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feat: Refactor hint system

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Hints are now accessible using the CLI subcommand `rustlings hint
<exercise name`.

BREAKING CHANGE: This fundamentally changes the way people interact with exercises.
This commit is contained in:
marisa 2019-11-11 16:51:38 +01:00
parent 627cdc07d0
commit 9bdb0a12e4
47 changed files with 400 additions and 1681 deletions
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30
exercises/enums/enums1.rs
View file

@ -1,5 +1,5 @@
// enums1.rs // enums1.rs
// Make me compile! Scroll down for hints! // Make me compile! Execute `rustlings hint enums1` for hints!
#[derive(Debug)] #[derive(Debug)]
enum Message { enum Message {
@ -12,31 +12,3 @@ fn main() {
println!("{:?}", Message::Move); println!("{:?}", Message::Move);
println!("{:?}", Message::ChangeColor); println!("{:?}", Message::ChangeColor);
} }
// Hint: The declaration of the enumeration type has not been defined yet.

37
exercises/enums/enums2.rs
View file

@ -1,5 +1,5 @@
// enums2.rs // enums2.rs
// Make me compile! Scroll down for hints // Make me compile! Execute `rustlings hint enums2` for hints!
#[derive(Debug)] #[derive(Debug)]
enum Message { enum Message {
@ -24,38 +24,3 @@ fn main() {
message.call(); message.call();
} }
} }
// Hint: you can create enumerations that have different variants with different types
// such as no data, anonymous structs, a single string, tuples, ...etc

35
exercises/error_handling/errors1.rs
View file

@ -4,7 +4,7 @@
// was, instead of just sometimes returning `None`. The 2nd test currently // was, instead of just sometimes returning `None`. The 2nd test currently
// does not compile or pass, but it illustrates the behavior we would like // does not compile or pass, but it illustrates the behavior we would like
// this function to have. // this function to have.
// Scroll down for hints!!! // Execute `rustlings hint errors1` for hints!
pub fn generate_nametag_text(name: String) -> Option<String> { pub fn generate_nametag_text(name: String) -> Option<String> {
if name.len() > 0 { if name.len() > 0 {
@ -38,36 +38,3 @@ mod tests {
); );
} }
} }
// `Err` is one of the variants of `Result`, so what the 2nd test is saying
// is that `generate_nametag_text` should return a `Result` instead of an
// `Option`.
// To make this change, you'll need to:
// - update the return type in the function signature to be a Result<String, String> that
// could be the variants `Ok(String)` and `Err(String)`
// - change the body of the function to return `Ok(stuff)` where it currently
// returns `Some(stuff)`
// - change the body of the function to return `Err(error message)` where it
// currently returns `None`
// - change the first test to expect `Ok(stuff)` where it currently expects
// `Some(stuff)`.

26
exercises/error_handling/errors2.rs
View file

@ -14,7 +14,7 @@
// and add. // and add.
// There are at least two ways to implement this that are both correct-- but // There are at least two ways to implement this that are both correct-- but
// one is a lot shorter! Scroll down for hints to both ways. // one is a lot shorter! Execute `rustlings hint errors2` for hints to both ways.
use std::num::ParseIntError; use std::num::ParseIntError;
@ -43,27 +43,3 @@ mod tests {
); );
} }
} }
// One way to handle this is using a `match` statement on
// `item_quantity.parse::<i32>()` where the cases are `Ok(something)` and
// `Err(something)`. This pattern is very common in Rust, though, so there's
// a `?` operator that does pretty much what you would make that match statement
// do for you! Take a look at this section of the Error Handling chapter:
// https://doc.rust-lang.org/book/ch09-02-recoverable-errors-with-result.html#a-shortcut-for-propagating-errors-the--operator
// and give it a try!

22
exercises/error_handling/errors3.rs
View file

@ -1,7 +1,8 @@
// errors3.rs // errors3.rs
// This is a program that is trying to use a completed version of the // This is a program that is trying to use a completed version of the
// `total_cost` function from the previous exercise. It's not working though! // `total_cost` function from the previous exercise. It's not working though!
// Why not? What should we do to fix it? Scroll for hints! // Why not? What should we do to fix it?
// Execute `rustlings hint errors3` for hints!
use std::num::ParseIntError; use std::num::ParseIntError;
@ -26,22 +27,3 @@ pub fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {
Ok(qty * cost_per_item + processing_fee) Ok(qty * cost_per_item + processing_fee)
} }
// If other functions can return a `Result`, why shouldn't `main`?

137
exercises/error_handling/errorsn.rs
View file

@ -13,7 +13,7 @@
// type goes where the question marks are, and how do we return // type goes where the question marks are, and how do we return
// that type from the body of read_and_validate? // that type from the body of read_and_validate?
// //
// Scroll down for hints :) // Execute `rustlings hint errors4` for hints :)
use std::error; use std::error;
use std::fmt; use std::fmt;
@ -110,138 +110,3 @@ impl error::Error for CreationError {
} }
} }
} }
// First hint: To figure out what type should go where the ??? is, take a look
// at the test helper function `test_with_str`, since it returns whatever
// `read_and_validate` returns and`test_with_str` has its signature fully
// specified.
// Next hint: There are three places in `read_and_validate` that we call a
// function that returns a `Result` (that is, the functions might fail).
// Apply the `?` operator on those calls so that we return immediately from
// `read_and_validate` if those function calls fail.
// Another hint: under the hood, the `?` operator calls `From::from`
// on the error value to convert it to a boxed trait object, a Box<dyn error::Error>,
// which is polymorphic-- that means that lots of different kinds of errors
// can be returned from the same function because all errors act the same
// since they all implement the `error::Error` trait.
// Check out this section of the book:
// https://doc.rust-lang.org/book/ch09-02-recoverable-errors-with-result.html#a-shortcut-for-propagating-errors-the--operator
// Another another hint: Note that because the `?` operator returns
// the *unwrapped* value in the `Ok` case, if we want to return a `Result` from
// `read_and_validate` for *its* success case, we'll have to rewrap a value
// that we got from the return value of a `?`ed call in an `Ok`-- this will
// look like `Ok(something)`.
// Another another another hint: `Result`s must be "used", that is, you'll
// get a warning if you don't handle a `Result` that you get in your
// function. Read more about that in the `std::result` module docs:
// https://doc.rust-lang.org/std/result/#results-must-be-used

30
exercises/error_handling/option1.rs
View file

@ -2,7 +2,7 @@
// This example panics because the second time it calls `pop`, the `vec` // This example panics because the second time it calls `pop`, the `vec`
// is empty, so `pop` returns `None`, and `unwrap` panics if it's called // is empty, so `pop` returns `None`, and `unwrap` panics if it's called
// on `None`. Handle this in a more graceful way than calling `unwrap`! // on `None`. Handle this in a more graceful way than calling `unwrap`!
// Scroll down for hints :) // Execute `rustlings hint option1` for hints :)
pub fn pop_too_much() -> bool { pub fn pop_too_much() -> bool {
let mut list = vec![3]; let mut list = vec![3];
@ -27,31 +27,3 @@ mod tests {
assert!(pop_too_much()); assert!(pop_too_much());
} }
} }
// Try using a `match` statement where the arms are `Some(thing)` and `None`.
// Or set a default value to print out if you get `None` by using the
// function `unwrap_or`.
// Or use an `if let` statement on the result of `pop()` to both destructure
// a `Some` value and only print out something if we have a value!

