add lec 04

lecture04/bstree.mli

@@ -0,0 +1,10 @@
+type bstree_size : 'a bstree -> int
+val bstree_height : 'a bstree -> int
+val bstree_empty : 'a bstree
+val bstree_is_empty : 'a bstree -> bool
+val bstree_insert : cmp:('a -> 'a -> int) -> 'a -> 'a bstree -> 'a bstree
+val bstree_of_list : cmp:('a -> 'a -> int) -> 'a list -> 'a bstree
+val bstree_mem : cmp:('a -> 'b -> int) -> 'a -> 'b bstree -> bool
+val bstree_largest : 'a bstree -> 'a
+val bstree_smallest : 'a bstree -> 'a
+val bstree_delete : cmp:('a -> 'a -> int) -> 'a -> 'a bstree -> 'a bstree