|Bill Allombert on Mon, 10 Jan 2005 14:05:19 +0100|
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|Re: Gaussian Integer factorisation at right angles|
On Sun, Jan 09, 2005 at 02:13:10PM +0100, Karim Belabas wrote: > * Phil Carmody [2005-01-06 17:31]: > > Is there any reason why things should get rotated by 90 degrees? > > > > (18:16) gp > factorback(factor(17+0*I)) > > The same one as for > > (14:16) gp > factorback(factor(-x)) > %1 = x > > (or worse, factor(x*y) ... ). > > factor() is a little inconsistent in that it factors up to units in the > chosen UFD, _except_ if the latter hapens to be Z, in which case > annoying factors (-1)^1 crop up. That is not entirely true: ? factor(17+0*I) %1 = [-I 1] [4 - I 1] [4 + I 1] factoring Gaussian integers report a unit. In this case, the unit is wrong. Cheers, Bill.