src/Tools/coherent.ML
author haftmann
Sun Sep 21 16:56:11 2014 +0200 (2014-09-21)
changeset 58410 6d46ad54a2ab
parent 55636 9d120886c50b
child 58839 ccda99401bc8
permissions -rw-r--r--
explicit separation of signed and unsigned numerals using existing lexical categories num and xnum
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(*  Title:      Tools/coherent.ML
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    Author:     Stefan Berghofer, TU Muenchen
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    Author:     Marc Bezem, Institutt for Informatikk, Universitetet i Bergen
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Prover for coherent logic, see e.g.
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  Marc Bezem and Thierry Coquand, Automating Coherent Logic, LPAR 2005
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for a description of the algorithm.
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*)
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signature COHERENT_DATA =
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sig
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  val atomize_elimL: thm
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  val atomize_exL: thm
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  val atomize_conjL: thm
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  val atomize_disjL: thm
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  val operator_names: string list
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end;
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signature COHERENT =
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sig
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  val trace: bool Config.T
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  val coherent_tac: Proof.context -> thm list -> int -> tactic
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end;
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functor Coherent(Data: COHERENT_DATA) : COHERENT =
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struct
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(** misc tools **)
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val (trace, trace_setup) = Attrib.config_bool @{binding coherent_trace} (K false);
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fun cond_trace ctxt msg = if Config.get ctxt trace then tracing (msg ()) else ();
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datatype cl_prf =
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  ClPrf of thm * (Type.tyenv * Envir.tenv) * ((indexname * typ) * term) list *
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  int list * (term list * cl_prf) list;
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val is_atomic = not o exists_Const (member (op =) Data.operator_names o #1);
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fun rulify_elim_conv ctxt ct =
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  if is_atomic (Logic.strip_imp_concl (term_of ct)) then Conv.all_conv ct
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  else Conv.concl_conv (length (Logic.strip_imp_prems (term_of ct)))
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    (Conv.rewr_conv (Thm.symmetric Data.atomize_elimL) then_conv
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     Raw_Simplifier.rewrite ctxt true (map Thm.symmetric
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       [Data.atomize_exL, Data.atomize_conjL, Data.atomize_disjL])) ct
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fun rulify_elim ctxt th = Simplifier.norm_hhf ctxt (Conv.fconv_rule (rulify_elim_conv ctxt) th);
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(* Decompose elimination rule of the form
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   A1 ==> ... ==> Am ==> (!!xs1. Bs1 ==> P) ==> ... ==> (!!xsn. Bsn ==> P) ==> P
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*)
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fun dest_elim prop =
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  let
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    val prems = Logic.strip_imp_prems prop;
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    val concl = Logic.strip_imp_concl prop;
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    val (prems1, prems2) =
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      take_suffix (fn t => Logic.strip_assums_concl t = concl) prems;
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  in
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    (prems1,
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     if null prems2 then [([], [concl])]
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     else map (fn t =>
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       (map snd (Logic.strip_params t), Logic.strip_assums_hyp t)) prems2)
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  end;
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fun mk_rule ctxt th =
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  let
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    val th' = rulify_elim ctxt th;
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    val (prems, cases) = dest_elim (prop_of th')
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  in (th', prems, cases) end;
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fun mk_dom ts = fold (fn t =>
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  Typtab.map_default (fastype_of t, []) (fn us => us @ [t])) ts Typtab.empty;
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val empty_env = (Vartab.empty, Vartab.empty);
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(* Find matcher that makes conjunction valid in given state *)
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fun valid_conj _ _ env [] = Seq.single (env, [])
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  | valid_conj ctxt facts env (t :: ts) =
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      Seq.maps (fn (u, x) => Seq.map (apsnd (cons x))
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        (valid_conj ctxt facts
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           (Pattern.match (Proof_Context.theory_of ctxt) (t, u) env) ts
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         handle Pattern.MATCH => Seq.empty))
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          (Seq.of_list (sort (int_ord o pairself snd) (Net.unify_term facts t)));
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(* Instantiate variables that only occur free in conlusion *)
