diff --git a/lib/dune b/lib/dune
index 9eb006f..af95ec8 100644
--- a/lib/dune
+++ b/lib/dune
@@ -18,3 +18,19 @@
    GT.ppx
    GT.ppx_all
    ppx_inline_test)))
+
+(library
+ (name lib2)
+ (modules lib_next)
+ (flags (-rectypes))
+ (libraries OCanren OCanren.tester)
+ (inline_tests)
+ (wrapped false)
+ (preprocess
+  (pps
+   OCanren-ppx.ppx_repr
+   OCanren-ppx.ppx_fresh
+   OCanren-ppx.ppx_distrib
+   GT.ppx
+   GT.ppx_all
+   ppx_inline_test)))
diff --git a/lib/lib.ml b/lib/lib.ml
index ac08465..97f6ca6 100644
--- a/lib/lib.ml
+++ b/lib/lib.ml
@@ -1,158 +1,13 @@
 open OCanren
 
-(* TODO: lift to logic domain *)
-type tag = Ref | ConstRef | ShallowCopy | ConstShallowCopy | DeepCopy | NoneRef;;
-(* MoveShallowCopy ? *)
+type data = int
 
-type typ = UnitT | IntT | BoolT | RefT of typ | PairT of typ * typ;;
-type mode = InM | OutM | InOutM;;
-type arg = Arg of tag * mode * typ;;
+type tag = Ref | Value
+type stmt = Call of data * data list | Read of data | Write of data
 
-type op = AddOp | SubOp | NotOp | LessOp | MoreOp | LessEqOp | MoreEqOp | EqOp | NotEqOp;;
+type body = stmt list
 
-type expr = IntE of int
-          | BoolE of bool
-          | VarE of string
-          (* pair *)
-          | PairE of expr * expr
-          | FstE of expr
-          | SndE of expr
-          (* pointers *)
-          | DerefE of expr
-          | RefE of expr;;
+type arg = data * tag
+type fun_decl = data * arg list * body
 
