Functions with generic parameter types

Question

I am trying to figure out how to define a function that works on multiple types of parameters (e.g. int and int64). As I understand it, function overloading is not possible

Answer 1

This works:

type T = T with
    static member ($) (T, n:int  ) = int   (sqrt (float n))
    static member ($) (T, n:int64) = int64 (sqrt (float n))

let inline sqrt_int (x:'t) :'t = T $ x

It uses static constraints and overloading, which makes a compile-time lookup on the type of the argument.

The static constraints are automatically generated in presence of an operator (operator $ in this case) but it can always be written by hand:

type T = T with
    static member Sqr (T, n:int  ) = int   (sqrt (float n))
    static member Sqr (T, n:int64) = int64 (sqrt (float n))

let inline sqrt_int (x:'N) :'N = ((^T or ^N) : (static member Sqr: ^T * ^N -> _) T, x)

More about this here.