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fun inst_extra_vars ctxt dom cs =
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  let
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    val vs = fold Term.add_vars (maps snd cs) [];
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    fun insts [] inst = Seq.single inst
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      | insts ((ixn, T) :: vs') inst =
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          Seq.maps (fn t => insts vs' (((ixn, T), t) :: inst))
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            (Seq.of_list
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              (case Typtab.lookup dom T of
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                NONE =>
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                  error ("Unknown domain: " ^
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                    Syntax.string_of_typ ctxt T ^ "\nfor term(s) " ^
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                    commas (maps (map (Syntax.string_of_term ctxt) o snd) cs))
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              | SOME ts => ts))
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  in
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    Seq.map (fn inst =>
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      (inst, map (apsnd (map (subst_Vars (map (apfst fst) inst)))) cs))
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        (insts vs [])
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  end;
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(* Check whether disjunction is valid in given state *)
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fun is_valid_disj _ _ [] = false
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  | is_valid_disj ctxt facts ((Ts, ts) :: ds) =
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      let val vs = map_index (fn (i, T) => Var (("x", i), T)) Ts in
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        (case Seq.pull (valid_conj ctxt facts empty_env
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            (map (fn t => subst_bounds (rev vs, t)) ts)) of
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          SOME _ => true
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        | NONE => is_valid_disj ctxt facts ds)
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      end;
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fun string_of_facts ctxt s facts =
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  Pretty.string_of (Pretty.big_list s
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    (map (Syntax.pretty_term ctxt) (map fst (sort (int_ord o pairself snd) (Net.content facts)))));
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fun valid ctxt rules goal dom facts nfacts nparams =
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  let
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    val seq =
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      Seq.of_list rules |> Seq.maps (fn (th, ps, cs) =>
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        valid_conj ctxt facts empty_env ps |> Seq.maps (fn (env as (tye, _), is) =>
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          let val cs' = map (fn (Ts, ts) =>
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            (map (Envir.subst_type tye) Ts, map (Envir.subst_term env) ts)) cs
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          in
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            inst_extra_vars ctxt dom cs' |>
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              Seq.map_filter (fn (inst, cs'') =>
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                if is_valid_disj ctxt facts cs'' then NONE
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                else SOME (th, env, inst, is, cs''))
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          end));
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  in
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    (case Seq.pull seq of
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      NONE =>
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        (if Context_Position.is_visible ctxt then
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          warning (string_of_facts ctxt "Countermodel found:" facts)
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         else (); NONE)
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    | SOME ((th, env, inst, is, cs), _) =>
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        if cs = [([], [goal])] then SOME (ClPrf (th, env, inst, is, []))
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        else
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          (case valid_cases ctxt rules goal dom facts nfacts nparams cs of
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            NONE => NONE
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          | SOME prfs => SOME (ClPrf (th, env, inst, is, prfs))))
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  end
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and valid_cases _ _ _ _ _ _ _ [] = SOME []
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  | valid_cases ctxt rules goal dom facts nfacts nparams ((Ts, ts) :: ds) =
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      let
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        val _ =
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          cond_trace ctxt (fn () =>
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            Pretty.string_of (Pretty.block
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              (Pretty.str "case" :: Pretty.brk 1 ::
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                Pretty.commas (map (Syntax.pretty_term ctxt) ts))));
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        val ps = map_index (fn (i, T) => ("par" ^ string_of_int (nparams + i), T)) Ts;
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        val (params, ctxt') = fold_map Variable.next_bound ps ctxt;
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        val ts' = map_index (fn (i, t) => (subst_bounds (rev params, t), nfacts + i)) ts;
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        val dom' =
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          fold (fn (T, p) => Typtab.map_default (T, []) (fn ps => ps @ [p])) (Ts ~~ params) dom;
