Subject: Re: Assignment no, dynamic scoping si (was: Re: [xsl] RE: Wishes for XSL revisions ... From: David Carlisle <davidc@xxxxxxxxx> Date: Thu, 3 Jan 2002 14:12:09 GMT |
Gunther > So, what are the disadvantages of dynamic scoping? > I can see only two There are others, not least that having two kinds of scoping working in parallel is confusing. There are languages that do this but normally one has either one sort of scope or the other. Especially in XSLT dynamic scope could have some surprising consequences due to the template match mechanism. Unlike some other more traditional languages, in XSLT the calling order of the templates is not at all explict in the program source and is driven by whatever document is passed in as data. This means that normally templates need to be written to work wherever they happen to match and _without_ regard to the particular calling sequence that caused them to fire. Dynamic scope would radically change that and mean that the behaviour of a template would much more directly depend on the stack of "currently active" templates. It is not at all clear to me that this would make XSLT an easier language to understand or work with. At present any dependency on previously called templates is (a) rare and (b) explictly flagged by the declaration and passing or parameters. This is a good thing (I believe) Of course the fact that the syntax for passing parameters is so verbose (even by XSL standards) means that it is sometimes a pain, but there have been some "syntactic sugar" proposals to help with that without changing the underlying execution model. David _____________________________________________________________________ This message has been checked for all known viruses by Star Internet delivered through the MessageLabs Virus Scanning Service. For further information visit http://www.star.net.uk/stats.asp or alternatively call Star Internet for details on the Virus Scanning Service. XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
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