From: Stan Devitt <jsdevitt@radicalflow.com>

Date: Tue, 11 Jul 2000 17:53:43 -0400

Message-ID: <004601bfeb82$7baeeac0$6561a8c0@devitt.local>

To: Gérald QUINTANA <quintana@lyon.objectif.fr>, <www-math@w3.org>

Date: Tue, 11 Jul 2000 17:53:43 -0400

Message-ID: <004601bfeb82$7baeeac0$6561a8c0@devitt.local>

To: Gérald QUINTANA <quintana@lyon.objectif.fr>, <www-math@w3.org>

Note that the important thing to do is to capture the information. The essence of a piecewise object is: 1. there is a bound variable 2. there is one or more conditions on that variable bound to outcomes, typically computed using that variable. 3. possibly a default outcome MathML does NOT evaluate or simplify its expressions. With this in mind, you probably want to choose between piecewise( bvar , (condition, value )*, default ) and piecewise( bvar , default , conditiongroup * ) where conditiongroup := conditiongroup( condition , value ) Either one will do the job. Both are easy to encode using csymbol, and bvar, at least in MathML 2.0. (There were some funny restrictions in MathML 1.0 that did not allow bvars in new expressions and required function wrappers in the first argument to apply.) In 2.0 the first of these would look something like: <apply> <bvar>x</bvar> <csymbol definitionURL="mydefinitionforpiecewise">piecewise</csymbol> <apply><lt/> ....</apply> <apply><times/> ...</apply> <apply></lt/> ... </apply> value 2 default value </apply> Note that reln is deprecated in MathML 2.0 Also, generally speaking it is a bad idea to encode essential information in comments as sometimes processing strips those comments away. There is no real need to use the lambda constructs as that information would already be contained in the formal definition, and is really more concerned with evaluation than representation. Stan Devitt ----- Original Message ----- From: Gérald QUINTANA To: www-math@w3.org Sent: Tuesday, July 11, 2000 11:45 AM Subject: Content markups, piecewise functions, conditions Hi, I am thinking about how I could code a piecewise function using content markups. I need content markups because I aim at making a small MathML "parser-compiler". I didn't understood exactly how conditions were working. So as to code the sign function (returns -1 when x<0, 0 when x=0 and +1 when x>0) what do you think of this ? How can I tell that those 3 definitions belongs to the same function ? <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE math SYSTEM "file://localhost/S:/java/xerces/mathml/mathml.dtd" > <math> <!--If x<0 then -1--> <lambda> <bvar> <ci>x</ci> </bvar> <apply> <bvar> <ci>x</ci> </bvar> <condition> <reln> <lt/> <ci>x</ci> <cn>0</cn> </reln> </condition> <apply> <minus/> <cn>1</cn> </apply> </apply> </lambda> <!--If x=0 then 0--> <lambda> <bvar> <ci>x</ci> </bvar> <apply> <bvar> <ci>x</ci> </bvar> <condition> <reln> <eq/> <ci>x</ci> <cn>0</cn> </reln> </condition> <cn>0</cn> </apply> </lambda> <!--If x>0 then +1--> <lambda> <bvar> <ci>x</ci> </bvar> <apply> <bvar> <ci>x</ci> </bvar> <condition> <reln> <eq/> <ci>x</ci> <cn>0</cn> </reln> </condition> <cn>1</cn> </apply> </lambda> </math> Thanks for your help, Gerald. ________________________________ Gérald QUINTANA gerald.quintana@ecl2000.ec-lyon.fr http://www.multimania.com/gquintanaReceived on Tuesday, 11 July 2000 17:48:48 UTC

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