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Core Intermediate

09 Closures

A closure is a small anonymous function that can capture variables from its surroundings. Return one from a function, then accept one as an argument -- the two shapes iterator chains are built from.

Step 2 / 2

Implement apply_twice: call the closure on x, then on the result.

Hints

Call a closure argument like any function: f(x).
Twice means feeding the result back in: f(f(x)).

09_closures.rs

// call f twice: f(f(x))
fn apply_twice(f: impl Fn(i32) -> i32, x: i32) -> i32 {
    todo!()
}

// call f twice: f(f(x))
fn apply_twice(f: impl Fn(i32) -> i32, x: i32) -> i32 {
    todo!()
}

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

Reveal solution

fn apply_twice(f: impl Fn(i32) -> i32, x: i32) -> i32 {
    f(f(x))
}

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09 Closures