I'm curious about the pp_def routines such as Cadd in Basic/complex.pd:
1 pdl> use PDL::Complex;
2 pdl> $x=1+2*i; # a complex number
3 pdl> $y=3+4*i; # another one
4 pdl> $z=pdl(5,6); # a 2-piddle
5 pdl> p Cadd($x, $y); # result is complex
6 4 +6i
7 pdl> p Cadd($x, $z) # result is also complex
8 6 +8i
9 pdl> p Cadd($z, $x); # result is a 2-piddle
10 [6 8]
11 pdl> p $x+$y; # result is complex
12 4 +6i
13 pdl> p $x+$z; # results are 2 complex numbers
14 [6 +2i 7 +2i]
15 pdl> p $z+$x; # results are 2 complex numbers
16 [6 +2i 7 +2i]
I wonder where in the code does Cadd decide that the result is a
PDL::Complex. Is it because the first argument is a PDL::Complex in
lines 4 and 7. Would this work for other classes that might descend
from PDL.
Does the output of pp_def routines inherit their type from their first
argument?
On the other hand, I understand the logic of lines 9-10,
where the two arguments are interpreted as the real and imaginary
parts of a complex number. I also understand the logic of lines 13-16,
where the 2-pdl is treated as an array of two real numbers each of
which is added to a complex number to yield an array of two complex
numbers. However the differences between the behaviour of the
subroutine call Cadd and that of the overloaded operator '+' might
surprise some users.
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o
W. Luis Mochán, | tel:(52)(777)329-1734 /<(*)
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