Hi Robert, >> You get the point. As far as I understand a RIF only return True if the >> interval are reduced to a single point. Is it right ? It would be better >> to >> return a special value like Unknown than False. But that's another >> question... >> >> [...] > > I certainly agree that 1-2 should be the general rule, I was just pointing > out an exception. I like the idea of returning an Unknown object on RIF > comparisons as well.
Not my idea. This was the way it worked in MuPAD. There was a three state boolean value, which was quite useful. Looking into python docs to see if we can have "and" and "or" work with a 3-state booleans, I found: " A rich comparison method may return the singleton NotImplemented if it does not implement the operation for a given pair of arguments. By convention, False and True are returned for a successful comparison. However, these methods can return any value, so if the comparison operator is used in a Boolean context (e.g., in the condition of an if statement), Python will call bool() on the value to determine if the result is true or false. " Wouldn't it be mor meaningful to return NotImplemented ? Cheers, Florent -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
