Rust by Example - страница 28
>
>}
>fn main() {
>let fn_plain = create_fn();
>let mut fn_mut = create_fnmut();
>let fn_once = create_fnonce();
>fn_plain();
>fn_mut();
>fn_once();
>}
>הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
>XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
Fn, FnMut, Generics and impl Trait.
This section contains a few examples of using closures from the std library.
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
>// `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));
>}
>הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
>XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
Iterator::find is a function which iterates over an iterator and searches for the first value which satisfies some condition. If none of the values satisfy the condition, it returns None. 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.
(&mut self, predicate: P) -> Option>fn find
>// `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();
>// `iter()` for vecs yields `&i32`, and we want to reference one of its
>// items, so we have to destructure `&&i32` to `i32`
>println!("Find 2 in vec1: {:?}", iter .find(|&&x| x == 2));
>// `into_iter()` for vecs yields `i32`, and we want to reference one of
>// its items, so we have to destructure `&i32` 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));
>}
>הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה