(*  Title:      Pure/drule.ML

    ID:         $Id$

    Author:     Lawrence C Paulson, Cambridge University Computer Laboratory

    Copyright   1993  University of Cambridge

Derived rules and other operations on theorems.

*)

infix 0 RS RSN RL RLN MRS MRL OF COMP INCR_COMP COMP_INCR;

signature BASIC_DRULE =

sig

  val mk_implies: cterm * cterm -> cterm

  val list_implies: cterm list * cterm -> cterm

  val strip_imp_prems: cterm -> cterm list

  val strip_imp_concl: cterm -> cterm

  val cprems_of: thm -> cterm list

  val cterm_fun: (term -> term) -> (cterm -> cterm)

  val ctyp_fun: (typ -> typ) -> (ctyp -> ctyp)

  val read_insts: theory -> (indexname -> typ option) * (indexname -> sort option) ->

    (indexname -> typ option) * (indexname -> sort option) -> string list ->

    (indexname * string) list -> (ctyp * ctyp) list * (cterm * cterm) list

  val types_sorts: thm -> (indexname-> typ option) * (indexname-> sort option)

  val forall_intr_list: cterm list -> thm -> thm

  val forall_intr_frees: thm -> thm

  val forall_intr_vars: thm -> thm

  val forall_elim_list: cterm list -> thm -> thm

  val forall_elim_var: int -> thm -> thm

  val forall_elim_vars: int -> thm -> thm

  val gen_all: thm -> thm

  val lift_all: cterm -> thm -> thm

  val freeze_thaw: thm -> thm * (thm -> thm)

  val freeze_thaw_robust: thm -> thm * (int -> thm -> thm)

  val implies_elim_list: thm -> thm list -> thm

  val implies_intr_list: cterm list -> thm -> thm

  val instantiate: (ctyp * ctyp) list * (cterm * cterm) list -> thm -> thm

  val zero_var_indexes_list: thm list -> thm list

  val zero_var_indexes: thm -> thm

  val implies_intr_hyps: thm -> thm

  val standard: thm -> thm

  val standard': thm -> thm

  val rotate_prems: int -> thm -> thm

  val rearrange_prems: int list -> thm -> thm

  val RSN: thm * (int * thm) -> thm

  val RS: thm * thm -> thm

  val RLN: thm list * (int * thm list) -> thm list

  val RL: thm list * thm list -> thm list

  val MRS: thm list * thm -> thm

  val MRL: thm list list * thm list -> thm list

  val OF: thm * thm list -> thm

  val compose: thm * int * thm -> thm list

  val COMP: thm * thm -> thm

  val INCR_COMP: thm * thm -> thm

  val COMP_INCR: thm * thm -> thm

  val read_instantiate_sg: theory -> (string*string)list -> thm -> thm

  val read_instantiate: (string*string)list -> thm -> thm

  val cterm_instantiate: (cterm*cterm)list -> thm -> thm

  val size_of_thm: thm -> int

  val reflexive_thm: thm

  val symmetric_thm: thm

  val transitive_thm: thm

  val symmetric_fun: thm -> thm

  val extensional: thm -> thm

  val equals_cong: thm

  val imp_cong: thm

  val swap_prems_eq: thm

  val asm_rl: thm

  val cut_rl: thm

  val revcut_rl: thm

  val thin_rl: thm

  val triv_forall_equality: thm

  val distinct_prems_rl: thm

  val swap_prems_rl: thm

  val equal_intr_rule: thm

  val equal_elim_rule1: thm

  val equal_elim_rule2: thm

  val instantiate': ctyp option list -> cterm option list -> thm -> thm

end;

signature DRULE =

sig

  include BASIC_DRULE

  val generalize: string list * string list -> thm -> thm

  val list_comb: cterm * cterm list -> cterm

  val strip_comb: cterm -> cterm * cterm list

  val strip_type: ctyp -> ctyp list * ctyp

  val beta_conv: cterm -> cterm -> cterm

  val add_used: thm -> string list -> string list

  val flexflex_unique: thm -> thm

  val store_thm: bstring -> thm -> thm

  val store_standard_thm: bstring -> thm -> thm

  val store_thm_open: bstring -> thm -> thm

  val store_standard_thm_open: bstring -> thm -> thm

  val compose_single: thm * int * thm -> thm

  val imp_cong_rule: thm -> thm -> thm

  val arg_cong_rule: cterm -> thm -> thm

  val binop_cong_rule: cterm -> thm -> thm -> thm

  val fun_cong_rule: thm -> cterm -> thm

  val beta_eta_conversion: cterm -> thm

  val eta_long_conversion: cterm -> thm

  val eta_contraction_rule: thm -> thm

  val norm_hhf_eq: thm

  val is_norm_hhf: term -> bool

  val norm_hhf: theory -> term -> term

  val norm_hhf_cterm: cterm -> cterm

  val protect: cterm -> cterm

  val protectI: thm

  val protectD: thm

  val protect_cong: thm

  val implies_intr_protected: cterm list -> thm -> thm

  val termI: thm

  val mk_term: cterm -> thm

  val dest_term: thm -> cterm

  val cterm_rule: (thm -> thm) -> cterm -> cterm

  val term_rule: theory -> (thm -> thm) -> term -> term

  val dummy_thm: thm

  val sort_triv: theory -> typ * sort -> thm list

  val unconstrainTs: thm -> thm

  val with_subgoal: int -> (thm -> thm) -> thm -> thm

  val rename_bvars: (string * string) list -> thm -> thm

  val rename_bvars': string option list -> thm -> thm

  val incr_type_indexes: int -> thm -> thm

  val incr_indexes: thm -> thm -> thm

  val incr_indexes2: thm -> thm -> thm -> thm

  val remdups_rl: thm

  val multi_resolve: thm list -> thm -> thm Seq.seq

  val multi_resolves: thm list -> thm list -> thm Seq.seq

  val abs_def: thm -> thm

  val read_instantiate_sg': theory -> (indexname * string) list -> thm -> thm

  val read_instantiate': (indexname * string) list -> thm -> thm

end;

