src/HOL/Tools/SMT/z3_proof_tools.ML
author boehmes
Mon Dec 20 22:02:57 2010 +0100 (2010-12-20)
changeset 41328 6792a5c92a58
parent 41281 679118e35378
child 41899 83dd157ec9ab
permissions -rw-r--r--
avoid ML structure aliases (especially single-letter abbreviations)
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(*  Title:      HOL/Tools/SMT/z3_proof_tools.ML
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    Author:     Sascha Boehme, TU Muenchen
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Helper functions required for Z3 proof reconstruction.
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*)
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signature Z3_PROOF_TOOLS =
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sig
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  (*modifying terms*)
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  val as_meta_eq: cterm -> cterm
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  (*theorem nets*)
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  val thm_net_of: ('a -> thm) -> 'a list -> 'a Net.net
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  val net_instance': ((thm -> thm option) -> 'a -> 'a option) -> 'a Net.net ->
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    cterm -> 'a option
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  val net_instance: thm Net.net -> cterm -> thm option
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  (*proof combinators*)
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  val under_assumption: (thm -> thm) -> cterm -> thm
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  val with_conv: conv -> (cterm -> thm) -> cterm -> thm
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  val discharge: thm -> thm -> thm
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  val varify: string list -> thm -> thm
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  val unfold_eqs: Proof.context -> thm list -> conv
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  val match_instantiate: (cterm -> cterm) -> cterm -> thm -> thm
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  val by_tac: (int -> tactic) -> cterm -> thm
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  val make_hyp_def: thm -> Proof.context -> thm * Proof.context
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  val by_abstraction: bool * bool -> Proof.context -> thm list ->
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    (Proof.context -> cterm -> thm) -> cterm -> thm
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  (*a faster COMP*)
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  type compose_data
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  val precompose: (cterm -> cterm list) -> thm -> compose_data
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  val precompose2: (cterm -> cterm * cterm) -> thm -> compose_data
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  val compose: compose_data -> thm -> thm
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  (*unfolding of 'distinct'*)
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  val unfold_distinct_conv: conv
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  (*simpset*)
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  val add_simproc: Simplifier.simproc -> Context.generic -> Context.generic
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  val make_simpset: Proof.context -> thm list -> simpset
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end
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structure Z3_Proof_Tools: Z3_PROOF_TOOLS =
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struct
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(* modifying terms *)
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fun as_meta_eq ct =
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  uncurry SMT_Utils.mk_cequals (Thm.dest_binop (SMT_Utils.dest_cprop ct))
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(* theorem nets *)
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fun thm_net_of f xthms =
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  let fun insert xthm = Net.insert_term (K false) (Thm.prop_of (f xthm), xthm)
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  in fold insert xthms Net.empty end
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fun maybe_instantiate ct thm =
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  try Thm.first_order_match (Thm.cprop_of thm, ct)
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  |> Option.map (fn inst => Thm.instantiate inst thm)
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fun net_instance' f net ct =
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  let
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    val xthms = Net.match_term net (Thm.term_of ct)
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    fun first_of f ct = get_first (f (maybe_instantiate ct)) xthms 
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    fun first_of' f ct =
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      let val thm = Thm.trivial ct
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      in get_first (f (try (fn rule => rule COMP thm))) xthms end
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  in (case first_of f ct of NONE => first_of' f ct | some_thm => some_thm) end
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val net_instance = net_instance' I
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(* proof combinators *)
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fun under_assumption f ct =
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  let val ct' = SMT_Utils.mk_cprop ct
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  in Thm.implies_intr ct' (f (Thm.assume ct')) end
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fun with_conv conv prove ct =
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  let val eq = Thm.symmetric (conv ct)
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  in Thm.equal_elim eq (prove (Thm.lhs_of eq)) end
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fun discharge p pq = Thm.implies_elim pq p
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fun varify vars = Drule.generalize ([], vars)
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fun unfold_eqs _ [] = Conv.all_conv
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  | unfold_eqs ctxt eqs =
