power-compare.c - Et program der tæller antallet af multiplikationer i de to potens funktioner.

Lektion 8 - slide 15 : 27 Program 1

#include <stdio.h>

double sqr(double);
int even (int);
int odd (int);

int mult_no_1, mult_no_2;

double power1(double number, int pow){
  double result; 

  if (pow == 0)
    result = 1.0;
  else if (pow > 0){
    result = number * power1(number, pow - 1);
    mult_no_1++;
  }
  else 
    result = 1.0 / power1(number, -pow);

  return result;
}

double power2(double number, int pow){
  double result; 

  if (pow == 0)
    result = 1.0;
  else if (pow > 0 && even(pow)){
    result = sqr(power2(number,pow/2));
    mult_no_2++;
  }
  else if (pow > 0 && odd(pow)){
    result = number * power2(number, pow - 1);
    mult_no_2++;
  }
  else 
    result = 1.0 / power2(number, -pow);

  return result;
}


int main(void) {
  int i;
  double res1, res2;

  for(i = 1; i < 500; i += 5){
    mult_no_1 = 0; mult_no_2 = 0;
    res1 = power1(1.01,i);
    res2 = power2(1.01,i);
    printf("power1(1.01,%i) = %7.5f (%i multiplications)\n" 
           "power2(1.01,%i) = %7.5f (%i multiplications). \n\n",
           i, res1, mult_no_1,
           i, res2, mult_no_2);
  }

  return 0;
}


double sqr(double d){
  return d*d;}

int even (int i){
  return i % 2 == 0;}

int odd (int i){
  return i % 2 != 0;}