structure Drule: DRULE =

struct

(** some cterm->cterm operations: faster than calling cterm_of! **)

(* A1==>...An==>B  goes to  [A1,...,An], where B is not an implication *)

fun strip_imp_prems ct =

  let val (cA, cB) = Thm.dest_implies ct

  in cA :: strip_imp_prems cB end

  handle TERM _ => [];

(* A1==>...An==>B  goes to B, where B is not an implication *)

fun strip_imp_concl ct =

  (case Thm.term_of ct of

    Const ("==>", _) $ _ $ _ => strip_imp_concl (Thm.dest_arg ct)

  | _ => ct);

(*The premises of a theorem, as a cterm list*)

val cprems_of = strip_imp_prems o cprop_of;

fun cterm_fun f ct = Thm.cterm_of (Thm.theory_of_cterm ct) (f (Thm.term_of ct));

fun ctyp_fun f cT = Thm.ctyp_of (Thm.theory_of_ctyp cT) (f (Thm.typ_of cT));

fun certify t = Thm.cterm_of (Context.the_theory (Context.the_thread_data ())) t;

val implies = certify Term.implies;

fun mk_implies (A, B) = Thm.capply (Thm.capply implies A) B;

(*cterm version of list_implies: [A1,...,An], B  goes to [|A1;==>;An|]==>B *)

fun list_implies([], B) = B

  | list_implies(A::AS, B) = mk_implies (A, list_implies(AS,B));

(*cterm version of list_comb: maps  (f, [t1,...,tn])  to  f(t1,...,tn) *)

fun list_comb (f, []) = f

  | list_comb (f, t::ts) = list_comb (Thm.capply f t, ts);

(*cterm version of strip_comb: maps  f(t1,...,tn)  to  (f, [t1,...,tn]) *)

fun strip_comb ct =

  let

    fun stripc (p as (ct, cts)) =

      let val (ct1, ct2) = Thm.dest_comb ct

      in stripc (ct1, ct2 :: cts) end handle CTERM _ => p

  in stripc (ct, []) end;

(* cterm version of strip_type: maps  [T1,...,Tn]--->T  to   ([T1,T2,...,Tn], T) *)

fun strip_type cT = (case Thm.typ_of cT of

    Type ("fun", _) =>

      let

        val [cT1, cT2] = Thm.dest_ctyp cT;

        val (cTs, cT') = strip_type cT2

      in (cT1 :: cTs, cT') end

  | _ => ([], cT));

(*Beta-conversion for cterms, where x is an abstraction. Simply returns the rhs

  of the meta-equality returned by the beta_conversion rule.*)

fun beta_conv x y =

  Thm.dest_arg (cprop_of (Thm.beta_conversion false (Thm.capply x y)));

(** reading of instantiations **)

fun absent ixn =

  error("No such variable in term: " ^ Term.string_of_vname ixn);

fun inst_failure ixn =

  error("Instantiation of " ^ Term.string_of_vname ixn ^ " fails");

fun read_insts thy (rtypes,rsorts) (types,sorts) used insts =

let

    fun is_tv ((a, _), _) =

      (case Symbol.explode a of "'" :: _ => true | _ => false);

    val (tvs, vs) = List.partition is_tv insts;

    fun sort_of ixn = case rsorts ixn of SOME S => S | NONE => absent ixn;

    fun readT (ixn, st) =

        let val S = sort_of ixn;

            val T = Sign.read_def_typ (thy,sorts) st;

        in if Sign.typ_instance thy (T, TVar(ixn,S)) then (ixn,T)

           else inst_failure ixn

        end

    val tye = map readT tvs;

    fun mkty(ixn,st) = (case rtypes ixn of

                          SOME T => (ixn,(st,typ_subst_TVars tye T))

                        | NONE => absent ixn);

    val ixnsTs = map mkty vs;

    val ixns = map fst ixnsTs

    and sTs  = map snd ixnsTs

    val (cts,tye2) = Thm.read_def_cterms(thy,types,sorts) used false sTs;

    fun mkcVar(ixn,T) =

        let val U = typ_subst_TVars tye2 T

        in cterm_of thy (Var(ixn,U)) end

    val ixnTs = ListPair.zip(ixns, map snd sTs)

in (map (fn (ixn, T) => (ctyp_of thy (TVar (ixn, sort_of ixn)),

      ctyp_of thy T)) (tye2 @ tye),

    ListPair.zip(map mkcVar ixnTs,cts))

end;

(*** Find the type (sort) associated with a (T)Var or (T)Free in a term

     Used for establishing default types (of variables) and sorts (of

     type variables) when reading another term.

     Index -1 indicates that a (T)Free rather than a (T)Var is wanted.

