Self-referential generics?

[Shawn Smith]

// ... imagine some comparison sort algorithm

func cmpSort[C Cmpable](x []C) {

    for i, val := range x {
        if i == 0 {
            continue
        }
        _ = val.Cmp(x[i-1])
    }
}

// Cmpable should include big.Int, big.Float, big.Rat, by virtue of their Cmp methods. So how do i define this better?

type Cmpable interface {
    Cmp(other any) int

}

// TODO: how do i replace "any" with "this type". "Cmpable" doesn't work as that would be any Cmpable, not THIS Cmpable.

[Axel Wagner]

You can use

type Comparable[T any] interface {

    Cmp(other T) int

}

then *big.Int implements `Comparable[*big.Int]` and you can write

func cmpSort[T Comparable[T]](x []C) { … }

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[Shawn Smith]

Thanks! This seems obvious now just looking at it, but it was stumping me.

I might add for someone that may see this later, in the future it *might* not be needed to do it this way, if all you really just want {Int | Float | Rat} as future versions are supposed to let us use methods in such constrained types if a method is present in all the types, like Cmp in this case, but I'm not sure if it clear that >1.18 will handle this particular case where it is only the same method signature if you note that the param type is the same as the method receiver type.