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Showing content from https://en.wikipedia.org/wiki/Comparison_of_programming_languages_(object-oriented_programming) below:

Comparison of programming languages (object-oriented programming)

From Wikipedia, the free encyclopedia

This comparison of programming languages compares how object-oriented programming languages such as C++, Java, Smalltalk, Object Pascal, Perl, Python, and others manipulate data structures.

Object construction and destruction[edit] construction destruction ABAP Objects

data variable type ref to class .
create object variable «exporting parameter = argument».

^[1] ^[2]^[3] APL (Dyalog) variable←⎕NEW class «parameters» ⎕EX 'variable' C++ class variable«(parameters)»;^[4] or
class *variable = new class«(parameters)»;^[5] delete pointer; C# class variable = new class(parameters); variable.Dispose();^[3] Java ^[3] D destroy(variable); eC class «instance handle» { «properties/data members assignments, instance method overrides» } delete instance handle; Objective-C (Cocoa) class *variable = [[class alloc ] init]; or
class *variable = [[class alloc ] initWithFoo:parameter «bar:parameter ...»]; [variable release]; Swift let variable = class(parameters) Python variable = class(parameters) del variable^[3] (Normally not needed) Visual Basic .NET Dim variable As New class(parameters) variable.Dispose()^[3] Xojo Dim variable As New class(parameters) variable = Nil Eiffel create variable or
create «{TYPE}» variable.make_foo «(parameters)» or
variable := create {TYPE} or
variable := create {TYPE}.make_foo «(parameters)» ^[3] PHP $variable = new class«(parameters)»; unset($variable);^[3] Perl 5 «my »$variable = class->new«(parameters)»; undef($variable); Raku «my »$variable = class.new«(parameters)»; $variable.undefine; Ruby variable = class.new«(parameters)» ^[3] Windows PowerShell $variable = New-Object «-TypeName» class ««-ArgumentList» parameters» Remove-Variable «-Name» variable OCaml let variable = new class «parameters» or
let variable = object members end^[6] ^[3] F# let variable = «new »class(«parameters») Smalltalk The class is an Object.
Just send a message to a class, usually #new or #new:, and many others, for example:

Point x: 10 y: 20.
Array with: -1 with: 3 with: 2.

JavaScript var variable = new class«(parameters)» or
var variable = { «key1: value1«, key2: value2 ...»»} ^[3] Object Pascal (Delphi) ClassVar := ClassType.ConstructorName(parameters); ClassVar.Free; Scala

val obj = new Object // no parameters
val obj = new Object(arg0, arg1, arg2...)
val obj = Object(arg0, arg1, arg2...) // case class
val obj = new Object(arg0, arg1, param1 = value1, ...) // named parameters

^[3] COBOL INVOKE class "NEW" RETURNING variable or
MOVE class::"NEW" TO variable Cobra variable «as class» = class(parameters) variable.dispose ISLISP (setq variable (create (class <some-class> [:field-1 value-1 [:field-2 value-2] ..]))) ^[3] class protocol namespace ABAP Objects

class name definition «inheriting from parentclass». «interfaces: interfaces.» method_and_field_declarations endclass.
class name implementation. method_implementations endclass.

interface name. members endinterface. — APL (Dyalog) :Class name «:parentclass» «,interfaces»
members
:EndClass :Interface name
members
:EndInterface :Namespace name
members
:EndNamespace C++ class name« : public parentclasses^[7]» { members }; namespace name { members } C# class name« : «parentclass»«, interfaces»» { members } interface name« : parentinterfaces» { members } D

module name; 

  members

eC class name« : base class» { «default member values assignments» «members» } namespace name; Java class name« extends parentclass»« implements interfaces» { members } interface name« extends parentinterfaces» { members } package name; members PHP namespace name; members Objective-C @interface name« : parentclass»^[8]

«< protocols >» { instance_fields } method_and_property_declarations @end 

   @implementation name method_implementations @end

^[9] @protocol name«< parentprotocols >» members @end ^[10] Swift class name« : «parentclass»«, protocols»» { members } protocol name« : parentprotocols» { members } Python

class name«(parentclasses^[7])»:

   Tab ↹ members

^[11] __all__ = [ member1,member2,... ] Visual Basic .NET

Class name« Inherits parentclass»« Implements interfaces»

  members 
End Class

Interface name« Inherits parentinterfaces»

  members 
End Interface

Namespace name

  members 
End Namespace

Xojo

Class name« Inherits parentclass»« Implements interfaces»

  members 
End Class

Interface name« Inherits parentinterfaces»

  members 
End Interface

Module name

  members 
End Module

Eiffel

class name« inherit parentclasses^[7]»

  members
end

— Perl package name; «@ISA = qw(parentclasses^[7]);» members 1; package name; members Raku class name «is parentclass «is parentclass ...^[7]»» «does role «does role ...»» { members } role name «does role «does role ...»» { members } module name { members } Ruby

class name« < parentclass» 

  members 
end

module name 

  members 
end

Windows PowerShell — OCaml

class name «parameters» = object «(self)» «inherit parentclass «parameters» «inherit parentclass «parameters» ...^[7]»» members end

module name 

  members

type name«(parameters)» «as this» = class «inherit parentclass«(parameters)» «as base»» members «interface interface with implementation «interface interface with implementation ...»» end

type name = interface members end

namespace name 

  members

Smalltalk ^[12] ^[13] JavaScript (ES6) class name «extends parentclass» { members } Object Pascal (Delphi)

ClassName = Class «(ClassParent, Interfaces)» private // Private members(include Methods and Fields) public // Public members protected // Protected members published // Published members end;

package name; members Scala

class ConcreteClass(constructor params)
extends ParentClass
with Trait1 with Trait2 with Trait2 {
// members
}

trait TraitName
extends OtherTrait1
with OtherTrait2 with OtherTrait3 {
// members
}

package name

COBOL CLASS-ID. name« INHERITS« FROM» parentclasses».

