+number+%7B%7D%22%2C+i+%2B+1%29%3B%0A++++%7D%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+This+time%2C+the+function+*declaration*+is+okay%2C+but+there%27s+something+wrong%0A%2F%2F+with+the+place+where+we%27re+calling+the+function.%0A)
-- ["functions4.rs"](https://play.rust-lang.org/?code=%2F%2F+functions4.rs%0A%2F%2F+Make+me+compile%21+Scroll+down+for+hints+%3A%29%0A%0A%2F%2F+This+store+is+having+a+sale+where+if+the+price+is+an+even+number%2C+you+get%0A%2F%2F+10+%28money+unit%29+off%2C+but+if+it%27s+an+odd+number%2C+it%27s+3+%28money+unit%29+less.%0A%0Afn+main%28%29+%7B%0A++++let+original_price+%3D+51%3B%0A++++println%21%28%22Your+sale+price+is+%7B%7D%22%2C+sale_price%28original_price%29%29%3B%0A%7D%0A%0Afn+sale_price%28price%3A+i32%29+-%3E+%7B%0A++++if+is_even%28price%29+%7B%0A++++++++price+-+10%0A++++%7D+else+%7B%0A++++++++price+-+3%0A++++%7D%0A%7D%0A%0Afn+is_even%28num%3A+i32%29+-%3E+bool+%7B%0A++++num+%25+2+%3D%3D+0%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+The+error+message+points+to+line+12+and+says+it+expects+a+type+after+the%0A%2F%2F+%60-%3E%60.+This+is+where+the+function%27s+return+type+should+be--+take+a+look+at%0A%2F%2F+the+%60is_even%60+function+for+an+example%21%0A)
-- ["functions5.rs"](https://play.rust-lang.org/?code=%2F%2F+functions5.rs%0A%2F%2F+Make+me+compile%21+Scroll+down+for+hints+%3A%29%0A%0Afn+main%28%29+%7B%0A++++let+answer+%3D+square%283%29%3B%0A++++println%21%28%22The+answer+is+%7B%7D%22%2C+answer%29%3B%0A%7D%0A%0Afn+square%28num%3A+i32%29+-%3E+i32+%7B%0A++++num+*+num%3B%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+This+is+a+really+common+error+that+can+be+fixed+by+removing+one+character.%0A%2F%2F+It+happens+because+Rust+distinguishes+between+expressions+and+statements%3A+expressions+return%0A%2F%2F+a+value+and+statements+don%27t.+We+want+to+return+a+value+from+the+%60square%60+function%2C+but+it%0A%2F%2F+isn%27t+returning+one+right+now...%0A)
+```bash
+rustlings verify
+```
 
-### Primitive types
+This will try to verify the completion of every exercise in a predetermined order (what we think is best for newcomers). If you don't want to rerun `verify` every time you change a file, you can run:
 
-[Relevant chapter in The Rust Programming
-Language](https://doc.rust-lang.org/book/second-edition/ch03-02-data-types.html)
+```bash
+rustlings watch
+```
 
-- ["primitive_types1.rs"](https://play.rust-lang.org/?code=%2F%2F+primitive_types1.rs%0A%2F%2F+Fill+in+the+rest+of+the+line+that+has+code+missing%21%0A%2F%2F+No+hints%2C+there%27s+no+tricks%2C+just+get+used+to+typing+these+%3A%29%0A%0Afn+main%28%29+%7B%0A++++%2F%2F+Booleans+%28%60bool%60%29%0A%0A++++let+is_morning+%3D+true%3B%0A++++if+is_morning+%7B%0A++++++++println%21%28%22Good+morning%21%22%29%3B%0A++++%7D%0A%0A++++let+%2F%2F+Finish+the+rest+of+this+line+like+the+example%21+Or+make+it+be+false%21%0A++++if+is_evening+%7B%0A++++++++println%21%28%22Good+evening%21%22%29%3B%0A++++%7D%0A%7D%0A)
-- ["primitive_types2.rs"](https://play.rust-lang.org/?code=%2F%2F+primitive_types2.rs%0A%2F%2F+Fill+in+the+rest+of+the+line+that+has+code+missing%21%0A%2F%2F+No+hints%2C+there%27s+no+tricks%2C+just+get+used+to+typing+these+%3A%29%0A%0Afn+main%28%29+%7B%0A++++%2F%2F+Characters+%28%60char%60%29%0A%0A++++let+my_first_initial+%3D+%27C%27%3B%0A++++if+my_first_initial.is_alphabetic%28%29+%7B%0A++++++++println%21%28%22Alphabetical%21%22%29%3B%0A++++%7D+else+if+my_first_initial.is_numeric%28%29+%7B%0A++++++++println%21%28%22Numerical%21%22%29%3B%0A++++%7D+else+%7B%0A++++++++println%21%28%22Neither+alphabetic+nor+numeric%21%22%29%3B%0A++++%7D%0A%0A++++let+%2F%2F+Finish+this+line+like+the+example%21+What%27s+your+favorite+character%3F%0A++++%2F%2F+Try+a+letter%2C+try+a+number%2C+try+a+special+character%2C+try+a+character%0A++++%2F%2F+from+a+different+language+than+your+own%2C+try+an+emoji%21%0A++++if+your_character.is_alphabetic%28%29+%7B%0A++++++++println%21%28%22Alphabetical%21%22%29%3B%0A++++%7D+else+if+your_character.is_numeric%28%29+%7B%0A++++++++println%21%28%22Numerical%21%22%29%3B%0A++++%7D+else+%7B%0A++++++++println%21%28%22Neither+alphabetic+nor+numeric%21%22%29%3B%0A++++%7D%0A%7D%0A)
-- ["primitive_types3.rs"](https://play.rust-lang.org/?code=%2F%2F+primitive_types3.rs%0A%2F%2F+Create+an+array+with+at+least+100+elements+in+it+where+the+%3F%3F%3F+is.+%0A%2F%2F+Scroll+down+for+hints%21%0A%0Afn+main%28%29+%7B%0A++++let+a+%3D+%3F%3F%3F%0A%0A++++if+a.len%28%29+%3E%3D+100+%7B%0A++++++++println%21%28%22Wow%2C+that%27s+a+big+array%21%22%29%3B%0A++++%7D+else+%7B%0A++++++++println%21%28%22Meh%2C+I+eat+arrays+like+that+for+breakfast.%22%29%3B%0A++++%7D%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+There%27s+a+shorthand+to+initialize+Arrays+with+a+certain+size+that+does+not+%0A%2F%2F+require+you+to+type+in+100+items+%28but+you+certainly+can+if+you+want%21%29.%0A%2F%2F+For+example%2C+you+can+do%3A%0A%2F%2F+let+array+%3D+%5B%22Are+we+there+yet%3F%22%3B+10%5D%3B%0A%0A%2F%2F+Bonus%3A+what+are+some+other+things+you+could+have+that+would+return+true%0A%2F%2F+for+%60a.len%28%29+%3E%3D+100%60%3F%0A)
-- ["primitive_types4.rs"](https://play.rust-lang.org/?code=%2F%2F+primitive_types4.rs%0A%2F%2F+Get+a+slice+out+of+Array+a+where+the+%3F%3F%3F+is+so+that+the+%60if%60+statement%0A%2F%2F+returns+true.+Scroll+down+for+hints%21%21%0A%0Afn+main%28%29+%7B%0A++++let+a+%3D+%5B1%2C+2%2C+3%2C+4%2C+5%5D%3B%0A%0A++++let+nice_slice+%3D+%3F%3F%3F%0A%0A++++if+nice_slice+%3D%3D+%5B2%2C+3%2C+4%5D+%7B%0A++++++++println%21%28%22Nice+slice%21%22%29%3B%0A++++%7D+else+%7B%0A++++++++println%21%28%22Not+quite+what+I+was+expecting...+I+see%3A+%7B%3A%3F%7D%22%2C+nice_slice%29%3B%0A++++%7D%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+Take+a+look+at+the+Understanding+Ownership+-%3E+Slices+-%3E+Other+Slices+section+of+the+book%3A%0A%2F%2F+https%3A%2F%2Fdoc.rust-lang.org%2Fstable%2Fbook%2Fsecond-edition%2Fch04-03-slices.html%23other-slices%0A%2F%2F+and+use+the+starting+and+ending+indices+of+the+items+in+the+Array%0A%2F%2F+that+you+want+to+end+up+in+the+slice.%0A%0A%2F%2F+If+you%27re+curious+why+the+right+hand+of+the+%60%3D%3D%60+comparison+does+not%0A%2F%2F+have+an+ampersand+for+a+reference+since+the+left+hand+side+is+a%0A%2F%2F+reference%2C+take+a+look+at+the+Deref+coercions+section+of+the+book%3A%0A%2F%2F+https%3A%2F%2Fdoc.rust-lang.org%2Fstable%2Fbook%2Fsecond-edition%2Fch15-02-deref.html%23implicit-deref-coercions-with-functions-and-methods%0A)
-- ["primitive_types5.rs"](https://play.rust-lang.org/?code=%2F%2F+primitive_types5.rs%0A%2F%2F+Destructure+the+%60cat%60+tuple+so+that+the+println+will+work.%0A%2F%2F+Scroll+down+for+hints%21%0A%0Afn+main%28%29+%7B%0A++++let+cat+%3D+%28%22Furry+McFurson%22%2C+3.5%29%3B%0A++++let+%2F*+your+pattern+here+*%2F+%3D+cat%3B%0A%0A++++println%21%28%22%7B%7D+is+%7B%7D+years+old.%22%2C+name%2C+age%29%3B%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+Take+a+look+at+the+Data+Types+-%3E+The+Tuple+Type+section+of+the+book%3A%0A%2F%2F+https%3A%2F%2Fdoc.rust-lang.org%2Fstable%2Fbook%2Fsecond-edition%2Fch03-02-data-types.html%23the-tuple-type%0A%2F%2F+Particularly+the+part+about+destructuring+%28second+to+last+example+in+the+section%29.+%0A%2F%2F+You%27ll+need+to+make+a+pattern+to+bind+%60name%60+and+%60age%60+to+the+appropriate+parts%0A%2F%2F+of+the+tuple.+You+can+do+it%21%21%0A)
-- ["primitive_types6.rs"](https://play.rust-lang.org/?code=%2F%2F+primitive_types6.rs%0A%2F%2F+Use+a+tuple+index+to+access+the+second+element+of+%60numbers%60.%0A%2F%2F+You+can+put+this+right+into+the+%60println%21%60+where+the+%3F%3F%3F+is.%0A%2F%2F+Scroll+down+for+hints%21%0A%0Afn+main%28%29+%7B%0A++++let+numbers+%3D+%281%2C+2%2C+3%29%3B%0A++++println%21%28%22The+second+number+is+%7B%7D%22%2C+%3F%3F%3F%29%3B%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+While+you+could+use+a+destructuring+%60let%60+for+the+tuple+here%2C+try+%0A%2F%2F+indexing+into+it+instead%2C+as+explained+in+the+last+example+of+the+%0A%2F%2F+Data+Types+-%3E+The+Tuple+Type+section+of+the+book%3A%0A%2F%2F+https%3A%2F%2Fdoc.rust-lang.org%2Fstable%2Fbook%2Fsecond-edition%2Fch03-02-data-types.html%23the-tuple-type%0A%2F%2F+Now+you+have+another+tool+in+your+toolbox%21%0A)
+This will do the same as verify, but won't quit after running and instead automatically rerun as soon as you change a file in the `exercises/` directory.
 
-### Tests
+In case you want to go by your own order, or want to only verify a single exercise, you can run:
 
-Going out of order from the book to cover tests-- many of the following exercises will ask you to
-make tests pass!
+```bash
+rustlings run exercises/path/to/exercise.rs
+```
 
-[Relevant chapter in The Rust Programming
-Language](https://doc.rust-lang.org/book/second-edition/ch11-01-writing-tests.html)
+Or if it's a `#[test]`:
 
-- ["tests1.rs"](https://play.rust-lang.org/?code=%2F%2F+tests1.rs%0A%2F%2F+Tests+are+important+to+ensure+that+your+code+does+what+you+think+it+should+do.%0A%2F%2F+Tests+can+be+run+on+this+file+with+the+following+command%3A%0A%2F%2F+rustc+--test+tests1.rs%0A%0A%2F%2F+This+test+has+a+problem+with+it+--+make+the+test+compile%21+Make+the+test%0A%2F%2F+pass%21+Make+the+test+fail%21+Scroll+down+for+hints+%3A%29%0A%0A%23%5Bcfg%28test%29%5D%0Amod+tests+%7B%0A++++%23%5Btest%5D%0A++++fn+you_can_assert%28%29+%7B%0A++++++++assert%21%28%29%3B%0A++++%7D%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+You+don%27t+even+need+to+write+any+code+to+test+--+you+can+just+test+values+and+run+that%2C+even%0A%2F%2F+though+you+wouldn%27t+do+that+in+real+life+%3A%29+%60assert%21%60+is+a+macro+that+needs+an+argument.%0A%2F%2F+Depending+on+the+value+of+the+argument%2C+%60assert%21%60+will+do+nothing+%28in+which+case+the+test+will%0A%2F%2F+pass%29+or+%60assert%21%60+will+panic+%28in+which+case+the+test+will+fail%29.+So+try+giving+different+values%0A%2F%2F+to+%60assert%21%60+and+see+which+ones+compile%2C+which+ones+pass%2C+and+which+ones+fail+%3A%29%0A)
-- ["tests2.rs"](https://play.rust-lang.org/?code=%2F%2F+tests2.rs%0A%2F%2F+This+test+has+a+problem+with+it+--+make+the+test+compile%21+Make+the+test%0A%2F%2F+pass%21+Make+the+test+fail%21+Scroll+down+for+hints+%3A%29%0A%0A%23%5Bcfg%28test%29%5D%0Amod+tests+%7B%0A++++%23%5Btest%5D%0A++++fn+you_can_assert_eq%28%29+%7B%0A++++++++assert_eq%21%28%29%3B%0A++++%7D%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+Like+the+previous+exercise%2C+you+don%27t+need+to+write+any+code+to+get+this+test+to+compile+and%0A%2F%2F+run.+%60assert_eq%21%60+is+a+macro+that+takes+two+arguments+and+compares+them.+Try+giving+it+two%0A%2F%2F+values+that+are+equal%21+Try+giving+it+two+arguments+that+are+different%21+Try+giving+it+two+values%0A%2F%2F+that+are+of+different+types%21+Try+switching+which+argument+comes+first+and+which+comes+second%21%0A)
-- ["tests3.rs"](https://play.rust-lang.org/?code=%2F%2F+tests3.rs%0A%2F%2F+This+test+isn%27t+testing+our+function+--+make+it+do+that+in+such+a+way+that%0A%2F%2F+the+test+passes.+Then+write+a+second+test+that+tests+that+we+get+the+result%0A%2F%2F+we+expect+to+get+when+we+call+%60is_even%285%29%60.+Scroll+down+for+hints%21%0A%0Apub+fn+is_even%28num%3A+i32%29+-%3E+bool+%7B%0A++++num+%25+2+%3D%3D+0%0A%7D%0A%0A%23%5Bcfg%28test%29%5D%0Amod+tests+%7B%0A++++use+super%3A%3A*%3B%0A%0A++++%23%5Btest%5D%0A++++fn+is_true_when_even%28%29+%7B%0A++++++++assert%21%28false%29%3B%0A++++%7D%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+You+can+call+a+function+right+where+you%27re+passing+arguments+to+%60assert%21%60+--+so+you+could+do%0A%2F%2F+something+like+%60assert%21%28having_fun%28%29%29%60.+If+you+want+to+check+that+you+indeed+get+false%2C+you%0A%2F%2F+can+negate+the+result+of+what+you%27re+doing+using+%60%21%60%2C+like+%60assert%21%28%21having_fun%28%29%29%60.%0A)
-- ["tests4.rs"](https://play.rust-lang.org/?code=%2F%2F+tests4.rs%0A%2F%2F+This+test+isn%27t+testing+our+function+--+make+it+do+that+in+such+a+way+that%0A%2F%2F+the+test+passes.+Then+write+a+second+test+that+tests+that+we+get+the+result%0A%2F%2F+we+expect+to+get+when+we+call+%60times_two%60+with+a+negative+number.%0A%2F%2F+No+hints%2C+you+can+do+this+%3A%29%0A%0Apub+fn+times_two%28num%3A+i32%29+-%3E+i32+%7B%0A++++num+*+2%0A%7D%0A%0A%23%5Bcfg%28test%29%5D%0Amod+tests+%7B%0A++++use+super%3A%3A*%3B%0A%0A++++%23%5Btest%5D%0A++++fn+returns_twice_of_positive_numbers%28%29+%7B%0A++++++++assert_eq%21%284%2C+4%29%3B%0A++++%7D%0A%7D%0A)
+```bash
+rustlings run --test exercises/path/to/exercise_with_test.rs
+```
 
-### If
+In case you get stuck, there is usually a hint at the bottom of each exercise.
 
