double frexp(double x, int *exp);

**frexp** breaks a floating-point number into a normalized fraction
and an integral power of 2.

**frexp** stores power of two in the **int** object
pointed to by **exp** and returns the value **x**,
such that **x** has a magnitude in the interval [1/2, 1) or zero,
and value equals **x** * 2^**exp**.

If **x** is zero, both parts of the result are zero.

If **x** is ∞ or NaN, **frexp** returns **x** and stores zero into
the int object pointed to by **exp**.