Why is there no error comparing Vector and Array in Rust?-CodePudding

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!                                                 
}

CodePudding user response：

Because Vec<T> implements 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).

CodePudding user response：

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], which matches [U; N] and therefore this works.