Re: [xsl] current-dateTime()

Subject: Re: [xsl] current-dateTime()
From: Liam Quin <liam@xxxxxx>
Date: Fri, 18 Apr 2008 10:24:59 -0400
On Fri, Apr 18, 2008 at 02:05:52PM +0100, Andrew Welch wrote:
> It should be straightforward to write an extension function instead...

Actually no.  A conformant implementation is allowed to call an
extension function only once for any given argument value, and
to remember the results, to make it stable.  A give implementation
might let you write such an extension function as you want, but
there's no guarantee.

In addition, suppose you have a stylesheet that does, say

    xsl:for-each 1 to 1000
	value-of current-time

the implementation doesn't have to start at 1 and evaluate the
"loop"  a thousand times.  Instead, this could be written as,
    map the items in the sequence (1 ... 1000)
    to the value of current-time
with current-time being called once.

Or, the implementation could start at 1000 and work downwards,
and as long as it ended at 1 and put the results in the right
order, you coudn't tell.

And yes, there are implementations that do that sort of thing :-)
at least for XQuery and quite possibly for XSLT.

So, best to think of XSLT as specifying a mapping, rather than
in terms of procedural instructions.

Hppe this helps, although it's perhaps notwhat you want to hear.



Liam Quin, W3C XML Activity Lead, *

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