-[Relevant chapter in The Rust Programming
-Language](https://doc.rust-lang.org/book/second-edition/ch03-05-control-flow.html)
+## Testing yourself
 
-- ["if1.rs"](https://play.rust-lang.org/?code=%2F%2F+if1.rs%0A%0Apub+fn+bigger%28a%3A+i32%2C+b%3Ai32%29+-%3E+i32+%7B%0A++++%2F%2F+Complete+this+function+to+return+the+bigger+number%21%0A++++%2F%2F+Do+not+use%3A%0A++++%2F%2F+-+return%0A++++%2F%2F+-+another+function+call%0A++++%2F%2F+-+additional+variables%0A++++%2F%2F+Scroll+down+for+hints.%0A%7D%0A%0A%23%5Bcfg%28test%29%5D%0Amod+tests+%7B%0A++++use+super%3A%3A*%3B%0A%0A++++%23%5Btest%5D%0A++++fn+ten_is_bigger_than_eight%28%29+%7B%0A++++++++assert_eq%21%2810%2C+bigger%2810%2C+8%29%29%3B%0A++++%7D%0A%0A++++%23%5Btest%5D%0A++++fn+fortytwo_is_bigger_than_thirtytwo%28%29+%7B%0A++++++++assert_eq%21%2842%2C+bigger%2832%2C+42%29%29%3B%0A++++%7D%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+It%27s+possible+to+do+this+in+one+line+if+you+would+like%21%0A%2F%2F+Some+similar+examples+from+other+languages%3A%0A%2F%2F+-+In+C%28%2B%2B%29+this+would+be%3A+%60a+%3E+b+%3F+a+%3A+b%60%0A%2F%2F+-+In+Python+this+would+be%3A++%60a+if+a+%3E+b+else+b%60%0A%2F%2F+Remember+in+Rust+that%3A%0A%2F%2F+-+the+%60if%60+condition+does+not+need+to+be+surrounded+by+parentheses%0A%2F%2F+-+%60if%60%2F%60else%60+conditionals+are+expressions%0A%2F%2F+-+Each+condition+is+followed+by+a+%60%7B%7D%60+block.%0A)
+After every couple of sections, there will be a test that'll test your knowledge on a bunch of sections at once. These tests are found in `exercises/testN.rs`.
 
-### Strings
+## Completion
 
-[Relevant chapter in The Rust Programming
-Language](https://doc.rust-lang.org/book/second-edition/ch08-02-strings.html)
+Rustlings isn't done; there are a couple of sections that are very experimental and don't have proper documentation. These include:
 
-- ["strings1.rs"](https://play.rust-lang.org/?code=%2F%2F+strings1.rs%0A%2F%2F+Make+me+compile+without+changing+the+function+signature%21+Scroll+down+for+hints+%3A%29%0A%0Afn+main%28%29+%7B%0A++++let+answer+%3D+current_favorite_color%28%29%3B%0A++++println%21%28%22My+current+favorite+color+is+%7B%7D%22%2C+answer%29%3B%0A%7D%0A%0Afn+current_favorite_color%28%29+-%3E+String+%7B%0A++++%22blue%22%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+The+%60current_favorite_color%60+function+is+currently+returning+a+string+slice+with+the+%60%27static%60%0A%2F%2F+lifetime.+We+know+this+because+the+data+of+the+string+lives+in+our+code+itself+--+it+doesn%27t%0A%2F%2F+come+from+a+file+or+user+input+or+another+program+--+so+it+will+live+as+long+as+our+program%0A%2F%2F+lives.+But+it+is+still+a+string+slice.+There%27s+one+way+to+create+a+%60String%60+by+converting+a%0A%2F%2F+string+slice+covered+in+the+Strings+chapter+of+the+book%2C+and+another+way+that+uses+the+%60From%60%0A%2F%2F+trait.%0A)
-- ["strings2.rs"](https://play.rust-lang.org/?code=%2F%2F+strings2.rs%0A%2F%2F+Make+me+compile+without+changing+the+function+signature%21+Scroll+down+for+hints+%3A%29%0A%0Afn+main%28%29+%7B%0A++++let+word+%3D+String%3A%3Afrom%28%22green%22%29%3B+%2F%2F+Try+not+changing+this+line+%3A%29%0A++++if+is_a_color_word%28word%29+%7B%0A++++++++println%21%28%22That+is+a+color+word+I+know%21%22%29%3B%0A++++%7D+else+%7B%0A++++++++println%21%28%22That+is+not+a+color+word+I+know.%22%29%3B%0A++++%7D%0A%7D%0A%0Afn+is_a_color_word%28attempt%3A+%26str%29+-%3E+bool+%7B%0A++++attempt+%3D%3D+%22green%22+%7C%7C+attempt+%3D%3D+%22blue%22+%7C%7C+attempt+%3D%3D+%22red%22%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+Yes%2C+it+would+be+really+easy+to+fix+this+by+just+changing+the+value+bound+to+%60word%60+to+be+a%0A%2F%2F+string+slice+instead+of+a+%60String%60%2C+wouldn%27t+it%3F%3F+There+is+a+way+to+add+one+character+to+line%0A%2F%2F+6%2C+though%2C+that+will+coerce+the+%60String%60+into+a+string+slice.%0A)
-- ["strings3.rs"](https://play.rust-lang.org/?code=%2F%2F+strings3.rs%0A%2F%2F+Ok%2C+here+are+a+bunch+of+values--+some+are+%60Strings%60%2C+some+are+%60%26strs%60.+Your%0A%2F%2F+task+is+to+call+one+of+these+two+functions+on+each+value+depending+on+what%0A%2F%2F+you+think+each+value+is.+That+is%2C+add+either+%60string_slice%60+or+%60string%60%0A%2F%2F+before+the+parentheses+on+each+line.+If+you%27re+right%2C+it+will+compile%21%0A%0Afn+string_slice%28arg%3A+%26str%29+%7B+println%21%28%22%7B%7D%22%2C+arg%29%3B+%7D%0Afn+string%28arg%3A+String%29+%7B+println%21%28%22%7B%7D%22%2C+arg%29%3B+%7D%0A%0Afn+main%28%29+%7B%0A++++%28%22blue%22%29%3B%0A++++%28%22red%22.to_string%28%29%29%3B%0A++++%28String%3A%3Afrom%28%22hi%22%29%29%3B%0A++++%28%22rust+is+fun%21%22.to_owned%28%29%29%3B%0A++++%28%22nice+weather%22.into%28%29%29%3B%0A++++%28format%21%28%22Interpolation+%7B%7D%22%2C+%22Station%22%29%29%3B%0A++++%28%26String%3A%3Afrom%28%22abc%22%29%5B0..1%5D%29%3B%0A++++%28%22++hello+there+%22.trim%28%29%29%3B%0A++++%28%22Happy+Monday%21%22.to_string%28%29.replace%28%22Mon%22%2C+%22Tues%22%29%29%3B%0A++++%28%22mY+sHiFt+KeY+iS+sTiCkY%22.to_lowercase%28%29%29%3B%0A%7D%0A)
+- Errors (`exercises/errors/`)
+- Option (`exercises/option/`)
+- Result (`exercises/result/`)
+- Move Semantics (could still be improved, `exercises/move_semantics/`)
 
-### Move semantics
+Additionally, we could use exercises on a couple of topics:
 
-These exercises are adapted from [pnkfelix]()'s [Rust
-Tutorial](https://pnkfelix.github.io/rust-examples-icfp2014/) -- thank you Felix!!!
+- Structs
+- Better ownership stuff
+- `impl`
+- ??? probably more
 
-Relevant chapters in the book:
+If you are interested in improving or adding new ones, please feel free to contribute! Read on for more information :)
 
-- [Ownership](https://doc.rust-lang.org/book/second-edition/ch04-01-what-is-ownership.html)
-- [References and borrowing](https://doc.rust-lang.org/book/second-edition/ch04-02-references-and-borrowing.html)
+## Contributing
 
-Note that the exercises in this section may look similar to each other but they are subtly
-different :)
+### Adding an exercise
 
-- ["move_semantics1.rs"](https://play.rust-lang.org/?code=%2F%2F+move_semantics1.rs%0A%2F%2F+Make+me+compile%21+Scroll+down+for+hints+%3A%29%0A%0Apub+fn+main%28%29+%7B%0A++++let+vec0+%3D+Vec%3A%3Anew%28%29%3B%0A%0A++++let+vec1+%3D+fill_vec%28vec0%29%3B%0A%0A++++println%21%28%22%7B%7D+has+length+%7B%7D+content+%60%7B%3A%3F%7D%60%22%2C+%22vec1%22%2C+vec1.len%28%29%2C+vec1%29%3B%0A%0A++++vec1.push%2888%29%3B%0A%0A++++println%21%28%22%7B%7D+has+length+%7B%7D+content+%60%7B%3A%3F%7D%60%22%2C+%22vec1%22%2C+vec1.len%28%29%2C+vec1%29%3B%0A%0A%7D%0A%0Afn+fill_vec%28vec%3A+Vec%3Ci32%3E%29+-%3E+Vec%3Ci32%3E+%7B%0A++++let+mut+vec+%3D+vec%3B%0A%0A++++vec.push%2822%29%3B%0A++++vec.push%2844%29%3B%0A++++vec.push%2866%29%3B%0A%0A++++vec%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+So+you%27ve+got+the+%22cannot+borrow+immutable+local+variable+%60vec1%60+as+mutable%22+error+on+line+11%2C%0A%2F%2F+right%3F+The+fix+for+this+is+going+to+be+adding+one+keyword%2C+and+the+addition+is+NOT+on+line+11%0A%2F%2F+where+the+error+is.%0A)
-- ["move_semantics2.rs"](https://play.rust-lang.org/?code=%2F%2F+move_semantics2.rs%0A%2F%2F+Make+me+compile+without+changing+line+10%21+Scroll+down+for+hints+%3A%29%0A%0Apub+fn+main%28%29+%7B%0A++++let+vec0+%3D+Vec%3A%3Anew%28%29%3B%0A%0A++++let+mut+vec1+%3D+fill_vec%28vec0%29%3B%0A%0A++++%2F%2F+Do+not+change+the+following+line%21%0A++++println%21%28%22%7B%7D+has+length+%7B%7D+content+%60%7B%3A%3F%7D%60%22%2C+%22vec0%22%2C+vec0.len%28%29%2C+vec0%29%3B%0A%0A++++vec1.push%2888%29%3B%0A%0A++++println%21%28%22%7B%7D+has+length+%7B%7D+content+%60%7B%3A%3F%7D%60%22%2C+%22vec1%22%2C+vec1.len%28%29%2C+vec1%29%3B%0A%0A%7D%0A%0Afn+fill_vec%28vec%3A+Vec%3Ci32%3E%29+-%3E+Vec%3Ci32%3E+%7B%0A++++let+mut+vec+%3D+vec%3B%0A%0A++++vec.push%2822%29%3B%0A++++vec.push%2844%29%3B%0A++++vec.push%2866%29%3B%0A%0A++++vec%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+So+%60vec0%60+is+being+*moved*+into+the+function+%60fill_vec%60+when+we+call+it+on%0A%2F%2F+line+7%2C+which+means+it+gets+dropped+at+the+end+of+%60fill_vec%60%2C+which+means+we%0A%2F%2F+can%27t+use+%60vec0%60+again+on+line+10+%28or+anywhere+else+in+%60main%60+after+the%0A%2F%2F+%60fill_vec%60+call+for+that+matter%29.+We+could+fix+this+in+a+few+ways%2C+try+them%0A%2F%2F+all%21%0A%2F%2F+1.+Make+another%2C+separate+version+of+the+data+that%27s+in+%60vec0%60+and+pass+that%0A%2F%2F+to+%60fill_vec%60+instead.%0A%2F%2F+2.+Make+%60fill_vec%60+borrow+its+argument+instead+of+taking+ownership+of+it%2C%0A%2F%2F+and+then+copy+the+data+within+the+function+in+order+to+return+an+owned%0A%2F%2F+%60Vec%3Ci32%3E%60%0A%2F%2F+3.+Make+%60fill_vec%60+*mutably*+borrow+its+argument+%28which+will+need+to+be%0A%2F%2F+mutable%29%2C+modify+it+directly%2C+then+not+return+anything.+Then+you+can+get+rid%0A%2F%2F+of+%60vec1%60+entirely+--+note+that+this+will+change+what+gets+printed+by+the%0A%2F%2F+first+%60println%21%60%0A)
-- ["move_semantics3.rs"](https://play.rust-lang.org/?code=%2F%2F+move_semantics3.rs%0A%2F%2F+Make+me+compile+without+adding+new+lines--+just+changing+existing+lines%21%0A%2F%2F+%28no+lines+with+multiple+semicolons+necessary%21%29%0A%2F%2F+Scroll+down+for+hints+%3A%29%0A%0Apub+fn+main%28%29+%7B%0A++++let+vec0+%3D+Vec%3A%3Anew%28%29%3B%0A%0A++++let+mut+vec1+%3D+fill_vec%28vec0%29%3B%0A%0A++++println%21%28%22%7B%7D+has+length+%7B%7D+content+%60%7B%3A%3F%7D%60%22%2C+%22vec1%22%2C+vec1.len%28%29%2C+vec1%29%3B%0A%0A++++vec1.push%2888%29%3B%0A%0A++++println%21%28%22%7B%7D+has+length+%7B%7D+content+%60%7B%3A%3F%7D%60%22%2C+%22vec1%22%2C+vec1.len%28%29%2C+vec1%29%3B%0A%0A%7D%0A%0Afn+fill_vec%28vec%3A+Vec%3Ci32%3E%29+-%3E+Vec%3Ci32%3E+%7B%0A++++vec.push%2822%29%3B%0A++++vec.push%2844%29%3B%0A++++vec.push%2866%29%3B%0A%0A++++vec%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+The+difference+between+this+one+and+the+previous+ones+is+that+the+first+line%0A%2F%2F+of+%60fn+fill_vec%60+that+had+%60let+mut+vec+%3D+vec%3B%60+is+no+longer+there.+You+can%2C%0A%2F%2F+instead+of+adding+that+line+back%2C+add+%60mut%60+in+one+place+that+will+change%0A%2F%2F+an+existing+binding+to+be+a+mutable+binding+instead+of+an+immutable+one+%3A%29%0A)
-- ["move_semantics4.rs"](https://play.rust-lang.org/?code=%2F%2F+move_semantics4.rs%0A%2F%2F+Refactor+this+code+so+that+instead+of+having+%60vec0%60+and+creating+the+vector%0A%2F%2F+in+%60fn+main%60%2C+we+instead+create+it+within+%60fn+fill_vec%60+and+transfer+the%0A%2F%2F+freshly+created+vector+from+fill_vec+to+its+caller.+Scroll+for+hints%21%0A%0Apub+fn+main%28%29+%7B%0A++++let+vec0+%3D+Vec%3A%3Anew%28%29%3B%0A%0A++++let+mut+vec1+%3D+fill_vec%28vec0%29%3B%0A%0A++++println%21%28%22%7B%7D+has+length+%7B%7D+content+%60%7B%3A%3F%7D%60%22%2C+%22vec1%22%2C+vec1.len%28%29%2C+vec1%29%3B%0A%0A++++vec1.push%2888%29%3B%0A%0A++++println%21%28%22%7B%7D+has+length+%7B%7D+content+%60%7B%3A%3F%7D%60%22%2C+%22vec1%22%2C+vec1.len%28%29%2C+vec1%29%3B%0A%0A%7D%0A%0Afn+fill_vec%28vec%3A+Vec%3Ci32%3E%29+-%3E+Vec%3Ci32%3E+%7B%0A++++let+mut+vec+%3D+vec%3B%0A%0A++++vec.push%2822%29%3B%0A++++vec.push%2844%29%3B%0A++++vec.push%2866%29%3B%0A%0A++++vec%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+Stop+reading+whenever+you+feel+like+you+have+enough+direction+%3A%29+Or+try%0A%2F%2F+doing+one+step+and+then+fixing+the+compiler+errors+that+result%21%0A%2F%2F+So+the+end+goal+is+to%3A%0A%2F%2F+-+get+rid+of+the+first+line+in+main+that+creates+the+new+vector%0A%2F%2F+-+so+then+%60vec0%60+doesn%27t+exist%2C+so+we+can%27t+pass+it+to+%60fill_vec%60%0A%2F%2F+-+we+don%27t+want+to+pass+anything+to+%60fill_vec%60%2C+so+its+signature+should%0A%2F%2F+++reflect+that+it+does+not+take+any+arguments%0A%2F%2F+-+since+we%27re+not+creating+a+new+vec+in+%60main%60+anymore%2C+we+need+to+create%0A%2F%2F+++a+new+vec+in+%60fill_vec%60%2C+similarly+to+the+way+we+did+in+%60main%60%0A)
+First step is to add the exercise! Call it `exercises/yourTopic/yourTopicN.rs`, make sure to
+put in some helpful links, and link to sections of the book in `exercises/yourTopic/README.md`.
 
