Subject: Re: [xsl] What is the "closure" of a function? From: "Abel Braaksma (Exselt) abel@xxxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> Date: Fri, 6 Jun 2014 11:39:36 -0000 |
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
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