I don't really get why using <math.h> would make the program more
complex, add to SLOC, make it slower... I don't think it is a big loss
to use -lm, as it is mostly a problem with the libc you might be using
if you have to link with an extra library for math functions.
Also, specifying something as a macro does not make it faster
automatically. The great thing about compilers is that they can make
your code faster by optimizing it themselves!
Finally, I don't think that reimplementing a function that already is in
the standard library for "more efficiency" makes any sense. Correctness
is most important, and I rather trust my C library implementation on that.
