相关疑难解决方法(0)

我只想要一个空格String，这些空格与从中获取的参数变量分开，该变量std::env::args()是我一直使用以下fold函数创建的：

std::env::args()
    .fold("".to_string(), |accum, s| accum + &s + " ")

然而，这在末端处产生了多余的空间，这是不需要的。我尝试使用该truncate函数，但未truncate返回a String，仅修改了现存的String，并且这将需要创建一个中间绑定，以便使用String的len()调用来定义被截断的长度String（这本身将需要我相信，由于Rust的当前词汇借用规则，中间绑定必不可少！）

我对此感到困惑：

use itertools::Itertools; // 0.10.0

fn main() {
    let combos = ["a", "b", "c"].iter().combinations(2).collect::<Vec<_>>();
    println!("{:#?}", combos[0].join(""));
}

error[E0599]: the method `join` exists for struct `Vec<&&str>`, but its trait bounds were not satisfied
   --> src/main.rs:5:33
    |
5   |       println!("{:#?}", combos[0].join(""));
    |                                   ^^^^ method cannot be called on `Vec<&&str>` due to unsatisfied trait bounds
    |
    = note: the following trait bounds were not satisfied:
            `Vec<&&str>: Iterator`
            which is required by `Vec<&&str>: Itertools`
            `<[&&str] as Join<_>>::Output = _`
            `[&&str]: Iterator`
            which is required …