extern int dyn_string_append_char (dyn_string_t, int);
extern int dyn_string_substring (dyn_string_t, dyn_string_t, int, int);
extern int dyn_string_eq (dyn_string_t, dyn_string_t);
extern int dyn_string_append_char (dyn_string_t, int);
extern int dyn_string_substring (dyn_string_t, dyn_string_t, int, int);
extern int dyn_string_eq (dyn_string_t, dyn_string_t);