FACTORY« IMPLEMENTS interfaces».

class-members

END FACTORY.

OBJECT« IMPLEMENTS interfaces».

instance-members

END OBJECT.

END CLASS name.

INTERFACE-ID. name« INHERITS« FROM» interfaces».

members

END INTERFACE name.

— Cobra

class name «inherits parentclass» «implements interfaces»

  Tab ↹ members

interface name «inherits parentinterfaces»

  Tab ↹ members

namespace name

  Tab ↹ members

ISLISP (defclass name (base-class) ((x :initform 0 :accessor get-x :initarg x)) (:abstractp nil)) Constructors and destructors[edit] constructor destructor finalizer^[14] ABAP Objects

methods constructor «importing parameter = argument»
method constructor. instructions endmethod.

^[15] — APL (Dyalog) ∇ name
:Implements Constructor «:Base «expr»»
instructions
∇ ∇ name
:Implements Destructor
instructions
∇ C++ class(«parameters») «: initializers^[16]» { instructions } ~class() { instructions } C# class(«parameters») { instructions } void Dispose(){ instructions } ~class() { instructions } D this(«parameters») { instructions } ~this() { instructions } eC class() { instructions } ~class() { instructions } Java class(«parameters») { instructions } void finalize() { instructions } Eiffel ^[17] ^[18] Objective-C (Cocoa)

- (id)init { instructions... return self; } or 
- (id)initWithFoo:parameter «bar:parameter ...» { instructions... return self; }

- (void)dealloc { instructions } - (void)finalize { instructions } Swift init(«parameters») { instructions } deinit { instructions } Python

def __init__(self«, parameters»):

  Tab ↹ instructions

def __del__(self):

  Tab ↹ instructions

Visual Basic .NET

Sub New(«parameters»)

  instructions 
End Sub

Sub Dispose()

  instructions 
End Sub

Overrides Sub Finalize()

  instructions 
End Sub

Xojo

Sub Constructor(«parameters»)

  instructions 
End Sub

Sub Destructor()

  instructions 
End Sub

PHP function __construct(«parameters») { instructions } function __destruct() { instructions } Perl sub new { my ($class«, parameters») = @_; my $self = {}; instructions ... bless($self, $class); return $self; } sub DESTROY { my ($self) = @_; instructions } Raku

submethod BUILD { instructions } or

  «multi » method new(««$self: »parameters») { self.bless(*, field1 => value1, ...); ... instructions }

submethod DESTROY { instructions } Ruby

def initialize«(parameters)» 

  instructions 
end

— Windows PowerShell — OCaml initializer instructions^[19] — F#

do instructions or
new(parameters) =  expression

^[20] member this.Dispose() = instructions override this.Finalize() = instructions JavaScript function name(«parameters») { instructions }^[21] — JavaScript (ES6) constructor(«parameters») { instructions } COBOL —^[22] — Cobra

cue init(parameters)

  Tab ↹ base.init

  Tab ↹ instructions

def dispose

  Tab ↹ instructions

ISLISP (defmethod initialize-object ((instance <class-name>) initvalues) public private protected friend ABAP Objects public section.^[23] data field type type. private section.^[23] data field type type. protected section.^[23] data field type type. ^[24] APL (Dyalog) :Field Public field «← value» :Field «Private» field «← value» C++ public: type field; private: type field; protected: type field; ^[25] C# public type field «= value»; private type field «= value»; protected type field «= value»; internal type field «= value»; D package type field «= value»; Java protected type field «= value»; type field «= value»; eC public type field; private type field; Eiffel

feature

  field: TYPE

feature {NONE}

  field: TYPE

feature {current_class} 

  field: TYPE

feature {FRIEND} 

  field: TYPE

Objective-C @public type field; @private type field; @protected type field; @package type field; Swift — Smalltalk — ^[26] — Python self.field = value^[27] —^[28] — Visual Basic .NET Public field As type «= value» Private field As type «= value» Protected field As type «= value» Friend field As type «= value» Xojo Public field As type «= value» Private field As type «= value» Protected field As type «= value» — PHP public $field «= value»; private $field «= value»; protected $field «= value»; Perl $self->{field} = value;^[27] — Raku has« type »$.field« is rw» has« type »$!field — Ruby — @field = value^[27] Windows PowerShell

Add-Member 

  «-MemberType »NoteProperty 

  «-Name »Bar «-Value »value
-InputObject variable

— OCaml — val «mutable» field = value — F# — let «mutable» field = value — JavaScript

this.field = value 
this["field"] = value

^[27] COBOL — level-number field clauses.^[29] — — Cobra var field «as type» «= value» var __field «as type» «= value» var _field «as type» «= value» ISLISP (field :initform value :accessor accessor-name :initarg keyword) basic/void method value-returning method ABAP Objects

methods name «importing parameter = argument» «exporting parameter = argument» «changing parameter = argument» «returning value(parameter)»
method name. instructions endmethod.

