Hi Ed, very nice! See comments inline.
On 26.03.21 06:40, Ed . wrote:
I’m currently working on making creal and cimag return real data rather than complex, which I’m doing by implementing a “real” type qualifier (in PP terminology), so: Pars => “a(); real [o] b()”
How do you do that? I tried to implement this and failed because I didn't know where to start. ;)
This is also necessary to implement irfftn() in PDL::FFTW3 with native complex data, because the library itself takes complex data and returns real, and currently PDL makes all data parameters be the same unless a type-qualifier is given, and I didn’t want to have to make separate cfloat and cdouble versions. I think that comparisons (including sorting) of complex data other than an equality test (and approx) should simply throw an exception, as they aren’t mathematically valid at all. I also think that the equivalent should be done in PDL::Complex, despite it not currently being an error. What do others think?
Iagree for the new native support, but I think PDL::Complex behaviour should be preserved since it is around for a long time. But then it might even improve old code by highlighting dubious behaviour. ;)
In a similar vein: is it really useful to call creal/cimag on real data? It seems to me that too should throw an exception.
I think it should just return the input and 0, respectively. Thus it can be used to write generic code that accepts real and complex input. carg should do the same. Even conj kind of works that way.
Best regards, Ed *From: *Luis Mochan <mailto:moc...@icf.unam.mx> *Sent: *26 March 2021 05:30 *To: *pdl-devel@lists.sourceforge.net <mailto:pdl-devel@lists.sourceforge.net> *Subject: *Re: [Pdl-devel] [Pdl-general] PDL 2.029 released I started playing with the new complex numbers. I find it nice and useful that creal and cimag can be applied to real pdl's, but the results are promoted to complex: pdl> $x=pdl(1) pdl> p $x 1 pdl> p $x->creal 1+0i pdl> p $x->cimag 0+0i Equality and inequality comparisons do work but they also return complex values: pdl> p $x==1 1 pdl> p $x->creal==1 1+0i pdl> p $x->creal==2 0+0i pdl> p $x->creal!=2 1+0i This is troublesome, as their boolean interpretation is not correct: pdl> print +($x->creal==1)?'yes':'no' yes pdl> print +($x->creal==2)?'yes':'no' yes pdl> print +($x==2)?'yes':'no' no On the other hand, greater than, lower than, etc. do compare the real parts only and return a real value. pdl> $y=ci pdl> p $y<1 1 pdl> p $y<ci 0 pdl> p $y<=0.01*ci 1 _______________________________________________ pdl-devel mailing list pdl-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/pdl-devel
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