# Error code E0368

A binary assignment operator like `+=` or `^=` was applied to a type that doesn't support it.

Erroneous code example:

    #![allow(unused)]
    fn main() {
    let mut x = 12f32; // error: binary operation `<<` cannot be applied to
                       //        type `f32`

    x <<= 2;
    }

To fix this error, please check that this type implements this binary operation. Example:

    #![allow(unused)]
    fn main() {
    let mut x = 12u32; // the `u32` type does implement the `ShlAssign` trait

    x <<= 2; // ok!
    }

It is also possible to overload most operators for your own type by implementing the `[OP]Assign` traits from `std::ops`.

Another problem you might be facing is this: suppose you've overloaded the `+` operator for some type `Foo` by implementing the `std::ops::Add` trait for `Foo`, but you find that using `+=` does not work, as in this example:

    use std::ops::Add;

    struct Foo(u32);

    impl Add for Foo {
        type Output = Foo;

        fn add(self, rhs: Foo) -> Foo {
            Foo(self.0 + rhs.0)
        }
    }

    fn main() {
        let mut x: Foo = Foo(5);
        x += Foo(7); // error, `+=` cannot be applied to the type `Foo`
    }

This is because `AddAssign` is not automatically implemented, so you need to manually implement it for your type.