Robert Kern wrote: > On Thu, Mar 12, 2009 at 17:45, Sturla Molden <stu...@molden.no> wrote: >> >> >> >>> 2009/3/13 Charles R Harris <charlesr.har...@gmail.com>: >>>> That said, I think it best to leave '%' with its C default and add a >>>> special >>>> modulus function for the python version. Changing its meaning in C-like >>>> code >>>> is going to confuse things. >>> This is Cython code, so I think there is an argument to be made that >>> it is Python-like! >> >> I'll just repeat what I've already said on the Cython mailing list: >> >> I think C types should behave like C types and Python objects like Python >> objects. If a C long suddenly starts to return double when divided by >> another C long, then that will be a major source of confusion on my part. >> If I want the behaviour of Python integers, Cython lets me use Python >> objects. I don't declare a variable cdef long if I want it to behave like >> a Python int.
Whether division returns float or not is an orthogonal and unrelated issue (and when it does, which is not the default, // is the C division operator). When we say that this affects division; what we mean is that -7 // 6 returns -2 in Python; so that (-7 // 6)*6 + (-7 % 6) == -2*6 + 5 == -7. With C behaviour of % and /, I believe -7 // 6 == -1. (And when I use // it is to be unambigious; by default you can use / as well for the same thing.) > That may be part of the confusion. The expression "-1%5" has no > variables. Perhaps Dag can clarify what he is asking about: > > # Constants? (No one uses just constants in expressions, > # really, but consistency with the other choices will > # affect this.) > -1 % 5 > > # Explicitly declared C types? > cdef long i, j, k > i = -1 > j = 5 > k = i % j This one is what I'm really asking about. > When I do (2147483647 + 2147483647) in current Cython, to choose > another operation, does it use C types, or does it construct PyInts? > I.e., do I get C wraparound arithmetic, or do I get a PyLong? C wraparound. Suggestions welcome :-) > I recommend making % behave consistently with the other operators; > i.e. if <x>+<y> uses C semantics, <x>%<y> should, too. -- Dag Sverre _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
