-bool lex_id_match_len (const char *keyword_string, size_t keyword_len,
- const char *token_string, size_t token_len);
-bool lex_id_match (const char *keyword_string, const char *token_string);
-int lex_id_to_token (const char *id, size_t len);
+bool lex_id_match (struct substring keyword, struct substring token);
+bool lex_id_match_n (struct substring keyword, struct substring token,
+ size_t n);
+int lex_id_to_token (struct substring);