Re: More "Logical" functions?

*To*: mathgroup at smc.vnet.net*Subject*: [mg4230] Re: [mg4144] More "Logical" functions?*From*: "Edward G. Neuman" <edneuman at math.siu.edu>*Date*: Tue, 18 Jun 1996 03:28:27 -0400*Sender*: owner-wri-mathgroup at wolfram.com

Scott Herod wrote: >I often find myself trying to solve big sets of polynomial equations. >I realize that there are Groebner basis packages for use in this but >many times I can get by with Reduce and Solve. My problem is this: > >Often I get results like > > {{ x -> 0 }, {x -> 0, y -> 5 }, {x -> 0, z -> -2}, ... } > >where {x -> 0} is common to all of the terms. I would like to be able >to factor out the x=0 from each equation. I don't need to see everything >else if x has to be zero anyway. > >Currently I'm doing a LogicalExpand[results && x != 0] to see the cases >where x does not have to be zero, but something to factor the x -> 0 >would be nicer. > >Does anyone know of an existing package do Logical expression operations? > >Scott Herod >(sherod at newton.colorado.edu) > > > To delete from your list expressions like x->c, where c is a number, you can use the rewrite-rule capability of Mathematica: a={{x->0},{x->0,y->5},{x->1,y->0}}; rule1=#/.{x->c_,y___}->{y}&; a//rule1 {{}, {y -> 5}, {y -> 0}} =============================================================================== Edward Neuman Phone: (618) 453-6501 Department of Mathematics Fax: (618) 453-5300 Southern Illinois University E-mail: edneuman at math.siu.edu Carbondale, Ill. 62901-4408 WWW: http://www.science.siu.edu/mathematics/neuman/ ==== [MESSAGE SEPARATOR] ====