#include <stdio.h>
#include <stdlib.h>

/* calcule factorielle n */
int facto(int n) {
  if(n<2)
    return 1;
  return facto(n-1)*n;
}

/* calcule x^n */
double power(double x, int n) {
  double result = 1;
  int i;
  for(i=0; i<n; i++) {
    result = result * x;
  }
  return result;
}

/* calcule exp(x) jusqu'à l'indice n */
double expon(double x, int n) {
  double result = 1;
  int i;

  for(i=1; i<n; i++) {
    result += power(x, i) / facto(i);
  }
  return result;
}

int main(int argc, char**argv) {
  double f;
  printf("valeur ?\n");
  scanf("%lf", &f);
  double e = expon(f, 20);
  printf("expon(%f) = %f\n", f, e);
  return EXIT_SUCCESS;
}