发生移动是因为 value 的类型为 Vec<T>，它没有实现 `Copy` 特征

Question

我正在编写一个非常简单的递归程序，用于查找两个数字之间的所有素数：

use std::cmp::PartialOrd;
use std::ops::{Add, Div, Rem, Sub};

fn _is_prime<T>(n: T, dividend: T, one: T) -> bool
where
    T: Copy + Rem<Output = T> + Sub<Output = T> + PartialOrd,
{
    if dividend == one {
        true
    } else {
        if n % dividend < one {
            false
        } else {
            _is_prime(n, dividend - one, one)
        }
    }
}

fn _primes_between<'a, T>(a: T, b: T, one: T, v: &'a mut Vec<T>) -> &'a mut Vec<T>
where
    T: Copy + Rem<Output = T> + Add<Output = T> + Sub<Output = T> + PartialOrd,
{
    if a <= b {
        if _is_prime(a, a - one, one) {
            v.push(a);
        }

        _primes_between(a + one, b, one, v)
    } else {
        v
    }
}

fn primes_between<T>(a: T, b: T) -> Vec<T>
where
    T: Copy + Div<Output = T> + Rem<Output = T> + Add<Output = T> + Sub<Output = T> + PartialOrd,
{
    let one = a / a;

    let mut v: Vec<T> = Vec::new();

    *_primes_between(a, b, one, &mut v)
}

fn main() {
    primes_between(3, 13).iter().for_each(|i| println!("{}", i));
}

问题是：

use std::cmp::PartialOrd;
use std::ops::{Add, Div, Rem, Sub};

fn _is_prime<T>(n: T, dividend: T, one: T) -> bool
where
    T: Copy + Rem<Output = T> + Sub<Output = T> + PartialOrd,
{
    if dividend == one {
        true
    } else {
        if n % dividend < one {
            false
        } else {
            _is_prime(n, dividend - one, one)
        }
    }
}

fn _primes_between<'a, T>(a: T, b: T, one: T, v: &'a mut Vec<T>) -> &'a mut Vec<T>
where
    T: Copy + Rem<Output = T> + Add<Output = T> + Sub<Output = T> + PartialOrd,
{
    if a <= b {
        if _is_prime(a, a - one, one) {
            v.push(a);
        }

        _primes_between(a + one, b, one, v)
    } else {
        v
    }
}

fn primes_between<T>(a: T, b: T) -> Vec<T>
where
    T: Copy + Div<Output = T> + Rem<Output = T> + Add<Output = T> + Sub<Output = T> + PartialOrd,
{
    let one = a / a;

    let mut v: Vec<T> = Vec::new();

    *_primes_between(a, b, one, &mut v)
}

fn main() {
    primes_between(3, 13).iter().for_each(|i| println!("{}", i));
}

我该如何解决该错误？

Answer 1

我不是 100% 确定，但我认为问题是_primes_between()返回第 31 行代码试图复制的引用。（通过操作员获得所有权*）您可以通过调用结果来解决问题.clone()，但我认为在这种情况下您不需要_primes_between()返回值 - 您只需向v参数添加适当的条目即可。就像是

fn _primes_between<T>(a: T, b: T, one: T, v: &mut Vec<T>)
where
    T: Copy + Rem<Output = T> + Add<Output = T> + Sub<Output = T> + PartialOrd,
{
    if a <= b {
        if _is_prime(a, a - one, one) {
            v.push(a);
        }

        _primes_between(a + one, b, one, v);
    }
}

fn primes_between<T>(a: T, b: T) -> Vec<T>
where
    T: Copy + Div<Output = T> + Rem<Output = T> + Add<Output = T> + Sub<Output = T> + PartialOrd,
{
    let one = a / a;

    let mut v: Vec<T> = Vec::new();

    _primes_between(a, b, one, &mut v);

    v
}