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Re: [xml-dev] Formulas in XML values

A simple XSLT implementation is to use the LR-parsing framework of
FXSL (func-LRparse.xsl) and produce a function, which acts as a simple
arithmetic interpreter.

In fact, this has already been done and used as the first and simplest
application of this framework:


and this interpreter, including the lexer and the regex token
definitions is just 220 lines of code.

Dimitre Novatchev
Truly great madness cannot be achieved without significant intelligence.
To invent, you need a good imagination and a pile of junk
Never fight an inanimate object
You've achieved success in your field when you don't know whether what
you're doing is work or play

On Thu, Jun 25, 2009 at 10:35 AM, COUTHURES
Alain<alain.couthures@agencexml.com> wrote:
> Formulas in XML values are a persistent concern for me for some days and
> xml-dev appears to be the best place to discuss this...
> From mathematical point of view, 35+7 and 42 are equals but human beings can
> interpret them differently. When a value has to be put in a field by an
> user, sometimes it's, in fact, the result of a basic computation and, when
> someone else has to verify the field value, the initial formula might help
> to understand. Excel users do that every day !
> XML is a text notation so it's not disturbing to write 35+7 where 42 can be.
> But, schema languages should evaluate values before testing if they are
> valid or not. XPath should, at least, do the same or, better, be able to say
> that 15+6 multiplied by 2 is (15+6)*2. Students calculators can do that
> already, don't they ?
> There are interesting possibilities with such a notation improvement :
> numbers such as 1/3, pi, sqrt(2) would be written as what they are and not
> just in a limited amount of digits. Of course, a bunch of mathematical
> functions and constants should be named...
> I will probably implement some basic approach for this in my XForms
> implementation (XSLTForms : http://www.agencexml.com/xsltforms) because I
> already need it for setting values in XBRL documents.
> XSLTForms has its own XPath implementation and XML Schema validation, both
> written in Javascript, and some eval() calls at the right place might be all
> what is needed. Formulas will then be submitted and stored as ordinary
> values would be. If needed, I will design an XSLT stylesheet to resolve
> formulas into values (XSLTForms already has an XPath 1.0 expression parser
> written in XSLT 1.0 ...).
> Thank you for your remarks and suggestions.
> Best regards,
> Alain Couthures
> <agenceXML>
> http://www.agencexml.com
> Bordeaux, France
> Twitter account: AlainCouthures
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