Re: Questions on operations on factorizations

[Bill Allombert <Bill.Allombert@math.u-bordeaux.fr>]

On Thu, Mar 05, 2026 at 03:39:50PM +0100, hermann@stamm-wilbrandt.de wrote:
> Recently I learned from Karim Belabas how to do divison of factorizations
> efficiently using matreduce(matconcat(...)):
> https://pari.math.u-bordeaux.fr/archives/pari-users-2602/msg00024.html
> 
> I did not find inverse function for factorint() in doc, is there one?

The function is called factorback.
? factorback([2,2;3,2;5,1])
%5 = 180

> Above are several functions on factorizations (divison, inverse of
> factorint, multiplication), there might be more that are useful to avoid
> factorint overhead. Are some of those available in GP already?

They are only available in C. (search for famat_*)

? install(famat_mul,GG)
? install(famat_reduce,mG)
? famat_reduce(famat_mul(factor(12),factor(15)))
%4 = [2,2;3,2;5,1]

Cheers,
Bill