|Bill Allombert on Tue, 27 Apr 2004 12:32:27 +0200|
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|Re: change variables in multivariant polynomials.|
On Thu, Apr 22, 2004 at 02:12:29PM +0100, Thomas Geffers wrote: > I am writing a program with gp with multivariant polynomials. Because of > the order of the variables I would like to change all the variables from > the input-polynomials. But my way is not very elegant (and by the way does > not work very good;-). > > ie: > g=(u^4-4*u)*z^4 + u*z^2 -1; > > variable(g) is now u. I get the other variable with > > variable(Vec(g)); \\ It gives the correct z. > > My problem is, that I can not change this variable with changevar. > I "solve" this problem with a loop with the following kernel: > > Pol(Vec(g)[i],w) \\ hence for each coefficient. Usually the proper way to rename z to w in g is to do subst(g,z,w). changevar should never be used, it just does not work, it might even be removed completly in the future. Cheers, Bill.