hermann on Tue, 27 May 2025 12:53:50 +0200


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Re: How to determine Mod(a,b) with t_COMPLEX b?


On 2025-05-27 00:40, Bill Allombert wrote:

The minimal residue of 1+4*I modulo 3+2*I is the yellow point -I in the
example:
https://en.wikipedia.org/wiki/Gaussian_integer#Describing_residue_classes

How can minimal residue of an input gaussian integer modulo a gaussian
integer be computed in PARI/GP?

nf=nfinit(i^2+1)
a=1+4*i;b=3+2*i;
nfeltdivrem(nf,a,b)
%4 = [[1,1]~,[0,-1]~]

Cheers,
Bill.

Thank you, so the rem part is what I asked for.
Interesting, "i" is free variable and not sqrt(-1) which is "I" in GP.

Now that type(b) is t_POL, Mod(a,b) works as well.
What is the meaning of "-5" in Mod(a,b) result?

? a=1+4*i;b=3+2*i;
? Mod(a,b)
Mod(-5, 2*i + 3)
?

Regards,

Hermann.