-### Modules
+Then, you'll want to make sure it gets verified when you run `rustlings verify`. Open `src/verify.rs` and
+put your exercise somewhere in there:
 
-[Relevant chapter in The Rust Programming
-Language](https://doc.rust-lang.org/book/second-edition/ch07-01-mod-and-the-filesystem.html)
+```diff
+  ...
+  compile_only("exercises/functions5.rs")?;
++ compile_only("exercises/yourTopic/yourTopicN.rs")?;
+  compile_only("exercises/test1.rs")?;
+  ...
+```
 
-- ["modules1.rs"](https://play.rust-lang.org/?code=%2F%2F+modules1.rs%0A%2F%2F+Make+me+compile%21+Scroll+down+for+hints+%3A%29%0A%0Amod+sausage_factory+%7B%0A++++fn+make_sausage%28%29+%7B%0A++++++++println%21%28%22sausage%21%22%29%3B%0A++++%7D%0A%7D%0A%0Afn+main%28%29+%7B%0A++++sausage_factory%3A%3Amake_sausage%28%29%3B%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+Everything+is+private+in+Rust+by+default--+but+there%27s+a+keyword+we+can+use%0A%2F%2F+to+make+something+public%21+The+compiler+error+should+point+to+the+thing+that%0A%2F%2F+needs+to+be+public.%0A)
-- ["modules2.rs"](https://play.rust-lang.org/?code=%2F%2F+modules2.rs%0A%2F%2F+Make+me+compile%21+Scroll+down+for+hints+%3A%29%0A%0Amod+us_presidential_frontrunners+%7B%0A++++use+self%3A%3Ademocrats%3A%3AHILLARY_CLINTON+as+democrat%3B%0A++++use+self%3A%3Arepublicans%3A%3ADONALD_TRUMP+as+republican%3B%0A%0A++++mod+democrats+%7B%0A++++++++pub+const+HILLARY_CLINTON%3A+%26%27static+str+%3D+%22Hillary+Clinton%22%3B%0A++++++++pub+const+BERNIE_SANDERS%3A+%26%27static+str+%3D+%22Bernie+Sanders%22%3B%0A++++%7D%0A%0A++++mod+republicans+%7B%0A++++++++pub+const+DONALD_TRUMP%3A+%26%27static+str+%3D+%22Donald+Trump%22%3B%0A++++++++pub+const+JEB_BUSH%3A+%26%27static+str+%3D+%22Jeb+Bush%22%3B%0A++++%7D%0A%7D%0A%0Afn+main%28%29+%7B%0A++++println%21%28%22candidates%3A+%7B%7D+and+%7B%7D%22%2C%0A+++++++++++++us_presidential_frontrunners%3A%3Ademocrat%2C%0A+++++++++++++us_presidential_frontrunners%3A%3Arepublican%29%3B%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+The+us_presidential_frontrunners+module+is+trying+to+present+an+external%0A%2F%2F+interface+%28the+%60democrat%60+and+%60republican%60+constants%29+that+is+different+than%0A%2F%2F+its+internal+structure+%28the+%60democrats%60+and+%60republicans%60+modules+and%0A%2F%2F+associated+constants%29.+It%27s+almost+there+except+for+one+keyword+missing+for%0A%2F%2F+each+constant.%0A)
+That's all!
 
-### Macros
+### Working on the source code
 
-Check out:
+`rustlings` is basically a glorified `rustc` wrapper. Therefore the source code
+isn't really that complicated since the bulk of the work is done by `rustc`.
+`src/main.rs` contains a simple `clap` CLI that loads from `src/verify.rs` and `src/run.rs`.
 
-- [The Macros section of the first edition of the book
-  book](https://doc.rust-lang.org/book/first-edition/macros.html)
-- [The Macros appendix of the second edition of the
-  book](https://doc.rust-lang.org/book/second-edition/appendix-04-macros.html)
-- [The Little Book of Rust Macros](https://danielkeep.github.io/tlborm/book/index.html)
+## Credits
 
-- ["macros1.rs"](https://play.rust-lang.org/?code=%2F%2F+macros1.rs%0A%2F%2F+Make+me+compile%21+Scroll+down+for+hints+%3A%29%0A%0Amacro_rules%21+my_macro+%7B%0A++++%28%29+%3D%3E+%7B%0A++++++++println%21%28%22Check+out+my+macro%21%22%29%3B%0A++++%7D%3B%0A%7D%0A%0Afn+main%28%29+%7B%0A++++my_macro%28%29%3B%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+When+you+call+a+macro%2C+you+need+to+add+something+special+compared+to+a%0A%2F%2F+regular+function+call.+If+you%27re+stuck%2C+take+a+look+at+what%27s+inside%0A%2F%2F+%60my_macro%60.%0A)
-- ["macros2.rs"](https://play.rust-lang.org/?code=%2F%2F+macros2.rs%0A%2F%2F+Make+me+compile%21+Scroll+down+for+hints+%3A%29%0A%0Afn+main%28%29+%7B%0A++++my_macro%21%28%29%3B%0A%7D%0A%0Amacro_rules%21+my_macro+%7B%0A++++%28%29+%3D%3E+%7B%0A++++++++println%21%28%22Check+out+my+macro%21%22%29%3B%0A++++%7D%3B%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+Macros+don%27t+quite+play+by+the+same+rules+as+the+rest+of+Rust%2C+in+terms+of%0A%2F%2F+what%27s+available+where.%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+Unlike+other+things+in+Rust%2C+the+order+of+%22where+you+define+a+macro%22+versus%0A%2F%2F+%22where+you+use+it%22+actually+matters.%0A)
-- ["macros3.rs"](https://play.rust-lang.org/?code=%2F%2F+macros3.rs%0A%2F%2F+Make+me+compile%2C+without+taking+the+macro+out+of+the+module%21+Scroll+down+for+hints+%3A%29%0A%0Amod+macros+%7B%0A++++macro_rules%21+my_macro+%7B%0A++++++++%28%29+%3D%3E+%7B%0A++++++++++++println%21%28%22Check+out+my+macro%21%22%29%3B%0A++++++++%7D%3B%0A++++%7D%0A%7D%0A%0Afn+main%28%29+%7B%0A++++my_macro%21%28%29%3B%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+In+order+to+use+a+macro+outside+of+its+module%2C+you+need+to+do+something%0A%2F%2F+special+to+the+module+to+lift+the+macro+out+into+its+parent.%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+The+same+trick+also+works+on+%22extern+crate%22+statements+for+crates+that+have%0A%2F%2F+exported+macros%2C+if+you%27ve+seen+any+of+those+around.%0A)
-- ["macros4.rs"](https://play.rust-lang.org/?code=%2F%2F+macros4.rs%0A%2F%2F+Make+me+compile%21+Scroll+down+for+hints+%3A%29%0A%0Amacro_rules%21+my_macro+%7B%0A++++%28%29+%3D%3E+%7B%0A++++++++println%21%28%22Check+out+my+macro%21%22%29%3B%0A++++%7D%0A++++%28%24val%3Aexpr%29+%3D%3E+%7B%0A++++++++println%21%28%22Look+at+this+other+macro%3A+%7B%7D%22%2C+%24val%29%3B%0A++++%7D%0A%7D%0A%0Afn+main%28%29+%7B%0A++++my_macro%21%28%29%3B%0A++++my_macro%21%287777%29%3B%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+You+only+need+to+add+a+single+character+to+make+this+compile.%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+The+way+macros+are+written%2C+it+wants+to+see+something+between+each%0A%2F%2F+%22macro+arm%22%2C+so+it+can+separate+them.%0A)
+`rustlings` was originally written by [Carol](https://github.com/carols10cents)!
 
