frexp() breaks a floating-point number into a normalized fraction
    and an integral power of 2. It stores the integer in the int
    object pointed to by the n parameter and returns the fraction
    part.

                           Entry-Point Names

    Generic                               Compaq
    Function   Data Type   OpenVMS        Tru64 UNIX
    Name       Required    Alpha          Alpha

    frexp      S_FLOAT     math$frexp_s   frexpf
               T_FLOAT     math$frexp_t   frexp
               X_FLOAT     math$frexp_x   frexpl
               F_FLOAT     math$frexp_f
               G_FLOAT     math$frexp_g