-type stmt = DeclS of string * typ
-          | AssignS of string * expr (* TODO: rvalue exprs *)
-          | SeqS of stmt * stmt
-          | ExprS of expr
-          | CallS of string * string list (* TODO: exprs?? *)
-          | IfS of expr * stmt * stmt;;
-
-type func_def = {
-  f_args: arg list;
-  f_body: stmt;
-};;
-
-type prog = {
-  p_func: (string * func_def) list;
-  p_code: stmt;
-};;
-
-(* ------ *)
-
-type value = IntV of int
-           | BoolV of bool
-           | BoxV of string (* ref to box, lvalue *)
-           | RefV of value
-           | PairV of value * value
-           | UnitV;;
-
-module M = Map.Make (String);;
-
-type func_env = func_def M.t;;
-type 'a frame = {
-  f_vars: 'a M.t;
-};;
-type 'a state = {
-  s_func: func_env;
-  s_frames: 'a frame list;
-  (* s_value: 'a; *)
-};;
-
-let init_state prog = { s_func = prog.p_func |> List.to_seq |> M.of_seq;
-                        s_frames = [];
-                        (* s_value = UnitV; *)
-                      };;
-
-let find_func name state = M.find_opt name state.s_func
-
-let find_frame_var name frame = M.find_opt name frame.f_vars;;
-let rec find_frames_var name frames =
-  match frames with
-  | [] -> None
-  | fr :: frs -> (match find_frame_var name fr with
-                  | Some x -> Some x
-                  | None -> find_frames_var name frs);;
-let find_var name state = find_frames_var name state.s_frames;;
-
-let add_var name value state =
-  match state.s_frames with
-  | [] -> failwith "No frames found"
-  | fr :: frs -> { state with s_frames = {f_vars = M.add name value fr.f_vars} :: frs};;
-
-let update_frame_var name value frame =
-  if M.find_opt name frame.f_vars != None then Some {f_vars = M.add name value frame.f_vars} else None;;
-let rec update_frames_var name value frames =
-  match frames with
-  | [] -> None
-  | fr :: frs -> (match update_frame_var name value fr with
-                  | Some fr -> Some (fr :: frs)
-                  | None -> Option.map (fun frs -> fr :: frs) @@ update_frames_var name value frs);;
-let update_var name value state =
-  Option.map (fun frs -> {state with s_frames = frs}) @@
-             update_frames_var name value state.s_frames ;;
-
-let check_op_types expr state = ();;
-
-(* TODO *)
-(* let ( let* ) = Option.bind;; *)
-
-(* TODO *)
-(* TODO: handle refs in proper way *)
-(* NOTE: exprs are pure and do not change state *)
-let rec check_expr_types expr state =
-  match expr with
-  | IntE _ -> IntT
-  | BoolE b -> BoolT
-  | VarE name -> RefT (Option.get @@ find_var name state)
-  (* pair *)
-  | PairE (fst_e, snd_e) -> PairT (check_expr_types fst_e state, check_expr_types snd_e state)
-  | FstE e ->
-    (match check_expr_types e state with
-     | PairT (t, _) -> t
-     | _ -> failwith "Fst type error")
-  | SndE e ->
-    (match check_expr_types e state with
-     | PairT (_, t) -> t
-     | _ -> failwith "Snd type error")
-  (* pointers *)
-  | DerefE e ->
-    (match check_expr_types e state with
-     | RefT t -> t
-     | _ -> failwith "Deref type eror")
-  | RefE e -> RefT (check_expr_types e state);;
-
-let expect_eq fst_val snd_val msg =
- if fst_val == snd_val then fst_val else failwith msg;;
-
-let expect_neq fst_val snd_val msg =
- if fst_val != snd_val then fst_val else failwith msg;;
-
-(* TODO *)
-let rec check_stmt_types stmt (state : typ state) =
-  match stmt with
-  | DeclS (name, typ) -> add_var name typ state
-  | AssignS (name, val_e) ->
-    let val_t = check_expr_types val_e state in
-    (match find_var name state with
-     | Some t -> ignore @@ expect_eq t val_t "Can't assign value of the different type"
-     | None -> failwith "Varible to assign is not found");
-    state
-  | SeqS (fst_e, snd_e) ->
-    let state = check_stmt_types fst_e state in
-    check_stmt_types snd_e state
-  | ExprS e -> ignore @@ check_expr_types e state; state
-  | CallS (name, args) ->
-    let func = find_func name state in
-    (* (match *) 
-    (* ) *)
-    failwith "Unimplemened"
-  | IfS (cond_e, then_e, else_e) ->
-    ignore @@ expect_eq (check_expr_types cond_e state) BoolT "If condition is not bool";
-    failwith "Unimplemened"
-    ;;
-
-(* TODO *)
-let parse str = ();;
-(* TODO *)
-let eval stmt state = ();;
+type prog = fun_decl list * body
diff --git a/lib/lib_next.ml b/lib/lib_next.ml
new file mode 100644
index 0000000..a780b90
--- /dev/null
+++ b/lib/lib_next.ml
@@ -0,0 +1,169 @@
+open OCanren
+
+(* TODO: lift to logic domain *)
+type tag = Ref | ConstRef | ShallowCopy | ConstShallowCopy | DeepCopy | NoneRef;;
+(* MoveShallowCopy ? *)
+
+type typ = UnitT | IntT | BoolT | RefT of typ | PairT of typ * typ;;
+type mode = InM | OutM | InOutM;;
+type arg = {
+  tag: tag;
+  mode: mode;
+  typ: typ;
+};;
+
+type op = AddOp | SubOp | NotOp | LessOp | MoreOp | LessEqOp | MoreEqOp | EqOp | NotEqOp;;
+
+type expr = IntE of int