21
exercises/error_handling/result1.rs
View file

@ -1,5 +1,5 @@
// result1.rs // result1.rs
// Make this test pass! Scroll down for hints :) // Make this test pass! Execute `rustlings hint option2` for hints :)
#[derive(PartialEq, Debug)] #[derive(PartialEq, Debug)]
struct PositiveNonzeroInteger(u64); struct PositiveNonzeroInteger(u64);
@ -25,22 +25,3 @@ fn test_creation() {
); );
assert_eq!(Err(CreationError::Zero), PositiveNonzeroInteger::new(0)); assert_eq!(Err(CreationError::Zero), PositiveNonzeroInteger::new(0));
} }
// `PositiveNonzeroInteger::new` is always creating a new instance and returning an `Ok` result.
// It should be doing some checking, returning an `Err` result if those checks fail, and only
// returning an `Ok` result if those checks determine that everything is... okay :)

40
exercises/functions/functions1.rs
View file

@ -1,44 +1,6 @@
// functions1.rs // functions1.rs
// Make me compile! Scroll down for hints :) // Make me compile! Execute `rustlings hint function1` for hints :)
fn main() { fn main() {
call_me(); call_me();
} }
// This main function is calling a function that it expects to exist, but the
// function doesn't exist. It expects this function to have the name `call_me`.
// It expects this function to not take any arguments and not return a value.
// Sounds a lot like `main`, doesn't it?

32
exercises/functions/functions2.rs
View file

@ -1,5 +1,5 @@
// functions2.rs // functions2.rs
// Make me compile! Scroll down for hints :) // Make me compile! Execute `rustlings hint functions2` for hints :)
fn main() { fn main() {
call_me(3); call_me(3);
@ -10,33 +10,3 @@ fn call_me(num) {
println!("Ring! Call number {}", i + 1); println!("Ring! Call number {}", i + 1);
} }
} }
// Rust requires that all parts of a function's signature have type annotations,
// but `call_me` is missing the type annotation of `num`.

32
exercises/functions/functions3.rs
View file

@ -1,5 +1,5 @@
// functions3.rs // functions3.rs
// Make me compile! Scroll down for hints :) // Make me compile! Execute `rustlings hint functions3` for hints :)
fn main() { fn main() {
call_me(); call_me();
@ -10,33 +10,3 @@ fn call_me(num: i32) {
println!("Ring! Call number {}", i + 1); println!("Ring! Call number {}", i + 1);
} }
} }
// This time, the function *declaration* is okay, but there's something wrong
// with the place where we're calling the function.

24
exercises/functions/functions4.rs
View file

@ -1,5 +1,5 @@
// functions4.rs // functions4.rs
// Make me compile! Scroll down for hints :) // Make me compile! Execute `rustlings hint functions4` for hints :)
// This store is having a sale where if the price is an even number, you get // This store is having a sale where if the price is an even number, you get
// 10 (money unit) off, but if it's an odd number, it's 3 (money unit) less. // 10 (money unit) off, but if it's an odd number, it's 3 (money unit) less.
@ -20,25 +20,3 @@ fn sale_price(price: i32) -> {
fn is_even(num: i32) -> bool { fn is_even(num: i32) -> bool {
num % 2 == 0 num % 2 == 0
} }
// The error message points to line 12 and says it expects a type after the
// `->`. This is where the function's return type should be-- take a look at
// the `is_even` function for an example!

38
exercises/functions/functions5.rs
View file

@ -1,5 +1,5 @@
// functions5.rs // functions5.rs
// Make me compile! Scroll down for hints :) // Make me compile! Execute `rustlings hint functions5` for hints :)
fn main() { fn main() {
let answer = square(3); let answer = square(3);
@ -9,39 +9,3 @@ fn main() {
fn square(num: i32) -> i32 { fn square(num: i32) -> i32 {
num * num; num * num;
} }
// This is a really common error that can be fixed by removing one character.
// It happens because Rust distinguishes between expressions and statements: expressions return
// a value based on its operand, and statements simply return a () type which behaves just like `void` in C/C++ language.
// We want to return a value of `i32` type from the `square` function, but it is returning a `()` type...
// They are not the same. There are two solutions:
// 1. Add a `return` ahead of `num * num;`
// 2. remove `;`, make it to be `num * num`

35
exercises/if/if1.rs
View file

@ -5,7 +5,7 @@ pub fn bigger(a: i32, b: i32) -> i32 {
// Do not use: // Do not use:
// - another function call // - another function call
// - additional variables // - additional variables
// Scroll down for hints. // Execute `rustlings hint if1` for hints
} }
// Don't mind this for now :) // Don't mind this for now :)
@ -23,36 +23,3 @@ mod tests {
assert_eq!(42, bigger(32, 42)); assert_eq!(42, bigger(32, 42));
} }
} }
// It's possible to do this in one line if you would like!
// Some similar examples from other languages:
// - In C(++) this would be: `a > b ? a : b`
// - In Python this would be: `a if a > b else b`
// Remember in Rust that:
// - the `if` condition does not need to be surrounded by parentheses
// - `if`/`else` conditionals are expressions
// - Each condition is followed by a `{}` block.

54
exercises/macros/macros1.rs
View file

@ -1,5 +1,5 @@
// macros1.rs // macros1.rs
// Make me compile! Scroll down for hints :) // Make me compile! Execute `rustlings hint macros1` for hints :)
macro_rules! my_macro { macro_rules! my_macro {
() => { () => {
@ -10,55 +10,3 @@ macro_rules! my_macro {
fn main() { fn main() {
my_macro(); my_macro();
} }
// When you call a macro, you need to add something special compared to a
// regular function call. If you're stuck, take a look at what's inside
// `my_macro`.

63
exercises/macros/macros2.rs
View file

@ -1,5 +1,5 @@
// macros2.rs // macros2.rs
// Make me compile! Scroll down for hints :) // Make me compile! Execute `rustlings hint macros2` for hints :)
fn main() { fn main() {
my_macro!(); my_macro!();
@ -10,64 +10,3 @@ macro_rules! my_macro {
println!("Check out my macro!"); println!("Check out my macro!");
}; };
} }
// Macros don't quite play by the same rules as the rest of Rust, in terms of
// what's available where.
// Unlike other things in Rust, the order of "where you define a macro" versus
// "where you use it" actually matters.

64
exercises/macros/macros3.rs
View file

@ -1,5 +1,6 @@
// macros3.rs // macros3.rs
// Make me compile, without taking the macro out of the module! Scroll down for hints :) // Make me compile, without taking the macro out of the module!
// Execute `rustlings hint macros3` for hints :)
mod macros { mod macros {
macro_rules! my_macro { macro_rules! my_macro {
@ -12,64 +13,3 @@ mod macros {
fn main() { fn main() {
my_macro!(); my_macro!();
} }
// In order to use a macro outside of its module, you need to do something
// special to the module to lift the macro out into its parent.
// The same trick also works on "extern crate" statements for crates that have
// exported macros, if you've seen any of those around.

63
exercises/macros/macros4.rs
View file

@ -1,5 +1,5 @@
// macros4.rs // macros4.rs
// Make me compile! Scroll down for hints :) // Make me compile! Execute `rustlings hint macros4` for hints :)
macro_rules! my_macro { macro_rules! my_macro {
() => { () => {
@ -14,64 +14,3 @@ fn main() {
my_macro!(); my_macro!();
my_macro!(7777); my_macro!(7777);
} }
// You only need to add a single character to make this compile.
// The way macros are written, it wants to see something between each
// "macro arm", so it can separate them.

33
exercises/modules/modules1.rs
View file

@ -1,5 +1,5 @@
// modules1.rs // modules1.rs
// Make me compile! Scroll down for hints :) // Make me compile! Execute `rustlings hint modules1` for hints :)
mod sausage_factory { mod sausage_factory {
fn make_sausage() { fn make_sausage() {
@ -10,34 +10,3 @@ mod sausage_factory {
fn main() { fn main() {
sausage_factory::make_sausage(); sausage_factory::make_sausage();
} }
// Everything is private in Rust by default-- but there's a keyword we can use
// to make something public! The compiler error should point to the thing that
// needs to be public.

24
exercises/modules/modules2.rs
View file

@ -1,5 +1,5 @@
// modules2.rs // modules2.rs
// Make me compile! Scroll down for hints :) // Make me compile! Execute `rustlings hint modules2` for hints :)
mod delicious_snacks { mod delicious_snacks {
use self::fruits::PEAR as fruit; use self::fruits::PEAR as fruit;
@ -23,25 +23,3 @@ fn main() {
delicious_snacks::veggie 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.

