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Re: [xsl] Re: "if-condition-return something" idiom : is it possible in XSLT 1 ?


Subject: Re: [xsl] Re: "if-condition-return something" idiom : is it possible in XSLT 1 ?
From: "Kerry, Richard richard.kerry@xxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>
Date: Mon, 16 Jun 2014 13:11:32 -0000

"you seem to want to replicate C++ programming idioms in XSLT. "

Not at all.

I thought of the process in those terms, as I am far more familiar with C/C++.
Having implemented part of the requirement in that way and found the result
unsatisfactory I'd like to know how better to do it.



"a verbose and ugly terrain"

That's what I've started seeing and led me to assume that it wasn't the best
way to do it - hence the question.



What I am doing is writing a callable template which will give dates in the
form yyyy-mm (y and m numeric) when given dates in a variety of formats
including those with strings for months (dd MMM yy, dd/mm/yyyy, mm/yy, and
many others).  So the input is a single string which needs to be tested
against a number of different formats and picked apart accordingly.  Perhaps I
can partly pick it apart then put the parts into a node-set and get a template
called on that.



"might look verbose"

I've got at least half a dozen input formats.  Before starting to consider
this if-condition-return idiom I was getting other ugly/verbose results.  If I
can get the language processor to do tests for me I'm happy to move to
many-templates.





Regards,

Richard.









________________________________
From: Ihe Onwuka ihe.onwuka@xxxxxxxxx
[xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx]
Sent: 16 June 2014 13:44
To: xsl-list
Subject: Re: [xsl] Re: "if-condition-return something" idiom : is it possible
in XSLT 1 ?

XSLT is a pattern matching language, so the short answer is that idiomatic
XSLT would use predicates in template rules for this

<xsl:template match="balance[. > 100]">
  things to do if balance is greater than 100
</xsl:template>

<xsl:template match="balance">
  default processing for balance
</xsl:template>

which might look verbose but if you code like this the processor will figure
out when to fire which rule  and what to do next.

This will probably not satisfy you as you seem to want to replicate C++
programming idioms in XSLT. Yes you can do it but there lies a verbose and
ugly terrain for which  I do not have the energy to travel but maybe someone
else does.





On Mon, Jun 16, 2014 at 1:19 PM, Kerry, Richard
richard.kerry@xxxxxxxx<mailto:richard.kerry@xxxxxxxx>
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx<mailto:xsl-list-service@xxxxxxxxxxxx
rytech.com>> wrote:
And just to be clear, I am asking about XSLT1.
(I am doing DocBook transformations and am trying to parse dates as strings)

________________________________________

In C/C++ programming the following idiom is quite common:

if (condition1)
  return value1;

if (condition2)
  return value2;

if (condition3)
  return value3;

return value4;

In other words each of these will test a condition and if it is satisfied
execution will stop and some value will be returned to the caller.  The run
stops with the first condition that succeeds.

I've tried to do something similar in XSLT and am getting somewhat
contradictory indications of whether or not it is working.  Please can someone
advise whether this should work, or if there is a similar form that I can
use.

What I have is like the following template, to be called by name.

<xsl:template name="test.1">
  <xsl:param name="string" select="''"/>

   <xsl:if test="$check.1 = 0">
     <xsl:value-of select="$value.1" />
   </xsl:if>

   <xsl:if test="$check.2 = 0">
     <xsl:value-of select="$value.2" />
   </xsl:if>

   <xsl:if test="$check.3 = 0">
     <xsl:value-of select="$value.3" />
   </xsl:if>

  <xsl:value-of select="$value.4" />
</xsl:template>

My theory of why it might work is based on knowing that the following will
work:

<xsl:template name="test.2">
  <xsl:param name="string" select="''"/>

  <xsl:value-of select="$value.4" />
</xsl:template>

I say "will work" in the sense that if the above template is called (by name)
it will return the value from value.4.  What I'm not sure of is whether that
should work if the "returning" value-of is a level down, in an xsl:if, as in
the other template (test.1).
It is only a theory of why it might work.  Practice may indicate otherwise,
and somewhere in the spec might be a reason.

Can someone please advise whether I can do this, or how to get broadly
equivalent behaviour ?

Regards,
Richard.



Richard Kerry
BNCS Engineer, SI SOL Telco & Media Vertical Practice
T: +44 (0)20 3618 2669
M: +44 (0)7812 325518
G300, Stadium House, Wood Lane, London, W12 7TA
richard.kerry@xxxxxxxx<mailto:richard.kerry@xxxxxxxx>


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