^[30] ^[31] APL (Dyalog) ∇ «left argument» name «right arguments»
instructions
∇ ∇ result ← «left argument» name «right arguments»
instructions
∇ C++^[32]

type foo(«parameters»);

The implementation of methods is usually provided in a separate source file, with the following syntax

type class::foo(«parameters») { instructions }^[33]

void foo(«parameters») { instructions } type foo(«parameters») { instructions ... return value; } C# D Java eC void ««type of 'this'»::»foo(«parameters») { instructions } type ««type of this»::»foo(«parameters») { instructions ... return value; } Eiffel

foo ( «parameters» )
do 

  instructions 
end

foo ( «parameters» ): TYPE 
do 

  instructions... 
Result := value 
end

Objective-C - (void)foo«:parameter «bar:parameter ...»» { instructions } - (type)foo«:parameter «bar:parameter ...»» { instructions... return value; } Swift func foo(«parameters») { instructions } func foo(«parameters») -> type { instructions... return value } Python

def foo(self«, parameters»):

   Tab ↹ instructions

def foo(self«, parameters»):

   Tab ↹ instructions

   Tab ↹ return value

Visual Basic .NET

Sub Foo(«parameters») 
instructions 

   End Sub

Function Foo(«parameters») As type 
instructions 

  ... 
Return value
End Function

Xojo

Sub Foo(«parameters») 
instructions 

   End Sub

Function Foo(«parameters») As type 
instructions 

  ... 
Return value
End Function

PHP function foo(«parameters»)«: void» { instructions } function foo(«parameters»)«: type» { instructions ... return value; } Perl sub foo { my ($self«, parameters») = @_; instructions } sub foo { my ($self«, parameters») = @_; instructions ... return value; } Raku «has »«multi »method foo(««$self: »parameters») { instructions } «has «type »»«multi »method foo(««$self: »parameters») { instructions ... return value; } Ruby

def foo«(parameters)» 

  instructions 
end

def foo«(parameters)» 

  instructions 

  expression resulting in return value 
end 

  or 
def foo«(parameters)» 

  instructions 
return value 
end

Windows PowerShell

Add-Member «-MemberType» ScriptMethod «-Name» foo «-Value» { «param(parameters)» instructions } -InputObject variable

Add-Member «-MemberType» ScriptMethod «-Name» foo «-Value» { «param(parameters)» instructions ... return value } -InputObject variable

OCaml — method foo «parameters» = expression F# member this.foo(«parameters») = expression JavaScript

this.method = function(«parameters») {instructions} 

  name«.prototype.method = function(«parameters») {instructions}

^[34]

 this.method = function(«parameters») {instructions... return value;} 

  name«.prototype.method = function(«parameters») {instructions... return value;}

^[34] Javascript (ES6) foo(«parameters») {instructions} foo(«parameters») {instructions... return value;} COBOL

METHOD-ID. foo.

  «DATA DIVISION.
LINKAGE SECTION.

  parameter declarations»
PROCEDURE DIVISION« USING parameters».

instructions

END METHOD foo.

METHOD-ID. foo.
DATA DIVISION.
LINKAGE SECTION.

  «parameter declarations»

  result-var declaration
PROCEDURE DIVISION« USING parameters» RETURNING result-var.

instructions

END METHOD foo.

Cobra

def foo(parameters)

  Tab ↹ instructions

def foo(parameters) as type

  Tab ↹ instructions

  Tab ↹ return value

ISLISP

(defgeneric method (arg1 arg2))

  (defmethod method ((arg1 <class1> arg2 <class2>) ...)

How to declare a property named "Bar"

Manually implemented[edit] read-write read-only write-only ABAP Objects — APL (Dyalog) :Property Bar
∇ result ← Get
instructions
∇
∇ Set arguments
instructions
∇
:EndProperty Bar :Property Bar
∇ result ← Get
instructions
∇
:EndProperty Bar :Property Bar
∇ Set arguments
instructions
∇
:EndProperty Bar C++ — C#

type Bar {

   get { instructions ... return value; }

   set { instructions } }

type Bar { get { instructions ... return value; } } type Bar { set { instructions } } D

@property type bar() { instructions ... return value; } 

   @property type bar(type value) { instructions ... return value; }

@property type bar() { instructions ... return value; } @property type bar(type value) { instructions ... return value; } eC

property type Bar {

   get { instructions ... return value; }

   set { instructions } }

property type Bar { get { instructions ... return value; } } property type Bar { set { instructions } } Java — Objective-C 2.0 (Cocoa)

@property (readwrite) type bar;

and then inside

@implementation 
- (type)bar { instructions } 
- (void)setBar:(type)value { instructions }

@property (readonly) type bar;

and then inside

@implementation 
- (type)bar { instructions }

— Swift var bar : type { get { instructions } set«(newBar)» { instructions } } var bar : type { instructions } — Eiffel

feature -- Access 

  x: TYPE assign set_x
feature -- Settings 

  set_x (a_x: like x) do instructions ensure x_set: verification end

Python

def setBar(self, value): 

  Tab ↹ instructions

   def getBar(self):

   Tab ↹ instructions

  Tab ↹ return value

  bar = property(getBar, setBar)

^[35]

def getBar(self): 

  Tab ↹ instructions

  Tab ↹ return value

  bar = property(getBar)

def setBar(self, value): 

  Tab ↹ instructions

  bar = property(fset = setBar)

Visual Basic .NET

Property Bar() As type
Get
instructions
Return value
End Get

   Set (ByVal Value As type)

  instructions

   End Set

   End Property

ReadOnly Property Bar() As type
Get
instructions
Return value
End Get

   End Property

WriteOnly Property Bar() As type
Set (ByVal Value As type)

  instructions
End Set

   End Property

Xojo

ComputedProperty Bar() As type
Get
instructions
Return value
End Get

   Set (ByVal Value As type)

  instructions

   End Set

   End ComputedProperty

ComputedProperty Bar() As type
Get
instructions
Return value
End Get

   End ComputedProperty

ComputedProperty Bar() As type
Set (value As type)

  instructions
End Set

   End ComputedProperty

PHP

function __get($property) {

   switch ($property) {

   case 'Bar' : instructions ... return value;

   } }

   function __set($property, $value) {

   switch ($property) {

   case 'Bar' : instructions

   } }

function __get($property) {

   switch ($property) {

   case 'Bar' : instructions ... return value;