20
exercises/move_semantics/move_semantics1.rs
View file

@ -1,5 +1,5 @@
// move_semantics1.rs // move_semantics1.rs
// Make me compile! Scroll down for hints :) // Make me compile! Execute `rustlings hint move_semantics1` for hints :)
fn main() { fn main() {
let vec0 = Vec::new(); let vec0 = Vec::new();
@ -22,21 +22,3 @@ fn fill_vec(vec: Vec<i32>) -> Vec<i32> {
vec vec
} }
// So you've got the "cannot borrow immutable local variable `vec1` as mutable" error on line 11,
// right? The fix for this is going to be adding one keyword, and the addition is NOT on line 11
// where the error is.

31
exercises/move_semantics/move_semantics2.rs
View file

@ -1,5 +1,6 @@
// move_semantics2.rs // move_semantics2.rs
// Make me compile without changing line 10! Scroll down for hints :) // Make me compile without changing line 10!
// Execute `rustlings hint move_semantics2` for hints :)
fn main() { fn main() {
let vec0 = Vec::new(); let vec0 = Vec::new();
@ -23,31 +24,3 @@ fn fill_vec(vec: Vec<i32>) -> Vec<i32> {
vec vec
} }
// So `vec0` is being *moved* into the function `fill_vec` when we call it on
// line 7, which means it gets dropped at the end of `fill_vec`, which means we
// can't use `vec0` again on line 10 (or anywhere else in `main` after the
// `fill_vec` call for that matter). We could fix this in a few ways, try them
// all!
// 1. Make another, separate version of the data that's in `vec0` and pass that
// to `fill_vec` instead.
// 2. Make `fill_vec` borrow its argument instead of taking ownership of it,
// and then copy the data within the function in order to return an owned
// `Vec<i32>`
// 3. Make `fill_vec` *mutably* borrow its argument (which will need to be
// mutable), modify it directly, then not return anything. Then you can get rid
// of `vec1` entirely -- note that this will change what gets printed by the
// first `println!`

23
exercises/move_semantics/move_semantics3.rs
View file

@ -1,7 +1,7 @@
// move_semantics3.rs // move_semantics3.rs
// Make me compile without adding new lines-- just changing existing lines! // Make me compile without adding new lines-- just changing existing lines!
// (no lines with multiple semicolons necessary!) // (no lines with multiple semicolons necessary!)
// Scroll down for hints :) // Execute `rustlings hint move_semantics3` for hints :)
fn main() { fn main() {
let vec0 = Vec::new(); let vec0 = Vec::new();
@ -22,24 +22,3 @@ fn fill_vec(vec: Vec<i32>) -> Vec<i32> {
vec vec
} }
// The difference between this one and the previous ones is that the first line
// of `fn fill_vec` that had `let mut vec = vec;` is no longer there. You can,
// instead of adding that line back, add `mut` in one place that will change
// an existing binding to be a mutable binding instead of an immutable one :)

24
exercises/move_semantics/move_semantics4.rs
View file

@ -1,7 +1,8 @@
// move_semantics4.rs // move_semantics4.rs
// Refactor this code so that instead of having `vec0` and creating the vector // Refactor this code so that instead of having `vec0` and creating the vector
// in `fn main`, we instead create it within `fn fill_vec` and transfer the // in `fn main`, we instead create it within `fn fill_vec` and transfer the
// freshly created vector from fill_vec to its caller. Scroll for hints! // freshly created vector from fill_vec to its caller.
// Execute `rustlings hint move_semantics4` for hints!
fn main() { fn main() {
let vec0 = Vec::new(); let vec0 = Vec::new();
@ -25,24 +26,3 @@ fn fill_vec() -> Vec<i32> {
vec vec
} }
// Stop reading whenever you feel like you have enough direction :) Or try
// doing one step and then fixing the compiler errors that result!
// So the end goal is to:
// - get rid of the first line in main that creates the new vector
// - so then `vec0` doesn't exist, so we can't pass it to `fill_vec`
// - we don't want to pass anything to `fill_vec`, so its signature should
// reflect that it does not take any arguments
// - since we're not creating a new vec in `main` anymore, we need to create
// a new vec in `fill_vec`, similarly to the way we did in `main`

36
exercises/primitive_types/primitive_types3.rs
View file

@ -1,6 +1,6 @@
// primitive_types3.rs // primitive_types3.rs
// Create an array with at least 100 elements in it where the ??? is. // Create an array with at least 100 elements in it where the ??? is.
// Scroll down for hints! // Execute `rustlings hint primitive_types3` for hints!
fn main() { fn main() {
let a = ??? let a = ???
@ -11,37 +11,3 @@ fn main() {
println!("Meh, I eat arrays like that for breakfast."); println!("Meh, I eat arrays like that for breakfast.");
} }
} }
// There's a shorthand to initialize Arrays with a certain size that does not
// require you to type in 100 items (but you certainly can if you want!).
// For example, you can do:
// let array = ["Are we there yet?"; 10];
// Bonus: what are some other things you could have that would return true
// for `a.len() >= 100`?

58
exercises/primitive_types/primitive_types4.rs
View file

@ -1,6 +1,6 @@
// primitive_types4.rs // primitive_types4.rs
// Get a slice out of Array a where the ??? is so that the `if` statement // Get a slice out of Array a where the ??? is so that the `if` statement
// returns true. Scroll down for hints!! // returns true. Execute `rustlings hint primitive_types4` for hints!!
#[test] #[test]
fn main() { fn main() {
@ -10,59 +10,3 @@ fn main() {
assert_eq!([2, 3, 4], nice_slice) assert_eq!([2, 3, 4], nice_slice)
} }
// Take a look at the Understanding Ownership -> Slices -> Other Slices section of the book:
// https://doc.rust-lang.org/book/ch04-03-slices.html
// and use the starting and ending indices of the items in the Array
// that you want to end up in the slice.
// If you're curious why the right hand of the `==` comparison does not
// have an ampersand for a reference since the left hand side is a
// reference, take a look at the Deref coercions section of the book:
// https://doc.rust-lang.org/book/ch15-02-deref.html

37
exercises/primitive_types/primitive_types5.rs
View file

@ -1,6 +1,6 @@
// primitive_types5.rs // primitive_types5.rs
// Destructure the `cat` tuple so that the println will work. // Destructure the `cat` tuple so that the println will work.
// Scroll down for hints! // Execute `rustlings hint primitive_types5` for hints!
fn main() { fn main() {
let cat = ("Furry McFurson", 3.5); let cat = ("Furry McFurson", 3.5);
@ -8,38 +8,3 @@ fn main() {
println!("{} is {} years old.", name, age); println!("{} is {} years old.", name, age);
} }
// Take a look at the Data Types -> The Tuple Type section of the book:
// https://doc.rust-lang.org/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!!

38
exercises/primitive_types/primitive_types6.rs
View file

@ -1,45 +1,9 @@
// primitive_types6.rs // primitive_types6.rs
// Use a tuple index to access the second element of `numbers`. // Use a tuple index to access the second element of `numbers`.
// You can put this right into the `println!` where the ??? is. // You can put this right into the `println!` where the ??? is.
// Scroll down for hints! // Execute `rustlings hint primitive_types6` for hints!
fn main() { fn main() {
let numbers = (1, 2, 3); let numbers = (1, 2, 3);
println!("The second number is {}", ???); println!("The second number is {}", ???);
} }
// 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/book/ch03-02-data-types.html#the-tuple-type
// Now you have another tool in your toolbox!

28
exercises/standard_library_types/arc1.rs
View file

@ -2,7 +2,7 @@
// Make this code compile by filling in a value for `shared_numbers` where the // Make this code compile by filling in a value for `shared_numbers` where the
// TODO comment is and creating an initial binding for `child_numbers` // TODO comment is and creating an initial binding for `child_numbers`
// somewhere. Try not to create any copies of the `numbers` Vec! // somewhere. Try not to create any copies of the `numbers` Vec!
// Scroll down for hints :) // Execute `rustlings help arc1` for hints :)
use std::sync::Arc; use std::sync::Arc;
use std::thread; use std::thread;
@ -27,29 +27,3 @@ fn main() {
handle.join().unwrap(); handle.join().unwrap();
} }
} }
// Make `shared_numbers` be an `Arc` from the numbers vector. Then, in order
// to avoid creating a copy of `numbers`, you'll need to create `child_numbers`
// inside the loop but still in the main thread.
// `child_numbers` should be a clone of the Arc of the numbers instead of a
// thread-local copy of the numbers.

101
exercises/standard_library_types/iterators2.rs
View file

@ -3,7 +3,7 @@
// Step 1. Complete the `capitalize_first` function to pass the first two cases // Step 1. Complete the `capitalize_first` function to pass the first two cases
// Step 2. Apply the `capitalize_first` function to a vector of strings, ensuring that it returns a vector of strings as well // Step 2. Apply the `capitalize_first` function to a vector of strings, ensuring that it returns a vector of strings as well
// Step 3. Apply the `capitalize_first` function again to a list, but try and ensure it returns a single string // Step 3. Apply the `capitalize_first` function again to a list, but try and ensure it returns a single string
// As always, there are hints below! // As always, there are hints if you execute `rustlings hint iterators2`!
pub fn capitalize_first(input: &str) -> String { pub fn capitalize_first(input: &str) -> String {
let mut c = input.chars(); let mut c = input.chars();
@ -44,102 +44,3 @@ mod tests {
assert_eq!(capitalized_words, "Hello World"); assert_eq!(capitalized_words, "Hello World");
} }
} }
// Step 1
// You need to call something on `first` before it can be collected
// Currently its type is `char`. Have a look at the methods that are available on that type:
// https://doc.rust-lang.org/std/primitive.char.html
// Step 2
// First you'll need to turn the Vec into an iterator
// Then you'll need to apply your function unto each item in the vector
// P.s. Don't forget to collect() at the end!
// Step 3.
// This is very similar to the previous test. The only real change is that you will need to
// alter the type that collect is coerced into. For a bonus you could try doing this with a
// turbofish

72
exercises/standard_library_types/iterators3.rs
View file

@ -4,8 +4,7 @@
// 1. Complete the divide function to get the first four tests to pass // 1. Complete the divide function to get the first four tests to pass
// 2. Uncomment the last two tests and get them to pass by filling in // 2. Uncomment the last two tests and get them to pass by filling in
// values for `x` using `division_results`. // values for `x` using `division_results`.
// Scroll down for a minor hint for part 2, and scroll down further for // Execute `rustlings hint iterators3` to get some hints!
// a major hint.
// Have fun :-) // Have fun :-)
#[derive(Debug, PartialEq, Eq)] #[derive(Debug, PartialEq, Eq)]
@ -75,72 +74,3 @@ mod tests {
} }
*/ */
} }
// Minor hint: In each of the two cases in the match in main, you can create x with either
// a 'turbofish' or by hinting the type of x to the compiler. You may try both.
// Major hint: Have a look at the Iter trait and at the explanation of its collect function.
// Especially the part about Result is interesting.

31
exercises/standard_library_types/iterators4.rs
View file

@ -9,7 +9,7 @@ pub fn factorial(num: u64) -> u64 {
// - additional variables // - additional variables
// For the most fun don't use: // For the most fun don't use:
// - recursion // - recursion
// Scroll down for hints. // Execute `rustlings hint iterators4` for hints.
} }
#[cfg(test)] #[cfg(test)]
@ -30,32 +30,3 @@ mod tests {
assert_eq!(24, factorial(4)); assert_eq!(24, factorial(4));
} }
} }
// In an imperative language you might write a for loop to iterate through
// multiply the values into a mutable variable. Or you might write code more
// functionally with recursion and a match clause. But you can also use ranges
// and iterators to solve this in rust.

38
exercises/strings/strings1.rs
View file

@ -1,5 +1,6 @@
// strings1.rs // strings1.rs
// Make me compile without changing the function signature! Scroll down for hints :) // Make me compile without changing the function signature!
// Execute `rustlings hint strings1` for hints ;)
fn main() { fn main() {
let answer = current_favorite_color(); let answer = current_favorite_color();
@ -9,38 +10,3 @@ fn main() {
fn current_favorite_color() -> String { fn current_favorite_color() -> String {
"blue" "blue"
} }
// The `current_favorite_color` function is currently returning a string slice with the `'static`
// lifetime. We know this because the data of the string lives in our code itself -- it doesn't
// come from a file or user input or another program -- so it will live as long as our program
// lives. But it is still a string slice. There's one way to create a `String` by converting a
// string slice covered in the Strings chapter of the book, and another way that uses the `From`
// trait.

32
exercises/strings/strings2.rs
View file

@ -1,5 +1,6 @@
// strings2.rs // strings2.rs
// Make me compile without changing the function signature! Scroll down for hints :) // Make me compile without changing the function signature!
// Execute `rustlings hint strings2` for hints :)
fn main() { fn main() {
let word = String::from("green"); // Try not changing this line :) let word = String::from("green"); // Try not changing this line :)
@ -13,32 +14,3 @@ fn main() {
fn is_a_color_word(attempt: &str) -> bool { fn is_a_color_word(attempt: &str) -> bool {
attempt == "green" || attempt == "blue" || attempt == "red" attempt == "green" || attempt == "blue" || attempt == "red"
} }
// Yes, it would be really easy to fix this by just changing the value bound to `word` to be a
// string slice instead of a `String`, wouldn't it?? There is a way to add one character to line
// 6, though, that will coerce the `String` into a string slice.

36
exercises/tests/tests1.rs
View file

@ -4,7 +4,7 @@
// rustlings run --test exercises/tests/tests1.rs // rustlings run --test exercises/tests/tests1.rs
// This test has a problem with it -- make the test compile! Make the test // This test has a problem with it -- make the test compile! Make the test
// pass! Make the test fail! Scroll down for hints :) // pass! Make the test fail! Execute `rustlings hint tests1` for hints :)
#[cfg(test)] #[cfg(test)]
mod tests { mod tests {
@ -13,37 +13,3 @@ mod tests {
assert!(); assert!();
} }
} }
// You don't even need to write any code to test -- you can just test values and run that, even
// though you wouldn't do that in real life :) `assert!` is a macro that needs an argument.
// Depending on the value of the argument, `assert!` will do nothing (in which case the test will
// pass) or `assert!` will panic (in which case the test will fail). So try giving different values
// to `assert!` and see which ones compile, which ones pass, and which ones fail :)

35
exercises/tests/tests2.rs
View file

@ -1,6 +1,6 @@
// tests2.rs // tests2.rs
// This test has a problem with it -- make the test compile! Make the test // This test has a problem with it -- make the test compile! Make the test
// pass! Make the test fail! Scroll down for hints :) // pass! Make the test fail! Execute `rustlings hint tests2` for hints :)
#[cfg(test)] #[cfg(test)]
mod tests { mod tests {
@ -9,36 +9,3 @@ mod tests {
assert_eq!(); assert_eq!();
} }
} }
// Like the previous exercise, you don't need to write any code to get this test to compile and
// run. `assert_eq!` is a macro that takes two arguments and compares them. Try giving it two
// values that are equal! Try giving it two arguments that are different! Try giving it two values
// that are of different types! Try switching which argument comes first and which comes second!

28
exercises/tests/tests3.rs
View file

@ -1,7 +1,8 @@
// tests3.rs // tests3.rs
// This test isn't testing our function -- make it do that in such a way that // 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 whether 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! // we expect to get when we call `is_even(5)`.
// Execute `rustlings hint tests3` for hints :)
pub fn is_even(num: i32) -> bool { pub fn is_even(num: i32) -> bool {
num % 2 == 0 num % 2 == 0
@ -16,28 +17,3 @@ mod tests {
assert!(); assert!();
} }
} }
// You can call a function right where you're passing arguments to `assert!` -- so you could do
// something like `assert!(having_fun())`. If you want to check that you indeed get false, you
// can negate the result of what you're doing using `!`, like `assert!(!having_fun())`.