+          | BoolE of bool
+          | VarE of string
+          (* pair *)
+          | PairE of expr * expr
+          | FstE of expr
+          | SndE of expr
+          (* pointers *)
+          | DerefE of expr
+          | RefE of expr
+          ;; (* TODO: op *)
+
+type stmt = DeclS of string * typ
+          | AssignS of string * expr (* TODO: rvalue exprs *)
+          | SeqS of stmt * stmt
+          | ExprS of expr
+          | CallS of string * string list (* TODO: exprs?? *)
+          | IfS of expr * stmt * stmt;;
+
+type func_def = {
+  f_args: arg list;
+  f_body: stmt;
+};;
+
+type prog = {
+  p_func: (string * func_def) list;
+  p_code: stmt;
+};;
+
+(* ------ *)
+
+type value = IntV of int
+           | BoolV of bool
+           | BoxV of string (* ref to box, lvalue *)
+           | RefV of value
+           | PairV of value * value
+           | UnitV;;
+
+module M = Map.Make (String);;
+
+type func_env = func_def M.t;;
+type 'a frame = {
+  f_vars: 'a M.t;
+};;
+type 'a state = {
+  s_func: func_env;
+  s_frames: 'a frame list;
+  (* s_value: 'a; *)
+};;
+
+let init_state prog = { s_func = prog.p_func |> List.to_seq |> M.of_seq;
+                        s_frames = [];
+                        (* s_value = UnitV; *)
+                      };;
+
+let find_func name state = M.find_opt name state.s_func
+
+let find_frame_var name frame = M.find_opt name frame.f_vars;;
+let rec find_frames_var name frames =
+  match frames with
+  | [] -> None
+  | fr :: frs -> (match find_frame_var name fr with
+                  | Some x -> Some x
+                  | None -> find_frames_var name frs);;
+let find_var name state = find_frames_var name state.s_frames;;
+
+let add_var name value state =
+  match state.s_frames with
+  | [] -> failwith "No frames found"
+  | fr :: frs -> { state with s_frames = {f_vars = M.add name value fr.f_vars} :: frs};;
+
+let update_frame_var name value frame =
+  if M.find_opt name frame.f_vars != None then Some {f_vars = M.add name value frame.f_vars} else None;;
+let rec update_frames_var name value frames =
+  match frames with
+  | [] -> None
+  | fr :: frs -> (match update_frame_var name value fr with
+                  | Some fr -> Some (fr :: frs)
+                  | None -> Option.map (fun frs -> fr :: frs) @@ update_frames_var name value frs);;
+let update_var name value state =
+  Option.map (fun frs -> {state with s_frames = frs}) @@
+             update_frames_var name value state.s_frames ;;
+
+let check_op_types expr state = ();;
+
+(* TODO *)
+(* let ( let* ) = Option.bind;; *)
+
+(* TODO *)
+(* TODO: handle refs in proper way *)
+(* NOTE: exprs are pure and do not change state *)
+let rec check_expr_types expr state =
+  match expr with
+  | IntE _ -> IntT
+  | BoolE b -> BoolT
+  | VarE name -> RefT (Option.get @@ find_var name state)
+  (* pair *)
+  | PairE (fst_e, snd_e) -> PairT (check_expr_types fst_e state, check_expr_types snd_e state)
+  | FstE e ->
+    (match check_expr_types e state with
+     | PairT (t, _) -> t
+     | _ -> failwith "Fst type error")
+  | SndE e ->
+    (match check_expr_types e state with
+     | PairT (_, t) -> t
+     | _ -> failwith "Snd type error")
+  (* pointers *)
+  | DerefE e ->
+    (match check_expr_types e state with
+     | RefT t -> t
+     | _ -> failwith "Deref type eror")
+  | RefE e -> RefT (check_expr_types e state);;
+
+let expect_eq fst_val snd_val msg =
+ if fst_val == snd_val then fst_val else failwith msg;;
+
+let expect_neq fst_val snd_val msg =
+ if fst_val != snd_val then fst_val else failwith msg;;
+
+let expect_some value msg =
+ if value != None then Option.get value else failwith msg;;
+
+(* TODO *)
+let rec check_stmt_types stmt (state : typ state) =
+  match stmt with
+  | DeclS (name, typ) -> add_var name typ state
+  | AssignS (name, val_e) ->
+    let val_t = check_expr_types val_e state in
+    (match find_var name state with
+     | Some t -> ignore @@ expect_eq t val_t "Can't assign value of the different type"
+     | None -> failwith "Varible to assign to is not found");
+    state
+  | SeqS (fst_s, snd_s) ->
+    let state = check_stmt_types fst_s state in
+    check_stmt_types snd_s state
+  | ExprS e -> ignore @@ check_expr_types e state; state
+  | CallS (name, args) ->
+    let func = expect_some (find_func name state) "Called function not found" in
+    List.iter2 (fun arg_t arg_v ->
+    let arg_vt = expect_some (find_var arg_v state) "Call: arg var not found" in
+    ignore @@ expect_eq arg_t.typ arg_vt "Call: wrong argument type"
+    ) func.f_args args;
+    state
+  | IfS (cond_e, then_s, else_s) ->
+    ignore @@ expect_eq (check_expr_types cond_e state) BoolT "If condition is not bool";
+    ignore @@ check_stmt_types then_s state;
+    ignore @@ check_stmt_types else_s state;
+    state
+
+(* TODO *)
+let parse str = ();;
+(* TODO *)
+let eval stmt state = ();;