Call an object method: Difference between revisions

=={{header|Haskell}}==

Haskell doesn't have objects in OOP sence (i.e. first-class sitizens

appearing in runtime with incapsulated state and ability to send messages (methods) to other objects).

Haskell has first-class immutable records with fields of any type, representing abstraction and incapsulation (due to purity).

Polymorphism is implemented via type-classes, which are similar to OOP interfaces.

Dummy example:

<lang haskell>data Obj = Obj { field :: Int, method :: Int -> Int }

-- smart constructor

mkAdder :: Int -> Obj

mkAdder x = Obj x (+x)

-- adding method from a type class

instanse Show Obj where

show o = "Obj " ++ show (field o) </lang>

<pre>*Main> let o1 = Obj 1 (*5)

*Main> field o1

1

*Main> method o1 6

30

*Main> show o1

Obj 1

*Main> let o2 = mkAdder 5

*Main> field o2

5

*Main> method o2 6

11

*Main> show o2

Obj 5</pre>