Hello Luis,
probably this does the trick:
pp_def('magnover',
HandleBad => 1,
Pars => "a(n); real [o]b();",
GenericTypes => [qw(H C G E D F)],
Then in t/ufunc.t (line 106) the expected type just needs to be
changed from 'cdouble' to 'double'.
Integer types will be promoted to float and complex types to their
real counterparts:
say cdouble('[1+i, 1-i, -1+i, -1-i]')->magnover->info;
say sequence($_, 4)->magnover->info for byte, long, float, double;
PDL: Double D []
PDL: Float D []
PDL: Float D []
PDL: Float D []
PDL: Double D []
Regards,
-jo
On Thu 24 Jul 2025 06:36:39 PM CEST, Luis Mochan <moc...@icf.unam.mx> wrote:
On Wed, Jul 23, 2025 at 11:56:00AM +0000, Jörg Sommrey wrote:
Hello Luis,
the results look fine when the expected types in the two failing tests are
adjusted. Don't know if it would break any "real" code, maybe "is_pdl" is
just too strict here.
I believe there are good reasons for the qualifier float+ in the case
of, for example, a vector of bytes: on one hand, the euclidean
magnitude of a vector of integers is not necessarily integer: (3,4)->5
but (1,1)->1.4142... On the other hand, the magnitude of a large
vector of bytes may overflow a byte. Nevertheless, I expect the
magnitude of a complex to be real, not a complex. A complex with a
zero imaginary part works but wastes some time and space. Thus, it would be
ideal if one could specify both, float+ and real as qualifiers of the
output of magnover, but that doesn't work. Is there an alternative for
a more flexible way to determine the correct type of an output
parameter based on that of the inputs? Meanwhile, I can simply
take the real part of the magnitudes :)
Regards,
Luis
t/ufunc.t:
is_pdl $empty->magnover, sbyte('BAD'), "bad flag gets set on empty
magnover";
is_pdl +(sequence(4)+i())->magnover, double(4.242640), 'magnover correct for
complex';
Best regards,
-jo
On Wed 23 Jul 2025 04:52:24 AM CEST, Luis Mochan <moc...@icf.unam.mx> wrote:
> Hello,
>
> In some of my programs I used the code such as
>
> $abs=$cvec->abs2->sumover->sqrt;
>
> to get the magnitude of a vector $cvec. I just replaced it to the cleaner
>
> $abs=$cvec->magnover;
>
> But then my program failed when I made the comparison
>
> if($abs > 0){...}
>
> with the message
>
> Can't compare complex numbers at lib/PDL/PP.pm line 1445.
>
> It is true that we shouldn't compare complex numbers, except for
> equality, but, shouldn't the magnitude of a complex vector be a real
> number instead of a complex number (with zero imaginary part)?
>
> I tried to fix it by replacing the qualifier 'float+' in the pp_def of
> magnover in Ufunc.pd by the qualifier 'real', but then the tests fail
> as bytes are not converted to floats.
>
> Best regards,
>
> Luis
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