unordered(x,y) returns the value 1 (true) if x, y, or both are a
    NaN and returns the value 0 (false) otherwise.

                           Entry-Point Names

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

    unordered  S_FLOAT     math$unordered_s       unorderedf
               T_FLOAT     math$unordered_t       unordered
               X_FLOAT     math$unordered_x       unorderedl
               F_FLOAT     math$unordered_f
               G_FLOAT     math$unordered_g