theory Fv

imports "Nominal2_Atoms" "Nominal2_Eqvt" "Nominal2_Supp" "Abs"

begin

atom_decl name

datatype rlam =

  rVar "name"

| rApp "rlam" "rlam"

| rLam "name" "rlam"

ML {*

  open Datatype_Aux (* typ_of_dtyp, DtRec, ... *);

  fun mk_atom ty = Const (@{const_name atom}, ty --> @{typ atom})

*}

ML {* dest_Type @{typ rlam} *}

ML {*

  val {descr, ...} = Datatype.the_info @{theory} "Fv.rlam";

  val sorts = [];

  fun nth_dtyp i = typ_of_dtyp descr sorts (DtRec i);

  val fv_names = Datatype_Prop.indexify_names (map (fn (i, _) =>

    "fv_" ^ name_of_typ (nth_dtyp i)) descr);

  val fv_types = map (fn (i, _) => nth_dtyp i --> @{typ "atom set"}) descr;

  val fv_frees = map Free (fv_names ~~ fv_types);

  (* TODO: should be optimized to avoid {}+{}+{} *)

  fun mk_union sets = foldr1 (HOLogic.mk_binop @{const_name union}) sets;

  fun fv_eq_constr i (cname, dts) =

    let

      val Ts = map (typ_of_dtyp descr sorts) dts;

      val names = Name.variant_list ["pi"] (Datatype_Prop.make_tnames Ts);

      val args = map Free (names ~~ Ts);

      val c = Const (cname, Ts ---> (nth_dtyp i));

      val fv_c = Free (nth fv_names i, (nth_dtyp i) --> @{typ "atom set"});

      fun fv_arg (dt, x) =

        if is_rec_type dt then

          nth fv_frees (body_index dt) $ x

        (* TODO: we just assume everything is a 'name' *)

        else HOLogic.mk_set @{typ atom} [mk_atom (type_of x) $ x]

     in

      (Attrib.empty_binding, HOLogic.mk_Trueprop (HOLogic.mk_eq

        (fv_c $ list_comb (c, args), mk_union (map fv_arg (dts ~~ args)))))

    end;

  fun fv_eq (i, (_, _, constrs)) = map (fv_eq_constr i) constrs;

  val fv_eqs = maps fv_eq descr

*}

local_setup {*

snd o (Primrec.add_primrec

  (map (fn s => (Binding.name s, NONE, NoSyn)) fv_names) fv_eqs)

*}

print_theorems

fun

  fv_rlam :: "rlam \<Rightarrow> atom set"

where

  "fv_rlam (rVar a) = {atom a}"

| "fv_rlam (rApp t1 t2) = (fv_rlam t1) \<union> (fv_rlam t2)"

| "fv_rlam (rLam a t) = (fv_rlam t) - {atom a}"

end