Generic higher order function

Question

Is there a reason why I can use a generic function with different type arguments when I pass it as a local value but not when passed as parameter? For example:

Answer 1

The reason for this is that when f is passed as parameter to g then the compiler will try to infer the type of f. Based on the usage of f in the body of function g, the compiler infers that the function is applied to both x and y that means that both x and y parameters has to be of same type and that is the type of the f parameter. In your code example you pass x as integer and that makes the compiler infer that y will also be of type integer.

UPDATE:

You can do something like:

let g (f:obj -> obj) (x : 'a,y : 'b) = (f x :?> 'a ,f y :?> 'b)
g id (1,"1") |> printfn "%A"

The function f need to make sure it returns the same main type that it receives as obj type