***)

fun types_sorts thm =

  let

    val vars = Thm.fold_terms Term.add_vars thm [];

    val frees = Thm.fold_terms Term.add_frees thm [];

    val tvars = Thm.fold_terms Term.add_tvars thm [];

    val tfrees = Thm.fold_terms Term.add_tfrees thm [];

    fun types (a, i) =

      if i < 0 then AList.lookup (op =) frees a else AList.lookup (op =) vars (a, i);

    fun sorts (a, i) =

      if i < 0 then AList.lookup (op =) tfrees a else AList.lookup (op =) tvars (a, i);

  in (types, sorts) end;

val add_used =

  (Thm.fold_terms o fold_types o fold_atyps)

    (fn TFree (a, _) => insert (op =) a

      | TVar ((a, _), _) => insert (op =) a

      | _ => I);

(** Standardization of rules **)

(* type classes and sorts *)

fun sort_triv thy (T, S) =

  let

    val certT = Thm.ctyp_of thy;

    val cT = certT T;

    fun class_triv c =

      Thm.class_triv thy c

      |> Thm.instantiate ([(certT (TVar ((Name.aT, 0), [c])), cT)], []);

  in map class_triv S end;

fun unconstrainTs th =

  fold (Thm.unconstrainT o Thm.ctyp_of (Thm.theory_of_thm th) o TVar)

    (Thm.fold_terms Term.add_tvars th []) th;

(*Generalization over a list of variables*)

val forall_intr_list = fold_rev forall_intr;

(*Generalization over all suitable Free variables*)

fun forall_intr_frees th =

    let

      val thy = Thm.theory_of_thm th;

      val {prop, hyps, tpairs, ...} = rep_thm th;

      val fixed = fold Term.add_frees (Thm.terms_of_tpairs tpairs @ hyps) [];

      val frees = Term.fold_aterms (fn Free v =>

        if member (op =) fixed v then I else insert (op =) v | _ => I) prop [];

    in fold (forall_intr o cterm_of thy o Free) frees th end;

(*Generalization over Vars -- canonical order*)

fun forall_intr_vars th =

  fold forall_intr

    (map (Thm.cterm_of (Thm.theory_of_thm th) o Var) (Thm.fold_terms Term.add_vars th [])) th;

val forall_elim_var = PureThy.forall_elim_var;

val forall_elim_vars = PureThy.forall_elim_vars;

fun outer_params t =

  let val vs = Term.strip_all_vars t

  in Name.variant_list [] (map (Name.clean o #1) vs) ~~ map #2 vs end;

(*generalize outermost parameters*)

fun gen_all th =

  let

    val thy = Thm.theory_of_thm th;

    val {prop, maxidx, ...} = Thm.rep_thm th;

    val cert = Thm.cterm_of thy;

    fun elim (x, T) = Thm.forall_elim (cert (Var ((x, maxidx + 1), T)));

  in fold elim (outer_params prop) th end;

(*lift vars wrt. outermost goal parameters

  -- reverses the effect of gen_all modulo higher-order unification*)

fun lift_all goal th =

  let

    val thy = Theory.merge (Thm.theory_of_cterm goal, Thm.theory_of_thm th);

    val cert = Thm.cterm_of thy;

    val maxidx = Thm.maxidx_of th;

    val ps = outer_params (Thm.term_of goal)

      |> map (fn (x, T) => Var ((x, maxidx + 1), Logic.incr_tvar (maxidx + 1) T));

    val Ts = map Term.fastype_of ps;

    val inst = Thm.fold_terms Term.add_vars th [] |> map (fn (xi, T) =>

      (cert (Var (xi, T)), cert (Term.list_comb (Var (xi, Ts ---> T), ps))));

  in

    th |> Thm.instantiate ([], inst)

    |> fold_rev (Thm.forall_intr o cert) ps

  end;

(*direct generalization*)

fun generalize names th = Thm.generalize names (Thm.maxidx_of th + 1) th;

(*specialization over a list of cterms*)

val forall_elim_list = fold forall_elim;

(*maps A1,...,An |- B  to  [| A1;...;An |] ==> B*)

val implies_intr_list = fold_rev implies_intr;

(*maps [| A1;...;An |] ==> B and [A1,...,An]  to  B*)

fun implies_elim_list impth ths = fold Thm.elim_implies ths impth;

(*Reset Var indexes to zero, renaming to preserve distinctness*)

fun zero_var_indexes_list [] = []

  | zero_var_indexes_list ths =

      let

        val thy = Theory.merge_list (map Thm.theory_of_thm ths);

        val certT = Thm.ctyp_of thy and cert = Thm.cterm_of thy;

        val (instT, inst) = TermSubst.zero_var_indexes_inst (map Thm.full_prop_of ths);

        val cinstT = map (fn (v, T) => (certT (TVar v), certT T)) instT;

        val cinst = map (fn (v, t) => (cert (Var v), cert t)) inst;

      in map (Thm.adjust_maxidx_thm ~1 o Thm.instantiate (cinstT, cinst)) ths end;

val zero_var_indexes = singleton zero_var_indexes_list;

(** Standard form of object-rule: no hypotheses, flexflex constraints,

    Frees, or outer quantifiers; all generality expressed by Vars of index 0.**)

(*Discharge all hypotheses.*)

fun implies_intr_hyps th =

  fold Thm.implies_intr (#hyps (Thm.crep_thm th)) th;

(*Squash a theorem's flexflex constraints provided it can be done uniquely.

