小编Exc*_*.P.的帖子

如：

let mut a : usize = 0xFF;
a += -1;  // -1 may be from other variable, so there can't be a -= 1;
println!("{}", a);

输出是：

let mut a : usize = 0xFF;
a += -1;  // -1 may be from other variable, so there can't be a -= 1;
println!("{}", a);

反正？

use std::fmt::Write;
use std::fs::File;
use std::io::Write;

fn main() -> std::io::Result<()> {
    let mut p = String::new();
    (1..6).for_each(|n| {
        write!(&mut p, "{},", n);
    });
    let mut file = File::create("a.csv")?;
    file.write_all(p.as_bytes())?;
    Ok(())
}

编译时出现错误：

use std::fmt::Write;
use std::fs::File;
use std::io::Write;

fn main() -> std::io::Result<()> {
    let mut p = String::new();
    (1..6).for_each(|n| {
        write!(&mut p, "{},", n);
    });
    let mut file = File::create("a.csv")?;
    file.write_all(p.as_bytes())?;
    Ok(())
}

和警告：

error[E0599]: no method named `write_all` found for type `std::fs::File` in the current scope

如何将数组连接到字符串并写入文件？