diff --git a/simplest_model_with_mods/.gitignore b/simplest_model_with_mods/.gitignore
new file mode 100644
index 0000000..a136337
--- /dev/null
+++ b/simplest_model_with_mods/.gitignore
@@ -0,0 +1 @@
+*.pdf
diff --git a/simplest_model_with_mods/analyzer.ml b/simplest_model_with_mods/analyzer.ml
new file mode 100644
index 0000000..e0a9c1e
--- /dev/null
+++ b/simplest_model_with_mods/analyzer.ml
@@ -0,0 +1,322 @@
+module Functional =
+struct
+
+  (* --- types --- *)
+
+  type data = int
+
+  type tag = Ref | Value
+  type stmt = Call of data * data list | Read of data | Write of data
+
+  type body = stmt list
+
+  type fun_decl = tag list * body
+
+  type prog = fun_decl list * fun_decl
+
+  (* --- exceptions --- *)
+
+  exception Incorrect_memory_access of int
+  exception Ref_rvalue_argument of int
+
+  (* --- static interpreter (no rec) --- *)
+
+  (* TODO: allow data (rvalue) in calls ?? *)
+  type arg = RValue | LValue of data
+  type value = UnitV | BotV (* NOTE: RefV of data - not needed for now *)
+
+  type env = (int * data) list
+
+  (* env * memory * last unused memory * assignments *) 
+  type state = env * value list * int * data list
+
+  (* TODO: replace with pairs *)
+  let rec list_replace xs id value = match (xs, id) with
+   | (_x :: xs, 0) -> value :: xs
+   | (x :: xs, _n) -> x :: list_replace xs (id - 1) value 
+   | ([], _) -> raise Not_found
+
+
+  let env_get state id = match state with
+    (env, _mem, _mem_len, _assignments) -> List.assoc id env
+
+  let env_add state id mem_id = match state with
+    (env, mem, mem_len, assignments) -> let env = (id, mem_id) :: env in
+                                        (env, mem, mem_len, assignments)
+
+  let inv_id mem_len id = mem_len - id - 1
+
+  let mem_get state id = match state with
+    (_env, mem, mem_len, _assignments) -> List.nth mem @@ inv_id mem_len @@ env_get state id
+
+  let mem_set state id value= match state with
+    (env, mem, mem_len, assignments) -> let mem_id = inv_id mem_len @@ env_get state id in
+                                        let mem = list_replace mem mem_id value in (env, mem, mem_len, id :: assignments)
+
+  let mem_add state value = match state with
+    (env, mem, mem_len, assignments) -> let mem = value :: mem in (env, mem, mem_len + 1, assignments)
+
+  let mem_check state id = if mem_get state id == BotV then raise @@ Incorrect_memory_access id else state
+
+
+  let arg_to_value state arg = match arg with
+    | RValue -> UnitV
+    | LValue id -> mem_get state id
+
+  let st_mem_len state =
+    match state with (_, _, mem_len, _) -> mem_len
+
+  let st_add_arg state state_before id arg_tag arg =
+    match (arg_tag, arg) with
+      | (Ref, RValue) -> raise @@ Ref_rvalue_argument id (* TODO: allow later ?? *) 
+      | (Ref, LValue arg) -> env_add state id (env_get state_before arg)
+      | (Value, arg) -> let state = mem_add state (arg_to_value state_before arg) in
+                        env_add state id (st_mem_len state - 1)
+
+  let st_spoil_assignments state =
+    match state with (env, mem, mem_len, assignments) ->
+    (* TODO: use env var ids instead of mem_ids ?? *)
+    (env, List.fold_left (fun mem id -> list_replace mem (inv_id mem_len @@ env_get state id) BotV) mem assignments, mem_len, [])
+
+  let list_drop n xs = List.of_seq @@ Seq.drop n @@ List.to_seq xs
+
+  let rec eval_stmt state prog stmt =
+    match stmt with
+      | Call (f_id, args) -> eval_fun state prog (List.nth prog f_id) (List.map (fun arg -> LValue arg) args)
+      | Read id -> mem_check state id
+      | Write id -> mem_set state id UnitV
+
+  and eval_body state prog body =
+    List.fold_left (fun state stmt -> eval_stmt state prog stmt) state body
+
+  and eval_fun state prog decl args =
+    match decl with (arg_tags, body) ->
+    match state with (env_before, mem_before, len_before, assignments_before) as state_before ->
+    let state = ([], mem_before, len_before, []) in
+    let (state, _) = List.fold_left2 (fun (state, id) arg_tag arg -> (st_add_arg state state_before id arg_tag arg, id + 1)) (state, 0) arg_tags args in
+    let state = eval_body state prog body in
+    let state = st_spoil_assignments state in
+    match state with (_env, mem, len, _assignments) ->
+    (env_before, list_drop (len - len_before) mem, len_before, assignments_before) (* TODO: save some assignments ?? *)
+
+  and eval_fun_empty_args state prog decl =
+    match decl with (arg_tags, _) ->
+    let args = List.map (fun _ -> RValue) arg_tags in
+    eval_fun state prog decl args
+
+  let empty_state = ([], [], 0, [])
+
+  let eval_prog (prog, main_decl) = ignore @@ eval_fun_empty_args empty_state prog main_decl
+
+  (* tests *)
+
+  (* >> tests without functions *)
+
+  let%expect_test "empty" =
+    eval_prog ([], ([], []));
+    Printf.printf "done!";
+    [%expect {| done! |}]
+
+  let%expect_test "ref param in main failure" =
+    try (eval_prog ([], ([Ref], []));
+         [%expect.unreachable])
+    with Ref_rvalue_argument id -> Printf.printf "%i" id;
+    [%expect {| 0 |}]
+
+  let%expect_test "read empty args" =
+    try (eval_prog ([], ([], [Read 0]));
+         [%expect.unreachable])
+    with Not_found -> Printf.printf "done!";
+    [%expect {| done! |}]
+
+  let%expect_test "write empty args" =
+    try (eval_prog ([], ([], [Write 0]));
+         [%expect.unreachable])
+    with Not_found -> Printf.printf "done!";
+    [%expect {| done! |}]
+
+  let%expect_test "simple write" =
+    eval_prog ([], ([Value], [Write 0]));
+    Printf.printf "done!";
+    [%expect {| done! |}]
+
+  let%expect_test "simple read" = (* NOTE: should not work with read-before-write check*)
+    eval_prog ([], ([Value], [Read 0]));
+    Printf.printf "done!";
+    [%expect {| done! |}]
+
+  let%expect_test "multiple read & write" =
+    eval_prog ([], ([Value], [Write 0; Read 0; Write 0; Write 0; Read 0; Read 0]));
+    Printf.printf "done!";
+    [%expect {| done! |}]
+
+  let%expect_test "multiple read & write, multiple args" =
+    eval_prog ([], ([Value; Value; Value], [Write 0; Read 0; Write 1; Write 0; Write 2; Read 1; Write 2; Read 0; Read 2]));
+    Printf.printf "done!";
+    [%expect {| done! |}]
+
+  let%expect_test "main, access out of range" =
+    try(eval_prog ([], ([Value], [Write 0; Read 5 ]));
+         [%expect.unreachable])
+    with Not_found -> Printf.printf "done!";
+    [%expect {| done! |}]
+
+  let%expect_test "main, access out of range" =
+    try(eval_prog ([], ([Value], [Write 0; Write 5 ]));
+         [%expect.unreachable])
+    with Not_found -> Printf.printf "done!";
+    [%expect {| done! |}]
+
+  (* >> tests with one function *)
+
+  let%expect_test "simple function call with value arg" =
+    eval_prog ([([Value], [Write 0; Read 0; Write 0])], ([Value], [Write 0; Call (0, [0]) ]));
+    Printf.printf "done!";
+    [%expect {| done! |}]
+
+  let%expect_test "simple function call with ref arg" =
+    eval_prog ([([Ref], [Write 0; Read 0; Write 0])], ([Value], [Write 0; Call (0, [0]) ]));
+    Printf.printf "done!";
+    [%expect {| done! |}]
+
+  let%expect_test "function with value arg & read" =
+    eval_prog ([([Value], [Write 0; Read 0; Write 0])], ([Value], [Write 0; Call (0, [0]); Read 0 ]));
+    Printf.printf "done!";
+    [%expect {| done! |}]
+
+  (* --- *)
+
+  let%expect_test "function with ref arg & read" =
+    try (eval_prog ([([Ref], [Read 0; Write 0])], ([Value], [Write 0; Call (0, [0]); Read 0 ]));
+         [%expect.unreachable])
+    with Incorrect_memory_access id -> Printf.printf "%i" id;
+    [%expect {| 0 |}]
+
+  let%expect_test "function with ref arg & call twice" =
+    try (eval_prog ([([Ref], [Read 0; Write 0])], ([Value], [Write 0; Call (0, [0]); Call (0, [0]) ]));
+         [%expect.unreachable])
+    with Incorrect_memory_access id -> Printf.printf "%i" id;
+    [%expect {| 0 |}]
+
+  let%expect_test "function with ref arg, write first & call twice" =
+    eval_prog ([([Ref], [Write 0; Read 0; Write 0])], ([Value], [Write 0; Call (0, [0]); Call (0, [0]) ]));
+    Printf.printf "done!";
+    [%expect {| done! |}]
+
+  let%expect_test "function with ref arg & read, write" =
+    try (eval_prog ([([Ref], [Read 0; Write 0])], ([Value], [Write 0; Call (0, [0]); Read 0; Write 0 ]));
+         [%expect.unreachable])
+    with Incorrect_memory_access id -> Printf.printf "%i" id;
+    [%expect {| 0 |}]
+
+  let%expect_test "function with ref arg & write, read" =
+    eval_prog ([([Ref], [Read 0; Write 0])], ([Value], [Write 0; Call (0, [0]); Write 0; Read 0 ]));
+    Printf.printf "done!";
+    [%expect {| done! |}]
+
+  let%expect_test "function with ref arg, no write inside & read" =
+    eval_prog ([([Ref], [Read 0; Read 0])], ([Value], [Write 0; Call (0, [0]); Read 0 ]));
+    Printf.printf "done!";
+    [%expect {| done! |}]
+
+  (* --- *)
+
+  let%expect_test "function with value arg, read out of range" =
+    try(eval_prog ([([Value], [Read 0; Read 1])], ([Value; Value], [Write 0; Call (0, [0]); Read 0 ]));
+         [%expect.unreachable])
+    with Not_found -> Printf.printf "done!";
+    [%expect {| done! |}]
+
+  let%expect_test "function with ref arg, read out of range" =
+    try(eval_prog ([([Ref], [Read 0; Read 1])], ([Value; Value], [Write 0; Call (0, [0]); Read 0 ]));
+         [%expect.unreachable])
+    with Not_found -> Printf.printf "done!";
+    [%expect {| done! |}]
+
+  let%expect_test "function with value arg, write out of range" =
+    try(eval_prog ([([Value], [Read 0; Write 1])], ([Value; Value], [Write 0; Call (0, [0]); Read 0 ]));
+         [%expect.unreachable])
+    with Not_found -> Printf.printf "done!";
+    [%expect {| done! |}]
+
+  let%expect_test "function with value arg, call out of range" =
+    try(eval_prog ([([Value], [Read 0])], ([Value; Value], [Write 0; Call (0, [2]); Read 0 ]));
+         [%expect.unreachable])
+    with Not_found -> Printf.printf "done!";
+    [%expect {| done! |}]
+
+  (* --- *)
+
+  let%expect_test "function with ref & value args, no write inside & read" =
+    eval_prog (
+      [([Ref; Value], [Read 0; Read 1])],
+      ([Value; Value], [Write 0; Write 1; Call (0, [0; 1]); Read 0; Read 1 ]));
+    Printf.printf "done!";
+    [%expect {| done! |}]
+
+  let%expect_test "function with ref & value args, write value inside & read" =
+    eval_prog (
+      [([Ref; Value], [Read 0; Read 1; Write 1; Read 1])],
+      ([Value; Value], [Write 0; Write 1; Call (0, [0; 1]); Read 0; Read 1 ]));
+    Printf.printf "done!";
+    [%expect {| done! |}]
+
+  let%expect_test "function with ref & value args, write both inside & read" =
+    try (eval_prog (
+      [([Ref; Value],[Read 0; Read 1; Write 0; Write 1; Read 1])],
+      ([Value; Value], [Write 0; Write 1; Call (0, [0; 1]); Read 0; Read 1 ]));
+         [%expect.unreachable])
+    with Incorrect_memory_access id -> Printf.printf "%i" id;
+    [%expect {| 0 |}]
+
+  (* --- *)
+
+  (* NOTE: maybe important case in the future *)
+  let%expect_test "function with ref two same ref args, read both & read" =
+    eval_prog (
+      [([Ref; Ref],[Read 0; Read 1; Read 1])],
+      ([Value], [Write 0; Call (0, [0; 0]); Read 0 ]));
+    Printf.printf "done!";
+    [%expect {| done! |}]
+
+  (* NOTE: maybe important case in the future *)
+  let%expect_test "function with ref two same ref args, read both & nothing" =
+    eval_prog (
+      [([Ref; Ref],[Read 0; Read 1; Write 0; Write 1; Read 1])],
+      ([Value], [Write 0; Call (0, [0; 0]); ]));
+    Printf.printf "done!";
+    [%expect {| done! |}]
+
+  (* >> tests with several functions *)
+
+  let%expect_test "two functions with ref arg, read func -> write func" =
+    eval_prog (
+      [([Ref], [Read 0]); ([Ref], [Write 0])],
+      ([Value], [Write 0; Call (0, [0]); Read 0; Call (1, [0]) ]));
+    Printf.printf "done!";
+    [%expect {| done! |}]
+
+  let%expect_test "two functions with ref arg, write func -> read func" =
+    try (eval_prog (
+      [([Ref], [Read 0]); ([Ref], [Write 0])],
+      ([Value], [Write 0; Call (1, [0]); Call (0, [0]) ]));
+         [%expect.unreachable])
+    with Incorrect_memory_access id -> Printf.printf "%i" id;
+    [%expect {| 0 |}]
+
+  let%expect_test "two functions: ref arg after value arg" =
+    eval_prog (
+      [([Ref], [Read 0; Write 0]); ([Value], [Read 0; Write 0])],
+      ([Value], [Write 0; Call (1, [0]); Read 0; Call (0, [0]) ]));
+    Printf.printf "done!";
+    [%expect {| done! |}]
+
+  let%expect_test "two functions: value arg after spoiled ref arg" =
+    try (eval_prog (
+      [([Ref], [Read 0; Write 0]); ([Value], [Read 0; Write 0])],
+      ([Value], [Write 0; Call (0, [0]); Call (1, [0]) ]));
+         [%expect.unreachable])
+    with Incorrect_memory_access id -> Printf.printf "%i" id;
+    [%expect {| 0 |}]
+
+end
diff --git a/simplest_model_with_mods/dune b/simplest_model_with_mods/dune
new file mode 100644
index 0000000..fb1ff19
--- /dev/null
+++ b/simplest_model_with_mods/dune
@@ -0,0 +1,64 @@
+; (env
+;  (_
+;   (flags
+;    (:standard -warn-error +5))))
+
+(library
+ (name analyzer_mods)
+ (modules analyzer)
+ (flags (-rectypes))
+ (libraries OCanren OCanren.tester)
+ (inline_tests)
+ (wrapped false)
+ (preprocess
+  (pps GT.ppx GT.ppx_all ppx_expect ppx_inline_test)))
+
+(library
+ (name tests_modt)
+ (modules tests)
+ (flags (-rectypes))
+ (libraries synthesizer_mods tests_f_mods)
+ (inline_tests)
+ (wrapped false)
+ (preprocess
+  (pps ppx_expect ppx_inline_test)))
+
+(library
+ (name tests_f_mods)
+ (modules tests_f)
+ (flags (-rectypes))
+ (libraries OCanren OCanren.tester synthesizer_mods)
+ (preprocessor_deps ../camlp5/pp5+gt+plugins+ocanren+dump.exe)
+ (wrapped false)
+ (preprocess
+  (pps
+   OCanren-ppx.ppx_repr
+   OCanren-ppx.ppx_deriving_reify
+   OCanren-ppx.ppx_fresh
+   GT.ppx
+   GT.ppx_all
+   OCanren-ppx.ppx_distrib
+   --
+   -pp
+   camlp5/pp5+gt+plugins+ocanren+dump.exe)))
+
+(library
+ (name synthesizer_mods)
+ (modules synthesizer)
+ (flags
+  ; (-dsource)
+  (:standard -rectypes))
+ (libraries OCanren OCanren.tester)
+ (preprocessor_deps ../camlp5/pp5+gt+plugins+ocanren+dump.exe)
+ (wrapped false)
+ (preprocess
+  (pps
+   OCanren-ppx.ppx_repr
+   OCanren-ppx.ppx_deriving_reify
+   OCanren-ppx.ppx_fresh
+   GT.ppx
+   GT.ppx_all
+   OCanren-ppx.ppx_distrib
+   --
+   -pp
+   camlp5/pp5+gt+plugins+ocanren+dump.exe)))
diff --git a/simplest_model_with_mods/synthesizer.ml b/simplest_model_with_mods/synthesizer.ml
new file mode 100644
index 0000000..aa2e4da
--- /dev/null
+++ b/simplest_model_with_mods/synthesizer.ml
@@ -0,0 +1,421 @@
+module Relational =
+struct
+  open GT
+  open OCanren
+  open OCanren.Std
+
+  type data_ground = Nat.ground (* with show, gmap *)
+  [@@deriving gt ~options:{ show; gmap }]
+  type data_logic = Nat.logic
+  [@@deriving gt ~options:{ show; gmap }]
+  type data_injected = Nat.injected
+
+  module Tag = struct
+    [@@@warning "-26-27-32-33-34-35-36-37-38-39-60-66-67"]
+    [%%ocanren_inject
+      type nonrec t = Ref | Val
+      [@@deriving gt ~options:{ show; gmap }]
+      type nonrec ground = t
+    ]
+
+    module Test = struct
+      @type answer = logic GT.list with show
+
+      let test _ = show(answer) (Stream.take (run q (fun q -> ocanren {q == Ref})
+                                                    (fun q -> q#reify reify)))
+    end
+  end
+
+  module Stmt = struct
+    [@@@warning "-26-27-32-33-34-35-36-37-38-39-60-66-67"]
+    [%%ocanren_inject
+      type nonrec ('d, 'dl) t = Call of 'd * 'dl | Read of 'd | Write of 'd
+      [@@deriving gt ~options:{ show; gmap }]
+      type nonrec ground = (Nat.ground, Nat.ground List.ground) t
+    ]
+
+    module Test = struct
+      @type answer = Nat.ground List.ground GT.list with show
+      @type answer'  = ground GT.list with show
+
+      let test1 _ = show(answer) (Stream.take (run q (fun q -> ocanren {Call (1, [2]) == Call (1, q)})
+                                                     (fun q -> q#reify (List.prj_exn Nat.prj_exn))))
+
+      let test2 _ = show(answer') (Stream.take (run q (fun q -> ocanren {Call (1, [2]) == q})
+                                                      (fun q -> q#reify (prj_exn))))
+    end
+  end
+
+  module FunDecl = struct
+    [@@@warning "-26-27-32-33-34-35-36-37-38-39-60-66-67"]
+    [%%ocanren_inject
+      type nonrec ('l, 'b) t = FunDecl of 'l * 'b
+      [@@deriving gt ~options:{ show; gmap }]
+      type nonrec ground = (Tag.ground List.ground, Stmt.ground List.ground) t
+    ]
+
+    module Test = struct
+      @type answer  = ground GT.list with show
+      let test _ = show(answer) (Stream.take (run q (fun q -> let open Tag in
+                                                              let open Stmt in
+                                                              ocanren {FunDecl ([Ref; Val], [Call (1, [0]); Write 1]) == q})
+                                                    (fun q -> q#reify (prj_exn))))
+    end
+  end
+
+  module Prog = struct
+    [@@@warning "-26-27-32-33-34-35-36-37-38-39-60-66-67"]
+    [%%ocanren_inject
+      type nonrec ('l, 'f) t = Prog of 'l * 'f
+      [@@deriving gt ~options:{ show; gmap }]
+      type nonrec ground = (FunDecl.ground List.ground, FunDecl.ground) t
+    ]
+
+    module Test = struct
+      @type answer  = ground GT.list with show
+      let test _ = show(answer) (Stream.take (run q (fun q -> let open FunDecl in
+                                                              let open Tag in
+                                                              let open Stmt in
+                                                              ocanren {Prog ([], FunDecl ([Val], [Write 0; Read 0])) == q})
+                                                    (fun q -> q#reify (prj_exn))))
+    end
+  end
+
+  module Arg = struct
+    [@@@warning "-26-27-32-33-34-35-36-37-38-39-60-66-67"]
+    [%%ocanren_inject
+      type nonrec 'd t = RValue | LValue of 'd
+      [@@deriving gt ~options:{ show; gmap }]
+      type nonrec ground = Nat.ground t
+    ]
+
+    module Test = struct
+      @type answer = logic GT.list with show
+      let test _ = show(answer) (Stream.take (run q (fun q -> ocanren {q == LValue 3})
+                                                    (fun q -> q#reify reify)))
+    end
+  end
+
+  module Value = struct
+    [@@@warning "-26-27-32-33-34-35-36-37-38-39-60-66-67"]
+    [%%ocanren_inject
+      type nonrec t = Unit | Bot
+      [@@deriving gt ~options:{ show; gmap }]
+      type nonrec ground = t
+    ]
+
+    module Test = struct
+      @type answer = logic GT.list with show
+      let test _ = show(answer) (Stream.take (run q (fun q -> ocanren {q == Bot | q == Unit})
+                                                    (fun q -> q#reify reify)))
+    end
+  end
+
+  module St = struct
+    [@@@warning "-26-27-32-33-34-35-36-37-38-39-60-66-67"]
+    [%%ocanren_inject
+      type nonrec ('env, 'mem, 'last_mem, 'assignments) t = St of 'env * 'mem * 'last_mem * 'assignments
+      [@@deriving gt ~options:{ show; gmap }]
+      type nonrec ground = (((Nat.ground, Nat.ground) Pair.ground) List.ground,
+                            Value.ground List.ground, Nat.ground, Nat.ground List.ground) t
+    ]
+
+    module Test = struct
+      @type answer  = ground GT.list with show
+      let test _ = show(answer) (Stream.take (run q (fun q -> let open Value in
+                                                              ocanren {St ([Std.pair 0 0], [Bot], 1, [0]) == q})
+                                                    (fun q -> q#reify (prj_exn))))
+    end
+  end
+
+  let rec list_replaceo xs id value ys = ocanren {
+    (* xs == [] & ys == [] | (* NOTE: error *) *)
+    { fresh x, xs' in
+        xs == x :: xs' &
+        id == Nat.o &
+        ys == value :: xs' } |
+    { fresh x, xs', id', ys' in
+        xs == x :: xs' &
+        id == Nat.s id' &
+        ys == x :: ys' &
+        list_replaceo xs' id' value ys' }
+    }
+
+  (* let rec list_assoco a xs v' = *)
+    (* ocanren { *)
+    (* fresh a', b', xs' in *)
+      (* (Std.pair a' b') :: xs' == xs & *)
+      (* { a =/= a' & list_assoco a xs' v' | *)
+        (* a == a' & v' == b' } *)
+  (* } *)
+  (* TODO: difference from List.assoco ?? *)
+
+  let env_geto state id mem_id' =
+    let open St in
+    ocanren {
+    fresh env, mem, mem_len, assignments in
+      state == St (env, mem, mem_len, assignments) &
+      List.assoco id env mem_id'
+  }
+
+  let env_addo state id mem_id state' =
+    let open St in
+    ocanren {
+    fresh env, env', mem, mem_len, assignments in
+      state == St (env, mem, mem_len, assignments) &
+      state' == St (env', mem, mem_len, assignments) &
+      (Std.pair id mem_id) :: env == env'
+  }
+
+  let inv_ido mem_len id id' = ocanren {
+    fresh inv_id_inc in
+      Nat.addo inv_id_inc id mem_len &
+      Nat.addo id' 1 inv_id_inc
+  }
+
+  (* --- *)
+
+  let rec list_ntho xs id x' = ocanren {
+    (* xs == [] | (* NOTE: error *) *)
+    { fresh y', xs' in
+      id == Nat.o &
+      y' :: xs' == xs &
+      x' == y' } |
+    { fresh id', y', xs' in
+      Nat.s id' == id &
+      y' :: xs' == xs &
+      list_ntho xs' id' x' }
+  }
+
+  let mem_geto state id value' =
+    let open St in
+    ocanren {
+    fresh mem, mem_len, mem_id, mem_id_inv, _env, _assignments in
+    state == St (_env, mem, mem_len, _assignments) &
+    env_geto state id mem_id &
+    inv_ido mem_len mem_id mem_id_inv &
+    list_ntho mem mem_id_inv value'
+  }
+
+  let mem_seto state id value state'=
+    let open St in
+    ocanren {
+    fresh env, mem, mem_len, assignments, mem_id, inv_mem_id, mem', assignments' in
+      state == St (env, mem, mem_len, assignments) &
+      env_geto state id mem_id &
+      inv_ido mem_len mem_id inv_mem_id &
+      list_replaceo mem inv_mem_id value mem' &
+      assignments' == id :: assignments &
+      state' == St (env, mem', mem_len, assignments')
+  }
+
+  let mem_addo state value state' =
+    let open St in
+    ocanren {
+    fresh env, mem, mem_len, mem_len', assignments, mem' in
+      state == St (env, mem, mem_len, assignments) &
+      mem' == value :: mem &
+      mem_len' == Nat.s mem_len &
+      state' == St (env, mem', mem_len', assignments)
+  }
+
+  let mem_checko state id state' =
+    let open Value in
+    ocanren {
+    mem_geto state id Unit & state' == state
+  }
+
+  (* --- *)
+
+  let rec list_foldlo f acc xs acc' = ocanren {
+    xs == [] & acc' == acc |
+    { fresh x', xs', acc_upd in
+      xs == x' :: xs' &
+      list_foldlo f acc xs' acc_upd &
+      f acc_upd x' acc' }
+  }
+
+  let rec list_foldro f acc xs acc' = ocanren {
+    xs == [] & acc' == acc |
+    { fresh x', xs', acc_upd in
+      xs == x' :: xs' &
+      f acc x' acc_upd &
+      list_foldro f acc_upd xs' acc' }
+    (* TODO: inf search on swap, investigate *)
+  }
+
+
+  let rec list_foldr2o f acc xs ys acc' = ocanren {
+    xs == [] & ys == [] & acc' == acc |
+    { fresh x', xs', y', ys', acc_upd in
+      xs == x' :: xs' &
+      ys == y' :: ys' &
+      f acc x' y' acc_upd &
+      list_foldr2o f acc_upd xs' ys' acc' }
+  }
+
+  let rec list_foldl2o f acc xs ys acc' = ocanren {
+    xs == [] & ys == [] & acc' == acc |
+    { fresh x', xs', y', ys', acc_upd in
+      xs == x' :: xs' &
+      ys == y' :: ys' &
+      list_foldl2o f acc xs' ys' acc_upd &
+      f acc_upd x' y' acc' }
+  }
+
+  let arg_to_valueo state arg value' =
+    let open Arg in
+    let open Value in
+    ocanren {
+    arg == RValue & value' == Unit |
+    { fresh id in
+      arg == LValue id &
+      mem_geto state id value' }
+  }
+
+  let arg_to_rvalueo _arg value' =
+    let open Arg in
+    ocanren { value' == RValue }
+
+  let st_mem_leno state mem_len' =
+    let open St in
+    ocanren {
+    fresh _env, _mem, _assignments in
+      state == St (_env, _mem, mem_len', _assignments)
+  }
+
+  let st_add_argo state state_before id arg_tag arg state'' =
+    (* let open Nat in *)
+    let open Arg in
+    let open Tag in
+    ocanren {
+    (* arg_tag == Tag.ref & arg == Arg.rvalue & state'' == state | *)
+      (* NOTE: error, TODO: allow later ?? *)
+    { fresh arg', value' in
+      arg_tag == Ref &
+      arg == LValue arg' &
+      env_geto state_before arg' value' &
+      env_addo state id value' state'' } |
+    { fresh value', state', mem_len_prev' in
+      arg_tag == Val &
+      arg_to_valueo state_before arg value' &
+      mem_addo state value' state' &
+      st_mem_leno state mem_len_prev' &
+      env_addo state' id mem_len_prev' state'' }
+  }
+
+  let st_spoil_foldero state id state' =
+    let open Value in
+    ocanren {
+    mem_seto state id Bot state'
+  }
+
+  let st_spoil_assignmentso state state' =
+    let open St in
+    ocanren {
+    fresh _env, _mem, _mem_len, assignments in
+      state == St (_env, _mem, _mem_len, assignments) &
+      list_foldlo st_spoil_foldero state assignments state'
+  }
+
+  (* --- *)
+
+  let arg_to_lvalueo arg arg' =
+    let open Arg in
+    ocanren { arg' == LValue arg }
+
+  let rec list_dropo n xs xs' = ocanren {
+    xs == [] & xs' == [] |
+    n == Nat.o & xs == xs' & xs =/= [] |
+    { fresh n', _y, ys in
+        Nat.s n' == n &
+        xs == _y :: ys &
+        list_dropo n' ys xs' }
+  }
+
+  let rec eval_stmto state prog stmt state' =
+    let open Stmt in
+    let open Value in
+    ocanren {
+    { fresh f_id, args, f, args' in
+      stmt == Call (f_id, args) &
+      list_ntho prog f_id f &
+      List.mapo arg_to_lvalueo args args' &
+      eval_funo state prog f args' state' } |
+    { fresh id in stmt == Read id & mem_checko state id state' } |
+    { fresh id in stmt === Write id & mem_seto state id Unit state' }
+  }
+
+  and eval_body_foldero prog state stmt state' =
+    eval_stmto state prog stmt state'
+
+  and eval_bodyo state prog body state' =
+    list_foldro (eval_body_foldero prog) state body state' 
+
+  and add_arg_foldero state_before state_c arg_tag arg state_c' =
+    ocanren {
+    fresh state, id, state', id' in
+      state_c == Std.pair state id &
+      st_add_argo state state_before id arg_tag arg state' &
+      id' == Nat.s id &
+      state_c' == Std.pair state' id'
+  }
+
+  and eval_funo state prog decl args state' =
+    let open FunDecl in
+    let open St in
+    ocanren {
+    fresh arg_tags, body,
+          env_before, mem_before, len_before, assignments_before,
+          state_clean,
+          state_with_vars, _counter,
+          state_evaled,
+          state_spoiled,
+          _env, mem_spoiled, len, _assignments,
+          mem_updated,
+          len_to_drop,
+          nil_env, nil_assignments in
+      nil_env == [] &
+      nil_assignments == [] &
+      decl == FunDecl (arg_tags, body) &
+      state == St (env_before, mem_before, len_before, assignments_before) &
+      state_clean == St (nil_env, mem_before, len_before, nil_assignments) &
+      list_foldr2o (add_arg_foldero state) (Std.pair state Nat.o) arg_tags args (Std.pair state_with_vars _counter) & (* TODO: or foldr2o ?? *)
+      eval_bodyo state_with_vars prog body state_evaled &
+      st_spoil_assignmentso state_evaled state_spoiled &
+      state_spoiled == St (_env, mem_spoiled, len, _assignments) &
+      Nat.addo len_to_drop len_before len &
+      list_dropo len_to_drop mem_spoiled mem_updated &
+      state' == St (env_before, mem_updated, len_before, assignments_before)
+  }
+
+  and eval_fun_empty_argso state prog decl state' =
+    let open FunDecl in
+    ocanren {
+    fresh arg_tags, args, _body in
+      decl == FunDecl (arg_tags, _body) &
+      List.mapo arg_to_rvalueo arg_tags args &
+      eval_funo state prog decl args state'
+  }
+
+  (* --- *)
+
+  let empty_stateo state =
+    let open St in
+    ocanren {
+    fresh nil_env, nil_mem, nil_assignments in
+      nil_env == [] &
+      nil_assignments == [] &
+      nil_mem == [] &
+      state == St (nil_env, nil_mem, Nat.o, nil_assignments)
+  }
+
+  let eval_progo all_prog state' =
+    let open Prog in
+    ocanren {
+    fresh prog, main_decl, state in
+      all_prog == Prog (prog, main_decl) &
+      empty_stateo state &
+      eval_fun_empty_argso state prog main_decl state'
+  }
+end
diff --git a/simplest_model_with_mods/tests.ml b/simplest_model_with_mods/tests.ml
new file mode 100644
index 0000000..6e7452f
--- /dev/null
+++ b/simplest_model_with_mods/tests.ml
@@ -0,0 +1,59 @@
+open Tests_f
+open Synthesizer
+open Relational
+
+(* type tests *)
+let%expect_test "Tag type test" = print_endline (Tag.Test.test ()); [%expect {| [Ref] |}]
+let%expect_test "Stmt type test (1)" = print_endline (Stmt.Test.test1 ()); [%expect {| [[S (S (O))]] |}]
+let%expect_test "Stmt type test (2)" = print_endline (Stmt.Test.test2 ()); [%expect {| [Call (S (O), [S (S (O))])] |}]
+let%expect_test "FunDecl type test" = print_endline (FunDecl.Test.test ()); [%expect {| [FunDecl ([Ref; Val], [Call (S (O), [O]); Write (S (O))])] |}]
+let%expect_test "Prog type test" = print_endline (Prog.Test.test ()); [%expect {| [Prog ([], FunDecl ([Val], [Write (O); Read (O)]))] |}]
+let%expect_test "Arg type test" = print_endline (Arg.Test.test ()); [%expect {| [LValue (S (S (S (O))))] |}]
+let%expect_test "Value type test" = print_endline (Value.Test.test ()); [%expect {| [Bot; Unit] |}]
+let%expect_test "St type test" = print_endline (St.Test.test ()); [%expect {| [St ([(O, O)], [Bot], S (O), [O])] |}]
+
+(* function tests *)
+let%expect_test "inv_id test 1" = print_endline (inv_id_t ()); [%expect {| [O] |}]
+let%expect_test "inv_id test 2" = print_endline (inv_id_t2 ()); [%expect {| [S (O)] |}]
+let%expect_test "inv_id test 3" = print_endline (inv_id_t3 ()); [%expect {| [S (O)] |}]
+let%expect_test "list_drop test" = print_endline (list_drop_t ()); [%expect {| [[S (S (S (O)))]] |}]
+let%expect_test "list_replace test" = print_endline (list_replace_t ()); [%expect {| [[S (O); O; S (S (S (O))); S (S (S (S (O))))]] |}]
+let%expect_test "arG_to_value test 1" = print_endline (arg_to_value_t ()); [%expect {| [Unit] |}]
+let%expect_test "st_add_arg test" = print_endline (st_add_arg_t ()); [%expect {| [St ([(O, O)], [Unit], S (O), [])] |}]
+let%expect_test "write eval test 1" = print_endline (write_eval_t1 ()); [%expect {| [St ([(S (O), S (O)); (O, O)], [Bot; Unit], S (S (O)), [O])] |}]
+let%expect_test "write eval test 2" = print_endline (write_eval_t2 ()); [%expect {| [St ([(S (O), S (O)); (O, O)], [Unit; Bot], S (S (O)), [S (O)])] |}]
+let%expect_test "multiple writes eval test" = print_endline (writes_eval_t ()); [%expect {| [St ([(S (O), S (O)); (O, O)], [Unit; Unit], S (S (O)), [S (O); O])] |}]
+let%expect_test "call eval test 1" = print_endline (call_eval_t1 ()); [%expect {| [St ([(O, O)], [Bot], S (O), [])] |}]
+let%expect_test "call eval test 2" = print_endline (call_eval_t2 ()); [%expect {| [St ([(S (O), S (O)); (O, O)], [Unit; Bot], S (S (O)), [])] |}]
+let%expect_test "call eval test 3" = print_endline (call_eval_t3 ()); [%expect {| [St ([(S (O), S (O)); (O, O)], [Bot; Unit], S (S (O)), [])] |}]
+let%expect_test "call eval test 4" = print_endline (call_eval_t4 ()); [%expect {| [St ([(S (O), S (O)); (O, O)], [Bot; Bot], S (S (O)), [])] |}]
+let%expect_test "call eval test 5" = print_endline (call_eval_t5 ()); [%expect {| [St ([(S (O), S (O)); (O, O)], [Bot; Bot], S (S (O)), [])] |}]
+let%expect_test "mem_set test 1" = print_endline (mem_set_t1 ()); [%expect {| [St ([(O, O)], [Unit], S (O), [O])] |}]
+let%expect_test "mem_set test 2" = print_endline (mem_set_t2 ()); [%expect {| [St ([(O, O)], [Bot], S (O), [O])] |}]
+let%expect_test "mem_set test 3" = print_endline (meem_set_t3 ()); [%expect {| [St ([(O, S (O))], [Bot; Unit], S (S (O)), [O])] |}]
+let%expect_test "add_arg_folder test" = print_endline (add_arg_folder_t ()); [%expect {| [St ([(O, O)], [Unit], S (O), [])] |}]
+let%expect_test "foldl2 test" = print_endline (foldl2_t ()); [%expect {| [St ([(O, O)], [Unit], S (O), [])] |}]
+let%expect_test "rvalue test" = print_endline (rvalue_t ()); [%expect {| [[]; [RValue]; [RValue; RValue]] |}]
+let%expect_test "empty_state test" = print_endline (empty_state_t ()); [%expect {| [St ([], [], O, [])] |}]
+let%expect_test "function eval test 1" = print_endline (fun_eval_t1 ()); [%expect {| [St ([], [], O, [])] |}]
+let%expect_test "function eval test 2" = print_endline (fun_eval_t2 ()); [%expect {| [St ([], [], O, [])] |}]
+let%expect_test "function eval test 3" = print_endline (fun_eval_t3 ()); [%expect {| [] |}]
+let%expect_test "function eval test 4" = print_endline (fun_eval_t4 ()); [%expect {| [] |}]
+let%expect_test "function eval test 5" = print_endline (fun_eval_t5 ()); [%expect {| [] |}]
+let%expect_test "prog eval test 1" = print_endline (prog_eval_t1 ()); [%expect {| [St ([], [], O, [])] |}]
+let%expect_test "prog eval test 2" = print_endline (prog_eval_t2 ()); [%expect {| [St ([], [], O, [])] |}]
+let%expect_test "prog eval test 3" = print_endline (prog_eval_t3 ()); [%expect {| [St ([], [], O, [])] |}]
+let%expect_test "prog eval test 4" = print_endline (prog_eval_t4 ()); [%expect {| [] |}]
+let%expect_test "synthesis test 1" = print_endline (synt_t1 ()); [%expect {| [Val] |}]
+let%expect_test "synthesis test 2" = print_endline (synt_t2 ()); [%expect {| [Ref; Val] |}]
+let%expect_test "synthesis test 3" = print_endline (synt_t3 ()); [%expect {| [[Ref; Val]; [Val; Val]] |}]
+let%expect_test "synthesis test 4" = print_endline (synt_t4 ()); [%expect {| [[Val]] |}]
+let%expect_test "synthesis test 5" = print_endline (synt_t5 ()); [%expect {| [[Ref; Ref]; [Ref; Val]; [Val; Ref]; [Val; Val]] |}]
+let%expect_test "synthesis test 6" = print_endline (synt_t6 ()); [%expect {| [[Ref; Ref]; [Val; Ref]; [Ref; Val]; [Val; Val]] |}]
+let%expect_test "synthesis test 7" = print_endline (synt_t7 ()); [%expect {| [[Ref; Val]; [Val; Val]] |}]
+let%expect_test "synthesis test 8" = print_endline (synt_t8 ()); [%expect {| [[Val; Ref]; [Val; Val]] |}]
+let%expect_test "synthesis test 9" = print_endline (synt_t9 ()); [%expect {| [[Val; Ref]; [Val; Val]] |}]
+
+(* NOTE: inf test in current model (without additional functional interfaces and ) *)
+(* let%expect_test "recursive eval test" = print_endline (rec_eval_t ()); [%expect {| [St ([], [], O, [])] |}] *)
+
diff --git a/simplest_model_with_mods/tests_f.ml b/simplest_model_with_mods/tests_f.ml
new file mode 100644
index 0000000..18ea63f
--- /dev/null
+++ b/simplest_model_with_mods/tests_f.ml
@@ -0,0 +1,438 @@
+open Synthesizer
+open Relational
+open GT
+open OCanren
+open OCanren.Std
+
+@type answer  = St.ground GT.list with show
+@type answerArgs = (Arg.ground List.ground) GT.list with show
+@type answerValue = Value.ground GT.list with show
+@type answerNat = Nat.ground GT.list with show
+@type answerNats = (Nat.ground List.ground) GT.list with show
+@type answerTag = Tag.ground GT.list with show
+@type answerTags = (Tag.ground List.ground) GT.list with show
+
+let inv_id_t _ = show(answerNat) (Stream.take (run q
+  (fun q -> ocanren { inv_ido 2 1 q })
+  (fun q -> q#reify Nat.prj_exn)))
+
+let inv_id_t2 _ = show(answerNat) (Stream.take (run q
+  (fun q -> ocanren { inv_ido 2 0 q })
+  (fun q -> q#reify Nat.prj_exn)))
+
+let inv_id_t3 _ = show(answerNat) (Stream.take (run q
+  (fun q -> ocanren { inv_ido 2 q 0 })
+  (fun q -> q#reify Nat.prj_exn)))
+
+let list_drop_t _ = show(answerNats) (Stream.take (run q
+  (fun q -> ocanren { list_dropo 2 [1; 2; 3] q })
+  (fun q -> q#reify (List.prj_exn Nat.prj_exn))))
+
+let list_replace_t  _ = show(answerNats) (Stream.take (run q
+  (fun q -> ocanren { list_replaceo [1; 2; 3; 4] 1 0 q })
+  (fun q -> q#reify (List.prj_exn Nat.prj_exn))))
+
+let arg_to_value_t _ = show(answerValue) (Stream.take (run q
+  (fun q -> let open Arg in
+            ocanren {
+    fresh s in
+      empty_stateo s &
+      arg_to_valueo s RValue q })
+  (fun q -> q#reify (Value.prj_exn))))
+
+let st_add_arg_t _ = show(answer) (Stream.take (run q
+  (fun q -> let open Arg in
+            let open Tag in
+            ocanren {
+    fresh s, s', cnt in
+      empty_stateo s &
+      empty_stateo s' &
+      st_add_argo s  s' Nat.o Val RValue q })
+  (fun q -> q#reify (St.prj_exn))))
+
+let write_eval_t1 _ = show(answer) (Stream.take (run q
+  (fun q -> let open Arg in
+            let open Tag in
+            let open Value in
+            let open St in
+            let open Stmt in
+            let open FunDecl in
+            ocanren {
+    fresh s, p, stmt in
+      s == St ([Std.pair 1 1; Std.pair 0 0], [Bot; Bot], 2, []) &
+      p == [FunDecl ([Ref; Ref], [Write 0; Write 1])] &
+      stmt == Write 0 &
+      eval_stmto s p stmt q})
+  (fun q -> q#reify (St.prj_exn))))
+
+let write_eval_t2 _ = show(answer) (Stream.take (run q
+  (fun q -> let open Arg in
+            let open Tag in
+            let open Value in
+            let open St in
+            let open Stmt in
+            let open FunDecl in
+            ocanren {
+    fresh s, p, stmt in
+      s == St ([Std.pair 1 1; Std.pair 0 0], [Bot; Bot], 2, []) &
+      p == [FunDecl ([Ref; Ref], [Write 0; Write 1])] &
+      stmt == Write 1 &
+      eval_stmto s p stmt q})
+  (fun q -> q#reify (St.prj_exn))))
+
+let writes_eval_t _ = show(answer) (Stream.take (run q
+  (fun q -> let open Arg in
+            let open Tag in
+            let open Value in
+            let open St in
+            let open Stmt in
+            let open FunDecl in
+            ocanren {
+    fresh s, p, stmts in
+      s == St ([Std.pair 1 1; Std.pair 0 0], [Bot; Bot], 2, []) &
+      p == [FunDecl ([Ref; Ref], [Write 0; Write 1])] &
+      stmts == [Write 0; Write 1] &
+      eval_bodyo s p stmts q})
+  (fun q -> q#reify (St.prj_exn))))
+
+let call_eval_t1 _ = show(answer) (Stream.take (run q
+  (fun q -> let open Arg in
+            let open Tag in
+            let open Value in
+            let open St in
+            let open Stmt in
+            let open FunDecl in
+            ocanren {
+    fresh s, p, stmt in
+      s == St ([Std.pair 0 0], [Unit], 1, []) &
+      p == [FunDecl ([Ref], [Write 0])] &
