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OCaml

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| Parametrised types
| Parametrised types
|
|
-
data D a = MkD (a -> a)
+
data DList a = MkDList ([a] -> [a])
-
data E a b = L a | R b
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data Either a b = Left a | Right b
|
|
-
type 'a d = MkD of ('a -> 'a)
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type 'a dlist = MkDList of ('a list -> 'a list)
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type ('a, 'b) e = L of 'a | R of 'b
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type ('a, 'b) either = Left of 'a | Right of 'b
|-
|-
| Pattern matching
| Pattern matching
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B x
B x
<nowiki>| x > 0 -> ...
<nowiki>| x > 0 -> ...
-
|</nowiki> otherwise -> ...
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|</nowiki> otherwise -> ...
C a b -> ...
C a b -> ...
-
case L () of
+
case Left () of
-
L x -> x
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Left x -> x
-
R x -> x
+
Right x -> x
|
|
match x with
match x with
B x when x > 0 -> ...
B x when x > 0 -> ...
-
B x -> ...
+
<nowiki>| B x -> ...
-
<nowiki>|</nowiki> C (a, b) -> ...
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|</nowiki> C (a, b) -> ...
-
match L () with
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match Left () with
-
L x <nowiki>|</nowiki> R x -> x
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Left x <nowiki>|</nowiki> Right x -> x
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|
|}
|}

Current revision

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 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.

2 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 DList a = MkDList ([a] -> [a])
data Either a b = Left a | Right b

type 'a dlist = MkDList of ('a list -> 'a list)
type ('a, 'b) either = Left of 'a | Right of 'b
Pattern matching 
case x of
  B x
    | x > 0 -> ...
    | otherwise -> ...
  C a b -> ...

case Left () of
  Left x -> x
  Right x -> x

match x with
    B x when x > 0 -> ...
  | B x -> ...
  | C (a, b) -> ...

match Left () with
  Left x | Right x -> x
Retrieved from "http://www.haskell.org/haskellwiki/OCaml"