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Core Advanced

11 Lifetimes

When a function or struct hands out a reference, the compiler needs to know how long it stays valid. Add the annotations that make these compile.

Step 1 / 2

Add lifetimes so longest compiles and returns the longer &str.

Hints

Tie inputs and output together: fn longest<'a>(x: &'a str, y: &'a str) -> &'a str.

11_lifetimes.rs

// add lifetimes so this compiles; return the longer &str
fn longest(x: &str, y: &str) -> &str {
    if x.len() >= y.len() { x } else { y }
}

// add lifetimes so this compiles; return the longer &str
fn longest(x: &str, y: &str) -> &str {
    if x.len() >= y.len() { x } else { y }
}

Reset to starterCompiled in a sandbox; hidden checks must pass.

Reveal solution

fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
    if x.len() >= y.len() { x } else { y }
}