相关疑难解决方法(0)

我正在做Rust示例教程,其中包含以下代码片段:

// Vec example
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));

// Array example
let array1 = [1, 2, 3];
let array2 = [4, 5, 6];

// `iter()` for arrays yields `&i32`.
println!("2 in array1: {}", array1.iter() …

我正在尝试编写一个涉及过滤和折叠数组的程序.我一直在使用The Rust Programming Language,第一版作为参考,但我不明白当我在数组上形成迭代器时会发生什么.这是一个例子:

fn compiles() {
    let range = (1..6);
    let range_iter = range.into_iter();
    range_iter.filter(|&x| x == 2);
}

fn does_not_compile() {
    let array = [1, 4, 3, 2, 2];
    let array_iter = array.into_iter();
    //13:34 error: the trait `core::cmp::PartialEq<_>` is not implemented for the type `&_` [E0277]
    array_iter.filter(|&x| x == 2);
}

fn janky_workaround() {
    let array = [1, 4, 3, 2, 2];
    let array_iter = array.into_iter();
    // Note the dereference in the lambda body
    array_iter.filter(|&x| …