72
exercises/threads/threads1.rs
View file

@ -1,8 +1,8 @@
// threads1.rs // threads1.rs
// Make this compile! Scroll down for hints :) The idea is the thread // Make this compile! Execute `rustlings hint threads1` for hints :)
// spawned on line 19 is completing jobs while the main thread is // The idea is the thread spawned on line 19 is completing jobs while the main thread is
// monitoring progress until 10 jobs are completed. If you see 6 lines // monitoring progress until 10 jobs are completed. If you see 6 lines
// of "waiting..." and the program ends without timing out the playground, // of "waiting..." and the program ends without timing out when running,
// you've got it :) // you've got it :)
use std::sync::Arc; use std::sync::Arc;
@ -27,69 +27,3 @@ fn main() {
thread::sleep(Duration::from_millis(500)); thread::sleep(Duration::from_millis(500));
} }
} }
// `Arc` is an Atomic Reference Counted pointer that allows safe, shared access
// to **immutable** data. But we want to *change* the number of `jobs_completed`
// so we'll need to also use another type that will only allow one thread to
// mutate the data at a time. Take a look at this section of the book:
// https://doc.rust-lang.org/book/ch16-03-shared-state.html#atomic-reference-counting-with-arct
// and keep scrolling if you'd like more hints :)
// Do you now have an `Arc` `Mutex` `JobStatus` at the beginning of main? Like:
// `let status = Arc::new(Mutex::new(JobStatus { jobs_completed: 0 }));`
// Similar to the code in the example in the book that happens after the text
// that says "We can use Arc<T> to fix this.". If not, give that a try! If you
// do and would like more hints, keep scrolling!!
// Make sure neither of your threads are holding onto the lock of the mutex
// while they are sleeping, since this will prevent the other thread from
// being allowed to get the lock. Locks are automatically released when
// they go out of scope.
// Ok, so, real talk, this was actually tricky for *me* to do too. And
// I could see a lot of different problems you might run into, so at this
// point I'm not sure which one you've hit :) Please see a few possible
// answers on https://github.com/carols10cents/rustlings/issues/3 --
// mine is a little more complicated because I decided I wanted to see
// the number of jobs currently done when I was checking the status.
// Please open an issue if you're still running into a problem that
// these hints are not helping you with, or if you've looked at the sample
// answers and don't understand why they work and yours doesn't.
// If you've learned from the sample solutions, I encourage you to come
// back to this exercise and try it again in a few days to reinforce
// what you've learned :)

37
exercises/variables/variables1.rs
View file

@ -1,42 +1,7 @@
// variables1.rs // variables1.rs
// Make me compile! Scroll down for hints :) // Make me compile! Execute the command `rustlings hint variables1` if you want a hint :)
fn main() { fn main() {
x = 5; x = 5;
println!("x has the value {}", x); println!("x has the value {}", x);
} }
// Hint: The declaration on line 5 is missing a keyword that is needed in Rust
// to create a new variable binding.

38
exercises/variables/variables2.rs
View file

@ -1,5 +1,5 @@
// variables2.rs // variables2.rs
// Make me compile! Scroll down for hints :) // Make me compile! Execute the command `rustlings hint variables2` if you want a hint :)
fn main() { fn main() {
let x; let x;
@ -9,39 +9,3 @@ fn main() {
println!("Not ten!"); println!("Not ten!");
} }
} }
// The compiler message is saying that Rust cannot infer the type that the
// variable binding `x` has with what is given here.
// What happens if you annotate line 5 with a type annotation?
// What if you give x a value?
// What if you do both?
// What type should x be, anyway?
// What if x is the same type as 10? What if it's a different type?

36
exercises/variables/variables3.rs
View file

@ -1,5 +1,5 @@
// variables3.rs // variables3.rs
// Make me compile! Scroll down for hints :) // Make me compile! Execute the command `rustlings hint variables3` if you want a hint :)
fn main() { fn main() {
let x = 3; let x = 3;
@ -7,37 +7,3 @@ fn main() {
x = 5; x = 5;
println!("Number {}", x); println!("Number {}", x);
} }
// In Rust, variable bindings are immutable by default. But here we're trying
// to reassign a different value to x! There's a keyword we can use to make
// a variable binding mutable instead.

40
exercises/variables/variables4.rs
View file

@ -1,45 +1,7 @@
// variables4.rs // variables4.rs
// Make me compile! Scroll down for hints :) // Make me compile! Execute the command `rustlings hint variables4` if you want a hint :)
fn main() { fn main() {
let x: i32; let x: i32;
println!("Number {}", x); println!("Number {}", x);
} }
// Oops! In this exercise, we have a variable binding that we've created on
// line 5, and we're trying to use it on line 6, but we haven't given it a
// value. We can't print out something that isn't there; try giving x a value!
// This is an error that can cause bugs that's very easy to make in any
// programming language -- thankfully the Rust compiler has caught this for us!

