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OCaml

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(Syntactic dictionary)
(Syntactic dictionary)
 
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This page aims to cover some of its differences from Haskell.
 
This page aims to cover some of its differences from Haskell.
 +
 +
== Conceptual differences ==
 +
 +
OCaml is strict by default, although it has some facility for introducing laziness.
 +
 +
OCaml's <tt>let</tt> is non-recursive by default, but has the form <tt>let rec</tt> 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.
  
 
== Syntactic dictionary ==
 
== Syntactic dictionary ==
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| Parametrised types
 
| Parametrised types
 
|
 
|
  data D a = D (a -> a)
+
  data DList a = MkDList ([a] -> [a])
  data E a b = L a | R b
+
  data Either a b = Left a | Right b
 
|
 
|
  type 'a d = D of ('a -> 'a)
+
  type 'a dlist = MkDList of ('a list -> 'a list)
  type ('a, 'b) e = L of 'a | R of 'b
+
  type ('a, 'b) either = Left of 'a | Right of 'b
 
|-
 
|-
 
| Pattern matching
 
| Pattern matching
 
|
 
|
 
  case x of
 
  case x of
   A x
+
   B x
     <nowiki>|</nowiki> x > 0 -> ...
+
     <nowiki>| x > 0 -> ...
 +
    |</nowiki> otherwise -> ...
 
   C a b -> ...
 
   C a b -> ...
 +
 +
case Left () of
 +
  Left x -> x
 +
  Right x -> x
 
|
 
|
 
  match x with
 
  match x with
  B x when x > 0 -> ...
+
    B x when x > 0 -> ...
   C (a, b) -> ...
+
   <nowiki>| B x -> ...
| There doesn't seem to be syntax for multiple guards
+
  |</nowiki> C (a, b) -> ...
|}
+
  
== Conceptual differences ==
+
match Left () with
 
+
  Left x <nowiki>|</nowiki> Right x -> x
OCaml is strict by default, although it has some facility for introducing laziness.
+
|
 
+
|}
OCaml's <tt>let</tt> is non-recursive by default, but has the form <tt>let rec</tt> 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.
+

Latest revision as of 05:28, 22 December 2012

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.

[edit] 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.

[edit] 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