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      Conv.top_sweep_conv (K (Conv.rewrs_conv eqs)) ctxt
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fun match_instantiate f ct thm =
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  Thm.instantiate (Thm.match (f (Thm.cprop_of thm), ct)) thm
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fun by_tac tac ct = Goal.norm_result (Goal.prove_internal [] ct (K (tac 1)))
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(*
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   |- c x == t x ==> P (c x)
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  ---------------------------
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      c == t |- P (c x)
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*) 
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fun make_hyp_def thm ctxt =
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  let
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    val (lhs, rhs) = Thm.dest_binop (Thm.cprem_of thm 1)
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    val (cf, cvs) = Drule.strip_comb lhs
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    val eq = SMT_Utils.mk_cequals cf (fold_rev Thm.cabs cvs rhs)
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    fun apply cv th =
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      Thm.combination th (Thm.reflexive cv)
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      |> Conv.fconv_rule (Conv.arg_conv (Thm.beta_conversion false))
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  in
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    yield_singleton Assumption.add_assumes eq ctxt
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    |>> Thm.implies_elim thm o fold apply cvs
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  end
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(* abstraction *)
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local
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fun abs_context ctxt = (ctxt, Termtab.empty, 1, false)
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fun context_of (ctxt, _, _, _) = ctxt
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fun replace (_, (cv, ct)) = Thm.forall_elim ct o Thm.forall_intr cv
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fun abs_instantiate (_, tab, _, beta_norm) =
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  fold replace (Termtab.dest tab) #>
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  beta_norm ? Conv.fconv_rule (Thm.beta_conversion true)
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fun lambda_abstract cvs t =
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  let
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    val frees = map Free (Term.add_frees t [])
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    val cvs' = filter (fn cv => member (op aconv) frees (Thm.term_of cv)) cvs
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    val vs = map (Term.dest_Free o Thm.term_of) cvs'
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  in (Term.list_abs_free (vs, t), cvs') end
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fun fresh_abstraction cvs ct (cx as (ctxt, tab, idx, beta_norm)) =
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  let val (t, cvs') = lambda_abstract cvs (Thm.term_of ct)
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  in
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    (case Termtab.lookup tab t of
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      SOME (cv, _) => (Drule.list_comb (cv, cvs'), cx)
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    | NONE =>
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        let
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          val (n, ctxt') = yield_singleton Variable.variant_fixes "x" ctxt
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          val cv = SMT_Utils.certify ctxt'
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            (Free (n, map SMT_Utils.typ_of cvs' ---> SMT_Utils.typ_of ct))
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          val cu = Drule.list_comb (cv, cvs')
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          val e = (t, (cv, fold_rev Thm.cabs cvs' ct))
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          val beta_norm' = beta_norm orelse not (null cvs')
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        in (cu, (ctxt', Termtab.update e tab, idx + 1, beta_norm')) end)
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  end
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fun abs_comb f g cvs ct =
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  let val (cf, cu) = Thm.dest_comb ct
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  in f cvs cf ##>> g cvs cu #>> uncurry Thm.capply end
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fun abs_arg f = abs_comb (K pair) f
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fun abs_args f cvs ct =
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  (case Thm.term_of ct of
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    _ $ _ => abs_comb (abs_args f) f cvs ct
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  | _ => pair ct)
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fun abs_list f g cvs ct =
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  (case Thm.term_of ct of
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    Const (@{const_name Nil}, _) => pair ct
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  | Const (@{const_name Cons}, _) $ _ $ _ =>
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      abs_comb (abs_arg f) (abs_list f g) cvs ct
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  | _ => g cvs ct)
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fun abs_abs f cvs ct =
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  let val (cv, cu) = Thm.dest_abs NONE ct
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  in f (cv :: cvs) cu #>> Thm.cabs cv end
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val is_atomic = (fn _ $ _ => false | Abs _ => false | _ => true)
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fun abstract (ext_logic, with_theories) =
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  let
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    fun abstr1 cvs ct = abs_arg abstr cvs ct