324
info.toml
View file

@ -4,21 +4,42 @@
name = "variables1" name = "variables1"
path = "exercises/variables/variables1.rs" path = "exercises/variables/variables1.rs"
mode = "compile" mode = "compile"
hint = """
Hint: The declaration on line 5 is missing a keyword that is needed in Rust
to create a new variable binding."""
[[exercises]] [[exercises]]
name = "variables2" name = "variables2"
path = "exercises/variables/variables2.rs" path = "exercises/variables/variables2.rs"
mode = "compile" mode = "compile"
hint = """
The compiler message is saying that Rust cannot infer the type that the
variable binding `x` has with what is given here.
What happens if you annotate line 5 with a type annotation?
What if you give x a value?
What if you do both?
What type should x be, anyway?
What if x is the same type as 10? What if it's a different type?"""
[[exercises]] [[exercises]]
name = "variables3" name = "variables3"
path = "exercises/variables/variables3.rs" path = "exercises/variables/variables3.rs"
mode = "compile" mode = "compile"
hint = """
In Rust, variable bindings are immutable by default. But here we're trying
to reassign a different value to x! There's a keyword we can use to make
a variable binding mutable instead."""
[[exercises]] [[exercises]]
name = "variables4" name = "variables4"
path = "exercises/variables/variables4.rs" path = "exercises/variables/variables4.rs"
mode = "compile" mode = "compile"
hint = """
Oops! In this exercise, we have a variable binding that we've created on
line 5, and we're trying to use it on line 6, but we haven't given it a
value. We can't print out something that isn't there; try giving x a value!
This is an error that can cause bugs that's very easy to make in any
programming language -- thankfully the Rust compiler has caught this for us!"""
# IF # IF
@ -26,6 +47,15 @@ mode = "compile"
name = "if1" name = "if1"
path = "exercises/if/if1.rs" path = "exercises/if/if1.rs"
mode = "test" mode = "test"
hint = """
It's possible to do this in one line if you would like!
Some similar examples from other languages:
- In C(++) this would be: `a > b ? a : b`
- In Python this would be: `a if a > b else b`
Remember in Rust that:
- the `if` condition does not need to be surrounded by parentheses
- `if`/`else` conditionals are expressions
- Each condition is followed by a `{}` block."""
# FUNCTIONS # FUNCTIONS
@ -33,26 +63,50 @@ mode = "test"
name = "functions1" name = "functions1"
path = "exercises/functions/functions1.rs" path = "exercises/functions/functions1.rs"
mode = "compile" mode = "compile"
hint = """
This main function is calling a function that it expects to exist, but the
function doesn't exist. It expects this function to have the name `call_me`.
It expects this function to not take any arguments and not return a value.
Sounds a lot like `main`, doesn't it?"""
[[exercises]] [[exercises]]
name = "functions2" name = "functions2"
path = "exercises/functions/functions2.rs" path = "exercises/functions/functions2.rs"
mode = "compile" mode = "compile"
hint = """
Rust requires that all parts of a function's signature have type annotations,
but `call_me` is missing the type annotation of `num`."""
[[exercises]] [[exercises]]
name = "functions3" name = "functions3"
path = "exercises/functions/functions3.rs" path = "exercises/functions/functions3.rs"
mode = "compile" mode = "compile"
hint = """
This time, the function *declaration* is okay, but there's something wrong
with the place where we're calling the function."""
[[exercises]] [[exercises]]
name = "functions4" name = "functions4"
path = "exercises/functions/functions4.rs" path = "exercises/functions/functions4.rs"
mode = "compile" mode = "compile"
hint = """
The error message points to line 12 and says it expects a type after the
`->`. This is where the function's return type should be-- take a look at
the `is_even` function for an example!"""
[[exercises]] [[exercises]]
name = "functions5" name = "functions5"
path = "exercises/functions/functions5.rs" path = "exercises/functions/functions5.rs"
mode = "compile" mode = "compile"
hint = """
This is a really common error that can be fixed by removing one character.
It happens because Rust distinguishes between expressions and statements: expressions return
a value based on its operand, and statements simply return a () type which behaves just like `void` in C/C++ language.
We want to return a value of `i32` type from the `square` function, but it is returning a `()` type...
They are not the same. There are two solutions:
1. Add a `return` ahead of `num * num;`
2. remove `;`, make it to be `num * num`
"""
# TEST 1 # TEST 1
@ -60,6 +114,7 @@ mode = "compile"
name = "test1" name = "test1"
path = "exercises/test1.rs" path = "exercises/test1.rs"
mode = "test" mode = "test"
hint = "No hints this time ;)"
# PRIMITIVE TYPES # PRIMITIVE TYPES
@ -67,31 +122,64 @@ mode = "test"
name = "primitive_types1" name = "primitive_types1"
path = "exercises/primitive_types/primitive_types1.rs" path = "exercises/primitive_types/primitive_types1.rs"
mode = "compile" mode = "compile"
hint = "No hints this time ;)"
[[exercises]] [[exercises]]
name = "primitive_types2" name = "primitive_types2"
path = "exercises/primitive_types/primitive_types2.rs" path = "exercises/primitive_types/primitive_types2.rs"
mode = "compile" mode = "compile"
hint = "No hints this time ;)"
[[exercises]] [[exercises]]
name = "primitive_types3" name = "primitive_types3"
path = "exercises/primitive_types/primitive_types3.rs" path = "exercises/primitive_types/primitive_types3.rs"
mode = "compile" mode = "compile"
hint = """
There's a shorthand to initialize Arrays with a certain size that does not
require you to type in 100 items (but you certainly can if you want!).
For example, you can do:
let array = ["Are we there yet?"; 10];
Bonus: what are some other things you could have that would return true
for `a.len() >= 100`?"""
[[exercises]] [[exercises]]
name = "primitive_types4" name = "primitive_types4"
path = "exercises/primitive_types/primitive_types4.rs" path = "exercises/primitive_types/primitive_types4.rs"
mode = "test" mode = "test"
hint = """
Take a look at the Understanding Ownership -> Slices -> Other Slices section of the book:
https://doc.rust-lang.org/book/ch04-03-slices.html
and use the starting and ending indices of the items in the Array
that you want to end up in the slice.
If you're curious why the right hand of the `==` comparison does not
have an ampersand for a reference since the left hand side is a
reference, take a look at the Deref coercions section of the book:
https://doc.rust-lang.org/book/ch15-02-deref.html
"""
[[exercises]] [[exercises]]
name = "primitive_types5" name = "primitive_types5"
path = "exercises/primitive_types/primitive_types5.rs" path = "exercises/primitive_types/primitive_types5.rs"
mode = "compile" mode = "compile"
hint = """
Take a look at the Data Types -> The Tuple Type section of the book:
https://doc.rust-lang.org/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!!"""
[[exercises]] [[exercises]]
name = "primitive_types6" name = "primitive_types6"
path = "exercises/primitive_types/primitive_types6.rs" path = "exercises/primitive_types/primitive_types6.rs"
mode = "compile" mode = "compile"
hint = """
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/book/ch03-02-data-types.html#the-tuple-type
Now you have another tool in your toolbox!"""
# STRUCTS # STRUCTS
@ -99,11 +187,13 @@ mode = "compile"
name = "structs1" name = "structs1"
path = "exercises/structs/structs1.rs" path = "exercises/structs/structs1.rs"
mode = "test" mode = "test"
hint = "No hints this time ;)"
[[exercises]] [[exercises]]
name = "structs2" name = "structs2"
path = "exercises/structs/structs2.rs" path = "exercises/structs/structs2.rs"
mode = "test" mode = "test"
hint = "No hints this time ;)"
# STRINGS # STRINGS
@ -111,11 +201,22 @@ mode = "test"
name = "strings1" name = "strings1"
path = "exercises/strings/strings1.rs" path = "exercises/strings/strings1.rs"
mode = "compile" mode = "compile"
hint = """
The `current_favorite_color` function is currently returning a string slice with the `'static`
lifetime. We know this because the data of the string lives in our code itself -- it doesn't
come from a file or user input or another program -- so it will live as long as our program
lives. But it is still a string slice. There's one way to create a `String` by converting a
string slice covered in the Strings chapter of the book, and another way that uses the `From`
trait."""
[[exercises]] [[exercises]]
name = "strings2" name = "strings2"
path = "exercises/strings/strings2.rs" path = "exercises/strings/strings2.rs"
mode = "compile" mode = "compile"
hint = """
Yes, it would be really easy to fix this by just changing the value bound to `word` to be a
string slice instead of a `String`, wouldn't it?? There is a way to add one character to line
6, though, that will coerce the `String` into a string slice."""
# TEST 2 # TEST 2
@ -123,6 +224,7 @@ mode = "compile"
name = "test2" name = "test2"
path = "exercises/test2.rs" path = "exercises/test2.rs"
mode = "compile" mode = "compile"
hint = "No hints this time ;)"
# ENUMS # ENUMS
@ -130,16 +232,22 @@ mode = "compile"
name = "enums1" name = "enums1"
path = "exercises/enums/enums1.rs" path = "exercises/enums/enums1.rs"
mode = "compile" mode = "compile"
hint = """
Hint: The declaration of the enumeration type has not been defined yet."""
[[exercises]] [[exercises]]
name = "enums2" name = "enums2"
path = "exercises/enums/enums2.rs" path = "exercises/enums/enums2.rs"
mode = "compile" mode = "compile"
hint = """
Hint: you can create enumerations that have different variants with different types
such as no data, anonymous structs, a single string, tuples, ...etc"""
[[exercises]] [[exercises]]
name = "enums3" name = "enums3"
path = "exercises/enums/enums3.rs" path = "exercises/enums/enums3.rs"
mode = "test" mode = "test"
hint = "No hints this time ;)"
# TESTS # TESTS
@ -147,16 +255,31 @@ mode = "test"
name = "tests1" name = "tests1"
path = "exercises/tests/tests1.rs" path = "exercises/tests/tests1.rs"
mode = "test" mode = "test"
hint = """
You don't even need to write any code to test -- you can just test values and run that, even
though you wouldn't do that in real life :) `assert!` is a macro that needs an argument.
Depending on the value of the argument, `assert!` will do nothing (in which case the test will
pass) or `assert!` will panic (in which case the test will fail). So try giving different values
to `assert!` and see which ones compile, which ones pass, and which ones fail :)"""
[[exercises]] [[exercises]]
name = "tests2" name = "tests2"
path = "exercises/tests/tests2.rs" path = "exercises/tests/tests2.rs"
mode = "test" mode = "test"
hint = """
Like the previous exercise, you don't need to write any code to get this test to compile and
run. `assert_eq!` is a macro that takes two arguments and compares them. Try giving it two
values that are equal! Try giving it two arguments that are different! Try giving it two values
that are of different types! Try switching which argument comes first and which comes second!"""
[[exercises]] [[exercises]]
name = "tests3" name = "tests3"
path = "exercises/tests/tests3.rs" path = "exercises/tests/tests3.rs"
mode = "test" mode = "test"
hint = """
You can call a function right where you're passing arguments to `assert!` -- so you could do
something like `assert!(having_fun())`. If you want to check that you indeed get false, you
can negate the result of what you're doing using `!`, like `assert!(!having_fun())`."""
# TEST 3 # TEST 3
@ -164,6 +287,7 @@ mode = "test"
name = "test3" name = "test3"
path = "exercises/test3.rs" path = "exercises/test3.rs"
mode = "test" mode = "test"
hint = "No hints this time ;)"
# MODULES # MODULES
@ -171,11 +295,21 @@ mode = "test"
name = "modules1" name = "modules1"
path = "exercises/modules/modules1.rs" path = "exercises/modules/modules1.rs"
mode = "compile" mode = "compile"
hint = """
Everything is private in Rust by default-- but there's a keyword we can use
to make something public! The compiler error should point to the thing that
needs to be public."""
[[exercises]] [[exercises]]
name = "modules2" name = "modules2"
path = "exercises/modules/modules2.rs" path = "exercises/modules/modules2.rs"
mode = "compile" mode = "compile"
hint = """
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."""
# MACROS # MACROS
@ -183,28 +317,48 @@ mode = "compile"
name = "macros1" name = "macros1"
path = "exercises/macros/macros1.rs" path = "exercises/macros/macros1.rs"
mode = "compile" mode = "compile"
hint = """
When you call a macro, you need to add something special compared to a
regular function call. If you're stuck, take a look at what's inside
`my_macro`."""
[[exercises]] [[exercises]]
name = "macros2" name = "macros2"
