mirror of https://github.com/rust-lang/rustlings
Auto merge of #231 - rust-lang:refactor-hints, r=jrvidal
Refactor hints Breaking change. This removes hints from the end of files, and puts them into `info.toml`. You can now access hints using: ``` rustlings hint <exerciseName> ``` ALSO this changes the exercise system to index by name for `run` and `hint`, so: ``` rustlings run exercises/if/if1.rs ``` becomes ``` rustlings run if1 ```pull/233/head
commit
9544ba1029
@ -1,241 +1,612 @@
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# VARIABLES
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[[exercises]]
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name = "variables1"
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path = "exercises/variables/variables1.rs"
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mode = "compile"
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hint = """
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Hint: The declaration on line 5 is missing a keyword that is needed in Rust
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to create a new variable binding."""
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[[exercises]]
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name = "variables2"
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path = "exercises/variables/variables2.rs"
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mode = "compile"
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hint = """
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The compiler message is saying that Rust cannot infer the type that the
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variable binding `x` has with what is given here.
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What happens if you annotate line 5 with a type annotation?
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What if you give x a value?
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What if you do both?
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What type should x be, anyway?
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What if x is the same type as 10? What if it's a different type?"""
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[[exercises]]
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name = "variables3"
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path = "exercises/variables/variables3.rs"
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mode = "compile"
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hint = """
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In Rust, variable bindings are immutable by default. But here we're trying
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to reassign a different value to x! There's a keyword we can use to make
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a variable binding mutable instead."""
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[[exercises]]
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name = "variables4"
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path = "exercises/variables/variables4.rs"
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mode = "compile"
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hint = """
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Oops! In this exercise, we have a variable binding that we've created on
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line 5, and we're trying to use it on line 6, but we haven't given it a
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value. We can't print out something that isn't there; try giving x a value!
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This is an error that can cause bugs that's very easy to make in any
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programming language -- thankfully the Rust compiler has caught this for us!"""
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# IF
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[[exercises]]
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name = "if1"
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path = "exercises/if/if1.rs"
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mode = "test"
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hint = """
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It's possible to do this in one line if you would like!
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Some similar examples from other languages:
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- In C(++) this would be: `a > b ? a : b`
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- In Python this would be: `a if a > b else b`
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Remember in Rust that:
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- the `if` condition does not need to be surrounded by parentheses
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- `if`/`else` conditionals are expressions
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- Each condition is followed by a `{}` block."""
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# FUNCTIONS
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[[exercises]]
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name = "functions1"
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path = "exercises/functions/functions1.rs"
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mode = "compile"
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hint = """
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This main function is calling a function that it expects to exist, but the
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function doesn't exist. It expects this function to have the name `call_me`.
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It expects this function to not take any arguments and not return a value.
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Sounds a lot like `main`, doesn't it?"""
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[[exercises]]
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name = "functions2"
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path = "exercises/functions/functions2.rs"
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mode = "compile"
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hint = """
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Rust requires that all parts of a function's signature have type annotations,
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but `call_me` is missing the type annotation of `num`."""
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[[exercises]]
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name = "functions3"
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path = "exercises/functions/functions3.rs"
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mode = "compile"
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hint = """
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This time, the function *declaration* is okay, but there's something wrong
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with the place where we're calling the function."""
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[[exercises]]
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name = "functions4"
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path = "exercises/functions/functions4.rs"
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mode = "compile"
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hint = """
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The error message points to line 12 and says it expects a type after the
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`->`. This is where the function's return type should be-- take a look at
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the `is_even` function for an example!"""
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[[exercises]]
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name = "functions5"
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path = "exercises/functions/functions5.rs"
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mode = "compile"
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hint = """
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This is a really common error that can be fixed by removing one character.
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It happens because Rust distinguishes between expressions and statements: expressions return
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a value based on its operand, and statements simply return a () type which behaves just like `void` in C/C++ language.
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We want to return a value of `i32` type from the `square` function, but it is returning a `()` type...
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They are not the same. There are two solutions:
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1. Add a `return` ahead of `num * num;`
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2. remove `;`, make it to be `num * num`"""
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# TEST 1
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[[exercises]]
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name = "test1"
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path = "exercises/test1.rs"
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mode = "test"
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hint = "No hints this time ;)"
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# PRIMITIVE TYPES
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[[exercises]]
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name = "primitive_types1"
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path = "exercises/primitive_types/primitive_types1.rs"
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mode = "compile"
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hint = "No hints this time ;)"
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[[exercises]]
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name = "primitive_types2"
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path = "exercises/primitive_types/primitive_types2.rs"
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mode = "compile"
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hint = "No hints this time ;)"
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[[exercises]]
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name = "primitive_types3"
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path = "exercises/primitive_types/primitive_types3.rs"
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mode = "compile"
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hint = """
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There's a shorthand to initialize Arrays with a certain size that does not
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require you to type in 100 items (but you certainly can if you want!).
