Returns its first argument multiplied by 2 raised to the power of
    its second argument; that is, x(2n).
    Format
      #include  <math.h>
      double ldexp  (double x, int n);
      float ldexp  (float x, int n); (Integrity servers, Alpha)
      long double ldexp  (long double x, int n);
                         (Integrity servers, Alpha)
1 – Arguments
 x
    A base value of type double, float, or long double that is to be
    multiplied by 2n.
 n
    The integer exponent value to which 2 is raised.
2 – Return Values
    x(2n)              The first argument multiplied by 2 raised to
                       the power of the second argument.
    0                  Underflow occurred; errno is set to ERANGE.
    HUGE_VAL           Overflow occurred; errno is set to ERANGE.
    NaN                x is NaN; errno is set to EDOM.