### 2-4 Absolute
Value Function

If your machine does not have an instruction
for computing the absolute value, this computation can usually be done in three
or four branch-free instructions. First, compute and
then one of the following:

By "2x"
we mean, of course, x + x or x
<< 1.

If you have a fast multiply by a variable
whose value is ?, the following will do: