Interpret CompE

spectec/src/backend-interpreter/interpreter.ml

@@ -244,9 +244,21 @@ and eval_expr env expr =
     )
   (* Data Structure *)
   | ListE el -> List.map (eval_expr env) el |> listV_of_list
-  (* | CompE (_, _) ->
-    (* TODO: interpret CompE *)
-    raise (Exception.MissingReturnValue "CompE") *)
+  | CompE (e1, e2) ->
+    let s1 = eval_expr env e1 |> unwrap_strv in
+    let s2 = eval_expr env e2 |> unwrap_strv in
+    List.map
+    (fun (id, v) ->
+    let arr1 = match !v with
+    | ListV arr_ref -> arr_ref
+    | _ -> failwith (sprintf "`%s` is not a list" (string_of_value !v))
+    in
+    let arr2 = match Record.find id s2 with
+    | ListV arr_ref -> arr_ref
+    | v -> failwith (sprintf "`%s` is not a list" (string_of_value v))
+    in
+    (id, Array.append !arr1 !arr2 |> listV |> ref)
+    ) s1 |> strV
   | CatE (e1, e2) ->
     let a1 = eval_expr env e1 |> unwrap_seq_to_array in
     let a2 = eval_expr env e2 |> unwrap_seq_to_array in