xml-dev - Re: SAX2 Namespace Support

[John Aldridge <john.aldridge@informatix.co.uk>]

At 10:12 05/01/00 -0500, David Megginson <david@megginson.com> wrote:
>John Aldridge <john.aldridge@informatix.co.uk> writes:
>
>In principle (the principle of least surprise), it's very bad
>behaviour for two objects to be == in C++ or equals() in Java if any
>of their publicly-accessible fields differ.  Think of sets, for
>example.

OK, let me try again...

---------

class QName {
public:
    wstring nsURI () const;        // http://www.w3c.org/1999/xhtml
    wstring localPart () const;    // p
    bool operator== (const QName &rhs) const;
};

class ElementInfo {
    QName name () const;
    wstring nsPrefix () const;     // html
    wstring prefixedName () const; // html:p
    AttributeList &attributes () const;
};

void startElement (const ElementInfo &info) throws SAXException;

----------

Advantages:

(a) All values can be lazily evaluated if this speeds things up (i.e. the
QName and ElementInfo classes need contain no more than a raw pointer into
the parser's internal data structures).

(b) ElementInfo can be extended later to add extra methods without source
level incompatibility.

(c) QName has no public fields which do not participate in equality
testing, yet the equality operator has the "right" behaviour.
-- 
Cheers,
John

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