/* now we have integer ** positive integer.
                   foo & (foo - 1) is zero only for a power of 2.  */
                if (!(baseuv & (baseuv - 1))) {
                    /* We are raising power-of-2 to postive integer.
                       The logic here will work for any base (even non-integer
                       bases) but it can be less accurate than
                       pow (base,power) or exp (power * log (base)) when the
                       intermediate values start to spill out of the mantissa.
                       With powers of 2 we know this can't happen.
                       And powers of 2 are the favourite thing for perl
                       programmers to notice ** not doing what they mean. */
                    NV result = 1.0;
                    NV base = baseuok ? baseuv : -(NV)baseuv;
                    int n = 0;

                    /* The logic is this.
                       x ** n === x ** m1 * x ** m2 where n = m1 + m2
                       so as 42 is 32 + 8 + 2
                       x ** 42 can be written as
                       x ** 32 * x ** 8 * x ** 2
                       I can calculate x ** 2, x ** 4, x ** 8 etc trivially:
                       x ** 2n is x ** n * x ** n
                       So I loop round, squaring x each time
                       (x, x ** 2, x ** 4, x ** 8) and multiply the result
                       by the x-value whenever that bit is set in the power.
                       To finish as soon as possible I zero bits in the power
                       when I've done them, so that power becomes zero when
                       I clear the last bit (no more to do), and the loop
                       terminates.  */