feat: add functions6.rs and move_semantics6.rs exercises about closures

This commit is contained in:
Enrico 2023-11-01 22:36:58 +01:00
parent 0c79f2ea3e
commit 1c27aeead9
5 changed files with 79 additions and 2 deletions

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@ -1,8 +1,9 @@
# Functions # Functions
Here, you'll learn how to write functions and how the Rust compiler can help you debug errors even Here, you'll learn how to write functions and how the Rust compiler can help you debug errors even
in more complex code. in more complex code. You will also learn what is the difference with closures.
## Further information ## Further information
- [How Functions Work](https://doc.rust-lang.org/book/ch03-03-how-functions-work.html) - [How Functions Work](https://doc.rust-lang.org/book/ch03-03-how-functions-work.html)
- [Closures](https://doc.rust-lang.org/book/ch13-01-closures.html)

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// functions6.rs
//
// Here you can practice special functions called `closures`, that can capture
// variables of their parent context.
// Fix the code below to make it compile, without changing the two closure
// definitions.
//
// Execute `rustlings hint functions6` or use the `hint` watch subcommand for
// some hints.
// I AM NOT DONE
fn main() {
let closure_1 = |input_var: u32| -> u32 {input_var + outer_var};
println!("Closure#1 returns {}", closure_1(5));
let closure_2 = |input_var| println!("Closure#2 (input_var {})", input_var);
closure_2(2);
closure_2("5");
}

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// move_semantics6.rs
//
// Here you will practice how mutable/immutable borrowing works in the context
// of a closure.
//
// Try to fix this code to make it compile and not panic.
// You can't change anything except removing 1 line.
//
// Execute `rustlings hint move_semantics7` or use the `hint` watch subcommand
// for a hint.
// I AM NOT DONE
fn main() {
let mut counter = 0;
let mut increment = || {
counter += 1;
println!("counter: {}", counter);
};
increment();
let _reborrowed_counter = &counter;
increment();
assert_eq!(counter, 2);
}

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| Exercise | Book Chapter | | Exercise | Book Chapter |
| ---------------------- | ------------------- | | ---------------------- | ------------------- |
| variables | §3.1 | | variables | §3.1 |
| functions | §3.3 | | functions | §3.3, §13.1 |
| if | §3.5 | | if | §3.5 |
| primitive_types | §3.2, §4.3 | | primitive_types | §3.2, §4.3 |
| vecs | §8.1 | | vecs | §8.1 |

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@ -187,6 +187,21 @@ There are two solutions:
1. Add the `return` keyword before `num * num;` 1. Add the `return` keyword before `num * num;`
2. Remove the semicolon `;` after `num * num`""" 2. Remove the semicolon `;` after `num * num`"""
[[exercises]]
name = "functions6"
path = "exercises/02_functions/functions6.rs"
mode = "compile"
hint = """
Hint FIX #1: Closures can capture variables defined in the outer context.
Hint FIX #2: Closures can infer both input and returned types, when they are not
specified in the signature. But the closure cannot be reused with different
input types.
Read more about closures in the rust book dedicated section:
https://doc.rust-lang.org/book/ch13-01-closures.html
"""
# IF # IF
[[exercises]] [[exercises]]
@ -391,6 +406,20 @@ The first problem is that `get_char` is taking ownership of the string. So
Once you've fixed that, `string_uppercase`'s function signature will also need Once you've fixed that, `string_uppercase`'s function signature will also need
to be adjusted.""" to be adjusted."""
[[exercises]]
name = "move_semantics6"
path = "exercises/06_move_semantics/move_semantics6.rs"
mode = "compile"
hint = """
When a closure capture a variable to modify it, it borrows that variable as a
mutable reference. In this exercise, as the closure mutably borrows `counter`
and is called later, any attempt to reborrow `counter` in between will lead to
an error.
You cannot immutably borrow a variable if a mutable closure is
called later in the scope.
"""
# STRUCTS # STRUCTS
[[exercises]] [[exercises]]