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structure Tree: TREE = struct
datatype ('k, 'v) t = Node of 'k * 'v * ('k, 'v) t * ('k, 'v) t | Empty
exception Exists
val empty = Empty
fun insert _ Empty k v = Node (k, v, Empty, Empty)
| insert cmp (Node (k', v', left, right)) k v =
case cmp k k' of
LESS => Node (k', v', insert cmp left k v, right)
| EQUAL => raise Exists
| GREATER => Node (k', v', left, insert cmp right k v)
fun lookup _ Empty _ = NONE
| lookup cmp (Node (k', v', left, right)) k =
case cmp k k' of
LESS => lookup cmp left k
| EQUAL => SOME v'
| GREATER => lookup cmp right k
datatype ('k, 'v) arc =
Left of 'k * 'v * ('k, 'v) t |
Right of 'k * 'v * ('k, 'v) t
fun assemble n buf =
let
fun assemble' tree (Left (k, v, right) :: tail) =
assemble' (Node (k, v, tree, right)) tail
| assemble' tree (Right (k, v, left) :: tail) =
assemble' (Node (k, v, left, tree)) tail
| assemble' tree [] = tree
in
assemble' n buf
end
fun lookup' _ _ Empty _ _ g = (g, NONE)
| lookup' buf cmp (Node (k', v', left, right)) k f g =
case cmp k k' of
LESS => lookup' (Left (k', v', right) :: buf) cmp left k f g
| GREATER => lookup' (Right (k', v', left) :: buf) cmp right k f g
| EQUAL =>
let
val (newV, result) = f v'
in
case newV of
NONE => (result, NONE)
| SOME v => (result, SOME (assemble (Node (k', v, left, right)) buf))
end
fun lookup2 cmp t k (f, g) =
let
val (result, newTree) = lookup' [] cmp t k f g
in
(result, case newTree of
NONE => t
| SOME t => t)
end
fun print t key2str value2str =
let
fun Pkey z = bindWith2str key2str z
fun Pvalue z = bindWith2str value2str z
fun print' off Empty = printf R off `"()\n" %
| print' off (Node (k, v, left, right)) = (
printf R off `"(" Pkey k `", " Pvalue v `"\n";
print' (off + 1) left;
print' (off + 1) right;
printf R off `")\n" %
)
in
print' 0 t
end
end
|
