为什么在 Rust 中比较 Vector 和 Array 没有错误？

Question

I know that Array and Vector are different types in Rust language, but I wonder why there is no error in comparing the two.

// Rust Programming Language
fn main() {
    let vec = vec!["a", "b", "c"];  // Vector
    let arr = ["a", "b", "c"];      // Array
    println!("{}", vec == arr);     // true!                                                 
}

Answer 1

Because Vec<T> implements PartialEq<[T; N]> PartialEq<[T; N]> , allowing you to compare vectors with array.

You can overload the equality operators in Rust by implementing the PartialEq trait, and it takes an (optional, defaulted to Self ) generic parameter to allow you to specify different type for the left side ( Self , the implementing type) and the right side (the generic parameter, by default the same).

Answer 2

The == operator works on any type that implements the PartialEq trait. The trait can be implemented for different types for the left and the right side. In this case, Vec<T> implements the trait for all of these slice types :

PartialEq<&'_ [U; N]>
PartialEq<&'_ [U]>
PartialEq<&'_ mut [U]>
PartialEq<[U; N]>
PartialEq<[U]>

The array in your code has the type [&str; 3] [&str; 3] , which matches [U; N] [U; N] and therefore this works.