1 files changed, 25 insertions, 0 deletions
diff --git a/stdlib/stack.mli b/stdlib/stack.mli
new file mode 100644
index 000000000..a1133edcc
--- /dev/null
+++ b/stdlib/stack.mli
@@ -0,0 +1,25 @@
+(* Stacks *)
+
+(* This modl implements stacks (LIFOs), with in-place modification. *)
+
+type 'a t
+        (* The type of stacks containing elements of type ['a]. *)
+
+exception Empty
+        (* Raised when [pop] is applied to an empty stack. *)
+
+val new: unit -> 'a t
+        (* Return a new stack, initially empty. *)
+val push: 'a -> 'a t -> unit
+        (* [push x s] adds the element [x] at the top of stack [s]. *)
+val pop: 'a t -> 'a
+        (* [pop s] removes and returns the topmost element in stack [s],
+           or raises [Empty] if the stack is empty. *)
+val clear : 'a t -> unit
+        (* Discard all elements from a stack. *)
+val length: 'a t -> int
+        (* Return the number of elements in a stack. *)
+val iter: ('a -> 'b) -> 'a t -> unit
+        (* [iter f s] applies [f] in turn to all elements of [s], from the
+           element at the top of the stack to the element at the
+           bottom of the stack. The stack itself is unchanged. *)