  This step can lose information.*)

fun flexflex_unique th =

  if null (tpairs_of th) then th else

    case distinct Thm.eq_thm (Seq.list_of (flexflex_rule th)) of

      [th] => th

    | []   => raise THM("flexflex_unique: impossible constraints", 0, [th])

    |  _   => raise THM("flexflex_unique: multiple unifiers", 0, [th]);

(* legacy standard operations *)

val standard' =

  implies_intr_hyps

  #> forall_intr_frees

  #> `Thm.maxidx_of

  #-> (fn maxidx =>

    forall_elim_vars (maxidx + 1)

    #> Thm.strip_shyps

    #> zero_var_indexes

    #> Thm.varifyT);

val standard =

  flexflex_unique

  #> standard'

  #> Thm.close_derivation;

(*Convert all Vars in a theorem to Frees.  Also return a function for

  reversing that operation.  DOES NOT WORK FOR TYPE VARIABLES.

  Similar code in type/freeze_thaw*)

fun freeze_thaw_robust th =

 let val fth = Thm.freezeT th

     val thy = Thm.theory_of_thm fth

     val {prop, tpairs, ...} = rep_thm fth

 in

   case List.foldr add_term_vars [] (prop :: Thm.terms_of_tpairs tpairs) of

       [] => (fth, fn i => fn x => x)   (*No vars: nothing to do!*)

     | vars =>

         let fun newName (Var(ix,_)) = (ix, gensym (string_of_indexname ix))

             val alist = map newName vars

             fun mk_inst (Var(v,T)) =

                 (cterm_of thy (Var(v,T)),

                  cterm_of thy (Free(((the o AList.lookup (op =) alist) v), T)))

             val insts = map mk_inst vars

             fun thaw i th' = (*i is non-negative increment for Var indexes*)

                 th' |> forall_intr_list (map #2 insts)

                     |> forall_elim_list (map (Thm.incr_indexes_cterm i o #1) insts)

         in  (Thm.instantiate ([],insts) fth, thaw)  end

 end;

(*Basic version of the function above. No option to rename Vars apart in thaw.

  The Frees created from Vars have nice names. FIXME: does not check for

  clashes with variables in the assumptions, so delete and use freeze_thaw_robust instead?*)

fun freeze_thaw th =

 let val fth = Thm.freezeT th

     val thy = Thm.theory_of_thm fth

     val {prop, tpairs, ...} = rep_thm fth

 in

   case List.foldr add_term_vars [] (prop :: Thm.terms_of_tpairs tpairs) of

       [] => (fth, fn x => x)

     | vars =>

         let fun newName (Var(ix,_), (pairs,used)) =

                   let val v = Name.variant used (string_of_indexname ix)

                   in  ((ix,v)::pairs, v::used)  end;

             val (alist, _) = List.foldr newName ([], Library.foldr add_term_names

               (prop :: Thm.terms_of_tpairs tpairs, [])) vars

             fun mk_inst (Var(v,T)) =

                 (cterm_of thy (Var(v,T)),

                  cterm_of thy (Free(((the o AList.lookup (op =) alist) v), T)))

             val insts = map mk_inst vars

             fun thaw th' =

                 th' |> forall_intr_list (map #2 insts)

                     |> forall_elim_list (map #1 insts)

         in  (Thm.instantiate ([],insts) fth, thaw)  end

 end;

(*Rotates a rule's premises to the left by k*)

fun rotate_prems 0 = I

  | rotate_prems k = permute_prems 0 k;

fun with_subgoal i f = rotate_prems (i - 1) #> f #> rotate_prems (1 - i);

(* permute prems, where the i-th position in the argument list (counting from 0)

   gives the position within the original thm to be transferred to position i.

   Any remaining trailing positions are left unchanged. *)

val rearrange_prems = let

  fun rearr new []      thm = thm

  |   rearr new (p::ps) thm = rearr (new+1)

     (map (fn q => if new<=q andalso q<p then q+1 else q) ps)

     (permute_prems (new+1) (new-p) (permute_prems new (p-new) thm))

  in rearr 0 end;

(*Resolution: exactly one resolvent must be produced.*)

fun tha RSN (i,thb) =

  case Seq.chop 2 (biresolution false [(false,tha)] i thb) of

      ([th],_) => th

    | ([],_)   => raise THM("RSN: no unifiers", i, [tha,thb])

    |      _   => raise THM("RSN: multiple unifiers", i, [tha,thb]);

(*resolution: P==>Q, Q==>R gives P==>R. *)

fun tha RS thb = tha RSN (1,thb);

(*For joining lists of rules*)

fun thas RLN (i,thbs) =

  let val resolve = biresolution false (map (pair false) thas) i

      fun resb thb = Seq.list_of (resolve thb) handle THM _ => []

  in maps resb thbs end;

fun thas RL thbs = thas RLN (1,thbs);

(*Resolve a list of rules against bottom_rl from right to left;

  makes proof trees*)

fun rls MRS bottom_rl =

  let fun rs_aux i [] = bottom_rl

        | rs_aux i (rl::rls) = rl RSN (i, rs_aux (i+1) rls)

  in  rs_aux 1 rls  end;

