On 12 Dec 2009, at 09:32, Ben Haller wrote: >>> You should not compare floating point numbers for equality in most cases. >>> This is true of any language on any platform. >> >> Indeed, some floating-point numbers (such as the one represented by the >> integer 0x7fc00000) will compare as not equal to themselves: > > I think what the OP really wanted to know (and I'm interested in the answer > too) is whether going out to the stringValue and back to the doubleValue is > guaranteed to yield a float that is bitwise identical to the original float, > or whether there is "drift" in the least significant bit or two due to the > changes in representation. Anyway, even if that's not the OP meant, that's > what I'd like to ask. :->
Nope, there are trivial counterexamples there too. All NaNs stringify to "nan", for instance, and all infinities stringify to either "inf" or "-inf", depending on sign. (And, even if you only care about finite numbers, Andy Lee has an excellent counterexample for that as well.)_______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
