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10 changed files with 106 additions and 6 deletions
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@ -26,6 +26,8 @@ bin = [
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{ name = "functions4_sol", path = "../solutions/02_functions/functions4.rs" },
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{ name = "functions5", path = "../exercises/02_functions/functions5.rs" },
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{ name = "functions5_sol", path = "../solutions/02_functions/functions5.rs" },
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{ name = "functions6", path = "../exercises/02_functions/functions6.rs" },
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{ name = "functions6_sol", path = "../solutions/02_functions/functions6.rs" },
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{ name = "if1", path = "../exercises/03_if/if1.rs" },
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{ name = "if1_sol", path = "../solutions/03_if/if1.rs" },
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{ name = "if2", path = "../exercises/03_if/if2.rs" },
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@ -60,6 +62,8 @@ bin = [
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{ name = "move_semantics4_sol", path = "../solutions/06_move_semantics/move_semantics4.rs" },
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{ name = "move_semantics5", path = "../exercises/06_move_semantics/move_semantics5.rs" },
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{ name = "move_semantics5_sol", path = "../solutions/06_move_semantics/move_semantics5.rs" },
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{ name = "move_semantics6", path = "../exercises/06_move_semantics/move_semantics6.rs" },
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{ name = "move_semantics6_sol", path = "../solutions/06_move_semantics/move_semantics6.rs" },
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{ name = "structs1", path = "../exercises/07_structs/structs1.rs" },
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{ name = "structs1_sol", path = "../solutions/07_structs/structs1.rs" },
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{ name = "structs2", path = "../exercises/07_structs/structs2.rs" },
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@ -1,8 +1,9 @@
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# Functions
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Here, you'll learn how to write functions and how the Rust compiler can help you debug errors even
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in more complex code.
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in more complex code. You will also learn what is the difference with closures.
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## Further information
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- [How Functions Work](https://doc.rust-lang.org/book/ch03-03-how-functions-work.html)
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- [Closures](https://doc.rust-lang.org/book/ch13-01-closures.html)
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19
exercises/02_functions/functions6.rs
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19
exercises/02_functions/functions6.rs
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@ -0,0 +1,19 @@
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// functions6.rs
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//
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// Here you can practice special functions called `closures`, that can capture
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// variables of their parent context.
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// Fix the code below to make it compile, without changing the two closure
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// definitions.
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//
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// Execute `rustlings hint functions6` or use the `hint` watch subcommand for
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// some hints.
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fn main() {
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// TODO: ensure the definition of captured variable
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let closure_1 = |input_var: u32| -> u32 {input_var + outer_var};
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println!("Closure#1 returns {}", closure_1(5));
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let closure_2 = |input_var| println!("Closure#2 (input_var {})", input_var);
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closure_2(2);
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closure_2("5"); // TODO: look at the captured variable type here
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}
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25
exercises/06_move_semantics/move_semantics6.rs
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25
exercises/06_move_semantics/move_semantics6.rs
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@ -0,0 +1,25 @@
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// move_semantics6.rs
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//
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// Here you will practice how mutable/immutable borrowing works in the context
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// of a closure.
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//
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// Try to fix this code to make it compile and not panic.
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// You can't change anything except removing 1 line.
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//
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// Execute `rustlings hint move_semantics7` or use the `hint` watch subcommand
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// for a hint.
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fn main() {
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let mut counter = 0;
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let mut increment = || {
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counter += 1;
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println!("counter equals {}", counter);
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};
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increment();
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let _reborrowed_counter = &counter; // TODO: figure out where to put this borrowing instruction
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increment();
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assert_eq!(counter, 2);
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}
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@ -4,9 +4,11 @@
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#[rustfmt::skip]
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#[allow(unused_variables, unused_assignments)]
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fn main() {
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let my_option: Option<()> = None;
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let my_option: Option<&str> = None;
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// Assume that you don't know the value of `my_option`.
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// In the case of `Some`, we want to print its value.
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if my_option.is_none() {
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println!("{:?}", my_option.unwrap());
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println!("{}", my_option.unwrap());
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}
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let my_arr = &[
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@ -3,7 +3,7 @@
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| Exercise | Book Chapter |
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| ---------------------- | ------------------- |
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| variables | §3.1 |
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| functions | §3.3 |
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| functions | §3.3, §13.1 |
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| if | §3.5 |
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| primitive_types | §3.2, §4.3 |
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| vecs | §8.1 |
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@ -187,6 +187,20 @@ There are two solutions:
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1. Add the `return` keyword before `num * num;`
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2. Remove the semicolon `;` after `num * num`"""
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[[exercises]]
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name = "functions6"
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dir = "02_functions"
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test = false
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hint = """
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Hint FIX #1: Closures can capture variables defined in the outer context.
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Hint FIX #2: Closures can infer both input and returned types, when they are not
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specified in the signature. But the closure cannot be reused with different
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input types.
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Read more about closures in the rust book dedicated section:
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https://doc.rust-lang.org/book/ch13-01-closures.html"""
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# IF
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[[exercises]]
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Once you've fixed that, `string_uppercase`'s function signature will also need
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to be adjusted."""
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[[exercises]]
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name = "move_semantics6"
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dir = "06_move_semantics"
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test = false
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hint = """
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When a closure captures a variable to modify it, it actually borrows that variable
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as a mutable reference. In this exercise, the closure mutably borrows the `counter`
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variable, thus, any attempt to borrow `counter` between closure calls leads to an error.
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You cannot immutably borrow a variable if a mutable closure is
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called later in the scope."""
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# STRUCTS
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[[exercises]]
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9
solutions/02_functions/functions6.rs
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9
solutions/02_functions/functions6.rs
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fn main() {
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let outer_var = 1;
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let closure_1 = |input_var: u32| -> u32 { input_var + outer_var };
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println!("Closure#1 returns {}", closure_1(5));
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let closure_2 = |input_var| println!("Closure#2 (input_var {})", input_var);
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closure_2(2);
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closure_2(5);
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}
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14
solutions/06_move_semantics/move_semantics6.rs
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14
solutions/06_move_semantics/move_semantics6.rs
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@ -0,0 +1,14 @@
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fn main() {
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let mut counter = 0;
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let mut increment = || {
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counter += 1;
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println!("counter equals {}", counter);
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};
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increment();
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increment();
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let _reborrowed_counter = &counter;
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assert_eq!(counter, 2);
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}
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@ -3,11 +3,11 @@ use std::mem;
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#[rustfmt::skip]
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#[allow(unused_variables, unused_assignments)]
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fn main() {
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let my_option: Option<()> = None;
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let my_option: Option<&str> = None;
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// `unwrap` of an `Option` after checking if it is `None` will panic.
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// Use `if-let` instead.
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if let Some(value) = my_option {
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println!("{value:?}");
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println!("{value}");
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}
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// A comma was missing.
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