OCaml
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.
Syntactic dictionary
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 = MkD (a -> a) data E a b = L a | R b |
type 'a d = MkD of ('a -> 'a) type ('a, 'b) e = L of 'a | R of 'b | |
Pattern matching |
case x of B x | x > 0 -> ... | otherwise -> ... C a b -> ... case L () of L x -> x R x -> x |
match x with B x when x > 0 -> ... B x -> ... | C (a, b) -> ... match L () with L x | R x -> x |
Conceptual differences
OCaml is strict by default, although it has some facility for introducing laziness.
OCaml's let is non-recursive by default, but has the form let rec for defining recursive functions.
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.