-### Error Handling
-
-The [Error
-Handling](https://doc.rust-lang.org/book/second-edition/ch09-02-recoverable-errors-with-result.html)
-and [Generics](https://doc.rust-lang.org/book/second-edition/ch10-01-syntax.html) sections are
-relevant.
-
-- ["option1.rs"](https://play.rust-lang.org/?code=%2F%2F+option1.rs%0A%2F%2F+This+example+panics+because+the+second+time+it+calls+%60pop%60%2C+the+%60vec%60%0A%2F%2F+is+empty%2C+so+%60pop%60+returns+%60None%60%2C+and+%60unwrap%60+panics+if+it%27s+called%0A%2F%2F+on+%60None%60.+Handle+this+in+a+more+graceful+way+than+calling+%60unwrap%60%21%0A%2F%2F+Scroll+down+for+hints+%3A%29%0A%0Afn+main%28%29+%7B%0A++++let+mut+list+%3D+vec%21%5B3%5D%3B%0A%0A++++let+last+%3D+list.pop%28%29.unwrap%28%29%3B%0A++++println%21%28%22The+last+item+in+the+list+is+%7B%3A%3F%7D%22%2C+last%29%3B%0A%0A++++let+second_to_last+%3D+list.pop%28%29.unwrap%28%29%3B%0A++++println%21%28%22The+second-to-last+item+in+the+list+is+%7B%3A%3F%7D%22%2C+second_to_last%29%3B%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+Try+using+a+%60match%60+statement+where+the+arms+are+%60Some%28thing%29%60+and+%60None%60.%0A%2F%2F+Or+set+a+default+value+to+print+out+if+you+get+%60None%60+by+using+the%0A%2F%2F+function+%60unwrap_or%60.%0A%2F%2F+Or+use+an+%60if+let%60+statement+on+the+result+of+%60pop%28%29%60+to+both+destructure%0A%2F%2F+a+%60Some%60+value+and+only+print+out+something+if+we+have+a+value%21%0A)
-- ["result1.rs"](https://play.rust-lang.org/?code=%2F%2F+result1.rs%0A%2F%2F+Make+this+test+pass%21+Scroll+down+for+hints+%3A%29%0A%0A%23%5Bderive%28PartialEq%2CDebug%29%5D%0Astruct+PositiveNonzeroInteger%28u64%29%3B%0A%0A%23%5Bderive%28PartialEq%2CDebug%29%5D%0Aenum+CreationError+%7B%0A++++Negative%2C%0A++++Zero%2C%0A%7D%0A%0Aimpl+PositiveNonzeroInteger+%7B%0A++++fn+new%28value%3A+i64%29+-%3E+Result%3CPositiveNonzeroInteger%2C+CreationError%3E+%7B%0A++++++++Ok%28PositiveNonzeroInteger%28value+as+u64%29%29%0A++++%7D%0A%7D%0A%0A%23%5Btest%5D%0Afn+test_creation%28%29+%7B%0A++++assert%21%28PositiveNonzeroInteger%3A%3Anew%2810%29.is_ok%28%29%29%3B%0A++++assert_eq%21%28Err%28CreationError%3A%3ANegative%29%2C+PositiveNonzeroInteger%3A%3Anew%28-10%29%29%3B%0A++++assert_eq%21%28Err%28CreationError%3A%3AZero%29%2C+PositiveNonzeroInteger%3A%3Anew%280%29%29%3B%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+%60PositiveNonzeroInteger%3A%3Anew%60+is+always+creating+a+new+instance+and+returning+an+%60Ok%60+result.%0A%2F%2F+It+should+be+doing+some+checking%2C+returning+an+%60Err%60+result+if+those+checks+fail%2C+and+only%0A%2F%2F+returning+an+%60Ok%60+result+if+those+checks+determine+that+everything+is...+okay+%3A%29%0A)
-- ["errors1.rs"](https://play.rust-lang.org/?code=%2F%2F+errors1.rs%0A%2F%2F+This+function+refuses+to+generate+text+to+be+printed+on+a+nametag+if%0A%2F%2F+you+pass+it+an+empty+string.+It%27d+be+nicer+if+it+explained+what+the+problem%0A%2F%2F+was%2C+instead+of+just+sometimes+returning+%60None%60.+The+2nd+test+currently%0A%2F%2F+does+not+compile+or+pass%2C+but+it+illustrates+the+behavior+we+would+like%0A%2F%2F+this+function+to+have.%0A%2F%2F+Scroll+down+for+hints%21%21%21%0A%0Apub+fn+generate_nametag_text%28name%3A+String%29+-%3E+Option%3CString%3E+%7B%0A++++if+name.len%28%29+%3E+0+%7B%0A++++++++Some%28format%21%28%22Hi%21+My+name+is+%7B%7D%22%2C+name%29%29%0A++++%7D+else+%7B%0A++++++++%2F%2F+Empty+names+aren%27t+allowed.%0A++++++++None%0A++++%7D%0A%7D%0A%0A%23%5Bcfg%28test%29%5D%0Amod+tests+%7B%0A++++use+super%3A%3A*%3B%0A%0A++++%2F%2F+This+test+passes+initially+if+you+comment+out+the+2nd+test.%0A++++%2F%2F+You%27ll+need+to+update+what+this+test+expects+when+you+change%0A++++%2F%2F+the+function+under+test%21%0A++++%23%5Btest%5D%0A++++fn+generates_nametag_text_for_a_nonempty_name%28%29+%7B%0A++++++++assert_eq%21%28%0A++++++++++++generate_nametag_text%28%22Beyonc%C3%A9%22.into%28%29%29%2C%0A++++++++++++Some%28%22Hi%21+My+name+is+Beyonc%C3%A9%22.into%28%29%29%0A++++++++%29%3B%0A++++%7D%0A%0A++++%23%5Btest%5D%0A++++fn+explains_why_generating_nametag_text_fails%28%29+%7B%0A++++++++assert_eq%21%28%0A++++++++++++generate_nametag_text%28%22%22.into%28%29%29%2C%0A++++++++++++Err%28%22%60name%60+was+empty%3B+it+must+be+nonempty.%22.into%28%29%29%0A++++++++%29%3B%0A++++%7D%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+%60Err%60+is+one+of+the+variants+of+%60Result%60%2C+so+what+the+2nd+test+is+saying%0A%2F%2F+is+that+%60generate_nametag_text%60+should+return+a+%60Result%60+instead+of+an%0A%2F%2F+%60Option%60.%0A%0A%2F%2F+To+make+this+change%2C+you%27ll+need+to%3A%0A%2F%2F+-+update+the+return+type+in+the+function+signature+to+be+a+Result+that%0A%2F%2F+++could+be+the+variants+%60Ok%28String%29%60+and+%60Err%28String%29%60%0A%2F%2F+-+change+the+body+of+the+function+to+return+%60Ok%28stuff%29%60+where+it+currently%0A%2F%2F+++returns+%60Some%28stuff%29%60%0A%2F%2F+-+change+the+body+of+the+function+to+return+%60Err%28error+message%29%60+where+it%0A%2F%2F+++currently+returns+%60None%60%0A%2F%2F+-+change+the+first+test+to+expect+%60Ok%28stuff%29%60+where+it+currently+expects%0A%2F%2F+++%60Some%28stuff%29%60.%0A)
-- ["errors2.rs"](https://play.rust-lang.org/?code=%2F%2F+errors2.rs%0A%2F%2F+Say+we%27re+writing+a+game+where+you+can+buy+items+with+tokens.+All+items+cost%0A%2F%2F+5+tokens%2C+and+whenever+you+purchase+items+there+is+a+processing+fee+of+1%0A%2F%2F+token.+A+player+of+the+game+will+type+in+how+many+items+they+want+to+buy%2C%0A%2F%2F+and+the+%60total_cost%60+function+will+calculate+the+total+number+of+tokens.%0A%2F%2F+Since+the+player+typed+in+the+quantity%2C+though%2C+we+get+it+as+a+string--+and%0A%2F%2F+they+might+have+typed+anything%2C+not+just+numbers%21%0A%0A%2F%2F+Right+now%2C+this+function+isn%27t+handling+the+error+case+at+all+%28and+isn%27t%0A%2F%2F+handling+the+success+case+properly+either%29.+What+we+want+to+do+is%3A%0A%2F%2F+if+we+call+the+%60parse%60+function+on+a+string+that+is+not+a+number%2C+that%0A%2F%2F+function+will+return+a+%60ParseIntError%60%2C+and+in+that+case%2C+we+want+to%0A%2F%2F+immediately+return+that+error+from+our+function+and+not+try+to+multiply%0A%2F%2F+and+add.%0A%0A%2F%2F+There+are+at+least+two+ways+to+implement+this+that+are+both+correct--+but%0A%2F%2F+one+is+a+lot+shorter%21+Scroll+down+for+hints+to+both+ways.%0A%0Ause+std%3A%3Anum%3A%3AParseIntError%3B%0A%0Apub+fn+total_cost%28item_quantity%3A+%26str%29+-%3E+Result%3Ci32%2C+ParseIntError%3E+%7B%0A++++let+processing_fee+%3D+1%3B%0A++++let+cost_per_item+%3D+5%3B%0A++++let+qty+%3D+item_quantity.parse%3A%3A%3Ci32%3E%28%29%3B%0A%0A++++Ok%28qty+*+cost_per_item+%2B+processing_fee%29%0A%7D%0A%0A%23%5Bcfg%28test%29%5D%0Amod+tests+%7B%0A++++use+super%3A%3A*%3B%0A%0A++++%23%5Btest%5D%0A++++fn+item_quantity_is_a_valid_number%28%29+%7B%0A++++++++assert_eq%21%28%0A++++++++++++total_cost%28%2234%22%29%2C%0A++++++++++++Ok%28171%29%0A++++++++%29%3B%0A++++%7D%0A%0A++++%23%5Btest%5D%0A++++fn+item_quantity_is_an_invalid_number%28%29+%7B%0A++++++++assert_eq%21%28%0A++++++++++++total_cost%28%22beep+boop%22%29.unwrap_err%28%29.to_string%28%29%2C%0A++++++++++++%22invalid+digit+found+in+string%22%0A++++++++%29%3B%0A++++%7D%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+One+way+to+handle+this+is+using+a+%60match%60+statement+on%0A%2F%2F+%60item_quantity.parse%3A%3A%3Ci32%3E%28%29%60+where+the+cases+are+%60Ok%28something%29%60+and%0A%2F%2F+%60Err%28something%29%60.+This+pattern+is+very+common+in+Rust%2C+though%2C+so+there%27s%0A%2F%2F+a+%60%3F%60+operator+that+does+pretty+much+what+you+would+make+that+match+statement%0A%2F%2F+do+for+you%21+Take+a+look+at+this+section+of+the+Error+Handling+chapter%3A%0A%2F%2F+https%3A%2F%2Fdoc.rust-lang.org%2Fstable%2Fbook%2Fsecond-edition%2Fch09-02-recoverable-errors-with-result.html%23a-shortcut-for-propagating-errors-the--operator%0A%2F%2F+and+give+it+a+try%21%0A)
-- ["errors3.rs"](https://play.rust-lang.org/?code=%2F%2F+errors3.rs%0A%2F%2F+This+is+a+program+that+is+trying+to+use+a+completed+version+of+the%0A%2F%2F+%60total_cost%60+function+from+the+previous+exercise.+It%27s+not+working+though--%0A%2F%2F+we+can%27t+use+the+%60%3F%60+operator+in+the+%60main%28%29%60+function%21+Why+not%3F%0A%2F%2F+What+should+we+do+instead%3F+Scroll+for+hints%21%0A%0Ause+std%3A%3Anum%3A%3AParseIntError%3B%0A%0Afn+main%28%29+%7B%0A++++let+mut+tokens+%3D+100%3B%0A++++let+pretend_user_input+%3D+%228%22%3B%0A%0A++++let+cost+%3D+total_cost%28pretend_user_input%29%3F%3B%0A%0A++++if+cost+%3E+tokens+%7B%0A++++++++println%21%28%22You+can%27t+afford+that+many%21%22%29%3B%0A++++%7D+else+%7B%0A++++++++tokens+-%3D+cost%3B%0A++++++++println%21%28%22You+now+have+%7B%7D+tokens.%22%2C+tokens%29%3B%0A++++%7D%0A%7D%0A%0Apub+fn+total_cost%28item_quantity%3A+%26str%29+-%3E+Result%3Ci32%2C+ParseIntError%3E+%7B%0A++++let+processing_fee+%3D+1%3B%0A++++let+cost_per_item+%3D+5%3B%0A++++let+qty+%3D+item_quantity.parse%3A%3A%3Ci32%3E%28%29%3F%3B%0A%0A++++Ok%28qty+*+cost_per_item+%2B+processing_fee%29%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+Since+the+%60%3F%60+operator+returns+an+%60Err%60+early+if+the+thing+it%27s+trying+to%0A%2F%2F+do+fails%2C+you+can+only+use+the+%60%3F%60+operator+in+functions+that+have+a%0A%2F%2F+%60Result%60+as+their+return+type.%0A%0A%2F%2F+Hence+the+error+that+you+get+if+you+run+this+code+is%3A%0A%0A%2F%2F+%60%60%60%0A%2F%2F+error%5BE0277%5D%3A+the+%60%3F%60+operator+can+only+be+used+in+a+function+that+returns+%60Result%60+%28or+another+type+that+implements+%60std%3A%3Aops%3A%3ATry%60%29%0A%2F%2F+%60%60%60%0A%0A%2F%2F+So+we+have+to+use+another+way+of+handling+a+%60Result%60+within+%60main%60.%0A%0A%2F%2F+Decide+what+we+should+do+if+%60pretend_user_input%60+has+a+string+value+that+does%0A%2F%2F+not+parse+to+an+integer%2C+and+implement+that+instead+of+using+the+%60%3F%60%0A%2F%2F+operator.%0A)
-- ["errorsn.rs"](https://play.rust-lang.org/?code=%2F%2F+errorsn.rs%0A%2F%2F+This+is+a+bigger+error+exercise+than+the+previous+ones%21%0A%2F%2F+You+can+do+it%21+%3A%29%0A%2F%2F%0A%2F%2F+Edit+the+%60read_and_validate%60+function+so+that+it+compiles+and%0A%2F%2F+passes+the+tests...+so+many+things+could+go+wrong%21%0A%2F%2F%0A%2F%2F+-+Reading+from+stdin+could+produce+an+io%3A%3AError%0A%2F%2F+-+Parsing+the+input+could+produce+a+num%3A%3AParseIntError%0A%2F%2F+-+Validating+the+input+could+produce+a+CreationError+%28defined+below%29%0A%2F%2F%0A%2F%2F+How+can+we+lump+these+errors+into+one+general+error%3F+That+is%2C+what%0A%2F%2F+type+goes+where+the+question+marks+are%2C+and+how+do+we+return%0A%2F%2F+that+type+from+the+body+of+read_and_validate%3F%0A%2F%2F%0A%2F%2F+Scroll+down+for+hints+%3A%29%0A%0Ause+std%3A%3Aerror%3B%0Ause+std%3A%3Afmt%3B%0Ause+std%3A%3Aio%3B%0A%0A%2F%2F+PositiveNonzeroInteger+is+a+struct+defined+below+the+tests.%0Afn+read_and_validate%28b%3A+%26mut+io%3A%3ABufRead%29+-%3E+Result%3CPositiveNonzeroInteger%2C+%3F%3F%3F%3E+%7B%0A++++let+mut+line+%3D+String%3A%3Anew%28%29%3B%0A++++b.read_line%28%26mut+line%29%3B%0A++++let+num%3A+i64+%3D+line.trim%28%29.parse%28%29%3B%0A++++let+answer+%3D+PositiveNonzeroInteger%3A%3Anew%28num%29%3B%0A++++answer%0A%7D%0A%0A%2F%2F+This+is+a+test+helper+function+that+turns+a+%26str+into+a+BufReader.%0Afn+test_with_str%28s%3A+%26str%29+-%3E+Result%3CPositiveNonzeroInteger%2C+Box%3Cerror%3A%3AError%3E%3E+%7B%0A++++let+mut+b+%3D+io%3A%3ABufReader%3A%3Anew%28s.as_bytes%28%29%29%3B%0A++++read_and_validate%28%26mut+b%29%0A%7D%0A%0A%23%5Btest%5D%0Afn+test_success%28%29+%7B%0A++++let+x+%3D+test_with_str%28%2242%5Cn%22%29%3B%0A++++assert_eq%21%28PositiveNonzeroInteger%2842%29%2C+x.unwrap%28%29%29%3B%0A%7D%0A%0A%23%5Btest%5D%0Afn+test_not_num%28%29+%7B%0A++++let+x+%3D+test_with_str%28%22eleven+billion%5Cn%22%29%3B%0A++++assert%21%28x.is_err%28%29%29%3B%0A%7D%0A%0A%23%5Btest%5D%0Afn+test_non_positive%28%29+%7B%0A++++let+x+%3D+test_with_str%28%22-40%5Cn%22%29%3B%0A++++assert%21%28x.is_err%28%29%29%3B%0A%7D%0A%0A%23%5Btest%5D%0Afn+test_ioerror%28%29+%7B%0A++++struct+Broken%3B%0A++++impl+io%3A%3ARead+for+Broken+%7B%0A++++++++fn+read%28%26mut+self%2C+_buf%3A+%26mut+%5Bu8%5D%29+-%3E+io%3A%3AResult%3Cusize%3E+%7B%0A++++++++++++Err%28io%3A%3AError%3A%3Anew%28io%3A%3AErrorKind%3A%3ABrokenPipe%2C+%22uh-oh%21%22%29%29%0A++++++++%7D%0A++++%7D%0A++++let+mut+b+%3D+io%3A%3ABufReader%3A%3Anew%28Broken%29%3B%0A++++assert%21%28read_and_validate%28%26mut+b%29.is_err%28%29%29%3B%0A++++assert_eq%21%28%22uh-oh%21%22%2C+read_and_validate%28%26mut+b%29.unwrap_err%28%29.to_string%28%29%29%3B%0A%7D%0A%0A%23%5Bderive%28PartialEq%2CDebug%29%5D%0Astruct+PositiveNonzeroInteger%28u64%29%3B%0A%0Aimpl+PositiveNonzeroInteger+%7B%0A++++fn+new%28value%3A+i64%29+-%3E+Result%3CPositiveNonzeroInteger%2C+CreationError%3E+%7B%0A++++++++if+value+%3D%3D+0+%7B%0A++++++++++++Err%28CreationError%3A%3AZero%29%0A++++++++%7D+else+if+value+%3C+0+%7B%0A++++++++++++Err%28CreationError%3A%3ANegative%29%0A++++++++%7D+else+%7B%0A++++++++++++Ok%28PositiveNonzeroInteger%28value+as+u64%29%29%0A++++++++%7D%0A++++%7D%0A%7D%0A%0A%23%5Btest%5D%0Afn+test_positive_nonzero_integer_creation%28%29+%7B%0A++++assert%21%28PositiveNonzeroInteger%3A%3Anew%2810%29.is_ok%28%29%29%3B%0A++++assert_eq%21%28Err%28CreationError%3A%3ANegative%29%2C+PositiveNonzeroInteger%3A%3Anew%28-10%29%29%3B%0A++++assert_eq%21%28Err%28CreationError%3A%3AZero%29%2C+PositiveNonzeroInteger%3A%3Anew%280%29%29%3B%0A%7D%0A%0A%23%5Bderive%28PartialEq%2CDebug%29%5D%0Aenum+CreationError+%7B%0A++++Negative%2C%0A++++Zero%2C%0A%7D%0A%0Aimpl+fmt%3A%3ADisplay+for+CreationError+%7B%0A++++fn+fmt%28%26self%2C+f%3A+%26mut+fmt%3A%3AFormatter%29+-%3E+fmt%3A%3AResult+%7B%0A++++++++f.write_str%28%28self+as+%26error%3A%3AError%29.description%28%29%29%0A++++%7D%0A%7D%0A%0Aimpl+error%3A%3AError+for+CreationError+%7B%0A++++fn+description%28%26self%29+-%3E+%26str+%7B%0A++++++++match+*self+%7B%0A++++++++++++CreationError%3A%3ANegative+%3D%3E+%22Negative%22%2C%0A++++++++++++CreationError%3A%3AZero+%3D%3E+%22Zero%22%2C%0A++++++++%7D%0A++++%7D%0A%7D%0A%0A%2F%2F+First+hint%3A+To+figure+out+what+type+should+go+where+the+%3F%3F%3F+is%2C+take+a+look%0A%2F%2F+at+the+test+helper+function+%60test_with_str%60%2C+since+it+returns+whatever%0A%2F%2F+%60read_and_validate%60+returns+and%60test_with_str%60+has+its+signature+fully%0A%2F%2F+specified.%0A%0A%2F%2F+Next+hint%3A+There+are+three+places+in+%60read_and_validate%60+that+we+call+a%0A%2F%2F+function+that+returns+a+%60Result%60+%28that+is%2C+the+functions+might+fail%29.%0A%2F%2F+Apply+the+%60%3F%60+operator+on+those+calls+so+that+we+return+immediately+from%0A%2F%2F+%60read_and_validate%60+if+those+function+calls+fail.%0A%0A%2F%2F+Another+hint%3A+under+the+hood%2C+the+%60%3F%60+operator+calls+%60From%3A%3Afrom%60%0A%2F%2F+on+the+error+value+to+convert+it+to+a+boxed+trait+object%2C+a+Box%3Cerror%3A%3AError%3E%2C%0A%2F%2F+which+is+polymorphic--+that+means+that+lots+of+different+kinds+of+errors%0A%2F%2F+can+be+returned+from+the+same+function+because+all+errors+act+the+same%0A%2F%2F+since+they+all+implement+the+%60error%3A%3AError%60+trait.%0A%2F%2F+Check+out+this+section+of+the+book%3A%0A%2F%2F+https%3A%2F%2Fdoc.rust-lang.org%2Fstable%2Fbook%2Fsecond-edition%2Fch09-02-recoverable-errors-with-result.html%23a-shortcut-for-propagating-errors-the--operator%0A%0A%2F%2F+Another+another+hint%3A+Note+that+because+the+%60%3F%60+operator+returns%0A%2F%2F+the+*unwrapped*+value+in+the+%60Ok%60+case%2C+if+we+want+to+return+a+%60Result%60+from%0A%2F%2F+%60read_and_validate%60+for+*its*+success+case%2C+we%27ll+have+to+rewrap+a+value%0A%2F%2F+that+we+got+from+the+return+value+of+a+%60%3F%60ed+call+in+an+%60Ok%60--+this+will%0A%2F%2F+look+like+%60Ok%28something%29%60.%0A%0A%2F%2F+Another+another+another+hint%3A+%60Result%60s+must+be+%22used%22%2C+that+is%2C+you%27ll%0A%2F%2F+get+a+warning+if+you+don%27t+handle+a+%60Result%60+that+you+get+in+your%0A%2F%2F+function.+Read+more+about+that+in+the+%60std%3A%3Aresult%60+module+docs%3A%0A%2F%2F+https%3A%2F%2Fdoc.rust-lang.org%2Fstd%2Fresult%2F%23results-must-be-used%0A)
-
-### Standard library types
-
-#### `Arc`
-
-The [Concurrency](https://doc.rust-lang.org/book/second-edition/ch16-03-shared-state.html) section
-is relevant.
-
-- ["arc1.rs"](https://play.rust-lang.org/?code=%2F%2F+arc1.rs%0A%2F%2F+Make+this+code+compile+by+filling+in+a+value+for+%60shared_numbers%60+where+the%0A%2F%2F+TODO+comment+is+and+creating+an+initial+binding+for+%60child_numbers%60%0A%2F%2F+somewhere.+Try+not+to+create+any+copies+of+the+%60numbers%60+Vec%21%0A%2F%2F+Scroll+down+for+hints+%3A%29%0A%0Ause+std%3A%3Async%3A%3AArc%3B%0Ause+std%3A%3Athread%3B%0A%0Afn+main%28%29+%7B%0A++++let+numbers%3A+Vec%3C_%3E+%3D+%280..100u32%29.collect%28%29%3B%0A++++let+shared_numbers+%3D+%2F%2F+TODO%0A++++let+mut+joinhandles+%3D+Vec%3A%3Anew%28%29%3B%0A%0A++++for+offset+in+0..8+%7B%0A++++++++joinhandles.push%28%0A++++++++thread%3A%3Aspawn%28move+%7C%7C+%7B%0A++++++++++++let+mut+i+%3D+offset%3B%0A++++++++++++let+mut+sum+%3D+0%3B%0A++++++++++++while+i+%3C+child_numbers.len%28%29+%7B%0A++++++++++++++++sum+%2B%3D+child_numbers%5Bi%5D%3B%0A++++++++++++++++i+%2B%3D+5%3B%0A++++++++++++%7D%0A++++++++++++println%21%28%22Sum+of+offset+%7B%7D+is+%7B%7D%22%2C+offset%2C+sum%29%3B%0A++++++++%7D%29%29%3B%0A++++%7D%0A++++for+handle+in+joinhandles.into_iter%28%29+%7B%0A++++++++handle.join%28%29.unwrap%28%29%3B%0A++++%7D%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+Make+%60shared_numbers%60+be+an+%60Arc%60+from+the+numbers+vector.+Then%2C+in+order%0A%2F%2F+to+avoid+creating+a+copy+of+%60numbers%60%2C+you%27ll+need+to+create+%60child_numbers%60%0A%2F%2F+inside+the+loop+but+still+in+the+main+thread.%0A%0A%2F%2F+%60child_numbers%60+should+be+a+clone+of+the+Arc+of+the+numbers+instead+of+a%0A%2F%2F+thread-local+copy+of+the+numbers.%0A)
-
-#### Iterators
-
-Do not adjust your monitors-- iterators 1 and 2 are indeed missing. Iterator 3 is a bit challenging
-so we're leaving space for some exercises to lead up to it!
-
-Check out the [Iterators chapter of the
-book](https://doc.rust-lang.org/book/second-edition/ch13-02-iterators.html) and the [Iterator
-docs](https://doc.rust-lang.org/stable/std/iter/trait.Iterator.html).
-
