The C99 spec I can find on the net has 6.5.13 (3) and (4). 3. The && operator shall yield 1 if both of it's operands compare unequal to 0; otherwise it yields 0. The result has type int.
4. Unlike the bitwise binary & operator, the && operator guarantees left-to-right evaluation; there is a sequence point after the evaluation of the first operand. If the firt operand compares equal to 0, the second operand is not evaluated. To my reading, and unless I have a totally bogus spec, that makes exactly the guarantee Jean-Daniel claims. On Aug 4, 2011, at 8:56, Graham Cox <graham....@bigpond.com> wrote: > > On 04/08/2011, at 1:52 AM, Jean-Daniel Dupas wrote: > >> One important difference for instance is that if you write if (a() & b()), >> both a() and b() will always be executed, while if you write if (a() && >> b()), b() will be executed only if a() is true. > > > The C language doesn't make any guarantees about that. While this > optimisation is to be expected, the order of execution (left to right) and > the optimisation (b not executed) is implementation dependent. > > This is a classic question for coding job interviews. > > --Graham > > > _______________________________________________ > > 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/rols%40rols.org > > This email sent to r...@rols.org _______________________________________________ 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