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For example, you can do:
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let array = ["Are we there yet?"; 10];
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Bonus: what are some other things you could have that would return true
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for `a.len() >= 100`?"""
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[[exercises]]
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name = "primitive_types4"
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path = "exercises/primitive_types/primitive_types4.rs"
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mode = "test"
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hint = """
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Take a look at the Understanding Ownership -> Slices -> Other Slices section of the book:
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https://doc.rust-lang.org/book/ch04-03-slices.html
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and use the starting and ending indices of the items in the Array
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that you want to end up in the slice.
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If you're curious why the right hand of the `==` comparison does not
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have an ampersand for a reference since the left hand side is a
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reference, take a look at the Deref coercions section of the book:
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https://doc.rust-lang.org/book/ch15-02-deref.html"""
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[[exercises]]
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name = "primitive_types5"
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path = "exercises/primitive_types/primitive_types5.rs"
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mode = "compile"
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hint = """
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Take a look at the Data Types -> The Tuple Type section of the book:
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https://doc.rust-lang.org/book/ch03-02-data-types.html#the-tuple-type
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Particularly the part about destructuring (second to last example in the section).
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You'll need to make a pattern to bind `name` and `age` to the appropriate parts
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of the tuple. You can do it!!"""
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[[exercises]]
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name = "primitive_types6"
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path = "exercises/primitive_types/primitive_types6.rs"
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mode = "compile"
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hint = """
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While you could use a destructuring `let` for the tuple here, try
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indexing into it instead, as explained in the last example of the
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Data Types -> The Tuple Type section of the book:
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https://doc.rust-lang.org/book/ch03-02-data-types.html#the-tuple-type
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Now you have another tool in your toolbox!"""
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# STRUCTS
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[[exercises]]
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name = "structs1"
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path = "exercises/structs/structs1.rs"
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mode = "test"
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hint = "No hints this time ;)"
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[[exercises]]
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name = "structs2"
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path = "exercises/structs/structs2.rs"
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mode = "test"
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hint = "No hints this time ;)"
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# STRINGS
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[[exercises]]
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name = "strings1"
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path = "exercises/strings/strings1.rs"
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mode = "compile"
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hint = """
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The `current_favorite_color` function is currently returning a string slice with the `'static`
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lifetime. We know this because the data of the string lives in our code itself -- it doesn't
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come from a file or user input or another program -- so it will live as long as our program
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lives. But it is still a string slice. There's one way to create a `String` by converting a
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string slice covered in the Strings chapter of the book, and another way that uses the `From`
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trait."""
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[[exercises]]
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name = "strings2"
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path = "exercises/strings/strings2.rs"
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mode = "compile"
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hint = """
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Yes, it would be really easy to fix this by just changing the value bound to `word` to be a
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string slice instead of a `String`, wouldn't it?? There is a way to add one character to line
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6, though, that will coerce the `String` into a string slice."""
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# TEST 2
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[[exercises]]
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name = "test2"
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path = "exercises/test2.rs"
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mode = "compile"
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hint = "No hints this time ;)"
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# ENUMS
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[[exercises]]
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name = "enums1"
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path = "exercises/enums/enums1.rs"
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mode = "compile"
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hint = """
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Hint: The declaration of the enumeration type has not been defined yet."""
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[[exercises]]
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name = "enums2"
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path = "exercises/enums/enums2.rs"
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mode = "compile"
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hint = """
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Hint: you can create enumerations that have different variants with different types
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such as no data, anonymous structs, a single string, tuples, ...etc"""
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[[exercises]]
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name = "enums3"
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path = "exercises/enums/enums3.rs"
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mode = "test"
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hint = "No hints this time ;)"
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# TESTS
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[[exercises]]
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name = "tests1"
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path = "exercises/tests/tests1.rs"
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mode = "test"
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||||
hint = """
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You don't even need to write any code to test -- you can just test values and run that, even
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though you wouldn't do that in real life :) `assert!` is a macro that needs an argument.
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Depending on the value of the argument, `assert!` will do nothing (in which case the test will
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pass) or `assert!` will panic (in which case the test will fail). So try giving different values
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to `assert!` and see which ones compile, which ones pass, and which ones fail :)"""
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[[exercises]]
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name = "tests2"
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path = "exercises/tests/tests2.rs"
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mode = "test"
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||||
hint = """
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||||
Like the previous exercise, you don't need to write any code to get this test to compile and
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run. `assert_eq!` is a macro that takes two arguments and compares them. Try giving it two
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values that are equal! Try giving it two arguments that are different! Try giving it two values
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that are of different types! Try switching which argument comes first and which comes second!"""
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||||
[[exercises]]
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||||
name = "tests3"
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path = "exercises/tests/tests3.rs"
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mode = "test"
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||||
hint = """
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You can call a function right where you're passing arguments to `assert!` -- so you could do
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something like `assert!(having_fun())`. If you want to check that you indeed get false, you
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can negate the result of what you're doing using `!`, like `assert!(!having_fun())`."""
