+void lexer_next_token(void);
+
+/* for debugging */
+void lexer_next_preprocessing_token(void);
+
+void init_lexer(void);
+void exit_lexer(void);
+
+void lexer_open_stream(FILE *stream, const char *input_name);
+
+const char *concat_strings(const char *string1, const char *string2);