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Re: [xsl] things about grouping


Subject: Re: [xsl] things about grouping
From: Ihe Onwuka <ihe.onwuka@xxxxxxxxx>
Date: Sat, 24 Nov 2012 15:58:59 +0000

On Sat, Nov 24, 2012 at 3:23 PM, Michael Kay <mike@xxxxxxxxxxxx> wrote:
>>3. If you group-starting-with it's weird to then see things not encompassed
>> by the starting-with expression appear as a group because they precede the
>> first occurrence of the starting-with expression. While this works as
>> specified because for-each-group is a total function over the population it
>> does result in a mismatch between the grammatical semantic and the exhibited
>> behaviour, or to put it another way it does what it says in the spec but
>> doesn't do what it says on the tin.
>
> Finding element and attribute names that enable people to guess the
> semantics without reading the spec is not always easy. Som programming
> languages get around this by using operators like ~:< whose semantics you
> can't even attempt to guess...
>
> The moral is, don't use any construct in any programming language without
> reading the spec.
>

A language that mandated such (thankfully XSLT is not one)  would  not
be ergonomically friendly and  I'm sure there are a plethora of such
languages that have fallen into disuse.

Now as it happens I've read the specification of those language
constructs. I am critiquing it FWIW.

It's not really an issue of people guessing the semantics though is
it. It's more a case of the chosen syntax suggesting a semantic which
is obviously intentional and rightly so.

Personally I have far less issue with ~:< as syntax than something
whose syntax suggests a semantic which it does not then deliver on.

I'm sure issues like this were given very careful consideration in the
design of the language. It is not perfect and not expected to be so
but if a language specification was the be all and end all we wouldn't
have progressed from COBOL, PL/1 and XSLT 1.0.


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