+struct casereader;
+struct dictionary;
+struct variable;
+
+
+/* Sort direction. */
+enum sort_direction
+ {
+ SRT_ASCEND, /* A, B, C, ..., X, Y, Z. */
+ SRT_DESCEND /* Z, Y, X, ..., C, B, A. */
+ };
+
+/* A sort criterion. */
+struct sort_criterion
+ {
+ int fv; /* Variable data index. */
+ int width; /* 0=numeric, otherwise string width. */
+ enum sort_direction dir; /* Sort direction. */
+ };
+
+/* A set of sort criteria. */
+struct sort_criteria
+ {
+ struct sort_criterion *crits;
+ size_t crit_cnt;
+ };
+
+
+void sort_destroy_criteria (struct sort_criteria *);
+
+struct casefile *sort_execute (struct casereader *,
+ const struct sort_criteria *);
+
+int sort_active_file_in_place (const struct sort_criteria *);
+
+struct casefile *sort_active_file_to_casefile (const struct sort_criteria *);