On Sun, 29 May 2011 22:19:49 +0100, Nobody wrote: > On Sun, 29 May 2011 10:29:28 +0000, Steven D'Aprano wrote: > >>> The correct answer to "nan == nan" is to raise an exception, >>> because >>> you have asked a question for which the answer is nether True nor >>> False. >> >> Wrong. > > That's overstating it. There's a good argument to be made for raising an > exception.
If so, I've never heard it, and I cannot imagine what such a good argument would be. Please give it. (I can think of *bad* arguments, like "NANs confuse me and I don't understand the reason for their existence, therefore I'll give them behaviours that make no sense and aren't useful". But you did state there is a *good* argument.) > Bear in mind that an exception is not necessarily an error, > just an "exceptional" condition. True, but what's your point? Testing two floats for equality is not an exceptional condition. >> The correct answer to "nan == nan" is False, they are not equal. > > There is no correct answer to "nan == nan". Why on earth not? > Defining it to be false is just the "least wrong" answer. So you say, but I think you are incorrect. > Arguably, "nan != nan" should also be false, > but that would violate the invariant "(x != y) == !(x == y)". I cannot imagine what that argument would be. Please explain. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
