Re: [xsl] XPath grammar questions

[Oleg Tkachenko <olegt at multiconn dot com>]

Sean Russell wrote:

> The first case is in a path submitted by Tobias Reif, that originated, as I 
> recall, from someone on this list:
> 
>  *[* and not(*/node()) and not(*[not(@style)]) and not(*/@style != */@style)]
> 
> Specifically, it's the 'not(*/node())' that I'm having trouble with.  The 
> XPath spec states that:
> 
>   not( boolean ) -> boolean
> 
> This would imply that '*/node()' evaluates to a boolean.
No, it says that *required* type of the argument must be boolean. 
Generally that is FunctionCall production (see 
http://www.w3.org/TR/xpath.html#NT-FunctionCall):
"A FunctionCall expression is evaluated by using the FunctionName to 
identify a function in the expression evaluation context function 
library, evaluating each of the Arguments, converting each argument to 
the type required by the function, and finally calling the function, 
passing it the converted arguments."
An argument is converted to boolean type "as if by calling boolean 
function".

> The second (and at this point, more critical) problem I'm having is with 
> function names.  Take:
> 
>   [normalize-space(@name)='x']
> 
> If you follow the grammar, the evaluation is:
> 
>    Predicate->Expr->OrExpr->AndExpr->EqualityExpr->RelationalExpr->
>    AdditiveExpr
> 
> at which point it matches the rule:
> 
>   AdditiveExpr:: AdditiveExpr '-' MultiplicativeExpr

No, it shouldn't.
"normalize-space" is NCName itself and according to the spec "When 
tokenizing, the longest possible token is always returned.", so lexer 
must parse it as FunctionName according to "If the character following 
an NCName (possibly after intervening ExprWhitespace) is (, then the 
token must be recognized as a NodeType or a FunctionName."

> 
> where you effectively have "normalize" "-" "space(@name)='x'".
No, lexer must return the longest token, which is "normalize-space" as 
NCName.

-- 
Oleg Tkachenko
Multiconn International, Israel


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