Re: Variable Scope

[David Carlisle <davidc at nag dot co dot uk>]

> What I'm not clear about is why the 'here' variable is updatable as the 
> for-each iterates, it was my understanding that variable values cannot be 
> changed. 

Essentially you can't change the value of a variable once it's bound,
but you can bind a new variable that has the same name. (XSLT imposes
some restrictions on when you can rebind, to avoid confusion, one
assumes)

The body of the for-each is a template, like the body of xsl:template
each time you go round the loop the template body is instantiated again
and you get a new variable called here, its scope ends at the end of
that template body, ie effectively you get a new variable created and
discarded each time round the loop.

Note this is completely different from the use of variables in loops in
procedural languages where the _same_ variable survives throughout the
loop, carrying state information (like how many times the loop has been
executed).

The "variable value can't change" mantra refers to the fact that there
is not an analogue of
x=x+1
which some people, corrupted by procedural languages seem to feel
is a natural thing to write, whereas it is obviously an affront to the
laws of nature, unless x happens to be 0:-)

David

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