-- ["iterator3.rs"](https://play.rust-lang.org/?code=%2F%2F+iterator3.rs%0A%2F%2F+This+is+a+bigger+exercise+than+most+of+the+others%21+You+can+do+it%21%0A%2F%2F+Here+is+your+mission%2C+should+you+choose+to+accept+it%3A%0A%2F%2F+1.+Complete+the+divide+function+to+get+the+first+four+tests+to+pass%0A%2F%2F+2.+Uncomment+the+last+two+tests+and+get+them+to+pass+by+filling+in%0A%2F%2F++++values+for+%60x%60+using+%60division_results%60.%0A%2F%2F+Scroll+down+for+a+minor+hint+for+part+2%2C+and+scroll+down+further+for%0A%2F%2F+a+major+hint.%0A%2F%2F+Have+fun+%3A-%29%0A%0A%23%5Bderive%28Debug%2C+PartialEq%2C+Eq%29%5D%0Apub+enum+DivisionError+%7B%0A++++NotDivisible%28NotDivisibleError%29%2C%0A++++DivideByZero%2C%0A%7D%0A%0A%23%5Bderive%28Debug%2C+PartialEq%2C+Eq%29%5D%0Apub+struct+NotDivisibleError+%7B%0A++++dividend%3A+i32%2C%0A++++divisor%3A+i32%2C%0A%7D%0A%0A%2F%2F+This+function+should+calculate+%60a%60+divided+by+%60b%60+if+%60a%60+is%0A%2F%2F+evenly+divisible+by+b.%0A%2F%2F+Otherwise%2C+it+should+return+a+suitable+error.%0Apub+fn+divide%28a%3A+i32%2C+b%3A+i32%29+-%3E+Result%3Ci32%2C+DivisionError%3E+%7B%0A%7D%0A%0A%23%5Bcfg%28test%29%5D%0Amod+tests+%7B%0A++++use+super%3A%3A*%3B%0A%0A++++%2F%2F+Tests+that+verify+your+%60divide%60+function+implementation%0A++++%23%5Btest%5D%0A++++fn+test_success%28%29+%7B%0A++++++++assert_eq%21%28divide%2881%2C+9%29%2C+Ok%289%29%29%3B%0A++++%7D%0A%0A++++%23%5Btest%5D%0A++++fn+test_not_divisible%28%29+%7B%0A++++++++assert_eq%21%28%0A++++++++++++divide%2881%2C+6%29%2C%0A++++++++++++Err%28DivisionError%3A%3ANotDivisible%28NotDivisibleError%7B%0A++++++++++++++++dividend%3A+81%2C%0A++++++++++++++++divisor%3A+6%0A++++++++++++%7D%29%29%0A++++++++%29%3B%0A++++%7D%0A%0A++++%23%5Btest%5D%0A++++fn+test_divide_by_0%28%29+%7B%0A++++++++assert_eq%21%28divide%2881%2C+0%29%2C+Err%28DivisionError%3A%3ADivideByZero%29%29%3B%0A++++%7D%0A%0A++++%23%5Btest%5D%0A++++fn+test_divide_0_by_something%28%29+%7B%0A++++++++assert_eq%21%28divide%280%2C+81%29%2C+Ok%280%29%29%3B%0A++++%7D%0A%0A++++%2F%2F+Iterator+exercises+using+your+%60divide%60+function%0A++++%2F*%0A++++%23%5Btest%5D%0A++++fn+result_with_list%28%29+%7B%0A++++++++let+numbers+%3D+vec%21%5B27%2C+297%2C+38502%2C+81%5D%3B%0A++++++++let+division_results+%3D+numbers.into_iter%28%29.map%28%7Cn%7C+divide%28n%2C+27%29%29%3B%0A++++++++let+x+%2F%2F...+Fill+in+here%21%0A++++++++assert_eq%21%28format%21%28%22%7B%3A%3F%7D%22%2C+x%29%2C+%22Ok%28%5B1%2C+11%2C+1426%2C+3%5D%29%22%29%3B%0A++++%7D%0A%0A++++%23%5Btest%5D%0A++++fn+list_of_results%28%29+%7B%0A++++++++let+numbers+%3D+vec%21%5B27%2C+297%2C+38502%2C+81%5D%3B%0A++++++++let+division_results+%3D+numbers.into_iter%28%29.map%28%7Cn%7C+divide%28n%2C+27%29%29%3B%0A++++++++let+x+%2F%2F...+Fill+in+here%21%0A++++++++assert_eq%21%28format%21%28%22%7B%3A%3F%7D%22%2C+x%29%2C+%22%5BOk%281%29%2C+Ok%2811%29%2C+Ok%281426%29%2C+Ok%283%29%5D%22%29%3B%0A++++%7D%0A++++*%2F%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+Minor+hint%3A+In+each+of+the+two+cases+in+the+match+in+main%2C+you+can+create+x+with+either+%0A%2F%2F+a+%27turbofish%27+or+by+hinting+the+type+of+x+to+the+compiler.+You+may+try+both.%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+Major+hint%3A+Have+a+look+at+the+Iter+trait+and+at+the+explanation+of+its+collect+function.+%0A%2F%2F+Especially+the+part+about+Result+is+interesting.%0A)
-- ["iterators4.rs"](https://play.rust-lang.org/?code=%2F%2F+iterators4.rs%0A%0Apub+fn+factorial%28num%3A+u64%29+-%3E+u64+%7B%0A++++%2F%2F+Complete+this+function+to+return+factorial+of+num%0A++++%2F%2F+Do+not+use%3A%0A++++%2F%2F+-+return%0A++++%2F%2F+For+extra+fun+don%27t+use%3A%0A++++%2F%2F+-+imperative+style+loops+%28for%2C+while%29%0A++++%2F%2F+-+additional+variables%0A++++%2F%2F+For+the+most+fun+don%27t+use%3A%0A++++%2F%2F+-+recursion%0A++++%2F%2F+Scroll+down+for+hints.%0A%7D%0A%0A%23%5Bcfg%28test%29%5D%0Amod+tests+%7B%0A++++use+super%3A%3A*%3B%0A%0A++++%23%5Btest%5D%0A++++fn+factorial_of_1%28%29+%7B%0A++++++++assert_eq%21%281%2C+factorial%281%29%29%3B%0A++++%7D%0A++++%23%5Btest%5D%0A++++fn+factorial_of_2%28%29+%7B%0A++++++++assert_eq%21%282%2C+factorial%282%29%29%3B%0A++++%7D%0A%0A++++%23%5Btest%5D%0A++++fn+factorial_of_4%28%29+%7B%0A++++++++assert_eq%21%2824%2C+factorial%284%29%29%3B%0A++++%7D%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+In+an+imperative+language+you+might+write+a+for+loop+to+iterate+through%0A%2F%2F+multiply+the+values+into+a+mutable+variable.+Or+you+might+write+code+more%0A%2F%2F+functionally+with+recursion+and+a+match+clause.+But+you+can+also+use+ranges%0A%2F%2F+and+iterators+to+solve+this+in+rust.%0A)
-
-### Threads
-
-See [the Dining Philosophers
-example](https://doc.rust-lang.org/1.4.0/book/dining-philosophers.html) and the
-[Concurrency Chapter](https://doc.rust-lang.org/book/second-edition/ch16-01-threads.html) from the
-book.
-
-- ["threads1.rs"](https://play.rust-lang.org/?code=%2F%2F+threads1.rs%0A%2F%2F+Make+this+compile%21+Scroll+down+for+hints+%3A%29+The+idea+is+the+thread%0A%2F%2F+spawned+on+line+19+is+completing+jobs+while+the+main+thread+is%0A%2F%2F+monitoring+progress+until+10+jobs+are+completed.+If+you+see+6+lines%0A%2F%2F+of+%22waiting...%22+and+the+program+ends+without+timing+out+the+playground%2C%0A%2F%2F+you%27ve+got+it+%3A%29%0A%0Ause+std%3A%3Async%3A%3AArc%3B%0Ause+std%3A%3Athread%3B%0Ause+std%3A%3Atime%3A%3ADuration%3B%0A%0Astruct+JobStatus+%7B%0A++++jobs_completed%3A+u32%2C%0A%7D%0A%0Afn+main%28%29+%7B%0A++++let+status+%3D+Arc%3A%3Anew%28JobStatus+%7B+jobs_completed%3A+0+%7D%29%3B%0A++++let+status_shared+%3D+status.clone%28%29%3B%0A++++thread%3A%3Aspawn%28move+%7C%7C+%7B%0A++++++++for+_+in+0..10+%7B%0A++++++++++++thread%3A%3Asleep%28Duration%3A%3Afrom_millis%28250%29%29%3B%0A++++++++++++status_shared.jobs_completed+%2B%3D+1%3B%0A++++++++%7D%0A++++%7D%29%3B%0A++++while+status.jobs_completed+%3C+10+%7B%0A++++++++println%21%28%22waiting...+%22%29%3B%0A++++++++thread%3A%3Asleep%28Duration%3A%3Afrom_millis%28500%29%29%3B%0A++++%7D%0A%7D%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+%60Arc%60+is+an+Atomic+Reference+Counted+pointer+that+allows+safe%2C+shared+access%0A%2F%2F+to+**immutable**+data.+But+we+want+to+*change*+the+number+of+%60jobs_completed%60%0A%2F%2F+so+we%27ll+need+to+also+use+another+type+that+will+only+allow+one+thread+to%0A%2F%2F+mutate+the+data+at+a+time.+Take+a+look+at+this+section+of+the+book%3A%0A%2F%2F+https%3A%2F%2Fdoc.rust-lang.org%2Fstable%2Fbook%2Fsecond-edition%2Fch16-03-shared-state.html%23atomic-reference-counting-with-arct%0A%2F%2F+and+keep+scrolling+if+you%27d+like+more+hints+%3A%29%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+Do+you+now+have+an+%60Arc%60+%60Mutex%60+%60JobStatus%60+at+the+beginning+of+main%3F+Like%3A%0A%2F%2F+%60let+status+%3D+Arc%3A%3Anew%28Mutex%3A%3Anew%28JobStatus+%7B+jobs_completed%3A+0+%7D%29%29%3B%60%0A%2F%2F+Similar+to+the+code+in+the+example+in+the+book+that+happens+after+the+text%0A%2F%2F+that+says+%22We+can+use+Arc%3CT%3E+to+fix+this.%22.+If+not%2C+give+that+a+try%21+If+you%0A%2F%2F+do+and+would+like+more+hints%2C+keep+scrolling%21%21%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%0A%2F%2F+Make+sure+neither+of+your+threads+are+holding+onto+the+lock+of+the+mutex%0A%2F%2F+while+they+are+sleeping%2C+since+this+will+prevent+the+other+thread+from%0A%2F%2F+being+allowed+to+get+the+lock.+Locks+are+automatically+released+when%0A%2F%2F+they+go+out+of+scope.%0A%0A%2F%2F+Ok%2C+so%2C+real+talk%2C+this+was+actually+tricky+for+*me*+to+do+too.+And%0A%2F%2F+I+could+see+a+lot+of+different+problems+you+might+run+into%2C+so+at+this%0A%2F%2F+point+I%27m+not+sure+which+one+you%27ve+hit+%3A%29+Please+see+a+few+possible%0A%2F%2F+answers+on+https%3A%2F%2Fgithub.com%2Fcarols10cents%2Frustlings%2Fissues%2F3+--%0A%2F%2F+mine+is+a+little+more+complicated+because+I+decided+I+wanted+to+see%0A%2F%2F+the+number+of+jobs+currently+done+when+I+was+checking+the+status.%0A%0A%2F%2F+Please+open+an+issue+if+you%27re+still+running+into+a+problem+that%0A%2F%2F+these+hints+are+not+helping+you+with%2C+or+if+you%27ve+looked+at+the+sample%0A%2F%2F+answers+and+don%27t+understand+why+they+work+and+yours+doesn%27t.%0A%0A%2F%2F+If+you%27ve+learned+from+the+sample+solutions%2C+I+encourage+you+to+come%0A%2F%2F+back+to+this+exercise+and+try+it+again+in+a+few+days+to+reinforce%0A%2F%2F+what+you%27ve+learned+%3A%29%0A)
-
-### Uncategorized
-
-A few exercises based on things I've encountered or had trouble with getting used to.
-
-- ["ex1.rs"](https://play.rust-lang.org/?code=%2F%2F+ex1.rs%0A%2F%2F+Make+me+compile%21+%3A%29%0A%0Afn+main%28%29+%7B%0A++++println%28%29%3B%0A%7D%0A)
-- ["ex2.rs"](https://play.rust-lang.org/?code=%2F%2F+ex2.rs%0A%2F%2F+Make+me+compile%21%0A%0Afn+something%28%29+-%3E+String+%7B%0A++++%22hi%21%22%0A%7D%0A%0Afn+main%28%29+%7B%0A++++println%21%28%22%7B%7D%22%2C+something%28%29%29%3B%0A%7D%0A)
-- ["ex3.rs"](https://play.rust-lang.org/?code=%2F%2F+ex3.rs%0A%2F%2F+Make+me+compile%21%0A%0Astruct+Foo+%7B%0A++++capacity%3A+i32%2C%0A%7D%0A%0Afn+main%28%29+%7B%0A++++println%21%28%22%7B%3A%3F%7D%22%2C+Foo+%7B+capacity%3A+3+%7D%29%3B%0A%7D%0A)
-- ["ex4.rs"](https://play.rust-lang.org/?code=%2F%2F+ex4.rs%0A%2F%2F+Make+me+compile%21%0A%0Afn+something%28%29+-%3E+Result%3Ci32%2C+std%3A%3Anum%3A%3AParseIntError%3E+%7B%0A++++let+x%3Ai32+%3D+%223%22.parse%28%29%3B%0A++++Ok%28x+*+4%29%0A%7D%0A%0Afn+main%28%29+%7B%0A++++match+something%28%29+%7B%0A++++++++Ok%28..%29+%3D%3E+println%21%28%22You+win%21%22%29%2C%0A++++++++Err%28e%29+%3D%3E+println%21%28%22Oh+no+something+went+wrong%3A+%7B%7D%22%2C+e%29%2C%0A++++%7D%0A%7D%0A)
-- ["ex5.rs"](https://play.rust-lang.org/?code=%2F%2F+ex5.rs%0A%2F%2F+Make+me+compile%21%0A%0Aenum+Reaction%3C%27a%3E+%7B%0A++++Sad%28%26%27a+str%29%2C%0A++++Happy%28%26%27a+str%29%2C%0A%7D%0A%0Afn+express%28sentiment%3A+Reaction%29+%7B%0A++++match+sentiment+%7B%0A++++++++Reaction%3A%3ASad%28s%29+%3D%3E+println%21%28%22%3A%28+%7B%7D%22%2C+s%29%2C%0A++++++++Reaction%3A%3AHappy%28s%29+%3D%3E+println%21%28%22%3A%29+%7B%7D%22%2C+s%29%2C%0A++++%7D%0A%7D%0A%0Afn+main+%28%29+%7B%0A++++let+x+%3D+Reaction%3A%3AHappy%28%22It%27s+a+great+day+for+Rust%21%22%29%3B%0A++++express%28x%29%3B%0A++++express%28x%29%3B%0A++++let+y+%3D+Reaction%3A%3ASad%28%22This+code+doesn%27t+compile+yet.%22%29%3B%0A++++express%28y%29%3B%0A%7D%0A)
-- ["ex6.rs"](https://play.rust-lang.org/?code=%2F%2F+ex6.rs%0D%0A%2F%2F+Make+me+compile%21+Scroll+down+for+hints+%3A%29%0D%0A%0D%0Afn+main%28%29+%7B%0D%0A++++let+robot_name+%3D+Some%28String%3A%3Afrom%28%22Bors%22%29%29%3B%0D%0A%0D%0A++++match+robot_name+%7B%0D%0A++++++++Some%28name%29+%3D%3E+println%21%28%22Found+a+name%3A+%7B%7D%22%2C+name%29%2C%0D%0A++++++++None+%3D%3E+%28%29%2C%0D%0A++++%7D%0D%0A%0D%0A++++println%21%28%22robot_name+is%3A+%7B%3A%3F%7D%22%2C+robot_name%29%3B%0D%0A%7D%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%0D%0A%2F%2F+Hint%3A+The+following+two+statements+are+equivalent%3A%0D%0A%2F%2F+let+x+%3D+%26y%3B%0D%0A%2F%2F+let+ref+x+%3D+y%3B%0D%0A)
-
-## To help with this repo/TODO list
-
-* File issues for problems or suggestions!
-* Contribute more exercises! Anything that took you time to get used to, or that you had trouble
-  with, or that deserves practice would be a good exercise!
-* How could the process of doing these exercises work better? This is an open-ended question :) Are
-  the playground links good enough? Are there ways that we could make going to the next exercise
-  easier without forking the playground??
diff --git a/default_out.md b/default_out.md
new file mode 100644
index 0000000..3e00c10
--- /dev/null
+++ b/default_out.md
@@ -0,0 +1,20 @@
+Thanks for installing `rustlings`!
+
+## Is this your first time?
+
+Let's make sure you're up to speed:
+- You have Rust installed, preferably via `rustup`
+- You have `~/.cargo/bin` added to your PATH variable
+- You have cloned this repository (https://github.com/rustlings/rustlings)
+- You have installed Rust language support for your editor
+- You have locally installed the `rustlings` command by running:
+
+```sh
+cargo install --path .
+```
+
+If you've done all of this (or even most of it), congrats! You're ready
+to start working with Rust.
+
+To get started, run `rustlings verify` in order to get the first exercise.
+Make sure to have your editor open!
\ No newline at end of file
diff --git a/ex1.rs b/ex1.rs
deleted file mode 100644
index dc5f9ca..0000000
--- a/ex1.rs
+++ /dev/null
@@ -1,6 +0,0 @@
-// ex1.rs
-// Make me compile! :)
-
-fn main() {
-    println();
-}
diff --git a/ex2.rs b/ex2.rs
deleted file mode 100644
index 0fd714d..0000000
--- a/ex2.rs
+++ /dev/null
@@ -1,10 +0,0 @@
-// ex2.rs
-// Make me compile!
-
-fn something() -> String {
-    "hi!"
-}
-
-fn main() {
-    println!("{}", something());
-}
diff --git a/ex3.rs b/ex3.rs
deleted file mode 100644
index db27ad2..0000000
--- a/ex3.rs
+++ /dev/null
@@ -1,10 +0,0 @@
-// ex3.rs
-// Make me compile!
-
-struct Foo {
-    capacity: i32,
-}
-
-fn main() {
-    println!("{:?}", Foo { capacity: 3 });
-}
diff --git a/ex4.rs b/ex4.rs
deleted file mode 100644
index 362a557..0000000
--- a/ex4.rs
+++ /dev/null
@@ -1,14 +0,0 @@
-// ex4.rs
-// Make me compile!
-
-fn something() -> Result<i32, std::num::ParseIntError> {
-    let x:i32 = "3".parse();
-    Ok(x * 4)
-}
-
-fn main() {
-    match something() {
-        Ok(..) => println!("You win!"),
-        Err(e) => println!("Oh no something went wrong: {}", e),
-    }
-}
diff --git a/ex5.rs b/ex5.rs
deleted file mode 100644
index 2eb8cfd..0000000
--- a/ex5.rs
+++ /dev/null
@@ -1,22 +0,0 @@
-// ex5.rs
-// Make me compile!
-
-enum Reaction<'a> {
-    Sad(&'a str),
-    Happy(&'a str),
-}
-
-fn express(sentiment: Reaction) {
-    match sentiment {
-        Reaction::Sad(s) => println!(":( {}", s),
-        Reaction::Happy(s) => println!(":) {}", s),
-    }
-}
-
-fn main () {
-    let x = Reaction::Happy("It's a great day for Rust!");
-    express(x);
-    express(x);
-    let y = Reaction::Sad("This code doesn't compile yet.");
-    express(y);
-}
diff --git a/ex6.rs b/ex6.rs
deleted file mode 100644
index 33e589d..0000000
--- a/ex6.rs
+++ /dev/null
@@ -1,47 +0,0 @@
-// ex6.rs
-// Make me compile! Scroll down for hints :)
-
-fn main() {
-    let robot_name = Some(String::from("Bors"));
-
-    match robot_name {
-        Some(name) => println!("Found a name: {}", name),
-        None => (),
-    }
-
-    println!("robot_name is: {:?}", robot_name);
-}
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// Hint: The following two statements are equivalent:
-// let x = &y;
-// let ref x = y;
diff --git a/exercises/error_handling/README.md b/exercises/error_handling/README.md
new file mode 100644
index 0000000..2a53803
--- /dev/null
+++ b/exercises/error_handling/README.md
@@ -0,0 +1,5 @@
+For this exercise check out the sections:
+- [Error Handling](https://doc.rust-lang.org/book/2018-edition/ch09-02-recoverable-errors-with-result.html) 
+- [Generics](https://doc.rust-lang.org/book/2018-edition/ch10-01-syntax.html) 
+
+of the Rust Book.
\ No newline at end of file
diff --git a/error_handling/errors1.rs b/exercises/error_handling/errors1.rs
index 14ed574..14ed574 100644..100755
--- a/error_handling/errors1.rs
+++ b/exercises/error_handling/errors1.rs
diff --git a/error_handling/errors2.rs b/exercises/error_handling/errors2.rs
index 15c21c8..15c21c8 100644..100755
--- a/error_handling/errors2.rs
+++ b/exercises/error_handling/errors2.rs
diff --git a/error_handling/errors3.rs b/exercises/error_handling/errors3.rs
index 9c29af5..9c29af5 100644..100755
--- a/error_handling/errors3.rs
+++ b/exercises/error_handling/errors3.rs
diff --git a/error_handling/errorsn.rs b/exercises/error_handling/errorsn.rs
index 15c6cd5..15c6cd5 100644..100755
--- a/error_handling/errorsn.rs
+++ b/exercises/error_handling/errorsn.rs
diff --git a/error_handling/option1.rs b/exercises/error_handling/option1.rs
index 9cf0bc9..9cf0bc9 100644..100755
--- a/error_handling/option1.rs
+++ b/exercises/error_handling/option1.rs
diff --git a/error_handling/result1.rs b/exercises/error_handling/result1.rs
index 851ab45..851ab45 100644..100755
--- a/error_handling/result1.rs
+++ b/exercises/error_handling/result1.rs
diff --git a/exercises/functions/REAMDE.md b/exercises/functions/REAMDE.md
new file mode 100644
index 0000000..c40755b
--- /dev/null
+++ b/exercises/functions/REAMDE.md
@@ -0,0 +1,7 @@
+### Functions
+
+Here, you'll learn how to write functions and how Rust's compiler can trace things way back.
+
+#### Book Sections
+
+- [How Functions Work](https://doc.rust-lang.org/stable/book/ch03-03-how-functions-work.html)
diff --git a/functions/functions1.rs b/exercises/functions/functions1.rs
index 396dd56..396dd56 100644..100755
--- a/functions/functions1.rs
+++ b/exercises/functions/functions1.rs
diff --git a/functions/functions2.rs b/exercises/functions/functions2.rs
index 1cf95c3..1cf95c3 100644..100755
--- a/functions/functions2.rs
+++ b/exercises/functions/functions2.rs
diff --git a/functions/functions3.rs b/exercises/functions/functions3.rs
index b17543b..b17543b 100644..100755
--- a/functions/functions3.rs
+++ b/exercises/functions/functions3.rs
diff --git a/functions/functions4.rs b/exercises/functions/functions4.rs
index 5baca0e..5baca0e 100644..100755
--- a/functions/functions4.rs
+++ b/exercises/functions/functions4.rs
diff --git a/functions/functions5.rs b/exercises/functions/functions5.rs
index d3ff002..d3ff002 100644..100755
--- a/functions/functions5.rs
+++ b/exercises/functions/functions5.rs
diff --git a/exercises/if/README.md b/exercises/if/README.md
new file mode 100644
index 0000000..996ac93
--- /dev/null
+++ b/exercises/if/README.md
@@ -0,0 +1,7 @@
+### If
+
+`if`, the most basic type of control flow, is what you'll learn here.
+
+#### Book Sections
+
+- [Control Flow - if expressions](https://doc.rust-lang.org/stable/book/ch03-05-control-flow.html#if-expressions)
diff --git a/if/if1.rs b/exercises/if/if1.rs
index 5118657..6dd64c0 100644..100755
--- a/if/if1.rs
+++ b/exercises/if/if1.rs
@@ -9,6 +9,7 @@ pub fn bigger(a: i32, b:i32) -> i32 {
     // Scroll down for hints.
 }
 