   } }

function __set($property, $value) {

   switch ($property) {

   case 'Bar' : instructions

   } }

Perl

sub Bar {
my $self = shift;
if (my $Bar = shift) {

  # setter

  $self->{Bar} = $Bar;

  return $self;

  } else {

  # getter
return $self->{Bar}; 

  }

  }

sub Bar {
my $self = shift;
if (my $Bar = shift) {

  # read-only
die "Bar is read-only\n";

  } else {

  # getter
return $self->{Bar}; 

  }

  }

sub Bar {
my $self = shift;
if (my $Bar = shift) {

  # setter

  $self->{Bar} = $Bar;

  return $self;

  } else {

  # write-only
die "Bar is write-only\n"; 

  }

  }

Raku — Ruby

def bar 

  instructions 

  expression resulting in return value 
end 
def bar=(value) 

  instructions 
end

def bar 

  instructions 

  expression resulting in return value 
end

def bar=(value) 

  instructions 
end

Windows PowerShell

Add-Member 

  «-MemberType »ScriptProperty 

  «-Name »Bar «-Value »{ instructions ... return value } 

  «-SecondValue »{ instructions } 
-InputObject variable

Add-Member 

  «-MemberType »ScriptProperty 

  «-Name »Bar «-Value »{ instructions ... return value} 
-InputObject variable

Add-Member 

  «-MemberType »ScriptProperty 

  «-Name »Bar -SecondValue { instructions } 
-InputObject variable

OCaml — F# member this.Bar with get() = expression and set(value) = expression member this.Bar = expression member this.Bar with set(value) = expression JavaScript (ES6) get bar(«parameters») { instructions ... return value}set bar(«parameters») { instructions } get bar(«parameters») { instructions ... return value} set bar(«parameters») { instructions } COBOL

METHOD-ID. GET PROPERTY bar.
DATA DIVISION.
LINKAGE SECTION.

  return-var declaration
PROCEDURE DIVISION RETURNING return-var.

instructions

END METHOD. METHOD-ID. SET PROPERTY bar. DATA DIVISION. LINKAGE SECTION. value-var declaration PROCEDURE DIVISION USING value-var.

instructions

END METHOD.

METHOD-ID. GET PROPERTY bar.
DATA DIVISION.
LINKAGE SECTION.

  return-var declaration
PROCEDURE DIVISION RETURNING return-var.

instructions

END METHOD.

METHOD-ID. SET PROPERTY bar.
DATA DIVISION.
LINKAGE SECTION.

  value-var declaration
PROCEDURE DIVISION USING value-var.

instructions

END METHOD.

Cobra

pro bar «as type»

  Tab ↹ get

  Tab ↹Tab ↹ instructions

  Tab ↹Tab ↹ return value

  Tab ↹ set

  Tab ↹Tab ↹ instructions

get bar «as type»

  Tab ↹ instructions

  Tab ↹ return value

set bar «as type»

  Tab ↹ instructions

ISLISP — Automatically implemented[edit] read-write read-only write-only ABAP Objects — C++ — C# type Bar { get; set; } type Bar { get; private set; } type Bar { private get; set; } D — Java — Objective-C 2.0 (Cocoa)

@property (readwrite) type bar;

and then inside

@implementation 
@synthesize bar;

@property (readonly) type bar;

and then inside

@implementation 
@synthesize bar;

— Swift var bar : type let bar : type — Eiffel Python

@property
def bar(self):

  Tab ↹instructions
@bar.setter
def bar(self, value):

  Tab ↹instructions

@property
def bar(self):

  Tab ↹instructions

bar = property()
@bar.setter
def bar(self, value):

  Tab ↹instructions

Visual Basic .NET Property Bar As type« = initial_value» (VB 10) PHP Perl^[36]

use base qw(Class::Accessor);
__PACKAGE__->mk_accessors('Bar');

use base qw(Class::Accessor);
__PACKAGE__->mk_ro_accessors('Bar');

use base qw(Class::Accessor);
__PACKAGE__->mk_wo_accessors('Bar');

Raku — Ruby attr_accessor :bar attr_reader :bar attr_writer :bar Windows PowerShell OCaml — F# member val Bar = value with get, set COBOL level-number bar clauses PROPERTY. level-number bar clauses PROPERTY «WITH» NO SET. level-number bar clauses PROPERTY «WITH» NO GET. Cobra pro bar from var «as type» get bar from var «as type» set bar from var «as type» Overloaded operators[edit] Standard operators[edit] unary binary function call ABAP Objects — C++ type operator symbol () { instructions } type operator symbol (type operand2) { instructions } type operator () («parameters») { instructions } C# static type operator symbol(type operand) { instructions } static type operator symbol(type operand1, type operand2) { instructions } — D type opUnary(string s)() if (s == "symbol") { instructions }

type opBinary(string s)(type operand2) if (s == "symbol") { instructions } 

  type opBinaryRight(string s)(type operand1) if (s == "symbol") switch (s) { instructions }

type opCall(«parameters») { instructions } Java — Objective-C Swift func symbol(operand1 : type) -> returntype { instructions } (outside class) func symbol(operand1 : type1, operand2 : type2) -> returntype { instructions } (outside class) Eiffel^[37]

op_name alias "symbol": TYPE 
do instructions end

op_name alias "symbol" (operand: TYPE1): TYPE2 
do instructions end

Python

def __opname__(self): 

   Tab ↹ instructions

   Tab ↹ return value

def __opname__(self, operand2): 

   Tab ↹ instructions

   Tab ↹ return value

def __call__(self«, parameters»): 

