= Struct Definition = 

Structs are similar to classes but more limited in ways that make them suitable [[BR]]
for representing lightweight value-container-only objects ( like a Point or Rectangle).

Unlike classes (reference type) they are a value type and they cannot be inherited or inherit[[BR]]
from another class or struct. 

Other differences from classes:[[BR]]
    * Within a struct declaration, fields cannot be initialized unless they are declared as const or static.
    * A struct may not declare a default constructor (a constructor without parameters) or a destructor.
    * Structs can only declare constructors that have parameters.
    * Structs are copied on assignment and when passed into methods. [[BR]]
      When a struct is assigned to a new variable or passed to a method, all the data is copied, and any modification to the [[BR]]
      new copy does not change the data for the original copy. 

However
    * A struct can implement interfaces.
    * A struct can be used as a nullable type and can be assigned a null value.

Structures and their contained instance members are public by default though this may be[[BR]]
overridden using the normal [wiki:AccessModifiers access modifiers] syntax.

Idomatic usage suggests structs should not modify their accessmodifiers for visibility and[[BR]]
should not declare any methods (If this is deemed necessary you should use a class instead).[[BR]]
They should only be used as publicly accessible value containers. 

The syntax/grammar for declaring structures is similar to that of classes [[BR]]
(barring the '''struct''' keyword and lack of the '''inherits''' clause)

== Grammar ==
{{{
struct <StructureName>  
    [is <AccessModifiers>]
    [has <Attributes>]
    [where <GenericParam> must be <GenericConstraints>]
    [implements <InterfaceName> [, <InterfaceName>]...]
    [<DocString>]
    [
        [<Variables>]
        [<Constants>]
        [<Properties>]
        [<Methods>
        [<Enums>]
        [<Sigs>]
        [<Invariants>]
        [<Tests>]
        [<SharedClause>]
    ]...

# empty (placeholder) structure
struct <StructureName>  
    [is <AccessModifiers>]
    [has <Attributes>]
    [where <GenericParam> must be <GenericConstraints>]
    [implements <InterfaceName> [, <InterfaceName>]...]
    [<DocString>]
        pass
}}}

== Platform ==

in .Net,  all structs inherit directly from System.!ValueType, which inherits from System.Object.

== Examples ==
{{{
#!cobra
# a simple Point-like struct
struct CoOrds
    var x as int
    var y as int

    cue init(p1 as int, p2 as int)
        .x = p1
        .y = p2


#// Declare and initialize struct objects.
class TestCoOrds
    def main is shared
        # Initialize:   
        coords1 = CoOrds()
        coords2 = CoOrds(10, 10)

        # Display results:
        print 'CoOrds 1: ' stop
        print 'x = [coords1.x], y = [coords1.y]'

        print 'CoOrds 2: ' stop
        print 'x = [coords2.x], y = [coords2.y]'
        
        assert coords1.x == 0 and coords1.y == 0
        assert coords2.x == 10 and coords2.y == 10

/# Output:
    CoOrds 1: x = 0, y = 0
    CoOrds 2: x = 10, y = 10
#/


}}}

== Notes ==

== See Also ==
[http://msdn.microsoft.com/en-us/library/ah19swz4.aspx struct(C# Reference)]

[http://msdn.microsoft.com/en-us/library/saxz13w4.aspx Structs(C# Programming Guide)]

[http://msdn.microsoft.com/en-us/library/0taef578.aspx Using Structs( C# Programming Guide)]


[wiki:LanguageTopics Back to LanguageTopics]