exp_calc.c

#include <stdio.h>

char exp_ovf;

#define ln10_val     2.302585093f

float exp_calc(float x)

{

  float eps  = 0.00000000001f;

  float elem = 1.0f;

  float sum  = 0.0f;

  char  nega = 0;

  int   i    = 1;

  exp_ovf= 0;

  if (x < 0.0f)

  {

    nega= 1;

    x= -x;

  }

  do

  {

    sum += elem;

    elem *= x / i;

    i++;

    if (sum> 1e37) break;

  } while (elem >= eps);

  if (sum> 1e37) exp_ovf= 1;

  if (nega)

  {

    return 1.0f / sum;

  }

  else return sum;

}

int main(void)

{

  char   ch;

  float  a, vu;

  float  z, x;

  a= 64.5f;                     // Verstaerkung in db

  vu= exp_calc((a/20.0f) * ln10_val);

  printf("\n\r Verstaerung von a= %.3f db entspricht Vu= %.3f \n\r",a, vu);

  z= 2431.5f;

  x= exp_calc(z);

  printf("\n\r Testergebnis : %.5f \n\r",x);

}