On Fri, Dec 5, 2008 at 1:11 AM, Christoph Mallon <[EMAIL PROTECTED]> wrote: > Garrett Cooper schrieb: >> >> (I feel like I'm getting off on a bikeshed topic, but...) >> >> 1. What dialect of C was it defined in? Is it still used in the >> standard dialect (honestly, this is the first time I've ever seen it >> before, but then again I am a younger generation user)? > > Dialect? The ! operator is plain vanilla standard C. It takes a scalar > operand and returns 1, if it compares equal to 0, otherwise it returns 0. > !!, i.e. two consecutive ! operators, is one of the oldest tricks in the > book, right next to (a > b) - (a < b) for comparison functions and countless > other idioms. > >> 3. What's the real loss of going to `? :', beyond maybe 3 extra >> keystrokes if it's easier for folks who may not be as experienced to >> read? > > I'd like my bikeshed grass green, please. > > Christoph
If you really want to split hairs, ! only negates the logic value, whereas ~ actually negates the bits. So technically, you're not flipping 0 to make 1 and vice versa, but instead flipping 0 to make non-zero, etc. There is a clear distinction in hardware. The point was that !! isn't obvious at first glancing the C code. It's important for code to be readable as well as functional (that's why we have style(9)). Getting down to it I'd like to see what the compiler optimizes each as, because I can see dumb compilers saying `!!' translates to `not, bne => set, else set, continue', whereas `? :' could be translated to `bne, set, else set, continue'; I'm sure gcc has moved passed these really minute details. Hopefully this helps shed more light on where I'm coming from. -Garrett _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "[EMAIL PROTECTED]"
