On Sunday, January 8, 2017 at 8:08:01 PM UTC, Emmanuel Charpentier wrote: > > Le dimanche 8 janvier 2017 16:16:06 UTC+1, Dima Pasechnik a écrit : >> >> IMHO there ought to be possible to return "Unknown" as the result. >> Indeed, in many cases such an exact computation is not feasible. >> > > ISTR that this discussion (binary vs "ternary" logic, "trools", or > introduction of an "Unknown" truth value) has already been discussed *ad > nauseam* on this list and on sage-support, with no conclusive results. > > Should this be discussed again, with a call for *VOTE* ? >
The vote for introduction of Unknown (or Fail, or whatever) is the only sensible way forward. Otherwise we're either accepting patently wrong output, or asking for potentially non-terminating (e.g. asking whether a finitely presented group is finite) computations. > > HTH, > > -- > Emmanuel Charpentier > > >> >> On Saturday, January 7, 2017 at 9:54:36 PM UTC, vdelecroix wrote: >>> >>> Hello, >>> >>> Some symbolic expressions claim that they are not real >>> >>> sage: cos(pi/7).is_real() >>> False >>> sage: (exp(I*pi/7) + exp(-I*pi/7)).is_real() >>> False >>> >>> But conversion to real floating points perfectly works >>> >>> sage: RR(cos(pi/7)) >>> 0.900968867902419 >>> sage: RR(exp(I*pi/7) + exp(-I*pi/7)) >>> 1.80193773580484 >>> >>> I guess we could (and should) make it consistent. See also the related >>> #16436. >>> >>> 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.
