Problems with easy simplifications

*To*: mathgroup at smc.vnet.net*Subject*: [mg54143] Problems with easy simplifications*From*: Antonio González <gonferh2o at esi.us.es>*Date*: Fri, 11 Feb 2005 03:34:47 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

I have found some weird behaviors of Mathematica (5.0) related to the simplifications of easy expressions. Take, for instance the function H[x_, a_, b_] = If[x < a, a + b, a - b] If I try now to evaluate H[x,0,0] the result If[x < 0, 0 + 0, 0 - 0] (the values of a and b are irrelevat, a similar result is obtained, for instance, with a=1, b= 2, or any integer, real or complex values). I cannot force (at least in a simple way) Mathematica to make the addition or the substraction. The action of Simplify or FullSimplify leaves the expression unchanged while a Map of Simplify MapAll[Simplify, H[x, 0, 0]] produces If[x < 0, Simplify[Simplify[0] + Simplify[0]], Simplify[Simplify[ 0] + Simplify[Simplify[-1] Simplify[0]]]] Something even worse happens if a use values already defined. For instance c = 0; d = 0; H[x_] = If[x < c, c + d, c - d] produces If[x < 0, c + d, c - d] In this case, the addition is not necessary. c = 0; d = 0; H[x_] = If[x < c, c, d] leads to If[x < 0, c, d] Similar problems arise using the function Which. Any explanation or help with this malfunction would be welcome. -- Antonio (Eliminar el agua para responder por e-mail - Remove water to reply by e-mail)

**Follow-Ups**:**Re: Problems with easy simplifications***From:*Chris Chiasson <chris.chiasson@gmail.com>