New to ML: How to store return values of type a* a* a*

Question

I have a program that returns int*int

(Example for illustration purposes): fun program(a,b) = (1,2)

I want to do something along the lines:

fun program(a,b)
if a = 0 then (1,2)
else
val x,y = program(a-1,b)
return (x-1, y)

Basically, I want to manipulate the tuple that is returned, and then return a modification of it.

Thanks

Answer 1

This works almost exactly as you wrote it, except that your syntax is a bit off:

fun program(a,b) =
  if a = 0 then (1,2)
  else
    let val (x,y) = program(a-1,b) in
      (x-1, y)
    end

Specifically:

1. Functions are defined by fun f args = body - you left out the =.
2. Variables are bound with let val foo = bar in baz end.
3. There is no return keyword in sml.