On Mon, Sep 7, 2015 at 5:42 PM, Antony Lee <antony....@berkeley.edu> wrote: > My 2c (not cc'ed to cython-devel, as I am not registered): > > - language_level=3 implies __future__ division. > - if __future__ division is set: int / int => float (whether variables are > untyped (= typed at runtime by python) or typed (including by the > inferencer)) > - if __future__ division is not set: int / int => int, with > opposite-sign-case and zero-divisor-case handled depending on cdivision > - in both cases, int // int => int, with opposite-sign-case and > zero-divisor-case handled depending on cdivision (also for % and divmod).
That's what I'm leaning towards as well, but it is backwards incompatible. Anyone else have any opinions? > 2015-09-07 17:15 GMT-07:00 Robert Bradshaw <rober...@gmail.com>: >> >> 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. >> >> -- >> >> --- >> 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