   Tab ↹ instructions

   Tab ↹ return value

Visual Basic .NET

Shared Operator symbol(operand As type) As type
instructions 

   End Operator

Shared Operator symbol(operand1 As type, operand2 As type) As type
instructions 

   End Operator

— Xojo

Function Operator_name(operand As type) As type
instructions 

   End Function

— PHP ^[38] function __invoke(«parameters») { instructions } (PHP 5.3+) Perl use overload "symbol" => sub { my ($self) = @_; instructions }; use overload "symbol" => sub { my ($self, $operand2, $operands_reversed) = @_; instructions }; Raku

«our «type »»«multi »method prefix:<symbol> («$operand: ») { instructions ... return value; } or

  «our «type »»«multi »method postfix:<symbol> («$operand: ») { instructions ... return value; } or

  «our «type »»«multi »method circumfix:<symbol1 symbol2> («$operand: ») { instructions ... return value; }

«our «type »»«multi »method infix:<symbol> («$operand1: » type operand2) { instructions ... return value; } «our «type »»«multi »method postcircumfix:<( )> («$self: » «parameters») { instructions } Ruby

def symbol 

  instructions 

  expression resulting in return value 
end

def symbol(operand2) 

  instructions 

  expression resulting in return value 
end

— Windows PowerShell — OCaml F# static member (symbol) operand = expression static member (symbol) (operand1, operand2) = expression — COBOL — ISLISP — read-write read-only write-only ABAP Objects — APL (Dyalog) :Property Numbered Default name
∇ result ← Get
instructions
∇
∇ Set arguments
instructions
∇
:EndProperty Bar :Property Numbered Default Bar
∇ result ← Get
instructions
∇
:EndProperty Bar :Property Numbered Default Bar
∇ Set arguments
instructions
∇
:EndProperty Bar C++ type& operator[](type index) { instructions } type operator[](type index) { instructions } C#

type this[type index] { 

   get{ instructions } 

   set{ instructions } }

type this[type index] { get{ instructions } } type this[type index] { set{ instructions } } D

type opIndex(type index) { instructions } 

  type opIndexAssign(type value, type index) { instructions }

type opIndex(type index) { instructions } type opIndexAssign(type value, type index) { instructions } Java — Objective-C (recent Clang compiler) —

- (id)objectAtIndexedSubscript:(NSUInteger)index { instructions return value; } or
- (id)objectForKeyedSubscript:(id)index { instructions return value; }

- (void)setObject:(id)value atIndexedSubscript:(NSUInteger)index { instructions } or
- (void)setObject:(id)value forKeyedSubscript:(id)index { instructions }

Swift subscript (index : type) -> returntype { get { instructions } set«(newIndex)» { instructions } } subscript (index : type) -> returntype { instructions } Eiffel^[37]

bracket_name alias "[]" (index: TYPE): TYPE assign set_item 
do instructions end 

  set_item (value: TYPE; index: TYPE): 
do instructions end

bracket_name alias "[]" (index: TYPE): TYPE 
do instructions end

Python

def __getitem__(self, index): 
Tab ↹ instructions 

  Tab ↹ return value 
def __setitem__(self, index, value): 

  Tab ↹ instructions

def __getitem__(self, index): 
Tab ↹ instructions 

  Tab ↹ return value

def __setitem__(self, index, value): 

  Tab ↹ instructions

Visual Basic .NET

Default Property Item(Index As type) As type 

   Get 
instructions 

   End Get 

   Set(ByVal Value As type) 
instructions 

   End Set 

   End Property

Default ReadOnly Property Item(Index As type) As type 

   Get 
instructions 

   End Get 

   End Property

Default WriteOnly Property Item(Index As type) As type 

   Set(ByVal Value As type) 
instructions 

   End Set 

   End Property

PHP ^[39] Perl ^[40] Raku

«our «type »»«multi »method postcircumfix:<[ ]> is rw («$self: » type $index) { instructions ... return value; } or

  «our «type »»«multi »method postcircumfix:<{ }> is rw («$self: » type $key) { instructions ... return value; }

«our «type »»«multi »method postcircumfix:<[ ]>(«$self: » type $index) { instructions ... return value; } or

  «our «type »»«multi »method postcircumfix:<{ }> («$self: » type $key) { instructions ... return value; }

— Ruby

def [](index) 

  instructions 

  expression resulting in return value 
end 
def []=(index, value) 

  instructions 
end

def [](index) 

  instructions 

  expression resulting in return value 
end

def []=(index, value) 

  instructions 
end

Windows PowerShell — OCaml F# member this.Item with get(index) = expression and set index value = expression member this.Item with get(index) = expression member this.Item with set index value = expression COBOL — Cobra

pro[index «as type»] as type

  Tab ↹ get

  Tab ↹Tab ↹ instructions

  Tab ↹Tab ↹ return value

  Tab ↹ set

  Tab ↹Tab ↹ instructions

get[index «as type»] as type

  Tab ↹ instructions

  Tab ↹ return value

set[index «as type»] as type

  Tab ↹ instructions

downcast upcast ABAP Objects — C++ operator returntype() { instructions } C# static explicit operator returntype(type operand) { instructions } static implicit operator returntype(type operand) { instructions } D T opCast(T)() if (is(T == type)) { instructions } eC property T { get { return «conversion code»; } } Java — Objective-C Eiffel^[37] Python Visual Basic .NET

Shared Narrowing Operator CType(operand As type) As returntype 
instructions  

   End Operator

Shared Widening Operator CType(operand As type) As returntype 
instructions  

   End Operator

PHP — Perl Raku multi method type«($self:)» is export { instructions } Ruby — Windows PowerShell OCaml F# COBOL —

How to access members of an object x

object member class member namespace member method field property ABAP Objects x->method(«parameters»).^[41] x->field — x=>field or x=>method(«parameters^[41]»). — C++

x.method(parameters) or
ptr->method(parameters)

x.field or
ptr->field

cls::member ns::member Objective-C [x method«:parameter «bar:parameter ...»»] x->field

x.property (2.0 only) or
[x property]