(*As above, but for rule lists*)

fun rlss MRL bottom_rls =

  let fun rs_aux i [] = bottom_rls

        | rs_aux i (rls::rlss) = rls RLN (i, rs_aux (i+1) rlss)

  in  rs_aux 1 rlss  end;

(*A version of MRS with more appropriate argument order*)

fun bottom_rl OF rls = rls MRS bottom_rl;

(*compose Q and [...,Qi,Q(i+1),...]==>R to [...,Q(i+1),...]==>R

  with no lifting or renaming!  Q may contain ==> or meta-quants

  ALWAYS deletes premise i *)

fun compose(tha,i,thb) =

    distinct Thm.eq_thm (Seq.list_of (bicompose false (false,tha,0) i thb));

fun compose_single (tha,i,thb) =

  case compose (tha,i,thb) of

    [th] => th

  | _ => raise THM ("compose: unique result expected", i, [tha,thb]);

(*compose Q and [Q1,Q2,...,Qk]==>R to [Q2,...,Qk]==>R getting unique result*)

fun tha COMP thb =

    case compose(tha,1,thb) of

        [th] => th

      | _ =>   raise THM("COMP", 1, [tha,thb]);

(** theorem equality **)

(*Useful "distance" function for BEST_FIRST*)

val size_of_thm = size_of_term o Thm.full_prop_of;

(*** Meta-Rewriting Rules ***)

val read_prop = certify o SimpleSyntax.read_prop;

fun store_thm name th =

  Context.>>> (Context.map_theory_result (PureThy.store_thm (name, th)));

fun store_thm_open name th =

  Context.>>> (Context.map_theory_result (PureThy.store_thm_open (name, th)));

fun store_standard_thm name th = store_thm name (standard th);

fun store_standard_thm_open name thm = store_thm_open name (standard' thm);

val reflexive_thm =

  let val cx = certify (Var(("x",0),TVar(("'a",0),[])))

  in store_standard_thm_open "reflexive" (Thm.reflexive cx) end;

val symmetric_thm =

  let val xy = read_prop "x::'a == y::'a"

  in store_standard_thm_open "symmetric" (Thm.implies_intr xy (Thm.symmetric (Thm.assume xy))) end;

val transitive_thm =

  let val xy = read_prop "x::'a == y::'a"

      val yz = read_prop "y::'a == z::'a"

      val xythm = Thm.assume xy and yzthm = Thm.assume yz

  in store_standard_thm_open "transitive" (Thm.implies_intr yz (Thm.transitive xythm yzthm)) end;

fun symmetric_fun thm = thm RS symmetric_thm;

fun extensional eq =

  let val eq' =

    abstract_rule "x" (Thm.dest_arg (fst (Thm.dest_equals (cprop_of eq)))) eq

  in equal_elim (eta_conversion (cprop_of eq')) eq' end;

val equals_cong =

  store_standard_thm_open "equals_cong" (Thm.reflexive (read_prop "x::'a == y::'a"));

val imp_cong =

  let

    val ABC = read_prop "A ==> B::prop == C::prop"

    val AB = read_prop "A ==> B"

    val AC = read_prop "A ==> C"

    val A = read_prop "A"

  in

    store_standard_thm_open "imp_cong" (implies_intr ABC (equal_intr

      (implies_intr AB (implies_intr A

        (equal_elim (implies_elim (assume ABC) (assume A))

          (implies_elim (assume AB) (assume A)))))

      (implies_intr AC (implies_intr A

        (equal_elim (symmetric (implies_elim (assume ABC) (assume A)))

          (implies_elim (assume AC) (assume A)))))))

  end;

val swap_prems_eq =

  let

    val ABC = read_prop "A ==> B ==> C"

    val BAC = read_prop "B ==> A ==> C"

    val A = read_prop "A"

    val B = read_prop "B"

  in

    store_standard_thm_open "swap_prems_eq" (equal_intr

      (implies_intr ABC (implies_intr B (implies_intr A

        (implies_elim (implies_elim (assume ABC) (assume A)) (assume B)))))

      (implies_intr BAC (implies_intr A (implies_intr B

        (implies_elim (implies_elim (assume BAC) (assume B)) (assume A))))))

  end;

val imp_cong_rule = Thm.combination o Thm.combination (Thm.reflexive implies);

fun arg_cong_rule ct th = Thm.combination (Thm.reflexive ct) th;    (*AP_TERM in LCF/HOL*)

fun fun_cong_rule th ct = Thm.combination th (Thm.reflexive ct);    (*AP_THM in LCF/HOL*)

fun binop_cong_rule ct th1 th2 = Thm.combination (arg_cong_rule ct th1) th2;

local

  val dest_eq = Thm.dest_equals o cprop_of

  val rhs_of = snd o dest_eq

in

fun beta_eta_conversion t =

  let val thm = beta_conversion true t

  in transitive thm (eta_conversion (rhs_of thm)) end

end;

fun eta_long_conversion ct = transitive (beta_eta_conversion ct)

  (symmetric (beta_eta_conversion (cterm_fun (Pattern.eta_long []) ct)));

(*Contract all eta-redexes in the theorem, lest they give rise to needless abstractions*)

fun eta_contraction_rule th =

  equal_elim (eta_conversion (cprop_of th)) th;

(* abs_def *)