+// Don't mind this for now :)
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/exercises/macros/README.md b/exercises/macros/README.md
new file mode 100644
index 0000000..b8f8e42
--- /dev/null
+++ b/exercises/macros/README.md
@@ -0,0 +1,10 @@
+### Macros
+
+Rust's macro system is very powerful, but also kind of difficult to wrap your
+head around. We're not going to teach you how to write your own fully-featured
+modules, instead we'll show you how to use and create them.
+
+#### Book Sections
+
+- [Macros](https://doc.rust-lang.org/stable/book/ch19-06-macros.html)
+- [The Little Book of Rust Macros](https://danielkeep.github.io/tlborm/book/index.html)
diff --git a/macros/macros1.rs b/exercises/macros/macros1.rs
index a7c78a5..a7c78a5 100644..100755
--- a/macros/macros1.rs
+++ b/exercises/macros/macros1.rs
diff --git a/macros/macros2.rs b/exercises/macros/macros2.rs
index bc2e56b..bc2e56b 100644..100755
--- a/macros/macros2.rs
+++ b/exercises/macros/macros2.rs
diff --git a/macros/macros3.rs b/exercises/macros/macros3.rs
index 84c4308..84c4308 100644..100755
--- a/macros/macros3.rs
+++ b/exercises/macros/macros3.rs
diff --git a/macros/macros4.rs b/exercises/macros/macros4.rs
index d844bb0..d844bb0 100644..100755
--- a/macros/macros4.rs
+++ b/exercises/macros/macros4.rs
diff --git a/exercises/modules/README.md b/exercises/modules/README.md
new file mode 100644
index 0000000..7a58d90
--- /dev/null
+++ b/exercises/modules/README.md
@@ -0,0 +1,7 @@
+### Modules
+
+In this section we'll give you an introduction to Rust's module system.
+
+#### Book Sections
+
+- [The Module System](https://doc.rust-lang.org/stable/book/ch07-02-modules-and-use-to-control-scope-and-privacy.html)
diff --git a/modules/modules1.rs b/exercises/modules/modules1.rs
index 0e092c5..0e092c5 100644..100755
--- a/modules/modules1.rs
+++ b/exercises/modules/modules1.rs
diff --git a/exercises/modules/modules2.rs b/exercises/modules/modules2.rs
new file mode 100755
index 0000000..d5946e5
--- /dev/null
+++ b/exercises/modules/modules2.rs
@@ -0,0 +1,45 @@
+// modules2.rs
+// Make me compile! Scroll down for hints :)
+
+mod delicious_snacks { 
+    use self::fruits::PEAR as fruit;
+    use self::veggies::CUCUMBER as veggie;
+
+    mod fruits {
+        pub const PEAR: &'static str = "Pear";
+        pub const APPLE: &'static str = "Apple";
+    }
+
+    mod veggies {
+        pub const CUCUMBER: &'static str = "Cucumber";
+        pub const CARROT: &'static str = "Carrot";
+    }
+}
+
+fn main() {
+    println!("favorite snacks: {} and {}",
+             delicious_snacks::fruit,
+             delicious_snacks::veggie);
+}
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+// The delicious_snacks module is trying to present an external
+// interface (the `fruit` and `veggie` constants) that is different than
+// its internal structure (the `fruits` and `veggies` modules and
+// associated constants). It's almost there except for one keyword missing for
+// each constant.
diff --git a/exercises/move_semantics/README.md b/exercises/move_semantics/README.md
new file mode 100644
index 0000000..1b9cab7
--- /dev/null
+++ b/exercises/move_semantics/README.md
@@ -0,0 +1,10 @@
+### 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
+
+For this section, the book links are especially important.
+
+- [Ownership](https://doc.rust-lang.org/stable/book/ch04-01-what-is-ownership.html)
+- [Reference and borrowing](https://doc.rust-lang.org/stable/book/ch04-02-references-and-borrowing.html)
diff --git a/move_semantics/move_semantics1.rs b/exercises/move_semantics/move_semantics1.rs
index 37038ec..37038ec 100644..100755
--- a/move_semantics/move_semantics1.rs
+++ b/exercises/move_semantics/move_semantics1.rs
diff --git a/move_semantics/move_semantics2.rs b/exercises/move_semantics/move_semantics2.rs
index b50e349..b50e349 100644..100755
--- a/move_semantics/move_semantics2.rs
+++ b/exercises/move_semantics/move_semantics2.rs
diff --git a/move_semantics/move_semantics3.rs b/exercises/move_semantics/move_semantics3.rs
index 8e7b0ad..8e7b0ad 100644..100755
--- a/move_semantics/move_semantics3.rs
+++ b/exercises/move_semantics/move_semantics3.rs
diff --git a/move_semantics/move_semantics4.rs b/exercises/move_semantics/move_semantics4.rs
index 903a330..903a330 100644..100755
--- a/move_semantics/move_semantics4.rs
+++ b/exercises/move_semantics/move_semantics4.rs
diff --git a/exercises/primitive_types/README.md b/exercises/primitive_types/README.md
new file mode 100644
index 0000000..b53394a
--- /dev/null
+++ b/exercises/primitive_types/README.md
@@ -0,0 +1,8 @@
+### 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
+
+- [Data Types](https://doc.rust-lang.org/stable/book/ch03-02-data-types.html)
diff --git a/primitive_types/primitive_types1.rs b/exercises/primitive_types/primitive_types1.rs
index c3d11fe..c3d11fe 100644..100755
--- a/primitive_types/primitive_types1.rs
+++ b/exercises/primitive_types/primitive_types1.rs
diff --git a/primitive_types/primitive_types2.rs b/exercises/primitive_types/primitive_types2.rs
index f5c8f87..f5c8f87 100644..100755
--- a/primitive_types/primitive_types2.rs
+++ b/exercises/primitive_types/primitive_types2.rs
diff --git a/primitive_types/primitive_types3.rs b/exercises/primitive_types/primitive_types3.rs
index 7ce2226..7ce2226 100644..100755
--- a/primitive_types/primitive_types3.rs
+++ b/exercises/primitive_types/primitive_types3.rs
diff --git a/primitive_types/primitive_types4.rs b/exercises/primitive_types/primitive_types4.rs
index 7dc9e47..1147cf7 100644..100755
--- a/primitive_types/primitive_types4.rs
+++ b/exercises/primitive_types/primitive_types4.rs
@@ -39,11 +39,11 @@ fn main() {
 
