RE: ES4 draft: Namespace

[Lars Hansen]

Draf 2 of the spec for Namespace objects.

--lars

Title: The class "Namespace"

The class Namespace

FILE:                       spec/library/Namespace.html
DRAFT STATUS:               DRAFT 2 - 2008-03-17
SOURCES:                    REFERENCES [1], [2]
REVIEWED AGAINST ES3:       N/A
REVIEWED AGAINST ERRATA:    N/A
REVIEWED AGAINST BASE DOC:  YES
REVIEWED AGAINST PROPOSALS: N/A
REVIEWED AGAINST CODE:      YES
IMPLEMENTATION STATUS:      ES4 RI (partly)


CHANGES SINCE DRAFT 1 (2008-03-05)

  * Presentation: added an explicit "extends Object" clause

  * Namespaces are explicitly designated nullable and a null value is
    tied to the compatibility namespace noNS.

  * The behavior of the 'toString' method has been tightly specified
    to allow Namespace objects to be compared predictably.


OPEN ISSUES

  * Namespace objects in ES4 are more opaque than the Namespace
    objects in the base document and in E4X, both of which expose
    "prefix" and "name" properties.  ES4 is not supporting E4X, and
    the base document was probably influenced by E4X, so this
    may not be a big deal, but it should be discussed.


REFERENCES

[1] Section 4.2.10.4 of the base document: http://wiki.ecmascript.org/lib/exe/fetch.php?id=resources%3Aresources&cache=cache&media=resources:as3lang.doc
[2] builtins/Namespace.es in the ES4 RI
[3] Language definition, section on Names (forthcoming).



 The class Namespace is a final, non-dynamic, nullable,
direct subclass of Object.  It reflects a namespace as an opaque
datum.

NOTE    Namespaces are created as a result of the evaluation of the
namespace pragma, which defines a new namespace and creates a
binding for it.  Namespaces are reflected as Namespace objects
when namespace bindings are referenced in expressions.

NOTE    A Namespace object can be created with an explicit name by
providing the name as a string in the namespace pragma.

NOTE    Generally a null namespace value is used to denote the
compatibility namespace noNS.

COMPATIBILITY NOTE    The Namespace class is new in the 4th Edition of this
Standard.

Synopsis

 The class Namespace provides the following interface:

__ES4__ final class Namespace extends Object
{
    intrinsic function toString(): string …
}


 The Namespace prototype object provides the following direct
properties:

    toString: function () …


Operators

 The operators == and === compare as equal two non-opaque
Namespace objects that are separately created from the same string;
similarly, the operators != and !== compare as not equal two
Namespace objects that are separately created from dissimilar strings.


Methods on the Namespace class object

 There are no methods on the Namespace class object.  In
particular, the class Namespace does not have a publicly
accessible constructor.


Methods on Namespace instances

intrinsic::toString()

Description 
 The intrinsic toString method converts the Namespace
object to a string.  If the Namespace object was created with an
explicit name then the string contains that name as a substring.

Returns 
 The toString method returns an implementation-defined
string.  

 Suppose the intrinsic toString method is invoked on two
namespaces N1 and N2 yielding strings T1 and T2,
respectively.  T1 and T2 are equal if and only if N1 is
equal to N2 (by === or ==).

 Suppose the intrinsic toString method is invoked on two
different non-opaque namespaces N1 and N2 created from strings
S1 and S2, yielding strings T1 and T2, respectively.
T1 and T2 have the same relationship (determined by the
relational operators) as S1 and S2.

Methods on the Namespace prototype object

Description 
 The methods on the Namespace prototype object delegate to
their corresponding intrinsic methods.

Returns 
 The methods on the Namespace prototype object return what
their corresponding intrinsic methods return.

Implementation
prototype function toString(this:Namespace)
    this.intrinsic::toString()

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