Question

I am trying out the following code in F# interactive and getting ‘error FS0001: the type ‘int -> int’ does not match the type ‘int’. Here is the code I am trying

> let rec factorial n = function
    | 0 -> 1
    | n -> n * factorial (n - 1);;

This is off of ‘F3 for scientist’ book example.
Thanks,

Answer 1

As you’ve defined it, factorial takes two arguments, but you’re only passing it one. Consequently, the second branch of the function is trying to multiply an int with a partially applied function of type int -> int.

The first line should read

let rec factorial = function

(sans n).