 
 // Take a look at the Understanding Ownership -> Slices -> Other Slices section of the book:
-// https://doc.rust-lang.org/stable/book/second-edition/ch04-03-slices.html#other-slices
+// https://doc.rust-lang.org/book/ch04-03-slices.html
 // and use the starting and ending indices of the items in the Array
 // that you want to end up in the slice.
 
 // If you're curious why the right hand of the `==` comparison does not
 // have an ampersand for a reference since the left hand side is a
 // reference, take a look at the Deref coercions section of the book:
-// https://doc.rust-lang.org/stable/book/second-edition/ch15-02-deref.html#implicit-deref-coercions-with-functions-and-methods
+// https://doc.rust-lang.org/book/ch15-02-deref.html
diff --git a/primitive_types/primitive_types5.rs b/exercises/primitive_types/primitive_types5.rs
index 4045e78..ae849b4 100644..100755
--- a/primitive_types/primitive_types5.rs
+++ b/exercises/primitive_types/primitive_types5.rs
@@ -39,7 +39,7 @@ fn main() {
 
 
 // Take a look at the Data Types -> The Tuple Type section of the book:
-// https://doc.rust-lang.org/stable/book/second-edition/ch03-02-data-types.html#the-tuple-type
+// https://doc.rust-lang.org/stable/book/ch03-02-data-types.html#the-tuple-type
 // Particularly the part about destructuring (second to last example in the section). 
 // You'll need to make a pattern to bind `name` and `age` to the appropriate parts
 // of the tuple. You can do it!!
diff --git a/primitive_types/primitive_types6.rs b/exercises/primitive_types/primitive_types6.rs
index 439a56b..634e56b 100644..100755
--- a/primitive_types/primitive_types6.rs
+++ b/exercises/primitive_types/primitive_types6.rs
@@ -41,5 +41,5 @@ fn main() {
 // While you could use a destructuring `let` for the tuple here, try 
 // indexing into it instead, as explained in the last example of the 
 // Data Types -> The Tuple Type section of the book:
-// https://doc.rust-lang.org/stable/book/second-edition/ch03-02-data-types.html#the-tuple-type
+// https://doc.rust-lang.org/stable/book/ch03-02-data-types.html#the-tuple-type
 // Now you have another tool in your toolbox!
diff --git a/exercises/standard_library_types/README.md b/exercises/standard_library_types/README.md
new file mode 100644
index 0000000..46d2ff2
--- /dev/null
+++ b/exercises/standard_library_types/README.md
@@ -0,0 +1,5 @@
+For the Arc exercise check out the chapter [Shared-State Concurrency](https://doc.rust-lang.org/book/2018-edition/ch16-03-shared-state.html) of the Rust Book.
+
+For the Iterator exercise check out the chapters [Iterator](https://doc.rust-lang.org/book/2018-edition/ch13-02-iterators.html) of the Rust Book and the [Iterator documentation](https://doc.rust-lang.org/stable/std/iter/trait.Iterator.htmlj).
+Do not adjust your monitors-- iterators 1 and 2 are indeed missing. Iterator 3 is a bit challenging so we're leaving space for some exercises to lead up to it!
+
diff --git a/standard_library_types/arc1.rs b/exercises/standard_library_types/arc1.rs
index c744a10..c744a10 100644..100755
--- a/standard_library_types/arc1.rs
+++ b/exercises/standard_library_types/arc1.rs
diff --git a/standard_library_types/iterator3.rs b/exercises/standard_library_types/iterator3.rs
index 1d2e135..1d2e135 100644..100755
--- a/standard_library_types/iterator3.rs
+++ b/exercises/standard_library_types/iterator3.rs
diff --git a/standard_library_types/iterators4.rs b/exercises/standard_library_types/iterators4.rs
index 13613a6..13613a6 100644..100755
--- a/standard_library_types/iterators4.rs
+++ b/exercises/standard_library_types/iterators4.rs
diff --git a/exercises/strings/REAMDE.md b/exercises/strings/REAMDE.md
new file mode 100644
index 0000000..b79ac06
--- /dev/null
+++ b/exercises/strings/REAMDE.md
@@ -0,0 +1,9 @@
+### 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
+
+- [Strings](https://doc.rust-lang.org/stable/book/ch08-02-strings.html)
diff --git a/strings/strings1.rs b/exercises/strings/strings1.rs
index 2e5088f..2e5088f 100644..100755
--- a/strings/strings1.rs
+++ b/exercises/strings/strings1.rs
diff --git a/strings/strings2.rs b/exercises/strings/strings2.rs
index c77e16f..c77e16f 100644..100755
--- a/strings/strings2.rs
+++ b/exercises/strings/strings2.rs
diff --git a/exercises/test1.rs b/exercises/test1.rs
new file mode 100644
index 0000000..f52513d
--- /dev/null
+++ b/exercises/test1.rs
@@ -0,0 +1,20 @@
+// test1.rs
+// This is a test for the following sections:
+// - Variables
+// - Functions
+
+// Mary is buying apples. One apple usually costs 2 dollars, but if you buy
+// more than 40 at once, each apple only costs 1! Write a function that calculates
+// the price of an order of apples given the order amount.
+
+fn main() {
+    let price1 = calculateprice(55);
+    let price2 = calculateprice(40);
+
+    // Don't modify this!
+    if price1 == 55 && price2 == 80 {
+        println!("Good job!");
+    } else {
+        panic!("Uh oh! Wrong price!");
+    }
+}
diff --git a/tests/tests4.rs b/exercises/test2.rs
index 23d444a..249abbc 100644..100755
--- a/tests/tests4.rs
+++ b/exercises/test2.rs
@@ -1,4 +1,7 @@
-// tests4.rs
+// test2.rs
+// This is a test for the following sections:
+// - Tests
+
 // This test isn't testing our function -- make it do that in such a way that
 // the test passes. Then write a second test that tests that we get the result
 // we expect to get when we call `times_two` with a negative number.
diff --git a/strings/strings3.rs b/exercises/test3.rs
index b6f6a1e..e94b069 100644..100755
--- a/strings/strings3.rs
+++ b/exercises/test3.rs
@@ -1,4 +1,7 @@
 // strings3.rs
+// This is a test for the following sections:
+// - Strings
+
 // Ok, here are a bunch of values-- some are `Strings`, some are `&strs`. Your
 // task is to call one of these two functions on each value depending on what
 // you think each value is. That is, add either `string_slice` or `string`
diff --git a/exercises/test4.rs b/exercises/test4.rs
new file mode 100644
index 0000000..e50f1b0
--- /dev/null
+++ b/exercises/test4.rs
@@ -0,0 +1,12 @@
+// test4.rs
+// This test covers the sections:
+// - Modules
+// - Macros
+
+// Write a macro that passes the test! No hints this time, you can do it!
+
+fn main() {
+    if my_macro!("world!") != "Hello world!" {
+        panic!("Oh no! Wrong output!");
+    }
+}
diff --git a/exercises/tests/README.md b/exercises/tests/README.md
new file mode 100644
index 0000000..243b913
--- /dev/null
+++ b/exercises/tests/README.md
@@ -0,0 +1,7 @@
+### 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
+
+- [Writing Tests](https://doc.rust-lang.org/stable/book/ch11-01-writing-tests.html)
diff --git a/tests/tests1.rs b/exercises/tests/tests1.rs
index 959ed85..b11221f 100644..100755
--- a/tests/tests1.rs
+++ b/exercises/tests/tests1.rs
@@ -1,7 +1,7 @@
 // tests1.rs
 // Tests are important to ensure that your code does what you think it should do.
 // Tests can be run on this file with the following command:
-// rustc --test tests1.rs
+// rustlings run --test exercises/tests/tests1.rs
 
 // This test has a problem with it -- make the test compile! Make the test
 // pass! Make the test fail! Scroll down for hints :)
diff --git a/tests/tests2.rs b/exercises/tests/tests2.rs
index 6775d61..6775d61 100644..100755
--- a/tests/tests2.rs
+++ b/exercises/tests/tests2.rs
diff --git a/tests/tests3.rs b/exercises/tests/tests3.rs
index e041f38..e10d2aa 100644..100755
--- a/tests/tests3.rs
+++ b/exercises/tests/tests3.rs
@@ -1,6 +1,6 @@
 // tests3.rs
 // This test isn't testing our function -- make it do that in such a way that
-// the test passes. Then write a second test that tests that we get the result
+// the test passes. Then write a second test that tests whether we get the result
 // we expect to get when we call `is_even(5)`. Scroll down for hints!
 