[cls method«:parameter «bar:parameter ...»»] Smalltalk x method«:parameter «bar:parameter ...»» — cls method«:parameter «bar:parameter ...»» Swift x.method(parameters) x.property cls.member APL (Dyalog) left argument» x.method «right argument(s)» x.field x.property cls.member ns.member C# x.method(parameters) Java — D x.property Python Visual Basic .NET Xojo Windows PowerShell [cls]::member F# — cls.member eC x.method«(parameters)» x.field x.property cls::member ns::member Eiffel x.method«(parameters)» x.field {cls}.member — Ruby — x.property cls.member PHP x->method(parameters) x->field x->property cls::member ns\member Perl x->method«(parameters)» x->{field} cls->method«(parameters)» ns::member Raku

x.method«(parameters)» or
x!method«(parameters)»

x.field or
x!field

cls.method«(parameters)» or

  cls!method«(parameters)»

ns::member OCaml x#method «parameters» — JavaScript

x.method(parameters)
x["method"](parameters)

x.field
x["field"]

x.property
x["property"]

cls.member
cls["member"]

— COBOL

INVOKE x "method" «USING parameters» «RETURNING result» or
x::"method"«(«parameters»)»

— property OF x

INVOKE cls "method" «USING parameters» «RETURNING result» or

  cls::"method"«(«parameters»)» or

  property OF cls

— Cobra x.method«(parameters)» x.field x.property cls.member ns.member Member availability[edit] Has member? Handler for missing member Method Field Method Field APL (Dyalog) 3=x.⎕NC'method' 2=x.⎕NC'method' — ABAP Objects — C++ Objective-C (Cocoa) [x respondsToSelector:@selector(method)] — forwardInvocation: — Smalltalk x respondsTo: selector — doesNotUnderstand: — C# (using reflection) eC Java D opDispatch() Eiffel — Python hasattr(x, "method") and callable(x.method) hasattr(x, "field") __getattr__() Visual Basic .NET (using reflection) Xojo (using Introspection) Windows PowerShell (using reflection) F# (using reflection) Ruby x.respond_to?(:method) — method_missing() — PHP method_exists(x, "method") property_exists(x, "field") __call() __get() / __set() Perl x->can("method") exists x->{field} AUTOLOAD Raku x.can("method") x.field.defined AUTOLOAD OCaml — JavaScript typeof x.method === "function" field in x COBOL — current object current object's parent object null reference Current Context of Execution Smalltalk self super nil thisContext ABAP Objects me super initial APL (Dyalog) ⎕THIS ⎕BASE ⎕NULL C++ *this ^[42] NULL, nullptr C# this base^[43] null Java super^[43] D JavaScript super^[43] (ECMAScript 6) null, undefined^[44] eC this null Objective-C self super^[43] nil Swift self super^[43] nil^[45] Python self^[46] super(current_class_name, self)^[7]
super() (3.x only) None Visual Basic .NET Me MyBase Nothing Xojo Me / Self Parent Nil Eiffel Current Precursor «{superclass}» «(args)»^[43]^[47] Void PHP $this parent^[43] null Perl $self^[46] $self->SUPER^[43] undef Raku self SUPER Nil Ruby self super«(args)»^[48] nil binding Windows PowerShell $this $NULL OCaml self^[49] super^[50] —^[51] F# this base^[43] null COBOL SELF SUPER NULL Cobra this base nil String representation Object copy Value equality Object comparison Hash code Object ID Human-readable Source-compatible ABAP Objects — APL (Dyalog) ⍕x ⎕SRC x ⎕NS x x = y — C++ x == y^[52] pointer to object can be converted into an integer ID C# x.ToString() x.Clone() x.Equals(y) x.CompareTo(y) x.GetHashCode() System.Runtime.CompilerServices.RuntimeHelpers.GetHashCode(x) Java x.toString() x.clone()^[53] x.equals(y) x.compareTo(y)^[54] x.hashCode() System.identityHashCode(x) JavaScript x.toString() D

x.toString() or 
std.conv.to!string(x)

x.stringof

x == y or 

  x.opEquals(y)

x.opCmp(y) x.toHash() eC

x.OnGetString(tempString, null, null) or 
PrintString(x)

y.OnCopy(x) x.OnCompare(y) object handle can be converted into an integer ID Objective-C (Cocoa) x.description x.debugDescription [x copy]^[55] [x isEqual:y] [x compare:y]^[56] x.hash pointer to object can be converted into an integer ID Swift x.description^[57] x.debugDescription^[58] x == y^[59] x < y^[60] x.hashValue^[61] reflect(x).objectIdentifier!.uintValue() Smalltalk x displayString x printString x copy x = y x hash x identityHash Python str(x)^[62] repr(x)^[63] copy.copy(x)^[64] x == y^[65] cmp(x, y)^[66] hash(x)^[67] id(x) Visual Basic .NET x.ToString() x.Clone() x.Equals(y) x.CompareTo(y) x.GetHashCode() Eiffel x.out x.twin x.is_equal(y) When x is COMPARABLE, one can simply do x < y When x is HASHABLE, one can use x.hash_code When x is IDENTIFIED, one can use x.object_id PHP $x->__toString() clone x^[68] x == y spl_object_hash(x) Perl "$x"^[69] Data::Dumper->Dump([$x],['x'])^[70] Storable::dclone($x)^[71] Scalar::Util::refaddr( $x )^[72] Raku ~x^[69] x.perl x.clone x eqv y x cmp y x.WHICH Ruby x.to_s x.inspect

x.dup or 

  x.clone

x == y or 

  x.eql?(y)

x <=> y x.hash x.object_id Windows PowerShell x.ToString() x.Clone() x.Equals(y) x.CompareTo(y) x.GetHashCode() OCaml Oo.copy x x = y Hashtbl.hash x Oo.id x F# string x or x.ToString() or sprintf "%O" x sprintf "%A" x x.Clone() x = y or x.Equals(y) compare x y or x.CompareTo(y) hash x or x.GetHashCode() COBOL — Get object type Is instance of (includes subtypes) Upcasting Downcasting Runtime check No check ABAP Objects —^[73] = ?= C++ typeid(x) dynamic_cast<type *>(&x) != nullptr —^[74] dynamic_cast<type*>(ptr)

