[xsl] Re: RE: Re: Re: An issue with XPath 2.0 sequences (Was Re: RE: Muenchian method, and keys 'n stuff)

Subject: [xsl] Re: RE: Re: Re: An issue with XPath 2.0 sequences (Was Re: RE: Muenchian method, and keys 'n stuff)
From: Dimitre Novatchev <dnovatchev@xxxxxxxxx>
Date: Fri, 1 Feb 2002 04:58:25 -0800 (PST)
> > Also as Jeni pointed out the weird case of sequences changing their
> > cardinality when mapped by a function that may return the null
> > sequence...
> 
> Or when mapped by any other function that doesn't preserve the 
> cardinality of its input. A function that returns two items for every

> supplied item works in exactly the same way as a function that 
> returns zero items for every supplied item: at least it's consistent!


It is not consistent in this case! If my function returns three items,
e.g. 1 () 2, there's no way to find out that 2 was the third item, not
the second!

A function may return a solution to a problem (as defined by an initial
state) expressed in a sequence of items (e.g. a sequence of moves in a
game or let's say a sequence of the XPath expressions (strings) of all
nodes that satisfy a condition specified by the argument), or the empty
sequence, in case there's no solution.

In case a sequence of problems is mapped with such a function, there
would be no way to pick up the individual solutions, even when every
solution consists of the same equal number of moves.

Please, do understand -- this is not just a matter of taste, this is
lack of useful functionality.

Cheers,
Dimitre Novatchev.

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