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Re: [xsl] '"as" SequenceType' vs 'TypeDeclaration' in XPath 3.0?


Subject: Re: [xsl] '"as" SequenceType' vs 'TypeDeclaration' in XPath 3.0?
From: Michael Kay <mike@xxxxxxxxxxxx>
Date: Fri, 3 Jan 2014 12:46:29 +0000

On 3 Jan 2014, at 12:08, Tony Graham <tgraham@xxxxxxxxxx> wrote:

> In XPath 3.0 [1], what tips the balance between the occurrence of '"as"
> SequenceType' in production [64] versus the occurrence of
> 'TypeDeclaration' in production [3], where 'TypeDeclaration' is defined as
> '"as" SequenceType' in production [66]?
>
> [64] InlineFunctionExpr ::= "function" "(" ParamList? ")" ("as"
> SequenceType)? FunctionBody
> [2] ParamList ::= Param ("," Param)*
> [3] Param ::= "$" EQName TypeDeclaration?
> [66] TypeDeclaration ::= "as" SequenceType
>


It's likely to be one of the following:

(a) sometimes the XPath 3.0 grammar is complicated by the desire to make it an
explicit subset of the XQuery 3.0 grammar
(b) sometimes the grammar is complicated by the constraints imposed by the
technology used for processing the grammar files and generating the parsing
applets
(c) sometimes the grammar is complicated by the desire to define meta-symbols
that are useful in defining the semantics
(d) sometimes (and I suspect here) there is simply an opportunity for
simplification that has been overlooked.

Michael Kay
Saxonica


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