Add a way to retrieve the code for a particular state

Signed-off-by: Danila Fedorin <danila.fedorin@gmail.com>

Language.agda

@@ -3,7 +3,7 @@ module Language where
 open import Data.Nat using (ℕ; suc; pred)
 open import Data.String using (String) renaming (_≟_ to _≟ˢ_)
 open import Data.Product using (Σ; _,_; proj₁; proj₂)
-open import Data.Vec using (Vec; foldr)
+open import Data.Vec using (Vec; foldr; lookup)
 open import Data.List using ([]; _∷_; List) renaming (foldr to foldrˡ; map to mapˡ)
 open import Data.List.Relation.Unary.All using (All; []; _∷_)
 open import Data.Fin using (Fin; suc; zero; fromℕ; inject₁) renaming (_≟_ to _≟ᶠ_)
@@ -83,6 +83,9 @@ record Program : Set where
     State : Set
     State = Fin length
 
+    code : State → Stmt
+    code = lookup stmts
+
     states : List State
     states = proj₁ (indices length)