+/**
+ * The type of a set compare function.
+ *
+ * @param elt pointer to an element
+ * @param key pointer to another element
+ *
+ * @return
+ * 0 if the elements are identically, non-zero else
+ */
+typedef int (*pset_cmp_fun) (const void *elt, const void *key);
+
+/**
+ * Creates a new pset.
+ *
+ * @param func The compare function of this pset.
+ * @param slots Initial number of collision chains. I.e., #slots
+ * different keys can be hashed without collisions.
+ *
+ * @returns
+ * created pset
+ */
+pset *new_pset (pset_cmp_fun func, int slots);
+
+/**
+ * Deletes a pset.
+ *
+ * @param pset the pset
+ *
+ * @note
+ * This does NOT delete the elements of this pset, just it's pointers!
+ */
+void del_pset (pset *pset);
+
+/**
+ * Returns the number of elements in a pset.
+ *
+ * @param pset the pset
+ */
+int pset_count (pset *pset);
+
+/**
+ * Searches an element pointer in a pset.
+ *
+ * @param pset the pset to search in
+ * @param key the element to search
+ * @param hash the hash value of key
+ *
+ * @return
+ * the pointer of the found element in the pset or NULL if it was not found
+ */
+void *pset_find (pset *pset, const void *key, unsigned hash);
+
+/**
+ * Inserts an element pointer into a pset.
+ *
+ * @param pset the pset to insert in
+ * @param key a pointer to the element to be inserted
+ * @param hash the hash-value of the element
+ *
+ * @return a pointer to the inserted element
+ *
+ * @note
+ * It is not possible to insert an element more than once. If an element
+ * that should be inserted is already in the set, this functions does
+ * nothing but returning its already existing set_entry.