GNU C用宏實現lambda表達式

看到一篇文章，利用GNU C提供的嵌套函數（nested function）來實現lambda表達式的功能，很有意思。原文在這裏。代碼如下：

#include <stdlib.h>
#include <stdio.h>
 
#define lambda(l_ret_type, l_arguments, l_body)         \
  ({                                                    \
    l_ret_type l_anonymous_functions_name l_arguments   \
      l_body                                            \
    &l_anonymous_functions_name;                        \
  })
 
int main (int argc, char *argv[]){
  int array[] = { 4, 3, 1, 2, 5 };
 
  void dump (void){
    int i;
    for (i = 0; i < sizeof (array) / sizeof (array[0]); i ++)
      printf ("%d ", array[i]);
    printf ("\n");
  }
 
  printf ("Initial: ");
  dump ();
 
  int comparison = 0;
 
  qsort (array, sizeof (array) / sizeof (array[0]), sizeof (array[0]),
         lambda (int, (const void *a, const void *b), {
                   dump ();
                   printf ("Comparison %d: %d and %d\n",
                           ++ comparison, *(const int *) a, *(const int *) b);
                   return *(const int *) a - *(const int *) b;
                 }));
 
  printf ("Sorted: ");
  dump ();
 
  return 0;
}