Subject: Re: [xsl] Scope of variables From: David Carlisle <davidc@xxxxxxxxx> Date: Fri, 9 May 2003 09:46:26 +0100 |
> [DAVID] What did you mean by this statement: > The "variable value can't change" mantra refers to the fact that there > is not an analogue of > x=x+1 > wich 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 The term variable comes from mathematics and if in mathematics you see x=x+1 then one could deduce (by subtracting x from both sides) that 0=1 which is false, implying the original statement is false. When I first was shown programming (Fortran at school in the mid 70's) this aspect of fortran allowing variables to change their definition was the main "strange" thing about programming languages that all the books stressed. that programming languages had these strange imperative features because they were designed to be easily executed by machines rather than easily understood by humans. A generation later and things have changed: machines are now more powerful and so programming languages using more natural declarative constructs are now feasible. Let the machine do the work and have the language more suitable for humans. But things are not so simple, it seems that in the intervening time humans have got used to the imperative machine-oriented languages and are now unsettled by human oriented declarative languages. You can't win.... David ________________________________________________________________________ This e-mail has been scanned for all viruses by Star Internet. The service is powered by MessageLabs. For more information on a proactive anti-virus service working around the clock, around the globe, visit: http://www.star.net.uk ________________________________________________________________________ XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
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