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        val facts' = fold (fn (t, i) => Net.insert_term op = (t, (t, i))) ts' facts;
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      in
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        (case valid ctxt' rules goal dom' facts' (nfacts + length ts) (nparams + length Ts) of
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          NONE => NONE
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        | SOME prf =>
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            (case valid_cases ctxt rules goal dom facts nfacts nparams ds of
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              NONE => NONE
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            | SOME prfs => SOME ((params, prf) :: prfs)))
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      end;
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(** proof replaying **)
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fun thm_of_cl_prf ctxt goal asms (ClPrf (th, (tye, env), insts, is, prfs)) =
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  let
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    val thy = Proof_Context.theory_of ctxt;
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    val cert = Thm.cterm_of thy;
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    val certT = Thm.ctyp_of thy;
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    val _ =
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      cond_trace ctxt (fn () =>
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        Pretty.string_of (Pretty.big_list "asms:" (map (Display.pretty_thm ctxt) asms)));
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    val th' =
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      Drule.implies_elim_list
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        (Thm.instantiate
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           (map (fn (ixn, (S, T)) => (certT (TVar ((ixn, S))), certT T)) (Vartab.dest tye),
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            map (fn (ixn, (T, t)) =>
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              (cert (Var (ixn, Envir.subst_type tye T)), cert t)) (Vartab.dest env) @
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            map (fn (ixnT, t) => (cert (Var ixnT), cert t)) insts) th)
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        (map (nth asms) is);
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    val (_, cases) = dest_elim (prop_of th');
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  in
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    (case (cases, prfs) of
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      ([([], [_])], []) => th'
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    | ([([], [_])], [([], prf)]) => thm_of_cl_prf ctxt goal (asms @ [th']) prf
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    | _ =>
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        Drule.implies_elim_list
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          (Thm.instantiate (Thm.match
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             (Drule.strip_imp_concl (cprop_of th'), goal)) th')
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          (map (thm_of_case_prf ctxt goal asms) (prfs ~~ cases)))
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  end
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and thm_of_case_prf ctxt goal asms ((params, prf), (_, asms')) =
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  let
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    val thy = Proof_Context.theory_of ctxt;
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    val cert = Thm.cterm_of thy;
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    val cparams = map cert params;
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    val asms'' = map (cert o curry subst_bounds (rev params)) asms';
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    val (prems'', ctxt') = fold_map Thm.assume_hyps asms'' ctxt;
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  in
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    Drule.forall_intr_list cparams
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      (Drule.implies_intr_list asms'' (thm_of_cl_prf ctxt' goal (asms @ prems'') prf))
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  end;
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(** external interface **)
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fun coherent_tac ctxt rules = SUBPROOF (fn {prems, concl, params, context = ctxt', ...} =>
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  rtac (rulify_elim_conv ctxt' concl RS Drule.equal_elim_rule2) 1 THEN
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  SUBPROOF (fn {prems = prems', concl, context = ctxt'', ...} =>
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    let
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      val xs =
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        map (term_of o #2) params @
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        map (fn (_, s) => Free (s, the (Variable.default_type ctxt'' s)))
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          (rev (Variable.dest_fixes ctxt''))  (* FIXME !? *)
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    in
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      (case
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        valid ctxt'' (map (mk_rule ctxt'') (prems' @ prems @ rules)) (term_of concl)
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          (mk_dom xs) Net.empty 0 0 of
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        NONE => no_tac
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      | SOME prf => rtac (thm_of_cl_prf ctxt'' concl [] prf) 1)
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    end) ctxt' 1) ctxt;
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val _ = Theory.setup
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  (trace_setup #>
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   Method.setup @{binding coherent}
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    (Attrib.thms >> (fn rules => fn ctxt =>
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        METHOD (fn facts => HEADGOAL (coherent_tac ctxt (facts @ rules)))))
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      "prove coherent formula");
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end;