Iterator::find is a function which when passed an iterator, will return
the first element which satisfies the predicate as an Option. Its
signature:
pub trait Iterator {
// The type being iterated over.
type Item;
// `find` takes `&mut self` meaning the caller may be borrowed
// and modified, but not consumed.
fn find<P>(&mut self, predicate: P) -> Option<Self::Item> where
// `FnMut` meaning any captured variable may at most be
// modified, not consumed. `&Self::Item` states it takes
// arguments to the closure by reference.
P: FnMut(&Self::Item) -> bool {}
}
fn main() {
let vec1 = vec![1, 2, 3];
let vec2 = vec![4, 5, 6];
// `iter()` for vecs yields `&i32`.
let mut iter = vec1.iter();
// `into_iter()` for vecs yields `i32`.
let mut into_iter = vec2.into_iter();
// A reference to what is yielded is `&&i32`. Destructure to `i32`.
println!("Find 2 in vec1: {:?}", iter .find(|&&x| x == 2));
// A reference to what is yielded is `&i32`. Destructure to `i32`.
println!("Find 2 in vec2: {:?}", into_iter.find(| &x| x == 2));
let array1 = [1, 2, 3];
let array2 = [4, 5, 6];
// `iter()` for arrays yields `&i32`
println!("Find 2 in array1: {:?}", array1.iter() .find(|&&x| x == 2));
// `into_iter()` for arrays unusually yields `&i32`
println!("Find 2 in array2: {:?}", array2.into_iter().find(|&&x| x == 2));
}