Re: Logical XOR

On Sep 21, 11:30 am, Martin Wells <war...@xxxxxxxxxx> wrote:
!!a != !!b

About three seconds after I sent that post I realised I cuda written:

!a != !b

fred.l.kleinschmidt@xxxxxxxxxx writes:
If a and b are always boolean values (0 or 1), just use
a^b

If they are not you can join those two techniques to form !a ^ !b which
is probably faster then !a != !b because no branching is used (at least
on some architectures).

But, I assume that if at least one of the values (say a) is boolean the
following will be even faster: ((unsigned)(((signed)a)-1)) & b. Not
sure if it's not implementation specific though. (If neither is boolean
replace a with !a). Disadvantage is that if b is not boolean this will
not produce a boolean value.

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