(*  Title:      Tools/misc_legacy.ML

Misc legacy stuff -- to be phased out eventually.

*)

signature MISC_LEGACY =

sig

  val mk_defpair: term * term -> string * term

  val get_def: theory -> xstring -> thm

  val simple_read_term: theory -> typ -> string -> term

  val METAHYPS: (thm list -> tactic) -> int -> tactic

end;

structure Misc_Legacy: MISC_LEGACY =

struct

fun mk_defpair (lhs, rhs) =

  (case Term.head_of lhs of

    Const (name, _) =>

      (Long_Name.base_name name ^ "_def", Logic.mk_equals (lhs, rhs))

  | _ => raise TERM ("Malformed definition: head of lhs not a constant", [lhs, rhs]));

fun get_def thy = Thm.axiom thy o Name_Space.intern (Theory.axiom_space thy) o Thm.def_name;

fun simple_read_term thy T s =

  let

    val ctxt = ProofContext.init_global thy

      |> ProofContext.allow_dummies

      |> ProofContext.set_mode ProofContext.mode_schematic;

    val parse = if T = propT then Syntax.parse_prop else Syntax.parse_term;

  in parse ctxt s |> Type.constraint T |> Syntax.check_term ctxt end;

(**** METAHYPS -- tactical for using hypotheses as meta-level assumptions

       METAHYPS (fn prems => tac prems) i

converts subgoal i, of the form !!x1...xm. [| A1;...;An] ==> A into a new

proof state A==>A, supplying A1,...,An as meta-level assumptions (in

"prems").  The parameters x1,...,xm become free variables.  If the

resulting proof state is [| B1;...;Bk] ==> C (possibly assuming A1,...,An)

then it is lifted back into the original context, yielding k subgoals.

Replaces unknowns in the context by Frees having the prefix METAHYP_

New unknowns in [| B1;...;Bk] ==> C are lifted over x1,...,xm.

DOES NOT HANDLE TYPE UNKNOWNS.

NOTE: This version does not observe the proof context, and thus cannot

work reliably.  See also Subgoal.SUBPROOF and Subgoal.FOCUS for

properly localized variants of the same idea.

****)

local

(*Strips assumptions in goal yielding  ( [x1,...,xm], [H1,...,Hn], B )

    H1,...,Hn are the hypotheses;  x1...xm are variants of the parameters.

  Main difference from strip_assums concerns parameters:

    it replaces the bound variables by free variables.  *)

fun strip_context_aux (params, Hs, Const ("==>", _) $ H $ B) =

      strip_context_aux (params, H :: Hs, B)

  | strip_context_aux (params, Hs, Const ("all",_) $ Abs (a, T, t)) =

      let val (b, u) = Syntax.variant_abs (a, T, t)

      in strip_context_aux ((b, T) :: params, Hs, u) end

  | strip_context_aux (params, Hs, B) = (rev params, rev Hs, B);

fun strip_context A = strip_context_aux ([], [], A);

(*Left-to-right replacements: ctpairs = [...,(vi,ti),...].

  Instantiates distinct free variables by terms of same type.*)

fun free_instantiate ctpairs =

  forall_elim_list (map snd ctpairs) o forall_intr_list (map fst ctpairs);

fun free_of s ((a, i), T) =

  Free (s ^ (case i of 0 => a | _ => a ^ "_" ^ string_of_int i), T)

fun mk_inst v = (Var v, free_of "METAHYP1_" v)

fun metahyps_split_prem prem =

  let (*find all vars in the hyps -- should find tvars also!*)

      val hyps_vars = fold Term.add_vars (Logic.strip_assums_hyp prem) []

      val insts = map mk_inst hyps_vars

      (*replace the hyps_vars by Frees*)

      val prem' = subst_atomic insts prem

      val (params,hyps,concl) = strip_context prem'

  in (insts,params,hyps,concl)  end;

fun metahyps_aux_tac tacf (prem,gno) state =

  let val (insts,params,hyps,concl) = metahyps_split_prem prem

      val maxidx = Thm.maxidx_of state

      val cterm = Thm.cterm_of (Thm.theory_of_thm state)

      val chyps = map cterm hyps

      val hypths = map Thm.assume chyps

      val subprems = map (Thm.forall_elim_vars 0) hypths

      val fparams = map Free params

      val cparams = map cterm fparams

      fun swap_ctpair (t,u) = (cterm u, cterm t)

