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?

Jeffrey Scofield · Accepted Answer · 2012-12-29 00:38:34Z

6

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.)

answered Dec 29, 2012 at 0:38

Jeffrey Scofield

67k2 gold badges77 silver badges109 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

@gasche: incr has type int ref -> unit. And it looks like the return from your function is pointless also -- it is always going to return var

Indeed, my mistake. I agree on the function return being pointless.