On Thu, Aug 21, 2008 at 12:21 AM, Thomas Davie <[EMAIL PROTECTED]> wrote: > > On 21 Aug 2008, at 09:06, Jules Colding wrote: > >> >> On 21/08/2008, at 01.56, John C. Randolph wrote: >> >>> >>> On Aug 20, 2008, at 4:15 PM, Torsten Curdt wrote: >>>> >>>> There was a common perception that NULL is not really the same as nil. >>>> But seems like in the end it really is (void*)0. >>> >>> >>> They differ in type, not in value. >>> >>> "NULL" is (void *) 0. >>> "nil" is (id) 0. >>> "Nil" is (Class) 0. >>> >>> Personally, I prefer "if (!foo)" over "if (foo == nil)", because the >>> latter has the hazard of a typo that compiles. You can lose a fair bit of >>> time staring at "if (foo = nil)" before you spot the mistake. >> >> Which is why you should always write "if (nil == foo)". > > Just to add my 2 cents to this discussion, I think there's something which > hasn't been brought up (and I guess isn't often brought up by C > programmers). > > One of the two options doesn't make sense here.
It may not make sense to those who aren't used to C (or, more accurately, are *more* used to another language), but it makes perfect sense to C programmers (just as [foo method: bar] doesn't make sense to C programmers, but makes perfect sense to Obj-C programmers). Different languages have different idioms. C programmers likely tend not to bring it up, because it is second nature to them. > Because of C's weak type system ! works on almost anything you throw at it. > However, it is a *boolean* operator. Boolean negating a pointer is a hack > that by happy coincidence works. This is not a "hack" or a "coincidence", this is by design. A non-NULL pointer *is* a boolean expression that evaluates to true, just as a non-zero integer is. Again, it doesn't work by coincidence, it is a guarantee of the language standard. Note, that the same is true in C++, which has a much stronger type system than C. > On the other hand, nil == foo is type > safe, and makes semantic sense. > > For that simple reason, I'd go for nil == foo every time. -- Clark S. Cox III [EMAIL PROTECTED] _______________________________________________ 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 [EMAIL PROTECTED]