path = "exercises/macros/macros2.rs" path = "exercises/macros/macros2.rs"
mode = "compile" mode = "compile"
hint = """
Macros don't quite play by the same rules as the rest of Rust, in terms of
what's available where.
Unlike other things in Rust, the order of "where you define a macro" versus
"where you use it" actually matters."""
[[exercises]] [[exercises]]
name = "macros3" name = "macros3"
path = "exercises/macros/macros3.rs" path = "exercises/macros/macros3.rs"
mode = "compile" mode = "compile"
hint = """
In order to use a macro outside of its module, you need to do something
special to the module to lift the macro out into its parent.
The same trick also works on "extern crate" statements for crates that have
exported macros, if you've seen any of those around."""
[[exercises]] [[exercises]]
name = "macros4" name = "macros4"
path = "exercises/macros/macros4.rs" path = "exercises/macros/macros4.rs"
mode = "compile" mode = "compile"
hint = """
You only need to add a single character to make this compile.
The way macros are written, it wants to see something between each
"macro arm", so it can separate them."""
# TEST 4 # TEST 4
[[exercises]] [[exercises]]
name = "test4" name = "test4"
path = "exercises/test4.rs" path = "exercises/test4.rs"
mode = "compile" mode = "compile"
hint = "No hints this time ;)"
# MOVE SEMANTICS # MOVE SEMANTICS
@ -212,21 +366,55 @@ mode = "compile"
name = "move_semantics1" name = "move_semantics1"
path = "exercises/move_semantics/move_semantics1.rs" path = "exercises/move_semantics/move_semantics1.rs"
mode = "compile" mode = "compile"
hint = """
So you've got the "cannot borrow immutable local variable `vec1` as mutable" error on line 11,
right? The fix for this is going to be adding one keyword, and the addition is NOT on line 11
where the error is."""
[[exercises]] [[exercises]]
name = "move_semantics2" name = "move_semantics2"
path = "exercises/move_semantics/move_semantics2.rs" path = "exercises/move_semantics/move_semantics2.rs"
mode = "compile" mode = "compile"
hint = """
So `vec0` is being *moved* into the function `fill_vec` when we call it on
line 7, which means it gets dropped at the end of `fill_vec`, which means we
can't use `vec0` again on line 10 (or anywhere else in `main` after the
`fill_vec` call for that matter). We could fix this in a few ways, try them
all!
1. Make another, separate version of the data that's in `vec0` and pass that
to `fill_vec` instead.
2. Make `fill_vec` borrow its argument instead of taking ownership of it,
and then copy the data within the function in order to return an owned
`Vec<i32>`
3. Make `fill_vec` *mutably* borrow its argument (which will need to be
mutable), modify it directly, then not return anything. Then you can get rid
of `vec1` entirely -- note that this will change what gets printed by the
first `println!`"""
[[exercises]] [[exercises]]
name = "move_semantics3" name = "move_semantics3"
path = "exercises/move_semantics/move_semantics3.rs" path = "exercises/move_semantics/move_semantics3.rs"
mode = "compile" mode = "compile"
hint = """
The difference between this one and the previous ones is that the first line
of `fn fill_vec` that had `let mut vec = vec;` is no longer there. You can,
instead of adding that line back, add `mut` in one place that will change
an existing binding to be a mutable binding instead of an immutable one :)"""
[[exercises]] [[exercises]]
name = "move_semantics4" name = "move_semantics4"
path = "exercises/move_semantics/move_semantics4.rs" path = "exercises/move_semantics/move_semantics4.rs"
mode = "compile" mode = "compile"
hint = """
Stop reading whenever you feel like you have enough direction :) Or try
doing one step and then fixing the compiler errors that result!
So the end goal is to:
- get rid of the first line in main that creates the new vector
- so then `vec0` doesn't exist, so we can't pass it to `fill_vec`
- we don't want to pass anything to `fill_vec`, so its signature should
reflect that it does not take any arguments
- since we're not creating a new vec in `main` anymore, we need to create
a new vec in `fill_vec`, similarly to the way we did in `main`"""
# ERROR HANDLING # ERROR HANDLING
@ -234,21 +422,78 @@ mode = "compile"
name = "errors1" name = "errors1"
path = "exercises/error_handling/errors1.rs" path = "exercises/error_handling/errors1.rs"
mode = "test" mode = "test"
hint = """
`Err` is one of the variants of `Result`, so what the 2nd test is saying
is that `generate_nametag_text` should return a `Result` instead of an
`Option`.
To make this change, you'll need to:
- update the return type in the function signature to be a Result<String, String> that
could be the variants `Ok(String)` and `Err(String)`
- change the body of the function to return `Ok(stuff)` where it currently
returns `Some(stuff)`
- change the body of the function to return `Err(error message)` where it
currently returns `None`
- change the first test to expect `Ok(stuff)` where it currently expects
`Some(stuff)`."""
[[exercises]] [[exercises]]
name = "errors2" name = "errors2"
path = "exercises/error_handling/errors2.rs" path = "exercises/error_handling/errors2.rs"
mode = "test" mode = "test"
hint = """
One way to handle this is using a `match` statement on
`item_quantity.parse::<i32>()` where the cases are `Ok(something)` and
`Err(something)`. This pattern is very common in Rust, though, so there's
a `?` operator that does pretty much what you would make that match statement
do for you! Take a look at this section of the Error Handling chapter:
https://doc.rust-lang.org/book/ch09-02-recoverable-errors-with-result.html#a-shortcut-for-propagating-errors-the--operator
and give it a try!"""
[[exercises]] [[exercises]]
name = "errors3" name = "errors3"
path = "exercises/error_handling/errors3.rs" path = "exercises/error_handling/errors3.rs"
mode = "test" mode = "test"
hint = """
If other functions can return a `Result`, why shouldn't `main`?"""
[[exercises]] [[exercises]]
name = "errors4" name = "errors4"
path = "exercises/error_handling/errorsn.rs" path = "exercises/error_handling/errorsn.rs"
mode = "test" mode = "test"
hint = """
First hint: To figure out what type should go where the ??? is, take a look
at the test helper function `test_with_str`, since it returns whatever
`read_and_validate` returns and`test_with_str` has its signature fully
specified.
Next hint: There are three places in `read_and_validate` that we call a
function that returns a `Result` (that is, the functions might fail).
Apply the `?` operator on those calls so that we return immediately from
`read_and_validate` if those function calls fail.
Another hint: under the hood, the `?` operator calls `From::from`
on the error value to convert it to a boxed trait object, a Box<dyn error::Error>,
which is polymorphic-- that means that lots of different kinds of errors
can be returned from the same function because all errors act the same
since they all implement the `error::Error` trait.
Check out this section of the book:
https://doc.rust-lang.org/book/ch09-02-recoverable-errors-with-result.html#a-shortcut-for-propagating-errors-the--operator
Another another hint: Note that because the `?` operator returns
the *unwrapped* value in the `Ok` case, if we want to return a `Result` from
`read_and_validate` for *its* success case, we'll have to rewrap a value
that we got from the return value of a `?`ed call in an `Ok`-- this will
look like `Ok(something)`.
Another another another hint: `Result`s must be "used", that is, you'll
get a warning if you don't handle a `Result` that you get in your
function. Read more about that in the `std::result` module docs:
https://doc.rust-lang.org/std/result/#results-must-be-used"""
# OPTIONS / RESULTS # OPTIONS / RESULTS
@ -256,11 +501,21 @@ mode = "test"
name = "option1" name = "option1"
path = "exercises/error_handling/option1.rs" path = "exercises/error_handling/option1.rs"
mode = "test" mode = "test"
hint = """
Try using a `match` statement where the arms are `Some(thing)` and `None`.
Or set a default value to print out if you get `None` by using the
function `unwrap_or`.
Or use an `if let` statement on the result of `pop()` to both destructure
a `Some` value and only print out something if we have a value!"""
[[exercises]] [[exercises]]
name = "option2" name = "option2"
path = "exercises/error_handling/result1.rs" path = "exercises/error_handling/result1.rs"
mode = "test" mode = "test"
hint = """
`PositiveNonzeroInteger::new` is always creating a new instance and returning an `Ok` result.
It should be doing some checking, returning an `Err` result if those checks fail, and only
returning an `Ok` result if those checks determine that everything is... okay :)"""
# STANDARD LIBRARY TYPES # STANDARD LIBRARY TYPES
@ -268,21 +523,56 @@ mode = "test"
name = "arc1" name = "arc1"
path = "exercises/standard_library_types/arc1.rs" path = "exercises/standard_library_types/arc1.rs"
mode = "compile" mode = "compile"
hint = """
Make `shared_numbers` be an `Arc` from the numbers vector. Then, in order
to avoid creating a copy of `numbers`, you'll need to create `child_numbers`
inside the loop but still in the main thread.
`child_numbers` should be a clone of the Arc of the numbers instead of a
thread-local copy of the numbers."""
[[exercises]] [[exercises]]
name = "iterators2" name = "iterators2"
path = "exercises/standard_library_types/iterators2.rs" path = "exercises/standard_library_types/iterators2.rs"
mode = "test" mode = "test"
hint = """
Step 1
You need to call something on `first` before it can be collected
Currently its type is `char`. Have a look at the methods that are available on that type:
https://doc.rust-lang.org/std/primitive.char.html
Step 2
First you'll need to turn the Vec into an iterator
Then you'll need to apply your function unto each item in the vector
P.s. Don't forget to collect() at the end!
Step 3.
This is very similar to the previous test. The only real change is that you will need to
alter the type that collect is coerced into. For a bonus you could try doing this with a
turbofish"""
[[exercises]] [[exercises]]
name = "iterators3" name = "iterators3"
path = "exercises/standard_library_types/iterators3.rs" path = "exercises/standard_library_types/iterators3.rs"
mode = "test" mode = "test"
hint = """
Minor hint: In each of the two cases in the match in main, you can create x with either
a 'turbofish' or by hinting the type of x to the compiler. You may try both.
Major hint: Have a look at the Iter trait and at the explanation of its collect function.
Especially the part about Result is interesting."""
[[exercises]] [[exercises]]
name = "iterators4" name = "iterators4"
path = "exercises/standard_library_types/iterators4.rs" path = "exercises/standard_library_types/iterators4.rs"
mode = "test" mode = "test"
hint = """
In an imperative language you might write a for loop to iterate through
multiply the values into a mutable variable. Or you might write code more
functionally with recursion and a match clause. But you can also use ranges
and iterators to solve this in rust."""
# THREADS # THREADS
@ -290,3 +580,35 @@ mode = "test"
name = "threads1" name = "threads1"
path = "exercises/threads/threads1.rs" path = "exercises/threads/threads1.rs"
mode = "compile" mode = "compile"
hint = """
`Arc` is an Atomic Reference Counted pointer that allows safe, shared access
to **immutable** data. But we want to *change* the number of `jobs_completed`
so we'll need to also use another type that will only allow one thread to
mutate the data at a time. Take a look at this section of the book:
https://doc.rust-lang.org/book/ch16-03-shared-state.html#atomic-reference-counting-with-arct
and keep reading if you'd like more hints :)
Do you now have an `Arc` `Mutex` `JobStatus` at the beginning of main? Like:
`let status = Arc::new(Mutex::new(JobStatus { jobs_completed: 0 }));`
Similar to the code in the example in the book that happens after the text
that says "We can use Arc<T> to fix this.". If not, give that a try! If you
do and would like more hints, keep reading!!
Make sure neither of your threads are holding onto the lock of the mutex
while they are sleeping, since this will prevent the other thread from
being allowed to get the lock. Locks are automatically released when
they go out of scope.
Ok, so, real talk, this was actually tricky for *me* to do too. And
I could see a lot of different problems you might run into, so at this
point I'm not sure which one you've hit :)
Please open an issue if you're still running into a problem that
these hints are not helping you with, or if you've looked at the sample
answers and don't understand why they work and yours doesn't.
If you've learned from the sample solutions, I encourage you to come
back to this exercise and try it again in a few days to reinforce
what you've learned :)"""

