reflexivity.
Qed.
-
+Open Scope string_scope.
+Fixpoint treeToString {T}{TT:ToString T}(t:Tree ??T) : string :=
+match t with
+ | T_Leaf None => "[]"
+ | T_Leaf (Some s) => "["+++s+++"]"
+ | T_Branch b1 b2 => treeToString b1 +++ ",," +++ treeToString b2
+end.
+Instance TreeToString {T}{TT:ToString T} : ToString (Tree ??T) := { toString := treeToString }.
(*******************************************************************************)
(* Lists *)
Variable eol : string.
Extract Constant eol => "'\n':[]".
+Class Monad {T:Type->Type} :=
+{ returnM : forall {a}, a -> T a
+; bindM : forall {a}{b}, T a -> (a -> T b) -> T b
+}.
+Implicit Arguments Monad [ ].
+Notation "a >>>= b" := (@bindM _ _ _ _ a b) (at level 50, left associativity).
(* the Error monad *)
Inductive OrError (T:Type) :=
rewrite e in v; apply OK; apply v.
apply (Error (error_message (length l) n)).
Defined.
+
+
+
+
+
+Variable Prelude_error : forall {A}, string -> A. Extract Inlined Constant Prelude_error => "Prelude.error".