-uint64_t sl_cas (skiplist_t *sl, void *key, uint64_t expected_val, uint64_t new_val);
-uint64_t sl_lookup (skiplist_t *sl, void *key);
-uint64_t sl_remove (skiplist_t *sl, void *key);
-uint64_t sl_count (skiplist_t *sl);
-void sl_print (skiplist_t *sl);
-void sl_free (skiplist_t *sl);
-void * sl_min_key (skiplist_t *sl);
+map_val_t sl_cas (skiplist_t *sl, map_key_t key, map_val_t expected_val, map_val_t new_val);
+map_val_t sl_lookup (skiplist_t *sl, map_key_t key);
+map_val_t sl_remove (skiplist_t *sl, map_key_t key);
+map_val_t sl_count (skiplist_t *sl);
+void sl_print (skiplist_t *sl);
+void sl_free (skiplist_t *sl);
+map_key_t sl_min_key (skiplist_t *sl);