Subject: [xsl] An issue with XPath 2.0 sequences (Was Re: RE: Muenchian method, and keys 'n stuff) From: Dimitre Novatchev <dnovatchev@xxxxxxxxx> Date: Wed, 30 Jan 2002 11:30:24 -0800 (PST) |
> > It's interesting that you can build a sequence of integers in XPath > > 2.0 with the 'to' operator, but not a sequence of characters. For this > > situation, it would be really nice to be able to do: > > > > <xsl:for-each select="'a' to 'z'"> > > ... > > </xsl:for-each> > > > > It's often been suggested that there should be char-to-unicode and > unicode-to-char functions, which would allow you to write > > <xsl:for-each > select="for $i in char-to-unicode('a') > to char-to-unicode('z') > return unicode-to-char($i)"> > ... > </xsl:for-each> > > That would be explicitly based on Unicode values; finding all the characters > that are between 'a' and 'z' in your default collating sequence sounds like > a more difficult challenge. This challenge is a result from the inability in XPath 2.0 to regard a string as a sequence of characters, and this is a consequence of the decision not to allow a sequence to have elements, which themselves are sequences. As can be seen, the last decision is the logical result of another decision to regard every simple value as a sequence consisting of one element. I already provided an example of a problem, which could be efficiently solved in case we could have a sequence of sequences. This problem is to produce simultaneously (in one pass) two sequences -- e.g. one that contains all the elements of a sequence, which satisfy a given predicate, and the other containing the rest. Several people already expressed their curiosity about what was the reason to forbid a sequence to have an element-sequence. I think that these examples show it would be better to allow elements-sequences and to treat simple values only as such and not as sequences. The latter also fits better the idea of type-checking as it gives a single value exactly one type, as opposed to two types now -- its true type and its type as a sequence. Cheers, Dimitre Novatchev. __________________________________________________ Do You Yahoo!? Great stuff seeking new owners in Yahoo! Auctions! http://auctions.yahoo.com XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
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