-/* Set a model for DEST, which is an GtkListStore of g_int's
- whose values are the indices into DICT */
-void set_dest_model (GtkTreeView *dest, PsppireDict *dict);
+/* Returns FALSE if the variables represented by the union of the rows
+ currently selected by SOURCE widget, and contents of the DEST
+ widget, are of different types.
+
+ In other words, this function when passed as the argument to
+ psppire_selector_set_allow, ensures that the selector selects only
+ string variables, or only numeric variables, not a mixture.
+*/
+gboolean homogeneous_types (GtkWidget *source, GtkWidget *dest);
+
+/* Returns TRUE if all of the variable(s) represented by the rows
+ currently selected by SOURCE widget, are numeric. DEST is ignored.
+
+ In other words, this function when passed as the argument to
+ psppire_selector_set_allow, ensures that the selector selects only
+ numeric variables.
+*/
+gboolean numeric_only (GtkWidget *source, GtkWidget *dest);