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Re: [xsl] What is the "closure" of a function?

2014-06-06 09:03:50
Thank you Abel,

I hope this could be fixed in the 3.1 documents.

On Fri, Jun 6, 2014 at 4:39 AM, Abel Braaksma (Exselt) 
abel(_at_)exselt(_dot_)net
<xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com> wrote:


On 23-5-2014 22:28, Dimitre Novatchev dnovatchev(_at_)gmail(_dot_)com wrote:
 The Functions and Operators 3.0 recommendation
(http://www.w3.org/TR/xpath-functions-30/) uses the term "closure" of
a function:

"In effect, the static and dynamic part of the context thus act as
part of the closure of the function item."

However, there is no formal definition of "closure".

A search for "closure " in the Data-Model 3.0" Recommendation yields 0 
results.

It appears to me that at some point the term "closure" was dropped. In
the public 06/2011 version of the XDM, a definition existed:

"[Definition: The combination of the variable values needed to execute a
function and the function implementation are called a closure.]" (see
http://www.w3.org/TR/2011/WD-xpath-datamodel-30-20110614/#function-items)

But in the following draft, 12/2011, this was dropped/revised.

It looks like the term closure was not fully removed in related documents.

However, the XDM defines the so called "nonlocal variable bindings":

"nonlocal variable bindings (a mapping from xs:QName to item()*): This
provides a value for each of the function's free variables (i.e.,
variables referenced by the function's implementation, other than
locals and parameters)."

My question is:

  Is it safe to assume that what is referred to as the "closure"
property of functions in the F & O document is the same as the
"nonlocal variable bindings" property of functions, defined in the
XDM?

Yes, I think that is a safe assumption.

Cheers,

Abel Braaksma
Exselt XSLT 3.0 streaming processor
http://exselt.net




-- 
Cheers,
Dimitre Novatchev
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