+/*-------------.
+| --features. |
+`-------------*/
+
+enum feature
+ {
+ feature_none = 0, /**< No additional feature. */
+ feature_caret = 1 << 0, /**< Enhance the output of errors with carets. */
+ feature_all = ~0 /**< All above features. */
+ };
+/** What additional features to use. */
+extern int feature_flag;