On Dec 23, 12:31 pm, Pavel Sutyrin <psuty...@cs.msu.su> wrote: > BTW, there is a question of basics: how to represent unknown/ > uncomputable. Say, you are going to intersect two unrestricted context- > free languages (each having a pushdown automaton or a grammar inside). > As far as this is generally unsolvable, you should get either UNKNOWN > or CHAOS value (if we ever turn to threefold true-false-chaos logic, > I'm totally unaware of Python and Sage in this respect), or get a kind > of UnsolvableException. In any case, we should represent these cases > in a consistent way.
Actually, it's quite easy to intersect two context-free languages A and B: the answer is "the intersection of A and B", and I think it would be great if Sage would allow you to form such an intersection (if you're going to have lots of different kinds of languages anyway). Of course, this intersection language would be missing many methods -- you can't (always) test non-emptiness, as the most obvious example -- but you can easily compute membership. Carl --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-devel@googlegroups.com To unsubscribe from this group, send email to sage-devel-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
