RE: [xsl] Increment a variable

["Michael Kay" <mike@xxxxxxxxxxxx>]

Let's see if I can try to add some clarity - you've been given a muddled set
of responses.

I'll start by saying that I don't understand C++, for example I've no idea
whether "var" and "Var" in your code below are the same variable.

Firstly, it's correct that XSLT is a functional programming language and
does not have mutable variables. Things that are achieved in other languages
using iteration and control variables are achieved in a functional language
using recursive calls with parameters.

However, reverse-engineering your code, it's clear that your requirement is
not the low-level requirement to increment a variable, but a higher-level
requirement something like this:

do 10 times {
  something
  do 100 times {
    something 
  }
  something
}

In XSLT 2.0 you can code that pretty directly as:

<xsl:for-each select="1 to 10">
  ...
  <xsl:for-each select="1 to 100">
  ...
  </xsl:for-each>
  ...
</xsl:for-each>

and you can access the current position in the loop using the position()
function.

In XSLT 1.0 that useful construct isn't available, instead you have to use
one of two approaches.

The clean functional approach is to replace the loops by recursive template
calls. You write a template that does "something", and give it a parameter
that says how many times to do it. The template does it once, and then calls
itself setting the parameter to N-1, and terminating (by doing nothing) when
N is zero.

But some people have a phobia about recursion, probably because it can be
quite hard to debug your inevitable mistakes when you're new to it, or
perhaps because of worries about performance, and they prefer the loop
style. In XSLT 1.0 you can iterate over a node-set using xsl:for-each, so if
you want to do something ten times you can select a set of ten arbitrary
nodes and iterate over it:

<xsl:for-each select="(//*)[position() &lt;= 10]">
  something
</xsl:for-each>

This is "trick programming", some would say it's a dirty trick, and it's a
matter of personal taste whether you use it.

Hope that makes things clearer.

Michael Kay
http://www.saxonica.com/ 

> -----Original Message-----
> From: ChandraShekar, A [mailto:ChandraShekar.A@xxxxxxxxxxx] 
> Sent: 18 August 2005 05:35
> To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
> Subject: [xsl] Increment a variable
> 
>  Hello,
> 	I don't know whether this question is stupid question or not?
> 	
> 	How can I achieve following c++ code in XSLT.
> 
> 	void fun1()
> 	{
> 		for(int i=0;i<1000;i++)
> 		{
> 		   fun2(i);
> 		}
> 	}
> 
> 	void fun2(int var)
> 	{
> 		if ( var == 0 )
> 		{
> 			var++;
> 			// do something
> 		}
> 		else
> 		{
> 			Var++;
> 			// do something
> 		}
> 		if ( var == 100 )
> 		{
> 			Var = 0;
> 			// do something			
> 		}
> 	}		
> 	
> 
> Thanks in advance,