Re: [xsl] mixed content grouping by whitespace

["Imsieke, Gerrit, le-tex" <gerrit.imsieke@xxxxxxxxx>]

On 13.04.2010 20:17, David Carlisle wrote:
> On 13/04/2010 19:08, Wendell Piez wrote:
> > only a mathematician is likely to find this more straightforward than
> > group-starting-with="h2". At least most of the time.
>
> Are there other people?

My maths tutor used to say: In mathematics, you learn either by insight 
or by habituation. It is only by habituation that I learned the 
distinction between patterns and expressions in grouping conditions. I 
never fully understood why in g-s-w/g-e-w groupings the population needs 
to be all nodes and not arbitrary sequences. I wonder whether it is 
because someone insisted that g-s-w/g-e-w conditions need to be patterns 
and hencefore the population need to be nodes, or whether it was the 
other way round. Maybe it is as it is for "historical reasons". Or maybe 
they thought: if we permit an arbitrary expression as g-s/e-w condition 
then we must check that an effective boolean value may be calculated for 
this expression, because it should be a yes/no decision whether a given 
item starts/ends a group. Maybe they found that a pattern that either 
matches or not is a more clear-cut and comprehensible binary criterion 
than arcane EBV semantics, at least for the common case of grouping 
nodes. I can imagine that they wanted to have patterns for all grouping 
conditions and very reluctantly accepted the fact that there must be 
more key values than true or false for group-by and group-adjacent.
I doubt that implementation considerations (such as a fictional: "a 
pattern match will typically be evaluated faster") have guided the decision.
To start a more general discussion: what are patterns for anyway? 
Couldn't the matching in template rules be performed by evaluating the 
EBV of an arbitrary expression in the match attribute? I think this 
wouldn't be XSLT (transforming nodes) any more if a template could 
match, for example, anything that is castable as xs:double.
But for g-s/e-w, I think an expression does make sense. If the 
expression's EBV (the EBV of the result of evaluating the expression, to 
be more precise) cannot be calculated, a type error will be raised. 
That's ok.

Only my 2 xs:currency.

Gerrit