(type*) ptr or 
static_cast<type*>(ptr)

C# x.GetType() x is type (type) x or x as type D typeid(x) cast(type) x Delphi x is type x as type eC x._class eClass_IsDerived(x._class, type) (type) x Java x.getClass() x instanceof class (type) x Objective-C (Cocoa) [x class]^[75] [x isKindOfClass:[class class]] (type*) x Swift x.dynamicType x is type x as! type
x as? type JavaScript x.constructor (If not rewritten.) x instanceof class —^[76] Visual Basic .NET x.GetType() TypeOf x Is type —^[74] CType(x, type) or TryCast(x, type) Xojo Introspection.GetType(x) x IsA type — CType(x, type) — Eiffel x.generating_type attached {TYPE} x attached {TYPE} x as down_x Python type(x) isinstance(x, type) —^[76] PHP get_class(x) x instanceof class Perl ref(x) x->isa("class") Raku x.WHAT x.isa(class) —^[74]

type(x) or

  x.type

Ruby x.class

x.instance_of?(type) or

  x.kind_of?(type)

—^[76] Smalltalk x class x isKindOf: class Windows PowerShell x.GetType() x -is [type] —^[74] [type]x or x -as [type] OCaml —^[77] (x :> type) — F# x.GetType() x :? type (x :?> type) COBOL — x AS type^[74] — Namespace management[edit] Import namespace Import item qualified unqualified ABAP Objects C++ using namespace ns; using ns::item ; C# using ns; using item = ns.item; D import ns; import ns : item; Java import ns.*; import ns.item; Objective-C Visual Basic .NET Imports ns Eiffel Python import ns from ns import * from ns import item PHP use ns; use ns\item; Perl use ns; use ns qw(item); Raku Ruby Windows PowerShell OCaml open ns F# COBOL — Precondition Postcondition Check Invariant Loop ABAP Objects — C++ C#

Spec#:

  type foo( «parameters» )

      requires expression 

  {

      body 

  }

Spec#:

  type foo( «parameters» )

      ensures expression 

  {

      body 

  }

Java — Objective-C Visual Basic .NET D

f 
in { asserts } 

   body{ instructions }

f 
out (result) { asserts } 

   body{ instructions }

assert(expression) invariant() { expression } Eiffel

f 
require tag: expression 
do end

f 
do 

   ensure tag: expression 
end

f 
do 
check tag: expression end 

   end

class X 
invariant tag: expression 
end

from  instructions 
invariant 

  tag: expression 
until 

  expr 
loop 

  instructions 
variant 

  tag: expression 
end

Python — PHP Perl Raku PRE { condition } POST { condition } Ruby — Windows PowerShell OCaml F# COBOL

Object-oriented programming

^ parameter = argument may be repeated if the constructor has several parameters
^ SAP reserved to himself the use of destruction
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l This language uses garbage collection to release unused memory.
^ This syntax creates an object value with automatic storage duration
^ This syntax creates an object with dynamic storage duration and returns a pointer to it
^ OCaml objects can be created directly without going through a class.
^ ^a ^b ^c ^d ^e ^f ^g This language supports multiple inheritance. A class can have more than one parent class
^ Not providing a parent class makes the class a root class. In practice, this is almost never done. One should generally use the conventional base class of the framework one is using, which is NSObject for Cocoa and GNUstep, or Object otherwise.
^ Usually the @interface portion is placed into a header file, and the @interface portion is placed into a separate source code file.
^ Prefixes to class and protocol names conventionally used as a kind of namespace
^ In Python interfaces are classes which methods have pass as their bodies
^ The class is an Object. Just send a message to the superclass (st-80) or the destination namespace (Visualworks).
^ The namespace is an Object. Just send a message to the parent namespace.
^ A finalizer is called by the garbage collector when an object is about to be garbage-collected. There is no guarantee on when it will be called or if it will be called at all.
^ In ABAP, the constructor is to be defined like a method (see comments about method) with the following restrictions: the method name must be "constructor", and only "importing" parameters can be defined
^ An optional comma-separated list of initializers for member objects and parent classes goes here. The syntax for initializing member objects is "member_name(parameters)" This works even for primitive members, in which case one parameter is specified and that value is copied into the member. The syntax for initializing parent classes is "class_name(parameters)". If an initializer is not specified for a member or parent class, then the default constructor is used.
^ Any Eiffel procedure can be used as a creation procedure, aka constructors. See Eiffel paragraph at Constructor (computer science).
^ Implementing {DISPOSABLE}.dispose ensures that dispose will be called when object is garbage collected.
^ This "initializer" construct is rarely used. Fields in OCaml are usually initialized directly in their declaration. Only when additional imperative operations are needed is "initializer" used. The "parameters to the constructor" in other languages are instead specified as the parameters to the class in OCaml. See the class declaration syntax for more details.
^ This syntax is usually used to overload constructors
^ In JavaScript, constructor is an object.
^ Constructors can be emulated with a factory method returning a class instance.
^ ^a ^b ^c Scope identifier must appear once in the file declaration, all variable declarations after this scope identifier have his scope, until another scope identifier or the end of class declaration is reached
^ In ABAP, specific fields or methods are not declared as accessible by outside things. Rather, outside classes are declared as friends to have access to the class's fields or methods.
^ In C++, specific fields are not declared as accessible by outside things. Rather, outside functions and classes are declared as friends to have access to the class's fields. See friend function and friend class for more details.

