Re: What is the "closure" of a function?

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@xxxxxxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>
>
> On 23-5-2014 22:28, Dimitre Novatchev dnovatchev@xxxxxxxxx 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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