#include <stdio.h>

typedef double (*combinator_fn)(double, double);

double combine_right(double a, double b, double c, double d, combinator_fn combiner){
  return combiner(a, combiner(b, combiner (c, d)));
}

double combine_left(double a, double b, double c, double d, 
                    combinator_fn combiner){
  return combiner(combiner(combiner(a, b), c), d);
}


double max (double a, double b){
  return a > b ? a : b;
}

double min (double a, double b){
  return a > b ? b : a;
}

double plus(double a, double b){
  return a + b;
}

double minus(double a, double b){
  return a - b;
}

int main(void) {
  double result;

  result = combine_right(5, 7, 8, 11, minus);  /* minus(5, minus(7, minus(8, 11))) = 5 - (7 - (8 - 11)) = -5 */
  printf("Minus combination result: %f\n", result);

  result = combine_right(5, 7, 8, 11, plus); 
  printf("Plus combination result: %f\n", result);

  result = combine_right(5, 7, 8, 11, min); 
  printf("Min combination result: %f\n", result);

  result = combine_right(5, 7, 8, 11, max); 
  printf("Max combination result: %f\n", result);

  return 0;
}