Or perhaps we should respect float division even with cdivision... Thoughts?
On Mon, Sep 7, 2015 at 5:13 PM, Robert Bradshaw <rober...@gmail.com> wrote: > Oh, that's another issue. I'll clarify this in the documentation. > > On Mon, Sep 7, 2015 at 3:59 PM, Antony Lee <antony....@berkeley.edu> wrote: >> Actually I realized that it's another problem; setting cdivision to True (as >> I did in the directive of the example I gave, because I basically always set >> this to True) overrides __future__ division and restores the C division >> semantic that int / int = int. The documentation actually says that the >> cdivision directive should only affect the case of operands with different >> signs and of division by zero, not whether int / int = int. >> Antony >> >> 2015-09-07 15:50 GMT-07:00 Robert Bradshaw <rober...@gmail.com>: >>> >>> On Mon, Sep 7, 2015 at 3:46 PM, Robert Bradshaw <rober...@gmail.com> >>> wrote: >>> > On Mon, Sep 7, 2015 at 3:29 PM, Antony Lee <antony....@berkeley.edu> >>> > wrote: >>> >> Sorry, I intended the entire discussion to apply to the case of Python3 >>> >> semantics. Indeed, even with language_level=3 and from __future__ >>> >> import >>> >> division, foo.decl(3, 3) prints "1, 2, 0, 1" whereas foo.nodecl(3, 3) >>> >> prints >>> >> "1.0, 0.5, 2.0, 1.0". >>> > >>> > from __future__ import division behaves as expected; I just added some >>> > even more explicit tests: >>> > >>> > https://github.com/cython/cython/commit/e61da2eb8a292bc34285c895aade523b6d353414 >>> > >>> > I'm surprised language_level=3 doesn't automatically set this directive. >>> >>> Are you sure you're setting it correctly? >>> https://github.com/cython/cython/blob/master/tests/run/cython3.pyx#L30 >>> >>> >> 2015-09-07 15:07 GMT-07:00 Robert Bradshaw <rober...@gmail.com>: >>> >>> >>> >>> On Mon, Sep 7, 2015 at 11:59 AM, Antony Lee <antony....@berkeley.edu> >>> >>> wrote: >>> >>> > I would like to suggest that division of integers with "/" prints a >>> >>> > warning >>> >>> > at compile time. In my opinion, "/" should be restricted to float >>> >>> > division, >>> >>> > and "//" should be used when rounding semantics are required. >>> >>> > >>> >>> > Otherwise, we get weird edge cases such as: >>> >>> > >>> >>> > #cython: cdivision=True, infer_types=True >>> >>> > def decl(int m, int n): >>> >>> > for i in range(1, m): >>> >>> > for j in range(1, n): >>> >>> > print(i / j) # integer division >>> >>> > >>> >>> > def nodecl(m, n): >>> >>> > for i in range(1, m): >>> >>> > for j in range(1, n): >>> >>> > print(i / j) # float division >>> >>> >>> >>> Slight correction: int or float division depending on whether you're >>> >>> using Python 2 or Python 3. The runtime type of i/j isn't something we >>> >>> can delegate to the C compiler. >>> >>> >>> >>> > (whose behavior may even change if type inference rules changes). >>> >>> > >>> >>> > A more extreme choice would be to have "/" always behave like float >>> >>> > (double) >>> >>> > division even with integer arguments. >>> >>> >>> >>> You mean like putting from __future__ import division at the top of >>> >>> your file? Or compiling with -3 (for Python 3 language semantics)? >>> >>> >>> >>> -- >>> >>> >>> >>> --- >>> >>> You received this message because you are subscribed to the Google >>> >>> Groups >>> >>> "cython-users" group. >>> >>> To unsubscribe from this group and stop receiving emails from it, send >>> >>> an >>> >>> email to cython-users+unsubscr...@googlegroups.com. >>> >>> For more options, visit https://groups.google.com/d/optout. >>> >> >>> >> >>> >> -- >>> >> >>> >> --- >>> >> You received this message because you are subscribed to the Google >>> >> Groups >>> >> "cython-users" group. >>> >> To unsubscribe from this group and stop receiving emails from it, send >>> >> an >>> >> email to cython-users+unsubscr...@googlegroups.com. >>> >> For more options, visit https://groups.google.com/d/optout. >>> >>> -- >>> >>> --- >>> You received this message because you are subscribed to the Google Groups >>> "cython-users" group. >>> To unsubscribe from this group and stop receiving emails from it, send an >>> email to cython-users+unsubscr...@googlegroups.com. >>> For more options, visit https://groups.google.com/d/optout. >> >> >> -- >> >> --- >> You received this message because you are subscribed to the Google Groups >> "cython-users" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to cython-users+unsubscr...@googlegroups.com. >> For more options, visit https://groups.google.com/d/optout. _______________________________________________ cython-devel mailing list cython-devel@python.org https://mail.python.org/mailman/listinfo/cython-devel
