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Author mark.dickinson
Recipients benjamin.peterson, mark.dickinson, pitrou
Date 2014-10-03.17:28:15
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This is not a bug, but a known and difficult-to-avoid issue with signed zeros and creating complex numbers from real and imaginary parts.  The safe way to do it is to use the `complex(real_part, imag_part)` construction.

In the first example, you're subtracting a complex number (0.j) from a float (-0.0).  The float gets promoted to a complex (by filling in an imaginary part of +0.0), and the imaginary literal is similarly treated as a complex number (by filling  in a 0.0 for the real part).  So the subtraction is doing:

  complex(-0.0, 0.0) - complex(0.0, -0.0)

which as expected gives a real part of -0.0, and an imaginary part of +0.0.
Date User Action Args
2014-10-03 17:28:16mark.dickinsonsetrecipients: + mark.dickinson, pitrou, benjamin.peterson
2014-10-03 17:28:16mark.dickinsonsetmessageid: <>
2014-10-03 17:28:16mark.dickinsonlinkissue22548 messages
2014-10-03 17:28:15mark.dickinsoncreate