pointer_to_function.c

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

typedef double (*math)(double, double);

double add(double a, double b) { return a + b; }
double sub(double a, double b) { return a - b; }
double mul(double a, double b) { return a * b; }
double divi(double a, double b) { return a / b; }

double operation(double a, double b, math func) {
  return func(a, b);
}

int main(int argc, char *argv[]) {
  double a, b;
  char ope;

  printf("Ingresa un número: ");
  scanf("%lf", &a);

  printf("Ingresa otro número: ");
  scanf("%lf", &b);
  
  printf("\nSelecciona una operacion: ");
  printf("'a' = Add, 's' = Sub, 'm' = Mul, 'd' = Div\n");

  scanf(" %c", &ope);

  math function;
  switch (ope) {
    case 'a':
      function = add;
      break;
    case 's':
      function = sub;
      break;
    case 'm':
      function = mul;
      break;
    case 'd':
      function = divi;
      break;
    default:
      printf("invalid action.\n");      
  }
  printf("El resultado es: %6.2lf\n", operation(a, b, function));

  return EXIT_SUCCESS;
}