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 exp()                   Calculate Exponential

 #include   <math.h>

 double     exp(x);
 double     x;                           Floating-point value

    exp() returns the exponential function of 'x'.

       Returns:     Exponential function of 'x'.  On overflow, matherr()
                    is called with an OVERFLOW error, errno is set to
                    ERANGE (defined in <errno.h>), and the value HUGE_VAL
                    (defined in <math.h>) is returned.  On underflow 0.0
                    is returned. (matherr() is not called on an
                    underflow, and 'errno' is not set.)

         Notes:     Error handling can be modified with the matherr()
                    routine.

                    OVERFLOW first occurs with 'x' greater than 7.0E2.

   -------------------------------- Example ---------------------------------

    The following statements continue printing the exponential function
    of the values in an array until an OVERFLOW error occurs.

           #include <math.h>       /* for exp() */
           #include <stdio.h>      /* for printf() */
           #include <errno.h>     /* for errno and ERANGE*/

                                /* the value 1000.0 will cause an error */
           double values[6] = {0.0, 1.0, -1.0, -500, 1000.0, -0.2};

           main()
           {
               double exponential;
               int i;

               errno = 0;
               for (i = 0;  !errno && i < 6;  i++) {
                   exponential = exp(values[i]);
                   if (errno == ERANGE) /* error is also printed to stderr */
                       printf("OVERFLOW error in exp()\n");
                   printf("exponential function of %f = %f\n",
                          values[i], exponential);
               }
           }