Question

This is absolutely driving me nuts. The supposed simplest thing I can imagine and I can’t do it.

I just want to computer factorial inputting an int and output a real.

I’ve tried to coerce in numerous way.

fun factorial 0 = 1 |
    factorial n = n * factorial(n-1);

Answer 1

To convert an int to a real, you use Real.fromInt. If you want to return reals, you should also return 1.0 instead of 1 as the base case. So your code becomes:

fun factorial 0 = 1.0
  | factorial n = (Real.fromInt n) * factorial(n-1);