rename Recursion

[coinductive-monad.git] / Computation / Eval.v

diff --git a/Computation/Eval.v b/Computation/Eval.v
new file mode 100644 (file)
index 0000000..07d79e4
--- /dev/null
+++ b/Computation/Eval.v
@@ -0,0 +1,26 @@
+Require Export Computation.Monad.
+Require Export Computation.Termination.
+
+(* evaluate up to [n] computation steps *)
+Fixpoint bounded_eval (A:Set) (n:nat) (c:#A) {struct n} : option A :=
+  match n with
+    | O      => None
+    | (S n') =>
+      match c with
+        | Return b   => Some b
+        | Bind _ f c' =>
+          match (bounded_eval _ n' c') with
+            | None   => None
+            | Some a => bounded_eval A n' (f a)
+          end
+      end
+  end.
+
+Inductive Unit : Set := unit : Unit.
+Definition eval (A:Set) (c:#A) (t:Terminates c) : A :=
+  match eval' c Unit (Return unit) (termination_is_safe A c t) with
+    | exist x pf => x
+  end.
+
+Implicit Arguments eval [A].
+Implicit Arguments bounded_eval [A].