+      stmt == Call (0, [0]) &
+      eval_stmto s p stmt q})
+  (fun q -> q#reify (St.prj_exn))))
+
+let call_eval_t2 _ = show(answer) (Stream.take (run q
+  (fun q -> let open Arg in
+            let open Tag in
+            let open Value in
+            let open St in
+            let open Stmt in
+            let open FunDecl in
+            ocanren {
+    fresh s, p, stmt in
+      s == St ([Std.pair 1 1; Std.pair 0 0], [Unit; Unit], 2, []) &
+      p == [FunDecl ([Ref], [Write 0])] &
+      stmt == Call (0, [0]) &
+      eval_stmto s p stmt q})
+  (fun q -> q#reify (St.prj_exn))))
+
+let call_eval_t3 _ = show(answer) (Stream.take (run q
+  (fun q -> let open Arg in
+            let open Tag in
+            let open Value in
+            let open St in
+            let open Stmt in
+            let open FunDecl in
+            ocanren {
+    fresh s, p, stmt in
+      s == St ([Std.pair 1 1; Std.pair 0 0], [Unit; Unit], 2, []) &
+      p == [FunDecl ([Ref], [Write 0])] &
+      stmt == Call (0, [1]) &
+      eval_stmto s p stmt q})
+  (fun q -> q#reify (St.prj_exn))))
+
+let call_eval_t4 _ = show(answer) (Stream.take (run q
+  (fun q -> let open Arg in
+            let open Tag in
+            let open Value in
+            let open St in
+            let open Stmt in
+            let open FunDecl in
+            ocanren {
+    fresh s, p, stmt in
+      s == St ([Std.pair 1 1; Std.pair 0 0], [Unit; Unit], 2, []) &
+      p == [FunDecl ([Ref; Ref], [Write 0; Write 1])] &
+      stmt == Call (0, [0; 1]) &
+      eval_stmto s p stmt q})
+  (fun q -> q#reify (St.prj_exn))))
+
+let call_eval_t5 _ = show(answer) (Stream.take (run q
+  (fun q -> let open Arg in
+            let open Tag in
+            let open Value in
+            let open St in
+            let open Stmt in
+            let open FunDecl in
+            ocanren {
+    fresh s, p, stmt in
+      s == St ([Std.pair 1 1; Std.pair 0 0], [Unit; Unit], 2, []) &
+      p == [FunDecl ([Ref; Ref], [Write 0; Write 1])] &
+      stmt == Call (0, [1; 0]) &
+      eval_stmto s p stmt q})
+  (fun q -> q#reify (St.prj_exn))))
+
+let mem_set_t1 _ = show(answer) (Stream.take (run q
+  (fun q -> let open Arg in
+            let open Tag in
+            let open Value in
+            let open St in
+            ocanren {
+    fresh s in
+      s == St ([Std.pair 0 0], [Bot], 1, []) &
+      mem_seto s 0 Unit q})
+  (fun q -> q#reify (St.prj_exn))))
+
+let mem_set_t2 _ = show(answer) (Stream.take (run q
+  (fun q -> let open Arg in
+            let open Tag in
+            let open Value in
+            let open St in
+            ocanren {
+    fresh s in
+      s == St ([Std.pair 0 0], [Unit], 1, []) &
+      mem_seto s 0 Bot q})
+  (fun q -> q#reify (St.prj_exn))))
+
+let meem_set_t3 _ = show(answer) (Stream.take (run q
+  (fun q -> let open Arg in
+            let open Tag in
+            let open Value in
+            let open St in
+            ocanren {
+    fresh s in
+      s == St ([Std.pair 0 1], [Unit; Unit], 2, []) &
+      mem_seto s 0 Bot q})
+  (fun q -> q#reify (St.prj_exn))))
+
+let add_arg_folder_t _ = show(answer) (Stream.take (run q
+  (fun q -> let open Arg in
+            let open Tag in
+            ocanren {
+    fresh s, s', cnt in
+      empty_stateo s &
+      empty_stateo s' &
+      add_arg_foldero s (Std.pair s' Nat.o) Val RValue (Std.pair q cnt) })
+  (fun q -> q#reify (St.prj_exn))))
+
+let foldl2_t _ = show(answer) (Stream.take (run q
+  (fun q -> let open Arg in
+            let open Tag in
+            ocanren {
+    fresh s, s', cnt, arg_tags, args in
+      arg_tags == [Val] &
+      args == [RValue] &
+      empty_stateo s &
+      empty_stateo s' &
+      list_foldl2o (add_arg_foldero s) (Std.pair s' Nat.o) arg_tags args (Std.pair q cnt) })
+  (fun q -> q#reify (St.prj_exn))))
+
+
+let rvalue_t _ = show(answerArgs) (Stream.take ~n:3 (run q
+  (fun q -> let open Arg in
+            ocanren {fresh v in List.mapo arg_to_rvalueo v q})
+  (fun q -> q#reify (List.prj_exn Arg.prj_exn))))
+
+(* empty state test *)
+let empty_state_t _ = show(answer) (Stream.take (run q
+  (fun q -> ocanren {empty_stateo q})
+  (fun q -> q#reify (St.prj_exn))))
+
+(* fun eval test *)
+let fun_eval_t1 _ = show(answer) (Stream.take (run q
+  (fun q -> (* let open Prog in *)
+            let open FunDecl in
+            let open Tag in
+            let open Stmt in
+            ocanren { fresh s, p, d in
+                        empty_stateo s &
+                        p == [] &
+                        d == FunDecl ([], []) &
+                        eval_fun_empty_argso s p d q })
+  (fun q -> q#reify (St.prj_exn))))
+
+(* fun eval test *)
+let fun_eval_t2 _ = show(answer) (Stream.take (run q
+  (fun q -> (* let open Prog in *)
+            let open FunDecl in
+            let open Tag in
+            let open Stmt in
+            ocanren { fresh s, p, d in
+                        empty_stateo s &
+                        p == [] &
+                        d == FunDecl ([Val], [Write 0; Read 0]) &
+                        eval_fun_empty_argso s p d q })
+  (fun q -> q#reify (St.prj_exn))))
+
+(* fun eval test *)
+let fun_eval_t3 _ = show(answer) (Stream.take (run q
+  (fun q -> (* let open Prog in *)
+            let open FunDecl in
+            let open Tag in
+            let open Stmt in
+            ocanren { fresh s, p, d in
+                        empty_stateo s &
+                        p == [FunDecl ([Ref], [Write 0])] &
+                        d == FunDecl ([Val], [Call (0, [0]); Read 0]) &
+                        eval_fun_empty_argso s p d q })
+  (fun q -> q#reify (St.prj_exn))))
+
+(* fun eval test *)
+let fun_eval_t4 _ = show(answer) (Stream.take (run q
+  (fun q -> (* let open Prog in *)
+            let open FunDecl in
+            let open Tag in
+            let open Stmt in
+            ocanren { fresh s, p, d in
+                        empty_stateo s &
+                        p == [FunDecl ([Ref], [Write 0])] &
+                        d == FunDecl ([Val; Val], [Call (0, [1]); Write 0; Read 1]) &
+                        eval_fun_empty_argso s p d q })
+  (fun q -> q#reify (St.prj_exn))))
+
+(* fun eval test *)
+let fun_eval_t5 _ = show(answer) (Stream.take (run q
+  (fun q -> (* let open Prog in *)
+            let open FunDecl in