      (*Subgoal variables: make Free; lift type over params*)

      fun mk_subgoal_inst concl_vars (v, T) =

          if member (op =) concl_vars (v, T)

          then ((v, T), true, free_of "METAHYP2_" (v, T))

          else ((v, T), false, free_of "METAHYP2_" (v, map #2 params ---> T))

      (*Instantiate subgoal vars by Free applied to params*)

      fun mk_ctpair (v, in_concl, u) =

          if in_concl then (cterm (Var v), cterm u)

          else (cterm (Var v), cterm (list_comb (u, fparams)))

      (*Restore Vars with higher type and index*)

      fun mk_subgoal_swap_ctpair (((a, i), T), in_concl, u as Free (_, U)) =

          if in_concl then (cterm u, cterm (Var ((a, i), T)))

          else (cterm u, cterm (Var ((a, i + maxidx), U)))

      (*Embed B in the original context of params and hyps*)

      fun embed B = list_all_free (params, Logic.list_implies (hyps, B))

      (*Strip the context using elimination rules*)

      fun elim Bhyp = implies_elim_list (forall_elim_list cparams Bhyp) hypths

      (*A form of lifting that discharges assumptions.*)

      fun relift st =

        let val prop = Thm.prop_of st

            val subgoal_vars = (*Vars introduced in the subgoals*)

              fold Term.add_vars (Logic.strip_imp_prems prop) []

            and concl_vars = Term.add_vars (Logic.strip_imp_concl prop) []

            val subgoal_insts = map (mk_subgoal_inst concl_vars) subgoal_vars

            val st' = Thm.instantiate ([], map mk_ctpair subgoal_insts) st

            val emBs = map (cterm o embed) (prems_of st')

            val Cth  = implies_elim_list st' (map (elim o Thm.assume) emBs)

        in  (*restore the unknowns to the hypotheses*)

            free_instantiate (map swap_ctpair insts @

                              map mk_subgoal_swap_ctpair subgoal_insts)

                (*discharge assumptions from state in same order*)

                (implies_intr_list emBs

                  (forall_intr_list cparams (implies_intr_list chyps Cth)))

        end

      (*function to replace the current subgoal*)

      fun next st = Thm.bicompose false (false, relift st, nprems_of st) gno state

  in Seq.maps next (tacf subprems (Thm.trivial (cterm concl))) end;

fun print_vars_terms n thm =

  let

    val thy = theory_of_thm thm

    fun typed s ty =

      "  " ^ s ^ " has type: " ^ Syntax.string_of_typ_global thy ty;

    fun find_vars (Const (c, ty)) =

          if null (Term.add_tvarsT ty []) then I

          else insert (op =) (typed c ty)

      | find_vars (Var (xi, ty)) =

          insert (op =) (typed (Term.string_of_vname xi) ty)

      | find_vars (Free _) = I

      | find_vars (Bound _) = I

      | find_vars (Abs (_, _, t)) = find_vars t

      | find_vars (t1 $ t2) = find_vars t1 #> find_vars t2;

    val prem = Logic.nth_prem (n, Thm.prop_of thm)

    val tms = find_vars prem []

  in warning (cat_lines ("Found schematic vars in assumptions:" :: tms)) end;

in

fun METAHYPS tacf n thm = SUBGOAL (metahyps_aux_tac tacf) n thm

  handle THM("assume: variables",_,_) => (print_vars_terms n thm; Seq.empty)

end;

end;