Rust by Example

Iterator::any is a function which when passed an iterator, will return true if any element satisfies the predicate. Otherwise false. Its signature:

pub trait Iterator {

// The type being iterated over.

type Item;

// `any` takes `&mut self` meaning the caller may be borrowed

// and modified, but not consumed.

fn any(&mut self, f: F) -> bool where

// `FnMut` meaning any captured variable may at most be

// modified, not consumed. `Self::Item` states it takes

// arguments to the closure by value.

F: FnMut(Self::Item) -> bool {}

}

fn main() {

let vec1 = vec![1, 2, 3];

let vec2 = vec![4, 5, 6];

// `iter()` for vecs yields `&i32`. Destructure to `i32`.

println!("2 in vec1: {}", vec1.iter()     .any(|&x| x == 2));

// `into_iter()` for vecs yields `i32`. No destructuring required.

println!("2 in vec2: {}", vec2.into_iter().any(| x| x == 2));

let array1 = [1, 2, 3];

let array2 = [4, 5, 6];

// `iter()` for arrays yields `&i32`.

println!("2 in array1: {}", array1.iter()     .any(|&x| x == 2));

// `into_iter()` for arrays unusually yields `&i32`.

println!("2 in array2: {}", array2.into_iter().any(|&x| x == 2));

}

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