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[Bug 10719] [XPath21] The text describing how function items are evaluated is not very precise

From: <bugzilla@jessica.w3.org>
Date: Tue, 12 Oct 2010 22:42:52 +0000
To: public-qt-comments@w3.org
Message-Id: <E1P5nYa-000154-F0@jessica.w3.org>
http://www.w3.org/Bugs/Public/show_bug.cgi?id=10719

John Snelson <john.snelson@marklogic.com> changed:

           What    |Removed                     |Added
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                 CC|                            |john.snelson@marklogic.com
           Severity|normal                      |trivial

--- Comment #1 from John Snelson <john.snelson@marklogic.com> 2010-10-12 22:42:52 UTC ---
(In reply to comment #0)
> 1.
> On an editorial note, the $f in point 3 should be in a monospaced font.

Accepted as an editorial amendment.

> 2.
> One reading of this text implies that the functions closure is added to the
> current context, but then the dynamic context used is defined by where the
> function item was declared, and so may not have these variables.

I believe that conceptually a function items closure contains values (ie: XDM
instances) rather than unevaluated expressions, so this makes no difference.

> 3.
> If $f is a function item then it is not a built-in or user-defined function
> (functions and function items are different things).  Thus the text never
> actually says how to evaluate a function item.

The text probably glosses over the distinction (or lack thereof) between
functions and function items. I think it's an editorial issue to tighten this
up.

> It may be better to rewrite this section in two parts: The first part
> explaining how a function is evaluated (mostly unchanged from XPath 2.0 /
> XQuery 1.0).  The second part should say (roughly)
> 
> The result of a function call on a function item is computed in the same way as
> the result of a call on the function described by the function, except that in
> the case of a user-defined function the dynamic context used to evaluate the
> function's body is augmented by the the set of variable values from the
> function item's closure.

I'll certainly consider that approach.

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Received on Tuesday, 12 October 2010 22:42:53 UTC

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