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Interoperability

This page describes how various OCaml concepts translate into the Erlang world.

Module names

The module List in ML, becomes list in Erlang. The module name BumpyCase becomes bumpyCase in Erlang. The module name Lower_case becomes lower_case in Erlang.

Atoms <-> Variants

Variants (regular and polymorphic) are turned into atoms or tuples. E.g. the polymorphic variant `Red is converted into the atom 'red', and the variant Rgb of int*int*int is turned into the tuple {rgb, {r,g,b}}.

Here is an example:

(* wdays.ml *)
type wday = Monday | Tuesday | Wednesday | Thursday | Friday | Saturday | Sunday

let day_of_week = function
  | Monday    -> 1
  | Tuesday   -> 2
  | Wednesday -> 3
  | Thursday  -> 4
  | Friday    -> 5
  | Saturday  -> 6
  | Sunday    -> 7

(*
$ erl
1> {ok, wednesday} = wdays:int_to_wday(wdays:day_of_week(wednesday)).
{ok,wednesday}
2> wdays:int_to_wday(8).
error
*)
let int_to_wday = function
  | 1 -> (`Ok Monday)
  | 2 -> (`Ok Tuesday)
  | 3 -> (`Ok Wednesday)
  | 4 -> (`Ok Thursday)
  | 5 -> (`Ok Friday)
  | 6 -> (`Ok Saturday)
  | 7 -> (`Ok Monday)
  | _ -> `Error