1 files changed, 44 insertions, 0 deletions

diff --git a/theories/lambda/interp.v b/theories/lambda/interp.v
new file mode 100644
index 0000000..5bc60d1
--- /dev/null
+++ b/theories/lambda/interp.v
@@ -0,0 +1,44 @@
+From mininix Require Export res lambda.operational_props.
+From stdpp Require Import options.
+
+Module Import lambda.
+Export lambda.
+
+Inductive thunk :=
+  Thunk { thunk_env : gmap string thunk; thunk_expr : expr }.
+Add Printing Constructor thunk.
+Notation env := (gmap string thunk).
+
+Inductive val :=
+  | VString (s : string)
+  | VClo (x : string) (E : env) (e : expr).
+
+Global Instance maybe_VClo : Maybe3 VClo := λ v,
+  if v is VClo x E e then Some (x, E, e) else None.
+
+Definition interp1 (interp : env → expr → res val) (E : env) (e : expr) : res val :=
+  match e with
+  | EString s =>
+      mret (VString s)
+  | EId x =>
+      t ← Res (E !! x);
+      interp (thunk_env t) (thunk_expr t)
+  | EAbs x e =>
+      mret (VClo x E e)
+  | EApp e1 e2 =>
+      v1 ← interp E e1;
+      '(x, E', e') ← Res (maybe3 VClo v1);
+      interp (<[x:=Thunk E e2]> E') e'
+  end.
+
+Fixpoint interp (n : nat) (E : env) (e : expr) : res val :=
+  match n with
+  | O => NoFuel
+  | S n => interp1 (interp n) E e
+  end.
+
+Global Opaque interp.
+
+End lambda.
+
+Add Printing Constructor lambda.thunk.