[Numpy-discussion] Poll: Semantics for % in Cython
Dag Sverre Seljebotn
dagss@student.matnat.uio...
Thu Mar 12 13:59:48 CDT 2009
(First off, is it OK to continue polling the NumPy list now and then on
Cython language decisions? Or should I expect that any interested Cython
users follow the Cython list?)
In Python, if I write "-1 % 5", I get 4. However, in C if I write "-1 %
5" I get -1. The question is, what should I get in Cython if I write (a
% b) where a and b are cdef ints? Should I
[ ] Get 4, because it should behave just like in Python, avoiding
surprises when adding types to existing algorithms (this will require
extra logic and be a bit slower)
[ ] Get -1, because they're C ints, and besides one isn't using
Cython if one doesn't care about performance
Whatever we do, this also affects the division operator, so that one in
any case will have a==(a//b)*b+a%b.
(Orthogonal to this, we can introduce compiler directives to change the
meaning of the operator from the default in a code blocks, and/or make
special functions for the semantics that are not chosen as default.)
--
Dag Sverre
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