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Tue Jan 23 21:39:53 CET 2007 · http://mail.python.org/pipermail/python-dev/2007-January/070759.html

"Jim Jewett" <jimjjewett at gmail.com> wrote:
> Tim Peters wrote:
> 
> >  complex_new() ends with:
> 
> >       cr.real -= ci.imag;
> >       cr.imag += ci.real;
> 
> > and I have no idea what that thinks it's doing.  Surely this isn't intended?!
> :
> 
> I think it is.  python.org/sf/1642844 adds comments to make it less unclear.

Agreed.

> 
> If "real" and "imag" are themselves complex numbers, then normalizing
> the result will move the imaginary portion of the "real" vector into
> the imaginary part and vice versa.

Not really.  What it does is to make complex(a,b) exactly equivalent
to a+1j*b.  For example:

>>> a = 1+2j
>>> b = 3+4j
>>> complex(a)
(1+2j)
>>> b*1j
(-4+3j)
>>> complex(a,b)
(-3+5j)

> Note that changing this (to discard the imaginary parts) would break
> passing complex numbers to their own constructor.

Eh?  Now, I am baffled.  There are several ways of changing it, all
of which would turn one bizarre behaviour into another - or would
raise an exception.  Personally, I would do the following:

complex(a) would permit a to be complex.

complex(a,b) would raise an exception if either a or b were complex.

But chacun a son gout (accents omitted).

Regards,
Nick Maclaren,
University of Cambridge Computing Service,
New Museums Site, Pembroke Street, Cambridge CB2 3QH, England.
Email:  nmm1 at cam.ac.uk
Tel.:  +44 1223 334761    Fax:  +44 1223 334679

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[Python-Dev] compex numbers (was Floor Division)