Function memoization

>>>>> "James" == James Fuller <[email protected]> writes:

    >> modified form, a proposal that Dimitre Novatchev originally
    >> requested for memomizing xsl:functions.

    >> The modification being that the memoization reqest be an
    >> extension instruction actually present within the xsl:function
    >> concerned (this seems to me necessary to preserve compliance
    >> with the specifications - user-defined data elements and
    >> extension attributes may not cause a different final result
    >> tree to be produced, and, in some cases, memoization of a
    >> function will do just that).


    James> I am interested in such a function as well.

OK. I shall try to define it's semantics:

func:memoize will be an extension instruction. No attributes. Only permitted contents is an xsl:fallback child.

The instruction must be an immediate child of an xsl:function or
func:function.
Good style suggests placing this immediately after the xsl:params, or
at the very end of the function body - but I do not think we need
mandate any such placement (except xsl:param must come first, as now).

An XSLT processor that supports func:memoize shall remember the
results of any calls to functions marked with a call to
func:memoize. If the function is called again with the same values for the arguments, 
it MUST return the remembered result.
It MUST NOT re-execute the function body, as this can cause different
results in some cases.


-- 
Colin Adams
Preston Lancashire