Re: [xsl] Re: Re: Incrementing a Global variable

[Mukul Gandhi <mukulw3@xxxxxxxxx>]

Hi Dimitre,
  Thanks for your ideas.. So I guess, we have to use
variables as they are in XSLT now, and do workarounds
like recursion etc. to simulate procedural kind of
tasks. Probably functional programming advantages far
out weigh the need felt for procedural features like
incrementing of variables..

Regards,
Mukul

--- Dimitre Novatchev <dnovatchev@xxxxxxxxx> wrote:
> 
> "Mukul Gandhi" <mukulw3@xxxxxxxxx> wrote in message
>
news:20030828014403.37385.qmail@xxxxxxxxxxxxxxxxxxxxxxxxxx
> > Hi Dimitre,
> >   I am convinced that side effects are bad in a
> > programming language.
> 
> I didn't say that... Waht I said is that
> uncontrolled side-effects are
> dangerous. There are ways to control side effects
> reliably (e.g. using a
> Monad Type Class) and these have been incorporated
> (supported at the
> syntactic level) in some languages (e.g. the "do
> notation" in Haskell).
> 
> For explanation of Monads see:
> Tackling the awkward squad: monadic input/output,
> concurrency, exceptions,
> and foreign-language calls in Haskell, by
> Simon-Peyton Jones at:
>
http://research.microsoft.com/Users/simonpj/papers/marktoberdorf/
> 
> This is also possible to implement in XSLT (and I
> have such an
> implementation). Probably, in version 4 or 5 XSLT
> might have such a
> mechanism incorporated into the language. A
> prerequisite for this is to make
> functions first class objects (to treat them as any
> other data type -- to
> allow functions to be passed as parameters and
> functions to be returned as
> the result), which could happen in version 3 of
> XSLT.
> 
> One could always control side-effects manually, but
> this is tedious and
> error-prone.
> 
> > Thanks for the links for
> > information about this topic. I believe the
> objective
> > of XSLT is to solve certain kind of problem(XML
> data
> > transformations). The problem of generating serial
> nos
> > comes frequently in real world situations.
> 
> This is not just one problem, but a class of
> problems. You haven't specified
> which is exactly your problem. Many of these "serial
> number generation" or
> "unique number generation" problems can be solved
> with a two-pass solution.
> 
> All of them can be solved by using recursive
> processing.
> 
> > Would it
> > not be helpful(for transformations) if we can have
> a
> > construct which can increment variables(not full
> scale
> > -- but with limited features which can *aid* in
> > transformations)?
> 
> If we have a robust mechanism for controlling side
> effects, then the answer
> is yes.
> 
> > Are we not justifying functional
> > nature of XSLT from a pure computer science view
> > point..
> 
> No, this is not "science for the science" but just
> common sense derived on
> very bad practical experience with side effects.
> 
> A programmer using an FP language must have
> understanding about the issue of
> side effects, otherwise this would be like an 8 yr
> old driving a car.
> 
> 
> =====
> Cheers,
> 
> Dimitre Novatchev.
> http://fxsl.sourceforge.net/ -- the home of FXSL
> 
> 
> 
> 
> 
>  XSL-List info and archive: 
> http://www.mulberrytech.com/xsl/xsl-list
> 


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