I know in general simplification and comparisons of equality are hard problems, but I'm afraid I'm not familiar with the formal mathematical results that demonstrate this. Practically the problem is obviously difficult, and I have heard on many occasions that equality of two expressions is undecidable in general, but I'm curious if these questions have some "formal" mathematical analysis behind them.
Can someone recommend some resources on automatic simplification, discussions of what "simplification" means, and issues related to undecidable equality cases? My motivation is this - for some cases equality is undecidable, for some it is undecidable in reasonable time, for others is is solvable (4^a=2^(2a) being the example in issue 191). If equality cannot be decided in general, perhaps there is a way to categorize expressions so that it is "decidable if the question is decidable", so to speak. I suppose the question is not terribly interesting from a theoretical mathematical standpoint, but if it should happen to be possible it would be very useful in CAS work. Maybe there isn't any way in general to make this systematic, but if not I would like to understand why that's the case. Any pointers appreciated. Cheers and thanks, CY __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com _______________________________________________ Axiom-developer mailing list Axiom-developer@nongnu.org http://lists.nongnu.org/mailman/listinfo/axiom-developer
