#include <stdio.h>

int i;

//pass by name
#define THREE_TIMES( a ) \
({                       \
  int total = 0;         \
  total += a;            \
  ++i;                   \
  total += a;            \
  ++i;                   \
  total += a;            \
  total;                 \
})
  
//same function, pass by value
int three_times( int a )
{
  int total = 0;       
  total += a;          
  ++i;                 
  total += a;          
  ++i;                 
  total += a;          
  return total;               
}


//called both ways
int main( )
{

  int array[] = {1,2,3};
  
  i = 0;
  printf( "pass by name: %d\n"  , THREE_TIMES(array[i]) );
  
  i = 0;
  printf( "pass by value: %d\n" , three_times(array[i]) );

  return 0;
}

pass by name: 6
pass by value: 3