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Topic: Re:[mg4144]More "Logical" functions?
Replies: 0

 Edward G. Neuman Posts: 13 Registered: 12/7/04
Re:[mg4144]More "Logical" functions?
Posted: Jun 16, 1996 2:13 AM

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
>
>
>

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@math.siu.edu
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