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something like algsubs (maple) in XCas/Giac?

Publié : mar. avr. 10, 2018 7:43 pm
par jocaps
Hi,

In maple there is a function called "algsubs" which allows me to use an expression (usually algebraic) on a given expression. For instance

Code : Tout sélectionner

algsubs(l2^2=1,l2^2+l2^3)
will yield "l2+1"

Is there a similar thing in XCas/giac (without going into complex method like grobner basis). For easy conditions this can be done by polynomial remainder, here is a giacpy code

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from giacpy import giac, rem
f=giac("l2**2+l2**3")
print rem(f,"l2**2-1","l2")
Jose

Re: something like algsubs (maple) in XCas/Giac?

Publié : mer. avr. 11, 2018 6:00 am
par parisse
algsubs does that in Xcas, but it selects one solution, this is not exactly what you want.

Re: something like algsubs (maple) in XCas/Giac?

Publié : mer. avr. 11, 2018 6:24 am
par parisse
To get l2+1, you can run

Code : Tout sélectionner

G:=gbasis([l2^2=1],[l2]);
greduce(l2^2+l2^3,G,[l2]);

Re:something like algsubs (maple) in XCas/Giac?

Publié : ven. avr. 27, 2018 12:09 pm
par jocaps
Well, I really did not want to use Gröbner basis for this. But thanks for the suggestion.

Jose