And what do you do with my_function1() or my_function2() or my_function3()
shortcut or not shortcut? The current state of Python is that some of the above functions might not be evaluated (ie shortcut) *before* knowing the return type. On 15 November 2016 at 09:41, Thierry <sage-googlesu...@lma.metelu.net> wrote: > On Tue, Nov 15, 2016 at 09:27:14AM +0100, Vincent Delecroix wrote: >> On 15 November 2016 at 09:19, Thierry <sage-googlesu...@lma.metelu.net> >> wrote: >> > On Tue, Nov 15, 2016 at 08:53:43AM +0100, Vincent Delecroix wrote: >> >> Not currently (though we have "Unknown"). The main problem is the >> >> interaction with Python booleans and the operators "or", "and", "not" >> >> (which are *not* logical operators). The Sage "Unknown" is badly >> >> broken for these reasons >> >> >> >> sage: not Unknown # waiting for Unknown >> >> True >> >> sage: Unknown or False # waiting for Unknown >> >> False >> >> >> >> So be careful if you start using it! >> >> >> >> If we would use the correct logical operators ~ (for negation), ^ (for >> >> xor) and & (for and) then we might be able to come up with something. >> >> But Sage sort of ignore them. >> >> >> >> This problem has been discussed a lot on this mailing list and there >> >> even exists a (refused) PEP request in this direction. >> > >> > For reference, it is https://www.python.org/dev/peps/pep-0335/ (the main >> > reason for rejecting the proposal was "too much discussions"...). >> > >> > Perhaps was the proposal too greedy, so i wonder whether there would be a >> > possibility to have a trool adding an Unknown to bool that does not >> > perturb the speed when only True and False are used, and so that the >> > "short-circuiting semantics" remains preserved. >> >> No way! In an expression such as >> >> "True or whatever_function(x)" >> >> the "whatever_function(x)" is *not* evaluated... >> >> sage: def f(): print "hello" >> sage: True or f() >> True > > I do not see your point. True or Unknown should be True, right ? So we can > shortcut here as well for trools, no ? > > Ciao, > Thierry > > >> >> > This could indeed be useful in testing equality of overlaping >> > real-intervals, undecidable problems in groups, equality of symbolic >> > expressions, ... >> >> But I agree that it could be useful. >> >> Vincent >> >> -- >> You received this message because you are subscribed to the Google Groups >> "sage-devel" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to sage-devel+unsubscr...@googlegroups.com. >> To post to this group, send email to sage-devel@googlegroups.com. >> Visit this group at https://groups.google.com/group/sage-devel. >> For more options, visit https://groups.google.com/d/optout. > > -- > You received this message because you are subscribed to the Google Groups > "sage-devel" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sage-devel+unsubscr...@googlegroups.com. > To post to this group, send email to sage-devel@googlegroups.com. > Visit this group at https://groups.google.com/group/sage-devel. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
