diff --git a/compiler/toy/dune b/compiler/toy/dune
new file mode 100644
index 00000000..0539ea11
--- /dev/null
+++ b/compiler/toy/dune
@@ -0,0 +1,7 @@
+(executable
+ (name scratch)
+ (package catala)
+ (public_name catala.toy)
+ (libraries cmdliner ubase ANSITerminal re bindlib catala.runtime_ocaml)
+ (preprocess
+  (pps ppx_yojson_conv)))
diff --git a/compiler/toy/scratch.ml b/compiler/toy/scratch.ml
new file mode 100644
index 00000000..6bc27159
--- /dev/null
+++ b/compiler/toy/scratch.ml
@@ -0,0 +1,166 @@
+(* λx.x *)
+type term =
+  | Var of term Bindlib.var
+  | Abs of (term, term) Bindlib.binder
+  | App of term * term
+
+let rec eval : term -> term =
+ fun t ->
+  match t with
+  | App (f, a) -> begin
+    match eval f with Abs b -> eval (Bindlib.subst b a) | _ -> t
+  end
+  | _ -> t
+
+module Expr = struct
+  open Bindlib
+
+  let mkfree : term var -> term = fun x -> Var x
+
+  let rec size : term -> int =
+   fun t ->
+    match t with
+    | Var _ -> 0
+    | Abs b ->
+      let _, t = unbind b in
+      1 + size t
+    | App (t, u) -> 1 + size t + size u
+
+  let var : term var -> term box = fun x -> box_var x
+
+  let abs_raw : (term, term) binder box -> term box =
+   fun b -> box_apply (fun b -> Abs b) b
+
+  let abs : term var -> term box -> term box = fun x t -> abs_raw (bind_var x t)
+
+  let app : term box -> term box -> term box =
+   fun t u -> box_apply2 (fun t u -> App (t, u)) t u
+
+  let rec box_term : term -> term box =
+   fun t ->
+    match t with
+    | Var x -> var x
+    | Abs b -> abs_raw (box_binder box_term b)
+    | App (t, u) -> app (box_term t) (box_term u)
+end
+
+module Var = struct
+  module Generic = struct
+    type t = RVar : 'e Bindlib.var -> t
+
+    let t v = RVar v
+    let get (RVar v) = Bindlib.copy_var v (fun x -> Var x) (Bindlib.name_of v)
+    let compare (RVar x) (RVar y) = Bindlib.compare_vars x y
+    let eq (RVar x) (RVar y) = Bindlib.eq_vars x y
+  end
+
+  module Map = struct
+    open Generic
+    open Map.Make (Generic)
+
+    type nonrec ('e, 'x) t = 'x t
+
+    let empty = empty
+    let singleton v x = singleton (t v) x
+    let add v x m = add (t v) x m
+    let update v f m = update (t v) f m
+    let find v m = find (t v) m
+    let find_opt v m = find_opt (t v) m
+    let bindings m = bindings m |> List.map (fun (v, x) -> get v, x)
+    let mem x m = mem (t x) m
+    let union f m1 m2 = union (fun v x1 x2 -> f (get v) x1 x2) m1 m2
+    let fold f m acc = fold (fun v x acc -> f (get v) x acc) m acc
+  end
+end
+
+(* λx.x *)
+let id : term =
+  let open Expr in
+  let x = Bindlib.new_var mkfree "x" in
+  Bindlib.unbox (abs x (var x))
+
+(* λx.λy.x *)
+let fst : term =
+  let open Expr in
+  let x = Bindlib.new_var mkfree "x" in
+  let y = Bindlib.new_var mkfree "x" in
+  Bindlib.unbox (abs x (abs y (var y)))
+
+(* λx.(x) x) (boxed) *)
+let delta : term Bindlib.box =
+  let open Expr in
+  let x = Bindlib.new_var mkfree "x" in
+  abs x (app (var x) (var x))
+
+(* (λx.(x) x) λx.(x) x *)
+let omega : term =
+  let open Expr in
+  Bindlib.unbox (app delta delta)
+
+(* λx.(x) x) *)
+let delta : term =
+  let open Expr in
+  Bindlib.unbox delta
+
+let rec to_string : Bindlib.ctxt -> term -> string =
+ fun ctxt t ->
+  match t with
+  | Var x -> Bindlib.name_of x
+  | Abs b ->
+    let x, t, ctxt = Bindlib.unbind_in ctxt b in
+    "λ" ^ Bindlib.name_of x ^ "." ^ to_string ctxt t
+  | App (t, u) -> "(" ^ to_string ctxt t ^ ") " ^ to_string ctxt u
+
+let to_string : term -> string =
+ fun t -> to_string (Bindlib.free_vars (Expr.box_term t)) t
+
+module P = struct
+  type term = Var of string | Abs of string * term | App of term * term
+  [@@deriving yojson]
+end
+
+let rec term_of_parseterm (ctx : ctx) (t : P.term) : term box =
+  let fix =
+    let ctx' = ctx in
+    let fix ?(ctx : ctx option) =
+      match ctx with
+      | None -> term_of_parseterm ctx'
+      | Some ctx -> term_of_parseterm ctx
+    in
+    fix
+  in
+  match t with
+  | P.Var x -> var (find_var ctx x)
+  | P.Abs (x, t) ->
+    let ctx = add_var ctx x in
+    abs (find_var ctx x) (fix ~ctx t)
+  | P.App (t1, t2) -> app (fix t1) (fix t2)
+
+let term_of_parseterm t : term = unbox (term_of_parseterm empty t)
+
+let rec parseterm_of_term (ctxt : ctxt) (t : term) : P.term =
+  match t with
+  | Var x -> P.Var (name_of x)
+  | Abs b ->
+    let x, t, ctxt = unbind_in ctxt b in
+    P.Abs (name_of x, parseterm_of_term ctxt t)
+  | App (t1, t2) -> P.App (parseterm_of_term ctxt t1, parseterm_of_term ctxt t2)
+
+let parseterm_of_term (t : term) : P.term =
+  parseterm_of_term (free_vars (box_term t)) t
+
+let _ =
+  ListLabels.iter
+    [id; fst; delta; omega; eval id]
+    ~f:(fun t ->
+      Format.printf "%d %s %a\n" (size t) (to_string t)
+        (Yojson.Safe.pretty_print ~std:true)
+        (P.yojson_of_term (parseterm_of_term t)))
+
+let _ =
+  assert (
+    ListLabels.for_all [id; fst; delta; omega] ~f:(fun t ->
+        let t' = parseterm_of_term t in
+        parseterm_of_term (term_of_parseterm t') = t'))
+
+let trans ctx e = assert false