function with multiple arguments in OCaml

Question

I am trying to write a function to increment a mutable int by a specified amount.

let increase var:int ref amount = (var := !var+amount;var);;

This is what I came up with, but it produces errors. What is the correct way to do it?

Answer 1

Your only problem is in the specification of the type of var . You need to use parentheses:

# let increase (var: int ref) amount = var := !var + amount; var;;
val increase : int ref -> int -> int ref = <fun>

For what it's worth, the type specification is optional. OCaml will infer the type.

(I would personally consider having the function return unit , which would make it analogous to the built-in function incr .)