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# TEST 3
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[[exercises]]
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name = "test3"
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||||
path = "exercises/test3.rs"
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||||
mode = "test"
|
||||
hint = "No hints this time ;)"
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||||
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# MODULES
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||||
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||||
[[exercises]]
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||||
name = "modules1"
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path = "exercises/modules/modules1.rs"
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||||
mode = "compile"
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||||
hint = """
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||||
Everything is private in Rust by default-- but there's a keyword we can use
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||||
to make something public! The compiler error should point to the thing that
|
||||
needs to be public."""
|
||||
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||||
[[exercises]]
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||||
name = "modules2"
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||||
path = "exercises/modules/modules2.rs"
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mode = "compile"
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||||
hint = """
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||||
The delicious_snacks module is trying to present an external
|
||||
interface (the `fruit` and `veggie` constants) that is different than
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||||
its internal structure (the `fruits` and `veggies` modules and
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associated constants). It's almost there except for one keyword missing for
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each constant."""
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# MACROS
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||||
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[[exercises]]
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||||
name = "macros1"
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path = "exercises/macros/macros1.rs"
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||||
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]]
|
||||
name = "macros2"
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||||
path = "exercises/macros/macros2.rs"
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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]]
|
||||
name = "macros3"
|
||||
path = "exercises/macros/macros3.rs"
|
||||
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]]
|
||||
name = "macros4"
|
||||
path = "exercises/macros/macros4.rs"
|
||||
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
|
||||
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||||
[[exercises]]
|
||||
name = "test4"
|
||||
path = "exercises/test4.rs"
|
||||
mode = "compile"
|
||||
hint = "No hints this time ;)"
|
||||
|
||||
# MOVE SEMANTICS
|
||||
|
||||
[[exercises]]
|
||||
name = "move_semantics1"
|
||||
path = "exercises/move_semantics/move_semantics1.rs"
|
||||
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]]
|
||||
name = "move_semantics2"
|
||||
path = "exercises/move_semantics/move_semantics2.rs"
|
||||
mode = "compile"
|
||||
|
||||
[[exercises]]
|
||||
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]]
|
||||
name = "move_semantics3"
|
||||
path = "exercises/move_semantics/move_semantics3.rs"
|
||||
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]]
|
||||
name = "move_semantics4"
|
||||
path = "exercises/move_semantics/move_semantics4.rs"
|
||||
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
|
||||
|
||||
[[exercises]]
|
||||
name = "errors1"
|
||||
path = "exercises/error_handling/errors1.rs"
|
||||
mode = "test"
|
||||
|
||||
[[exercises]]
|
||||
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]]
|
||||
name = "errors2"
|
||||
path = "exercises/error_handling/errors2.rs"
|
||||
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]]
|
||||
name = "errors3"
|
||||
path = "exercises/error_handling/errors3.rs"
|
||||
mode = "test"
|
||||
hint = """
|
||||
If other functions can return a `Result`, why shouldn't `main`?"""
|
||||
|
||||
[[exercises]]
|
||||
name = "errorsn"
|
||||
path = "exercises/error_handling/errorsn.rs"
|
||||
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
|
||||
|
||||
[[exercises]]
|
||||
name = "option1"
|
||||
path = "exercises/error_handling/option1.rs"
|
||||
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]]
|
||||
name = "result1"
|
||||
path = "exercises/error_handling/result1.rs"
|
||||
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
|
||||
|
||||
[[exercises]]
|
||||
name = "arc1"
|
||||
path = "exercises/standard_library_types/arc1.rs"
|
||||
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]]
|
||||
name = "iterators2"
|
||||
path = "exercises/standard_library_types/iterators2.rs"
|
||||
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]]
|
||||
name = "iterators3"
|
||||
path = "exercises/standard_library_types/iterators3.rs"
|
||||
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]]
|
||||
name = "iterators4"
|
||||
path = "exercises/standard_library_types/iterators4.rs"
|
||||
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
|
||||
|
||||
[[exercises]]
|
||||
name = "threads1"
|
||||
path = "exercises/threads/threads1.rs"
|
||||
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 :)"""
|
||||
|
@ -1,7 +1,11 @@
|
||||
[[exercises]]
|
||||
name = "compFailure"
|
||||
path = "compFailure.rs"
|
||||
mode = "compile"
|
||||
hint = ""
|
||||
|
||||
[[exercises]]
|
||||
name = "testFailure"
|
||||
path = "testFailure.rs"
|
||||
mode = "test"
|
||||
mode = "test"
|
||||
hint = "Hello!"
|
||||
|
@ -1,7 +1,11 @@
|
||||
[[exercises]]
|
||||
name = "compSuccess"
|
||||
path = "compSuccess.rs"
|
||||
mode = "compile"
|
||||
hint = """"""
|
||||
|
||||
[[exercises]]
|
||||
name = "testSuccess"
|
||||
path = "testSuccess.rs"
|
||||
mode = "test"
|
||||
mode = "test"
|
||||
hint = """"""
|
||||
|
Loading…
Reference in New Issue