使用切片

Question

我已经编写了一些测试，我需要声明两个数组相等。有些数组是[u8; 48]，而其他数组是[u8; 188]：

#[test]
fn mul() {
    let mut t1: [u8; 48] = [0; 48];
    let t2: [u8; 48] = [0; 48];

    // some computation goes here.

    assert_eq!(t1, t2, "\nExpected\n{:?}\nfound\n{:?}", t2, t1);
}

我在这里遇到了多个错误：

error[E0369]: binary operation `==` cannot be applied to type `[u8; 48]`
 --> src/main.rs:8:5
  |
8 |     assert_eq!(t1, t2, "\nExpected\n{:?}\nfound\n{:?}", t2, t1);
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: an implementation of `std::cmp::PartialEq` might be missing for `[u8; 48]`
  = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)

error[E0277]: the trait bound `[u8; 48]: std::fmt::Debug` is not satisfied
 --> src/main.rs:8:57
  |
8 |     assert_eq!(t1, t2, "\nExpected\n{:?}\nfound\n{:?}", t2, t1);
  |                                                         ^^ `[u8; 48]` cannot be formatted using `:?`; if it is defined in your crate, add `#[derive(Debug)]` or manually implement it
  |
  = help: the trait `std::fmt::Debug` is not implemented for `[u8; 48]`
  = note: required by `std::fmt::Debug::fmt`

尝试将它们打印为t2[..]或t1[..]之类的切片似乎无法正常工作。

如何将assert与这些数组一起使用并打印出来？

Answer 1

对于比较部分，您可以将数组转换为迭代器并进行元素比较。

assert_eq!(t1.len(), t2.len(), "Arrays don't have the same length");
assert!(t1.iter().zip(t2.iter()).all(|(a,b)| a == b), "Arrays are not equal");

Answer 2

使用切片

作为解决方法，您只需使用 &t1[..] （而不是t1[..]）即可将数组转换为切片。您必须为比较和格式化执行此操作。

assert_eq!(&t1[..], &t2[..], "\nExpected\n{:?}\nfound\n{:?}", &t2[..], &t1[..]);

或

assert_eq!(t1[..], t2[..], "\nExpected\n{:?}\nfound\n{:?}", &t2[..], &t1[..]);

直接格式化数组

理想情况下，原始代码应该编译，但现在不行。原因是标准库implements common traits（例如Eq和Debug）适用于最多32个元素的数组，原因是lack of const generics

因此，您可以比较和格式化较短的数组，如：

let t1: [u8; 32] = [0; 32];
let t2: [u8; 32] = [1; 32];
assert_eq!(t1, t2, "\nExpected\n{:?}\nfound\n{:?}", t2, t1);

Answer 3

使用Iterator::eq，可以将任何可以转换为迭代器的内容进行比较：

let mut t1: [u8; 48] = [0; 48];
let t2: [u8; 48] = [0; 48];
assert!(t1.iter().eq(t2.iter()));

Answer 4

你可以让Vec出来。

fn main() {
    let a: [u8; 3] = [0, 1, 2];
    let b: [u8; 3] = [2, 3, 4];
    let c: [u8; 3] = [0, 1, 2];

    let va: Vec<u8> = a.to_vec();
    let vb: Vec<u8> = b.to_vec();
    let vc: Vec<u8> = c.to_vec();

    println!("va==vb {}", va == vb);
    println!("va==vc {}", va == vc);
    println!("vb==vc {}", vb == vc);
}

使用assert_eq或打印大型固定大小的数组并不起作用

4 个答案:

使用切片

直接格式化数组