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Re: [xsl] are all strings in a sequence valid potential QNames

2010-02-04 03:38:11
At 2010-02-04 09:29 +0000, Andrew Welch wrote:
>> Could you do a  fn:prefix-from-QName($x) = fn:in-scope-prefixes(.)
>> check before doing the castable as check?
>
> Nope:
>
>  http://www.w3.org/TR/2007/REC-xpath20-20070123/#id-castable
>  "[if] the input argument of the expression is of type xs:string but it is
>   not a literal string, the result of the castable expression is false."

To help me understand that :-)

Not a problem, Andrew ... I get asked about this terminology in the classroom.

can you provide an example of a user
constructed string that is not a string literal?

For example, tokenizing a string into a sequence of strings... they
are all string literals aren't they?

Nope ... a string literal is "literally a string in the stylesheet" written with string delimiters. The term "literal" here is in reference to the XPath written syntax.

A sequence of strings is just that: a sequence of string values in memory.

A literal string in the stylesheet is just that: a string value literally delimited in the stylesheet. See production 74 of the XPath syntax:

  http://www.w3.org/TR/2007/REC-xpath20-20070123/#doc-xpath-StringLiteral

The difference is a syntax issue: a string literal is a type of primary expression (production 41) written in the stylesheet syntax and it is the way to represent a string value in the XPath syntax different from the representations of other literal values.

I hope that clarifies the distinction.

. . . . . . . . . . Ken


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