(*

   f ?x1 ... ?xn == u

  --------------------

   f == %x1 ... xn. u

*)

local

fun contract_lhs th =

  Thm.transitive (Thm.symmetric (beta_eta_conversion

    (fst (Thm.dest_equals (cprop_of th))))) th;

fun var_args ct =

  (case try Thm.dest_comb ct of

    SOME (f, arg) =>

      (case Thm.term_of arg of

        Var ((x, _), _) => update (eq_snd (op aconvc)) (x, arg) (var_args f)

      | _ => [])

  | NONE => []);

in

fun abs_def th =

  let

    val th' = contract_lhs th;

    val args = var_args (Thm.lhs_of th');

  in contract_lhs (fold (uncurry Thm.abstract_rule) args th') end;

end;

(*** Some useful meta-theorems ***)

(*The rule V/V, obtains assumption solving for eresolve_tac*)

val asm_rl = store_standard_thm_open "asm_rl" (Thm.trivial (read_prop "?psi"));

val _ = store_thm "_" asm_rl;

(*Meta-level cut rule: [| V==>W; V |] ==> W *)

val cut_rl =

  store_standard_thm_open "cut_rl"

    (Thm.trivial (read_prop "?psi ==> ?theta"));

(*Generalized elim rule for one conclusion; cut_rl with reversed premises:

     [| PROP V;  PROP V ==> PROP W |] ==> PROP W *)

val revcut_rl =

  let val V = read_prop "V"

      and VW = read_prop "V ==> W";

  in

    store_standard_thm_open "revcut_rl"

      (implies_intr V (implies_intr VW (implies_elim (assume VW) (assume V))))

  end;

(*for deleting an unwanted assumption*)

val thin_rl =

  let val V = read_prop "V"

      and W = read_prop "W";

  in store_standard_thm_open "thin_rl" (implies_intr V (implies_intr W (assume W))) end;

(* (!!x. PROP ?V) == PROP ?V       Allows removal of redundant parameters*)

val triv_forall_equality =

  let val V  = read_prop "V"

      and QV = read_prop "!!x::'a. V"

      and x  = certify (Free ("x", Term.aT []));

  in

    store_standard_thm_open "triv_forall_equality"

      (equal_intr (implies_intr QV (forall_elim x (assume QV)))

        (implies_intr V  (forall_intr x (assume V))))

  end;

(* (PROP ?Phi ==> PROP ?Phi ==> PROP ?Psi) ==>

   (PROP ?Phi ==> PROP ?Psi)

*)

val distinct_prems_rl =

  let

    val AAB = read_prop "Phi ==> Phi ==> Psi"

    val A = read_prop "Phi";

  in

    store_standard_thm_open "distinct_prems_rl"

      (implies_intr_list [AAB, A] (implies_elim_list (assume AAB) [assume A, assume A]))

  end;

(* (PROP ?PhiA ==> PROP ?PhiB ==> PROP ?Psi) ==>

   (PROP ?PhiB ==> PROP ?PhiA ==> PROP ?Psi)

   `thm COMP swap_prems_rl' swaps the first two premises of `thm'

*)

val swap_prems_rl =

  let val cmajor = read_prop "PhiA ==> PhiB ==> Psi";

      val major = assume cmajor;

      val cminor1 = read_prop "PhiA";

      val minor1 = assume cminor1;

      val cminor2 = read_prop "PhiB";

      val minor2 = assume cminor2;

  in store_standard_thm_open "swap_prems_rl"

       (implies_intr cmajor (implies_intr cminor2 (implies_intr cminor1

         (implies_elim (implies_elim major minor1) minor2))))

  end;

(* [| PROP ?phi ==> PROP ?psi; PROP ?psi ==> PROP ?phi |]

   ==> PROP ?phi == PROP ?psi

   Introduction rule for == as a meta-theorem.

*)

val equal_intr_rule =

  let val PQ = read_prop "phi ==> psi"

      and QP = read_prop "psi ==> phi"

  in

    store_standard_thm_open "equal_intr_rule"

      (implies_intr PQ (implies_intr QP (equal_intr (assume PQ) (assume QP))))

  end;

(* PROP ?phi == PROP ?psi ==> PROP ?phi ==> PROP ?psi *)

val equal_elim_rule1 =

  let val eq = read_prop "phi::prop == psi::prop"

      and P = read_prop "phi"

  in store_standard_thm_open "equal_elim_rule1"

    (Thm.equal_elim (assume eq) (assume P) |> implies_intr_list [eq, P])

  end;

(* PROP ?psi == PROP ?phi ==> PROP ?phi ==> PROP ?psi *)

val equal_elim_rule2 =

  store_standard_thm_open "equal_elim_rule2" (symmetric_thm RS equal_elim_rule1);

(* "[| PROP ?phi; PROP ?phi; PROP ?psi |] ==> PROP ?psi" *)

val remdups_rl =

  let val P = read_prop "phi" and Q = read_prop "psi";

  in store_standard_thm_open "remdups_rl" (implies_intr_list [P, P, Q] (Thm.assume Q)) end;

(*(PROP ?phi ==> (!!x. PROP ?psi(x))) == (!!x. PROP ?phi ==> PROP ?psi(x))

