Inequalities

*To*: mathgroup at yoda.physics.unc.edu*Subject*: Inequalities*From*: mstankus at oba.ucsd.edu (Mark Stankus)*Date*: Fri, 16 Oct 92 14:18:52 PDT

In relation to a previous posting about geq0: The problem is that 2 x^2 is not of the form x_^2. A good start may be: mySgn[c_?NumberQ] := Sgn[c]; mySgn[x_^n_?(EvenQ[#]&)] := 1; mySgn[c_ d_] := mySgn[c] mySgn[d]; mySgn[c_ + d_] := mySgn[c] /; mySgn[c] == mySgn[d] geq0[expr_] := If[mySgn[x] == 1, True,False,unknown]; I have written some code which takes a list of recorded facts (such as x>=1 and y <= 2) and if you ask if ask if x>= 2 it says unknown and if you ask x>= 0 , it says True. This code is beta-ish, but it works for my application (a symbolic variant of Mora's algorithm -- noncommutative Groebner basis). Send me a note if you want a copy of my beta code. Mark Stankus