typedef struct symbol *SYMBOL;

/*
 * symbol_lookup() finds the SYMBOL object for a given text identifier.
 * If the symbol is not previously known, it creates it.
 * It only returns NULL for out of memory.
 */
extern SYMBOL symbol_lookup(char *id);

/*
 * symbol_getname() yields the original text identifier for a symbol.
 */
extern char *symbol_getname(SYMBOL x);

extern int symbol_count();  /* return number of symbols created so far */
extern void symbol_set_seen(SYMBOL x, int stmt);
extern int live_range_is_overlapping(SYMBOL x, SYMBOL y);  /* boolean */

/*
 * We also need to be able to manipulate an "index" value representing this
 * symbol's position in the graph data structure.
 */
extern void symbol_setindex(SYMBOL x, int i);
extern int symbol_getindex(SYMBOL x);

/* iterator class to traverse all symbols */
typedef struct symbol_iter *SYMBOL_ITER;
extern SYMBOL_ITER new_symbol_iter();
extern SYMBOL first_symbol(SYMBOL_ITER x), next_symbol(SYMBOL_ITER x);