On Wednesday 22 July 2009 15:14:32 Citi, Luca wrote: > In [2]: a + a > Out[2]: array([144], dtype=uint8) > > Please do not "fix" this, that IS the correct output.
No, I did not mean to fix this. (Although it should be noted that in C/C++, the result of uint8+uint8 is int.) > If instead, you refer to > In [3]: numpy.add(a, a, numpy.empty((1, ), dtype = numpy.uint32)) > Out[3]: array([144], dtype=uint32) > in this case I agree with you, the expected result should be 400. Yes, that's what I meant. > The inputs could be casted to the output type before performing the > operation. I do not think performing the operations with the output dtype > would break something. > Even in borderline cases like the following: > >>> b = numpy.array([400], numpy.int16) > >>> c = numpy.array([200], numpy.int16) > >>> numpy.subtract(b.astype(numpy.int8), c.astype(numpy.int8), > >>> numpy.empty((1, ), dtype = numpy.int8)) Indeed - I thought we had to take more care, but will this also work with int<->float conversions? No: In [22]: a, b = numpy.array([[8.6,4.9]]).T In [23]: numpy.subtract(a, b, numpy.empty((1, ), dtype = numpy.uint8)) Out[23]: array([3], dtype=uint8) In [24]: numpy.subtract(a.astype(numpy.uint8), b.astype(numpy.uint8)) Out[24]: array([4], dtype=uint8) However, I admit that this is a contrived example. ;-) Greetings, Hans _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