2
src/exercise.rs
View file

@ -27,6 +27,7 @@ pub struct Exercise {
pub name: String, pub name: String,
pub path: PathBuf, pub path: PathBuf,
pub mode: Mode, pub mode: Mode,
pub hint: String,
} }
impl Exercise { impl Exercise {
@ -74,6 +75,7 @@ mod test {
name: String::from("example"), name: String::from("example"),
path: PathBuf::from("example.rs"), path: PathBuf::from("example.rs"),
mode: Mode::Test, mode: Mode::Test,
hint: String::from(""),
}; };
exercise.clean(); exercise.clean();
assert!(!Path::new(&temp_file()).exists()); assert!(!Path::new(&temp_file()).exists());

20
src/main.rs
View file

@ -27,6 +27,12 @@ fn main() {
.about("Runs/Tests a single exercise") .about("Runs/Tests a single exercise")
.arg(Arg::with_name("name").required(true).index(1)), .arg(Arg::with_name("name").required(true).index(1)),
) )
.subcommand(
SubCommand::with_name("hint")
.alias("h")
.about("Returns a hint for the current exercise")
.arg(Arg::with_name("name").required(true).index(1)),
)
.get_matches(); .get_matches();
if None == matches.subcommand_name() { if None == matches.subcommand_name() {
@ -71,6 +77,20 @@ fn main() {
run(&exercise).unwrap_or_else(|_| std::process::exit(1)); run(&exercise).unwrap_or_else(|_| std::process::exit(1));
} }
if let Some(ref matches) = matches.subcommand_matches("hint") {
let name = matches.value_of("name").unwrap_or_else(|| {
println!("Please supply an exercise name!");
std::process::exit(1);
});
let exercise = exercises.iter().find(|e| name == e.name).unwrap_or_else(|| {
println!("No exercise found for your given name!");
std::process::exit(1)
});
println!("{}", exercise.hint);
}
if matches.subcommand_matches("verify").is_some() { if matches.subcommand_matches("verify").is_some() {
verify(&exercises).unwrap_or_else(|_| std::process::exit(1)); verify(&exercises).unwrap_or_else(|_| std::process::exit(1));
} }

2
tests/fixture/failure/info.toml
View file

@ -2,8 +2,10 @@
name = "compFailure" name = "compFailure"
path = "compFailure.rs" path = "compFailure.rs"
mode = "compile" mode = "compile"
hint = """"""
[[exercises]] [[exercises]]
name = "testFailure" name = "testFailure"
path = "testFailure.rs" path = "testFailure.rs"
mode = "test" mode = "test"
hint = """"""

2
tests/fixture/success/info.toml
View file

@ -2,8 +2,10 @@
name = "compSuccess" name = "compSuccess"
path = "compSuccess.rs" path = "compSuccess.rs"
mode = "compile" mode = "compile"
hint = """"""
[[exercises]] [[exercises]]
name = "testSuccess" name = "testSuccess"
path = "testSuccess.rs" path = "testSuccess.rs"
mode = "test" mode = "test"
hint = """"""