Personal tools

OCaml

From HaskellWiki

Revision as of 22:50, 11 December 2012 by Benmachine (Talk | contribs)

Jump to: navigation, search

OCaml is a functional programming language in the ML family, an extension of the Caml language with object-oriented constructs.

This page aims to cover some of its differences from Haskell.

1 Syntactic differences

Language Haskell OCaml Comments
Anonymous functions
\x y -> ...
fun x y -> ...
Multiple assignments
let
  x = 4
  y = 5
 in ...
let x = 4
and y = 5
 in ...
Types
Int, Bool, (Double, Char), a
int, bool, float * char, 'a
float is a double type
Type signatures
const :: a -> b -> a
const : 'a -> 'b -> 'a
Signatures usually omitted in OCaml
Type declarations
data A = B Int | C Char Bool
x = B 3
y = C 'a' True
type a = B of int | C of char * bool
let x = B 3
and y = C ('a', true)
Parametrised types
data D a = D (a -> a)
data E a b = L a | R b
type 'a d = D of ('a -> 'a)
type ('a, 'b) e = L of 'a | R of 'b
Pattern matching
case x of
  A x -> ...
  C a b -> ...
match x with
  B x -> ...
  C (a, b) -> ...

2 Conceptual differences

OCaml's let is non-recursive and strict by default, but has keywords rec (as in let rec) and lazy to introduce the Haskell behaviour.

OCaml is impure. Although it makes heavy use of immutable data, it also has mutable references and arrays available, and IO is performed by ordinary functions.