^ Just send a message to the class class addInstVarName: field. class removeInstVarName: field.

^ ^a ^b ^c ^d Just assign a value to it in a method
^ Python doesn't have private fields - all fields are publicly accessible at all times. A community convention exists to prefix implementation details with one underscore, but this is unenforced by the language.
^ All class data is 'private' because the COBOL standard does not specify any way to access it.
^ The declaration and implementation of methods in ABAP are separate. methods statement is to be used inside the class definition. method (without "s") is to be used inside the class implementation. parameter = argument can be repeated if there are several parameters.
^ In ABAP, the return parameter name is explicitly defined in the method signature within the class definition
^ In C++, declaring and implementing methods is usually separate. Methods are declared in the class definition (which is usually included in a header file) using the syntax
^ Although the body of a method can be included with the declaration inside the class definition, as shown in the table here, this is generally bad practice. Because the class definition must be included with every source file which uses the fields or methods of the class, having code in the class definition causes the method code to be compiled with every source file, increasing the size of the code. Yet, in some circumstances, it is useful to include the body of a method with the declaration. One reason is that the compiler will try to inline methods that are included in the class declaration; so if a very short one-line method occurs, it may make it faster to allow a compiler to inline it, by including the body along with the declaration. Also, if a template class or method occurs, then all the code must be included with the declaration, because only with the code can the template be instantiated.
^ ^a ^b Just assign a function to it in a method

^ Alternative implementation: def bar(): doc = "The bar property." def fget(self): return self._bar def fset(self, value): self._bar = value return locals() bar = property(**bar())

^ these examples need the Class::Accessor module installed
^ ^a ^b ^c Although Eiffel does not support overloading of operators, it can define operators
^ PHP does not support operator overloading natively, but support can be added using the "operator" PECL package.
^ The class must implement the ArrayAccess interface.
^ The class must overload '@{}' (array dereference) or subclass one of Tie::Array or Tie::StdArray to hook array operations
^ ^a ^b In ABAP, arguments must be passed using this syntax: x->method(«exporting parameter = argument» «importing parameter = argument» «changing parameter = argument» «returning value(parameter)» parameter = argument can be repeated if there are several parameters
^ C++ doesn't have a "super" keyword, because multiple inheritance is possible, and so it may be ambiguous which base class is referenced. Instead, the BaseClassName::member syntax can be used to access an overridden member in the specified base class. Microsoft Visual C++ provides a non-standard keyword "__super" for this purpose; but this is unsupported in other compilers.[1]
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ The keyword here is not a value, and it can only be used to access a method of the superclass.
^ But be afraid, they have not the same value.
^ only for Optional types
^ ^a ^b In this language, instance methods are passed the current object as the first parameter, which is conventionally named "self", but this is not required to be the case.
^ "Precursor" in Eiffel is actually a call to the method of the same name in the superclass. So Precursor(args) is equivalent to "super.currentMethodName(args)" in Java. There is no way of calling a method of different name in the superclass.
^ "super" in Ruby, unlike in other languages, is actually a call to the method of the same name in the superclass. So super(args) in Ruby is equivalent to "super.currentMethodName(args)" in Java. There is no way of calling a method of different name in the superclass.
^ In OCaml, an object declaration can optionally start with a parameter which will be associated with the current object. This parameter is conventionally named "self", but this is not required to be the case. It is good practice to put a parameter there so that one can call one's own methods.
^ In OCaml, an inheritance declaration ("inherit") can optionally be associated with a value, with the syntax "inherit parent_class «parameters» as super". Here "super" is the name given to the variable associated with this parent object. It can be named differently.
^ However, if the ability to have an "optional" value in OCaml is needed, then wrap the value inside an option type, which values are None and Some x, which could be used to represent "null reference" and "non-null reference to an object" as in other languages.
^ assuming that "x" and "y" are the objects (and not pointers). Can be customized by overloading the object's == operator
^ Only accessible from within the class, since the clone() method inherited from Object is protected, unless the class overrides the method and makes it public. If using the clone() inherited from Object, the class must implement the Cloneable interface to allow cloning.
^ The class should implement the interface Comparable for this method to be standardized.
^ Implemented by the object's copyWithZone: method
^ compare: is the conventional name for the comparison method in Foundation classes. However, no formal protocol exists
^ Only if object conforms to the Printable protocol
^ Only if object conforms to the DebugPrintable protocol
^ Only if object conforms to the Equatable protocol
^ Only if object conforms to the Comparable protocol
^ Only if object conforms to the hashValue protocol
^ Can be customized by the object's __str__() method
^ Can be customized by the object's __repr__() method
^ Can be customized by the object's __copy__() method
^ Can be customized by the object's __eq__() method
^ Only in Python 2.x and before (removed in Python 3.0). Can be customized by the object's __cmp__() method
^ Can be customized by the object's __hash__() method. Not all types are hashable (mutable types are usually not hashable)
^ Can be customized by the object's __clone() method
^ ^a ^b Can be customized by overloading the object's string conversion operator
^ This example requires useing Data::Dumper
^ This example requires useing Storable
^ This example requires useing Scalar::Util
^ Run-time type information in ABAP can be gathered by using different description Classes like CL_ABAP_CLASSDESCR.
^ ^a ^b ^c ^d ^e Upcasting is implicit in this language. A subtype instance can be used where a supertype is needed.
^ Only for non-class objects. If x is a class object, [x class] returns only x. The runtime method object_getClass(x) will return the class of x for all objects.
^ ^a ^b ^c This language is dynamically typed. Casting between types is unneeded.
^ This language doesn't give run-time type information. It is unneeded because it is statically typed and downcasting is impossible.

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