  Rewrite rule for HHF normalization.*)

val norm_hhf_eq =

  let

    val aT = TFree ("'a", []);

    val all = Term.all aT;

    val x = Free ("x", aT);

    val phi = Free ("phi", propT);

    val psi = Free ("psi", aT --> propT);

    val cx = certify x;

    val cphi = certify phi;

    val lhs = certify (Logic.mk_implies (phi, all $ Abs ("x", aT, psi $ Bound 0)));

    val rhs = certify (all $ Abs ("x", aT, Logic.mk_implies (phi, psi $ Bound 0)));

  in

    Thm.equal_intr

      (Thm.implies_elim (Thm.assume lhs) (Thm.assume cphi)

        |> Thm.forall_elim cx

        |> Thm.implies_intr cphi

        |> Thm.forall_intr cx

        |> Thm.implies_intr lhs)

      (Thm.implies_elim

          (Thm.assume rhs |> Thm.forall_elim cx) (Thm.assume cphi)

        |> Thm.forall_intr cx

        |> Thm.implies_intr cphi

        |> Thm.implies_intr rhs)

    |> store_standard_thm_open "norm_hhf_eq"

  end;

val norm_hhf_prop = Logic.dest_equals (Thm.prop_of norm_hhf_eq);

fun is_norm_hhf tm =

  let

    fun is_norm (Const ("==>", _) $ _ $ (Const ("all", _) $ _)) = false

      | is_norm (t $ u) = is_norm t andalso is_norm u

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

      | is_norm _ = true;

  in is_norm (Envir.beta_eta_contract tm) end;

fun norm_hhf thy t =

  if is_norm_hhf t then t

  else Pattern.rewrite_term thy [norm_hhf_prop] [] t;

fun norm_hhf_cterm ct =

  if is_norm_hhf (Thm.term_of ct) then ct

  else cterm_fun (Pattern.rewrite_term (Thm.theory_of_cterm ct) [norm_hhf_prop] []) ct;

(* var indexes *)

(*Increment the indexes of only the type variables*)

fun incr_type_indexes inc th =

  let val tvs = term_tvars (prop_of th)

      and thy = theory_of_thm th

      fun inc_tvar ((a,i),s) = pairself (ctyp_of thy) (TVar ((a,i),s), TVar ((a,i+inc),s))

  in Thm.instantiate (map inc_tvar tvs, []) th end;

fun incr_indexes th = Thm.incr_indexes (Thm.maxidx_of th + 1);

fun incr_indexes2 th1 th2 =

  Thm.incr_indexes (Int.max (Thm.maxidx_of th1, Thm.maxidx_of th2) + 1);

fun th1 INCR_COMP th2 = incr_indexes th2 th1 COMP th2;

fun th1 COMP_INCR th2 = th1 COMP incr_indexes th1 th2;

(*** Instantiate theorem th, reading instantiations in theory thy ****)

(*Version that normalizes the result: Thm.instantiate no longer does that*)

fun instantiate instpair th =

  Thm.adjust_maxidx_thm ~1 (Thm.instantiate instpair th COMP_INCR asm_rl);

fun read_instantiate_sg' thy sinsts th =

    let val ts = types_sorts th;

        val used = add_used th [];

    in  instantiate (read_insts thy ts ts used sinsts) th  end;

fun read_instantiate_sg thy sinsts th =

  read_instantiate_sg' thy (map (apfst Syntax.read_indexname) sinsts) th;

(*Instantiate theorem th, reading instantiations under theory of th*)

fun read_instantiate sinsts th =

    read_instantiate_sg (Thm.theory_of_thm th) sinsts th;

fun read_instantiate' sinsts th =

    read_instantiate_sg' (Thm.theory_of_thm th) sinsts th;

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

  Instantiates distinct Vars by terms, inferring type instantiations. *)

local

  fun add_types ((ct,cu), (thy,tye,maxidx)) =

    let

        val thyt = Thm.theory_of_cterm ct;

        val thyu = Thm.theory_of_cterm cu;

        val {t, T, maxidx = maxt, ...} = Thm.rep_cterm ct;

        val {t = u, T = U, maxidx = maxu, ...} = Thm.rep_cterm cu;

        val maxi = Int.max(maxidx, Int.max(maxt, maxu));

        val thy' = Theory.merge(thy, Theory.merge(thyt, thyu))

        val (tye',maxi') = Sign.typ_unify thy' (T, U) (tye, maxi)

          handle Type.TUNIFY => raise TYPE ("Ill-typed instantiation:\nType\n" ^

            Sign.string_of_typ thy' (Envir.norm_type tye T) ^

            "\nof variable " ^

            Sign.string_of_term thy' (Term.map_types (Envir.norm_type tye) t) ^

            "\ncannot be unified with type\n" ^

            Sign.string_of_typ thy' (Envir.norm_type tye U) ^ "\nof term " ^

            Sign.string_of_term thy' (Term.map_types (Envir.norm_type tye) u),

            [T, U], [t, u])

    in  (thy', tye', maxi')  end;

in

fun cterm_instantiate [] th = th

  | cterm_instantiate ctpairs0 th =

  let val (thy,tye,_) = List.foldr add_types (Thm.theory_of_thm th, Vartab.empty, 0) ctpairs0

      fun instT(ct,cu) =

        let val inst = cterm_of thy o Term.map_types (Envir.norm_type tye) o term_of

        in (inst ct, inst cu) end

      fun ctyp2 (ixn, (S, T)) = (ctyp_of thy (TVar (ixn, S)), ctyp_of thy (Envir.norm_type tye T))

  in  instantiate (map ctyp2 (Vartab.dest tye), map instT ctpairs0) th  end

  handle TERM _ =>

           raise THM("cterm_instantiate: incompatible theories",0,[th])

       | TYPE (msg, _, _) => raise THM(msg, 0, [th])

end;

