Phil Carmody on Thu, 27 Jul 2006 09:17:14 +0200


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divisors/factor problem in 2.4.0 (development CHANGES-1.1570)


In some contexts, divisors(3)=[1], and factor(3)=[;] alas.
Not had time to check other versions or anything.
Once you have a value that refuses to factor, it 'infects' all other values it
touches (so factor(round(broken*210.0))=[;] too).

Divisors() not including the constant factors I can live with, but being unable
to put them back manually is shall we say more of an inconvenience.


bash-3.1$ gp
         GP/PARI CALCULATOR Version 2.4.0 (development CHANGES-1.1570)
           i686 running linux (ix86/GMP-4.1.4 kernel) 32-bit version
    compiled: Jul 22 2006, gcc-4.1.2 20060613 (prerelease) (Debian 4.1.1-5)
                 (readline v5.1 enabled, extended help enabled)
...
parisize = 4000000, primelimit = 500000
? pdiv
%60 = [1, x, x^2, x^3]
? poly=3*x^3
%61 = 3*x^3
? pdiv=divisors(poly)
%62 = [1, x, x^2, x^3]
? const=poly/pdiv[length(pdiv)]
%63 = 3
? cdiv=divisors(const)
%64 = [1]
? factor(const)
%65 = [;]



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