Efficient coding considered harmful?

[Guy Harris]

>:     o   Use the ^ operator because many times,
>:                 a = !a;
>:         should really be,
>:                 a ^= 1;
>
>However, some machines can't do ^ very well, so take care.

And some code for reasons of, well, *microefficiency* may rely on the
fact that any non-zero value, not just 1, is considered "true" by C; the
only safe way of inverting such a boolean is with "a = !a". 

Too bad C doesn't have a Boolean type....