 pub fn is_even(num: i32) -> bool {
@@ -13,7 +13,7 @@ mod tests {
 
     #[test]
     fn is_true_when_even() {
-        assert!(false);
+        assert!();
     }
 }
 
diff --git a/exercises/threads/README.md b/exercises/threads/README.md
new file mode 100644
index 0000000..90581fa
--- /dev/null
+++ b/exercises/threads/README.md
@@ -0,0 +1 @@
+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/2018-edition/ch16-01-threads.html) of the Rust Book.
\ No newline at end of file
diff --git a/threads/threads1.rs b/exercises/threads/threads1.rs
index 4f9aa89..4f9aa89 100644..100755
--- a/threads/threads1.rs
+++ b/exercises/threads/threads1.rs
diff --git a/exercises/variables/README.md b/exercises/variables/README.md
new file mode 100644
index 0000000..6ae26cb
--- /dev/null
+++ b/exercises/variables/README.md
@@ -0,0 +1,7 @@
+### Variables
+
+Here you'll learn about simple variables.
+
+#### Book Sections
+
+- [Variables and Mutability](https://doc.rust-lang.org/stable/book/ch03-01-variables-and-mutability.html)
diff --git a/variables/variables1.rs b/exercises/variables/variables1.rs
index 1cdd270..1cdd270 100644..100755
--- a/variables/variables1.rs
+++ b/exercises/variables/variables1.rs
diff --git a/variables/variables2.rs b/exercises/variables/variables2.rs
index a0b4a37..a0b4a37 100644..100755
--- a/variables/variables2.rs
+++ b/exercises/variables/variables2.rs
diff --git a/variables/variables3.rs b/exercises/variables/variables3.rs
index 165a277..165a277 100644..100755
--- a/variables/variables3.rs
+++ b/exercises/variables/variables3.rs
diff --git a/variables/variables4.rs b/exercises/variables/variables4.rs
index 71ebf0f..71ebf0f 100644..100755
--- a/variables/variables4.rs
+++ b/exercises/variables/variables4.rs
diff --git a/modules/modules2.rs b/modules/modules2.rs
deleted file mode 100644
index 164dfb0..0000000
--- a/modules/modules2.rs
+++ /dev/null
@@ -1,45 +0,0 @@
-// modules2.rs
-// Make me compile! Scroll down for hints :)
-
-mod us_presidential_frontrunners {
-    use self::democrats::HILLARY_CLINTON as democrat;
-    use self::republicans::DONALD_TRUMP as republican;
-
-    mod democrats {
-        pub const HILLARY_CLINTON: &'static str = "Hillary Clinton";
-        pub const BERNIE_SANDERS: &'static str = "Bernie Sanders";
-    }
-
-    mod republicans {
-        pub const DONALD_TRUMP: &'static str = "Donald Trump";
-        pub const JEB_BUSH: &'static str = "Jeb Bush";
-    }
-}
-
-fn main() {
-    println!("candidates: {} and {}",
-             us_presidential_frontrunners::democrat,
-             us_presidential_frontrunners::republican);
-}
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-// The us_presidential_frontrunners module is trying to present an external
-// interface (the `democrat` and `republican` constants) that is different than
-// its internal structure (the `democrats` and `republicans` modules and
-// associated constants). It's almost there except for one keyword missing for
-// each constant.
diff --git a/src/bin/generate_readme.rs b/src/bin/generate_readme.rs
deleted file mode 100644
index a502fea..0000000
--- a/src/bin/generate_readme.rs
+++ /dev/null
@@ -1,49 +0,0 @@
-// This script reads README-template.md and generates the playground links
-// from the Rust source files in the various directories.
-
-// To add a new exercise, add it to the appropriate place in README-template.md
-// and then make sure to recompile this script (because the template gets
-// included at compile time and then run it to generate a new version of
-// README.md.
-
-extern crate handlebars;
-extern crate prlink;
-#[macro_use]
-extern crate serde_json;
-
-use handlebars::{Handlebars, Helper, RenderContext, RenderError};
-
-use std::fs::File;
-use std::io::prelude::*;
-use std::path::PathBuf;
-
-fn main() {
-    let mut template_file = File::open("README-template.hbs").unwrap();
-    let mut template = String::new();
-    template_file.read_to_string(&mut template).unwrap();
-
-    let autogenerated_notice = "This file was autogenerated by the script in src/bin/generate_readme.rs.
-Please edit either the script or the template in README-template.md in
-order to make changes here rather than committing the changes directly.";
-
-    let mut generated_readme = File::create("README.md").unwrap();
-
-    let mut hbs = Handlebars::new();
-    hbs.register_helper("playground_link", Box::new(playground_link_helper));
-
-    write!(
-        generated_readme,
-        "{}",
-        hbs.render_template(
-            &template,
-            &json!({ "autogenerated_notice": autogenerated_notice }),
-        ).unwrap()
-    ).unwrap();
-}
-
-fn playground_link_helper(h: &Helper, _: &Handlebars, rc: &mut RenderContext) -> Result<(), RenderError> {
-    let filename = PathBuf::from(h.param(0).unwrap().value().as_str().unwrap());
-    let link = prlink::linkify_file(&filename);
-    rc.writer.write(link.into_bytes().as_ref())?;
-    Ok(())
-}
diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..8f9ccea
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,96 @@
+use crate::run::run;
+use crate::verify::verify;
+use clap::{crate_version, App, Arg, SubCommand};
+use notify::DebouncedEvent;
+use notify::{RecommendedWatcher, RecursiveMode, Watcher};
+use std::io::BufRead;
+use std::sync::mpsc::channel;
+use std::time::Duration;
+use syntect::easy::HighlightFile;
+use syntect::highlighting::{Style, ThemeSet};
+use syntect::parsing::SyntaxSet;
+use syntect::util::as_24_bit_terminal_escaped;
+
+mod run;
+mod util;
+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")
+        .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("file").required(true).index(1))
+                .arg(Arg::with_name("test").short("t").long("test").help("Run the file as a test")),
+        )
+        .get_matches();
+
+    let ss = SyntaxSet::load_defaults_newlines();
+    let ts = ThemeSet::load_defaults();
+
+    if None == matches.subcommand_name() {
+        println!("");
+        println!(r#"       welcome to...                      "#);
+        println!(r#"                 _   _ _                  "#);
+        println!(r#"  _ __ _   _ ___| |_| (_)_ __   __ _ ___  "#);
+        println!(r#" | '__| | | / __| __| | | '_ \ / _` / __| "#);
+        println!(r#" | |  | |_| \__ \ |_| | | | | | (_| \__ \ "#);
+        println!(r#" |_|   \__,_|___/\__|_|_|_| |_|\__, |___/ "#);
+        println!(r#"                               |___/      "#);
+        println!("");
+    }
+
+    if let Some(matches) = matches.subcommand_matches("run") {
+        run(matches.clone());
+    }
+
+    if let Some(_) = matches.subcommand_matches("verify") {
+        match verify() {
+            Ok(_) => {}
+            Err(_) => std::process::exit(1),
+        }
+    }
+
+    if let Some(_) = matches.subcommand_matches("watch") {
+        watch().unwrap();
+    }
+
+    if let None = matches.subcommand_name() {
+        let mut highlighter =
+            HighlightFile::new("default_out.md", &ss, &ts.themes["base16-eighties.dark"]).unwrap();
+        for maybe_line in highlighter.reader.lines() {
+            let line = maybe_line.unwrap();
+            let regions: Vec<(Style, &str)> = highlighter.highlight_lines.highlight(&line, &ss);
+            println!("{}", as_24_bit_terminal_escaped(&regions[..], true));
+        }
+    }
+
+    println!("\x1b[0m");
+}
+
+fn watch() -> notify::Result<()> {
+    let (tx, rx) = channel();
+
+    let mut watcher: RecommendedWatcher = Watcher::new(tx, Duration::from_secs(2))?;
+    watcher.watch("./exercises", RecursiveMode::Recursive)?;
+
+    let _ignored = verify();
+
+    loop {
+        match rx.recv() {
+            Ok(event) => match event {
+                DebouncedEvent::Chmod(_) | DebouncedEvent::Write(_) => {
+                    let _ignored = verify();
+                }
+                _ => {}
+            },
+            Err(e) => println!("watch error: {:?}", e),
+        }
+    }
+}
diff --git a/src/run.rs b/src/run.rs
new file mode 100644
index 0000000..809b79d
--- /dev/null
+++ b/src/run.rs
@@ -0,0 +1,55 @@
+use crate::util::clean;
+use crate::verify::test;
+use console::{style, Emoji};
+use indicatif::ProgressBar;
+use std::process::Command;
+
+pub fn run(matches: clap::ArgMatches) {
+    if let Some(filename) = matches.value_of("file") {
+        if matches.is_present("test") {
+            match test(filename) {
+                Ok(_) => (),
+                Err(_) => (),
+            }
+            std::process::exit(0);
+        }
+        let bar = ProgressBar::new_spinner();
+        bar.set_message(format!("Compiling {}...", filename).as_str());
+        bar.enable_steady_tick(100);
+        let compilecmd = Command::new("rustc")
+            .args(&[filename, "-o", "temp"])
+            .output()
+            .expect("fail");
+        bar.set_message(format!("Running {}...", filename).as_str());
+        if compilecmd.status.success() {
+            let runcmd = Command::new("./temp").output().expect("fail");
+            bar.finish_and_clear();
+
+            if runcmd.status.success() {
+                println!("{}", String::from_utf8_lossy(&runcmd.stdout));
+                let formatstr = format!("{} Successfully ran {}", Emoji("✅", "✓"), filename);
+                println!("{}", style(formatstr).green());
+                clean();
+            } else {
+                println!("{}", String::from_utf8_lossy(&runcmd.stdout));
+                println!("{}", String::from_utf8_lossy(&runcmd.stderr));
+
+                let formatstr = format!("{} Ran {} with errors", Emoji("⚠️ ", "!"), filename);
+                println!("{}", style(formatstr).red());
+                clean();
+            }
+        } else {
+            bar.finish_and_clear();
+            let formatstr = format!(
+                "{} Compilation of {} failed! Compiler error message:\n",
+                Emoji("⚠️ ", "!"),
+                filename
+            );
+            println!("{}", style(formatstr).red());
+            println!("{}", String::from_utf8_lossy(&compilecmd.stderr));
+            clean();
+        }
+    } else {
+        panic!("Please supply a filename!");
+    }
+}
diff --git a/src/util.rs b/src/util.rs
new file mode 100644
index 0000000..37a2028
--- /dev/null
+++ b/src/util.rs
@@ -0,0 +1,5 @@
+use std::fs::remove_file;
+
+pub fn clean() {
+    let _ignored = remove_file("temp");
+}
diff --git a/src/verify.rs b/src/verify.rs
new file mode 100644
index 0000000..9aa3a4b
--- /dev/null
+++ b/src/verify.rs
@@ -0,0 +1,106 @@
+use crate::util::clean;
+use console::{style, Emoji};
+use indicatif::ProgressBar;
+use std::process::Command;
+
+pub fn verify() -> Result<(), ()> {
+    compile_only("exercises/variables/variables1.rs")?;
+    compile_only("exercises/variables/variables2.rs")?;
+    compile_only("exercises/variables/variables3.rs")?;
+    compile_only("exercises/variables/variables4.rs")?;
+    test("exercises/if/if1.rs")?;
+    compile_only("exercises/functions/functions1.rs")?;
+    compile_only("exercises/functions/functions2.rs")?;
+    compile_only("exercises/functions/functions3.rs")?;
+    compile_only("exercises/functions/functions4.rs")?;
+    compile_only("exercises/functions/functions5.rs")?;
+    compile_only("exercises/test1.rs")?;
+    compile_only("exercises/primitive_types/primitive_types1.rs")?;
+    compile_only("exercises/primitive_types/primitive_types2.rs")?;
+    compile_only("exercises/primitive_types/primitive_types3.rs")?;
+    compile_only("exercises/primitive_types/primitive_types4.rs")?;
+    compile_only("exercises/primitive_types/primitive_types5.rs")?;
+    compile_only("exercises/primitive_types/primitive_types6.rs")?;
+    test("exercises/tests/tests1.rs")?;
+    test("exercises/tests/tests2.rs")?;
+    test("exercises/tests/tests3.rs")?;
+    test("exercises/test2.rs")?;
+    compile_only("exercises/strings/strings1.rs")?;
+    compile_only("exercises/strings/strings2.rs")?;
+    compile_only("exercises/test3.rs")?;
+    compile_only("exercises/modules/modules1.rs")?;
+    compile_only("exercises/modules/modules2.rs")?;
+    compile_only("exercises/macros/macros1.rs")?;
+    compile_only("exercises/macros/macros2.rs")?;
+    compile_only("exercises/macros/macros3.rs")?;
+    compile_only("exercises/macros/macros4.rs")?;
+    compile_only("exercises/test4.rs")?;
+    compile_only("exercises/move_semantics/move_semantics1.rs")?;
+    compile_only("exercises/move_semantics/move_semantics2.rs")?;
+    compile_only("exercises/move_semantics/move_semantics3.rs")?;
+    compile_only("exercises/move_semantics/move_semantics4.rs")?;
+    test("exercises/error_handling/errors1.rs")?;
+    test("exercises/error_handling/errors2.rs")?;
+    test("exercises/error_handling/errors3.rs")?;
+    test("exercises/error_handling/errorsn.rs")?;
+    compile_only("exercises/error_handling/option1.rs")?;
+    test("exercises/error_handling/result1.rs")?;
+    Ok(())
+}
+
+fn compile_only(filename: &str) -> Result<(), ()> {
+    let bar = ProgressBar::new_spinner();
+    bar.set_message(format!("Compiling {}...", filename).as_str());
+    bar.enable_steady_tick(100);
+    let compilecmd = Command::new("rustc")
+        .args(&[filename, "-o", "temp", "--color", "always"])
+        .output()
+        .expect("fail");
+    bar.finish_and_clear();
+    if compilecmd.status.success() {
+        let formatstr = format!(
+            "{} Successfully compiled {}!",
+            Emoji("✅", "✓"),
+            filename
+        );
+        println!("{}", style(formatstr).green());
+        clean();
+        Ok(())
+    } else {
+        let formatstr = format!(
+            "{} Compilation of {} failed! Compiler error message:\n",
+            Emoji("⚠️ ", "!"),
+            filename
+        );
+        println!("{}", style(formatstr).red());
+        println!("{}", String::from_utf8_lossy(&compilecmd.stderr));
+        clean();
+        Err(())
+    }
+}
+
+pub fn test(filename: &str) -> Result<(), ()> {
+    let bar = ProgressBar::new_spinner();
+    bar.set_message(format!("Testing {}...", filename).as_str());
+    bar.enable_steady_tick(100);
+    let testcmd = Command::new("rustc")
+        .args(&["--test", filename, "-o", "temp"])
+        .output()
+        .expect("fail");
+    bar.finish_and_clear();
+    if testcmd.status.success() {
+        let formatstr = format!("{} Successfully tested {}!", Emoji("✅", "✓"), filename);
+        println!("{}", style(formatstr).green());
+        clean();
+        Ok(())
+    } else {
+        let formatstr = format!(
+            "{} Testing of {} failed! Please try again.",
+            Emoji("⚠️ ", "!"),
+            filename
+        );
+        println!("{}", style(formatstr).red());
+        clean();
+        Err(())
+    }
+}