#include <iostream> 

double foo(int x , bool y) 
{ 
  if ( y ) 
    x *= 2; 
  else 
    x *= 3; 

  return x + .52; 
} 

int main(int argc, char** argv) 
{ 
  // declare a function pointer named ptr that returns a double and takes an int and bool argument
  double (*ptr)(int, bool); 

  // assign the address of the function to the pointer
  ptr = foo; 

  // call foo via the function pointer
  std::cout << ptr(5, true) << std::endl; 

  // declare a reference to a function
  double (&ref)(int, bool) = foo;

  // call foo via the reference to function
  std::cout << ref(6, false) << std::endl; 

  return 0; 
}