(** protected propositions and embedded terms **)

local

  val A = certify (Free ("A", propT));

  val get_axiom = Thm.unvarify o Thm.get_axiom (Context.the_theory (Context.the_thread_data ()));

  val prop_def = get_axiom "prop_def";

  val term_def = get_axiom "term_def";

in

  val protect = Thm.capply (certify Logic.protectC);

  val protectI = store_thm "protectI" (PureThy.kind_rule Thm.internalK (standard

      (Thm.equal_elim (Thm.symmetric prop_def) (Thm.assume A))));

  val protectD = store_thm "protectD" (PureThy.kind_rule Thm.internalK (standard

      (Thm.equal_elim prop_def (Thm.assume (protect A)))));

  val protect_cong = store_standard_thm_open "protect_cong" (Thm.reflexive (protect A));

  val termI = store_thm "termI" (PureThy.kind_rule Thm.internalK (standard

      (Thm.equal_elim (Thm.symmetric term_def) (Thm.forall_intr A (Thm.trivial A)))));

end;

fun implies_intr_protected asms th =

  let val asms' = map protect asms in

    implies_elim_list

      (implies_intr_list asms th)

      (map (fn asm' => Thm.assume asm' RS protectD) asms')

    |> implies_intr_list asms'

  end;

fun mk_term ct =

  let

    val thy = Thm.theory_of_cterm ct;

    val cert = Thm.cterm_of thy;

    val certT = Thm.ctyp_of thy;

    val T = Thm.typ_of (Thm.ctyp_of_term ct);

    val a = certT (TVar (("'a", 0), []));

    val x = cert (Var (("x", 0), T));

  in Thm.instantiate ([(a, certT T)], [(x, ct)]) termI end;

fun dest_term th =

  let val cprop = strip_imp_concl (Thm.cprop_of th) in

    if can Logic.dest_term (Thm.term_of cprop) then

      Thm.dest_arg cprop

    else raise THM ("dest_term", 0, [th])

  end;

fun cterm_rule f = dest_term o f o mk_term;

fun term_rule thy f t = Thm.term_of (cterm_rule f (Thm.cterm_of thy t));

val dummy_thm = mk_term (certify (Term.dummy_pattern propT));

(** variations on instantiate **)

(* instantiate by left-to-right occurrence of variables *)

fun instantiate' cTs cts thm =

  let

    fun err msg =

      raise TYPE ("instantiate': " ^ msg,

        map_filter (Option.map Thm.typ_of) cTs,

        map_filter (Option.map Thm.term_of) cts);

    fun inst_of (v, ct) =

      (Thm.cterm_of (Thm.theory_of_cterm ct) (Var v), ct)

        handle TYPE (msg, _, _) => err msg;

    fun tyinst_of (v, cT) =

      (Thm.ctyp_of (Thm.theory_of_ctyp cT) (TVar v), cT)

        handle TYPE (msg, _, _) => err msg;

    fun zip_vars xs ys =

      zip_options xs ys handle Library.UnequalLengths =>

        err "more instantiations than variables in thm";

    (*instantiate types first!*)

    val thm' =

      if forall is_none cTs then thm

      else Thm.instantiate

        (map tyinst_of (zip_vars (rev (Thm.fold_terms Term.add_tvars thm [])) cTs), []) thm;

    val thm'' =

      if forall is_none cts then thm'

      else Thm.instantiate

        ([], map inst_of (zip_vars (rev (Thm.fold_terms Term.add_vars thm' [])) cts)) thm';

    in thm'' end;

(** renaming of bound variables **)

(* replace bound variables x_i in thm by y_i *)

(* where vs = [(x_1, y_1), ..., (x_n, y_n)]  *)

fun rename_bvars [] thm = thm

  | rename_bvars vs thm =

      let

        val cert = Thm.cterm_of (Thm.theory_of_thm thm);

        fun ren (Abs (x, T, t)) = Abs (AList.lookup (op =) vs x |> the_default x, T, ren t)

          | ren (t $ u) = ren t $ ren u

          | ren t = t;

      in equal_elim (reflexive (cert (ren (Thm.prop_of thm)))) thm end;

(* renaming in left-to-right order *)

fun rename_bvars' xs thm =

  let

    val cert = Thm.cterm_of (Thm.theory_of_thm thm);

    val prop = Thm.prop_of thm;

    fun rename [] t = ([], t)

      | rename (x' :: xs) (Abs (x, T, t)) =

          let val (xs', t') = rename xs t

          in (xs', Abs (the_default x x', T, t')) end

      | rename xs (t $ u) =

          let

            val (xs', t') = rename xs t;

            val (xs'', u') = rename xs' u

          in (xs'', t' $ u') end

      | rename xs t = (xs, t);

  in case rename xs prop of

      ([], prop') => equal_elim (reflexive (cert prop')) thm

    | _ => error "More names than abstractions in theorem"

  end;

(** multi_resolve **)

local

fun res th i rule =

  Thm.biresolution false [(false, th)] i rule handle THM _ => Seq.empty;

fun multi_res _ [] rule = Seq.single rule

  | multi_res i (th :: ths) rule = Seq.maps (res th i) (multi_res (i + 1) ths rule);

in

val multi_resolve = multi_res 1;