+            let open Tag in
+            let open Stmt in
+            ocanren { fresh s, p, d in
+                        empty_stateo s &
+                        p == [FunDecl ([Ref; Ref], [Write 0; Write 1])] &
+                        d == FunDecl ([Val; Val], [Call (0, [1; 0]); Write 0; Read 0; Read 1]) &
+                        eval_fun_empty_argso s p d q })
+  (fun q -> q#reify (St.prj_exn))))
+
+(* prog eval test *)
+let prog_eval_t1 _ = show(answer) (Stream.take (run q
+  (fun q -> let open Prog in
+            let open FunDecl in
+            let open Tag in
+            let open Stmt in
+            ocanren {eval_progo (Prog ([], FunDecl ([Val], [Write 0; Read 0]))) q})
+  (fun q -> q#reify (St.prj_exn))))
+
+(* prog with func eval test *)
+let prog_eval_t2 _ = show(answer) (Stream.take (run q
+  (fun q -> let open Prog in
+            let open FunDecl in
+            let open Tag in
+            let open Stmt in
+            ocanren {eval_progo (Prog ([FunDecl ([Val], [Write 0; Read 0])], FunDecl ([Val], [Write 0; Read 0; Call (0, [0])]))) q})
+  (fun q -> q#reify (St.prj_exn))))
+
+(* prog with func eval test *)
+let prog_eval_t3 _ = show(answer) (Stream.take (run q
+  (fun q -> let open Prog in
+            let open FunDecl in
+            let open Tag in
+            let open Stmt in
+            ocanren {eval_progo (Prog ([FunDecl ([Ref], [Write 0; Read 0])], FunDecl ([Val], [Write 0; Read 0; Call (0, [0])]))) q})
+  (fun q -> q#reify (St.prj_exn))))
+
+(* prog with func eval test *)
+let prog_eval_t4 _ = show(answer) (Stream.take (run q
+  (fun q -> let open Prog in
+            let open FunDecl in
+            let open Tag in
+            let open Stmt in
+            ocanren {eval_progo (Prog ([FunDecl ([Ref], [Write 0])], FunDecl ([Val], [Call (0, [0]); Read 0]))) q})
+  (fun q -> q#reify (St.prj_exn))))
+
+(* annotation gen prog test *)
+let synt_t1 _ = show(answerTag) (Stream.take (run q
+  (fun q -> let open Prog in
+            let open FunDecl in
+            let open Tag in
+            let open Stmt in
+            let open St in
+            ocanren {eval_progo (Prog ([FunDecl ([q], [Write 0])], FunDecl ([Val], [Call (0, [0]); Read 0]))) (St ([], [], 0, []))})
+  (fun q -> q#reify (Tag.prj_exn))))
+
+(* annotation gen prog test *)
+let synt_t2 _ = show(answerTag) (Stream.take (run q
+  (fun q -> let open Prog in
+            let open FunDecl in
+            let open Tag in
+            let open Stmt in
+            let open St in
+            ocanren {eval_progo (Prog ([FunDecl ([q], [Write 0])], FunDecl ([Val], [Call (0, [0]); Write 0; Read 0]))) (St ([], [], 0, []))})
+  (fun q -> q#reify (Tag.prj_exn))))
+
+(* annotation gen prog test *)
+let synt_t3 _ = show(answerTags) (Stream.take (run qr
+  (fun q r -> let open Prog in
+            let open FunDecl in
+            let open Tag in
+            let open Stmt in
+            let open St in
+            ocanren {eval_progo (Prog ([FunDecl ([q], [Write 0])], FunDecl ([r], [Call (0, [0]); Write 0; Read 0]))) (St ([], [], 0, []))})
+  (fun q r -> [q#reify (Tag.prj_exn); r#reify (Tag.prj_exn)])))
+
+(* annotation gen prog test *)
+let synt_t4 _ = show(answerTags) (Stream.take (run q
+  (fun q -> let open Prog in
+            let open FunDecl in
+            let open Tag in
+            let open Stmt in
+            let open St in
+            ocanren {eval_progo (Prog ([FunDecl ([q], [Write 0])], FunDecl ([Val; Val], [Call (0, [1]); Write 0; Read 1]))) (St ([], [], 0, []))})
+  (fun q -> [q#reify (Tag.prj_exn)]))) (* -> [Val] *)
+
+(* annotation gen prog test *)
+let synt_t5 _ = show(answerTags) (Stream.take (run qr
+  (fun q r -> let open Prog in
+            let open FunDecl in
+            let open Tag in
+            let open Stmt in
+            let open St in
+            ocanren {eval_progo (Prog ([FunDecl ([q; r], [Write 0])], FunDecl ([Val; Val], [Call (0, [0; 1]); Write 0; Read 0]))) (St ([], [], 0, []))})
+  (fun q r -> [q#reify (Tag.prj_exn); r#reify (Tag.prj_exn)]))) (* all variants *)
+
+(* annotation gen prog test *)
+let synt_t6 _ = show(answerTags) (Stream.take (run qr
+  (fun q r -> let open Prog in
+            let open FunDecl in
+            let open Tag in
+            let open Stmt in
+            let open St in
+            ocanren {eval_progo (Prog ([FunDecl ([q; r], [Write 0])], FunDecl ([Val; Val], [Call (0, [1; 0]); Write 0; Read 0]))) (St ([], [], 0, []))})
+  (fun q r -> [q#reify (Tag.prj_exn); r#reify (Tag.prj_exn)]))) (* all variants *)
+
+(* annotation gen prog test *)
+let synt_t7 _ = show(answerTags) (Stream.take (run qr
+  (fun q r -> let open Prog in
+            let open FunDecl in
+            let open Tag in
+            let open Stmt in
+            let open St in
+            ocanren {eval_progo (Prog ([FunDecl ([q; r], [Write 0; Write 1])], FunDecl ([Val; Val], [Call (0, [0; 1]); Write 0; Read 0; Read 1]))) (St ([], [], 0, []))})
+  (fun q r -> [q#reify (Tag.prj_exn); r#reify (Tag.prj_exn)])))
+
+(* annotation gen prog test *)
+let synt_t8 _ = show(answerTags) (Stream.take (run qr
+  (fun q r -> let open Prog in
+            let open FunDecl in
+            let open Tag in
+            let open Stmt in
+            let open St in
+            ocanren {eval_progo (Prog ([FunDecl ([q; r], [Write 0; Write 1])], FunDecl ([Val; Val], [Call (0, [1; 0]); Write 0; Read 0; Read 1]))) (St ([], [], 0, []))})
+  (fun q r -> [q#reify (Tag.prj_exn); r#reify (Tag.prj_exn)])))
+
+(* annotation gen prog test *)
+let synt_t9 _ = show(answerTags) (Stream.take (run qr
+  (fun q r -> let open Prog in
+            let open FunDecl in
+            let open Tag in
+            let open Stmt in
+            let open St in
+            ocanren {eval_progo (Prog ([FunDecl ([q; r], [Write 0; Read 1])], FunDecl ([Val; Val], [Call (0, [0; 1]); Read 0; Read 1]))) (St ([], [], 0, []))})
+  (fun q r -> [q#reify (Tag.prj_exn); r#reify (Tag.prj_exn)])))
+
+(* prog with recursive function call *)
+let rec_eval_t _ = show(answer) (Stream.take (run q
+  (fun q -> let open Prog in
+            let open FunDecl in
+            let open Tag in
+            let open Stmt in
+            ocanren {eval_progo (Prog ([FunDecl ([Ref], [Write 0; Call (0, [0])])], FunDecl ([Val], [Call (0, [0]); Write 0; Read 0]))) q})
+  (fun q -> q#reify (St.prj_exn))))
+