struct freq {
  char *word;
  int freq;
  struct freq *next;
};

typedef struct freq *freq_list;


#define fl_empty NULL

extern freq_list new_freq_list();
extern freq_list fl_insert(char *word, freq_list fl);
extern struct freq *fl_lookup(char *word, freq_list fl);
extern void fl_foreach(void (*fn)(char *, int), freq_list fl);
extern freq_list fl_destroy(freq_list fl);