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Re: [xsl] "if-condition-return something" idiom : is it possible in XSLT ?


Subject: Re: [xsl] "if-condition-return something" idiom : is it possible in XSLT ?
From: "Kerry, Richard richard.kerry@xxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>
Date: Tue, 17 Jun 2014 15:37:03 -0000

"think of XSLT as a functional language"
XSLT is the only language I've ever used that is described as Functional, so I
don't know what impact that has generically.  I am, as you can all see, now
learning a bit more about the implications.

"There's no concept of an "early return" from a mathematical function"
Indeed not.
"nor from an XSLT one."
That was the core of my question.  How to express a problem which I can easily
express in that way in a form suitable for XSLT.


Appreciatively,
Richard.




________________________________________
From: Liam R E Quin liam@xxxxxx [xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx]
Sent: 16 June 2014 21:12
To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
Subject: Re: [xsl] "if-condition-return something" idiom : is it possible in
XSLT ?

On Mon, 2014-06-16 at 13:00 +0000, Kerry, Richard richard.kerry@xxxxxxxx
wrote:
> I tend to view (*) xsl:choose as similar to C's "switch", which needs
> to do a single calculation to work out which branch to run.
> (*)  I may well be wrong in this.....

xsl:choose is like a sequence of C if statements in practice, and is
what yu want for your C++-like example.

But I think it better to think of xsl:choose in the mathematical sense,
e.g.

 A := f(x)
       0 when x <= 1
      17 when x <= 7
       A(x - 1) . A(x - 2) when x^2 + 1 is prime
      31x / 7 otherwise

That is, I prefer to think of XSLT as a functional language in which one
is describing the end result rather than as a procedural language with
loops and returns.

There's no concept of an "early return" from a mathematical function,
nor from an XSLT one.

Liam


--
Liam Quin - XML Activity Lead, W3C, http://www.w3.org/People/Quin/
Pictures from old books: http://fromoldbooks.org/
Ankh: irc.sorcery.net irc.gnome.org freenode/#xml


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