How can a range be used in a Vec?

Question

This code works fine:

fn main() {
    let v: i32 = vec![1, 2, 3, 4, 5].iter().map(|&x: &i32| x.pow(2)).sum();
    println!("{}", v);
}

I tried to replace the vec![1, 2, 3, 4, 5] with vec![1..5] but iter and map did not work:

fn main() {
    let v: i32 = vec![1, 2, 3, 4, 5].iter().map(|&x: &i32| x.pow(2)).sum();
    println!("{}", v);
}

I've also asked this question on the Rust user's forum.

Answer 1

像这样的范围1..5已经是一个迭代器，因此您不必调用iter()来创建迭代器：

let v: i32 = (1..5).map(|x: i32| x.pow(2)).sum();

另请注意，引用消失了，因为此迭代器迭代值。

如果您绝对需要 a Vec，则需要首先将范围收集到其中：

let v: i32 = (1..5)
    .collect::<Vec<i32>>()
    .iter()
    .map(|&x: &i32| x.pow(2))
    .sum();