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    and abstr2 cvs ct = abs_comb abstr1 abstr cvs ct
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    and abstr3 cvs ct = abs_comb abstr2 abstr cvs ct
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    and abstr_abs cvs ct = abs_arg (abs_abs abstr) cvs ct
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    and abstr cvs ct =
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      (case Thm.term_of ct of
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        @{const Trueprop} $ _ => abstr1 cvs ct
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      | @{const "==>"} $ _ $ _ => abstr2 cvs ct
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      | @{const True} => pair ct
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      | @{const False} => pair ct
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      | @{const Not} $ _ => abstr1 cvs ct
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      | @{const HOL.conj} $ _ $ _ => abstr2 cvs ct
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      | @{const HOL.disj} $ _ $ _ => abstr2 cvs ct
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      | @{const HOL.implies} $ _ $ _ => abstr2 cvs ct
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      | Const (@{const_name HOL.eq}, _) $ _ $ _ => abstr2 cvs ct
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      | Const (@{const_name distinct}, _) $ _ =>
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          if ext_logic then abs_arg (abs_list abstr fresh_abstraction) cvs ct
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          else fresh_abstraction cvs ct
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      | Const (@{const_name If}, _) $ _ $ _ $ _ =>
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          if ext_logic then abstr3 cvs ct else fresh_abstraction cvs ct
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      | Const (@{const_name All}, _) $ _ =>
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          if ext_logic then abstr_abs cvs ct else fresh_abstraction cvs ct
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      | Const (@{const_name Ex}, _) $ _ =>
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          if ext_logic then abstr_abs cvs ct else fresh_abstraction cvs ct
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      | t => (fn cx =>
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          if is_atomic t orelse can HOLogic.dest_number t then (ct, cx)
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          else if with_theories andalso
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            Z3_Interface.is_builtin_theory_term (context_of cx) t
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          then abs_args abstr cvs ct cx
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          else fresh_abstraction cvs ct cx))
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  in abstr [] end
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val cimp = Thm.cterm_of @{theory} @{const "==>"}
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fun with_prems thms f ct =
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  fold_rev (Thm.mk_binop cimp o Thm.cprop_of) thms ct
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  |> f
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  |> fold (fn prem => fn th => Thm.implies_elim th prem) thms
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in
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fun by_abstraction mode ctxt thms prove = with_prems thms (fn ct =>
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  let val (cu, cx) = abstract mode ct (abs_context ctxt)
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  in abs_instantiate cx (prove (context_of cx) cu) end)
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end
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(* a faster COMP *)
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type compose_data = cterm list * (cterm -> cterm list) * thm
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fun list2 (x, y) = [x, y]
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fun precompose f rule = (f (Thm.cprem_of rule 1), f, rule)
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fun precompose2 f rule = precompose (list2 o f) rule
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fun compose (cvs, f, rule) thm =
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  discharge thm (Thm.instantiate ([], cvs ~~ f (Thm.cprop_of thm)) rule)
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(* unfolding of 'distinct' *)
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local
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  val set1 = @{lemma "x ~: set [] == ~False" by simp}
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  val set2 = @{lemma "x ~: set [x] == False" by simp}
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  val set3 = @{lemma "x ~: set [y] == x ~= y" by simp}
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  val set4 = @{lemma "x ~: set (x # ys) == False" by simp}
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  val set5 = @{lemma "x ~: set (y # ys) == x ~= y & x ~: set ys" by simp}
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  fun set_conv ct =
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    (Conv.rewrs_conv [set1, set2, set3, set4] else_conv
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    (Conv.rewr_conv set5 then_conv Conv.arg_conv set_conv)) ct
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  val dist1 = @{lemma "distinct [] == ~False" by (simp add: distinct_def)}
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  val dist2 = @{lemma "distinct [x] == ~False" by (simp add: distinct_def)}
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  val dist3 = @{lemma "distinct (x # xs) == x ~: set xs & distinct xs"
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    by (simp add: distinct_def)}
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  fun binop_conv cv1 cv2 = Conv.combination_conv (Conv.arg_conv cv1) cv2
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in
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fun unfold_distinct_conv ct =
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  (Conv.rewrs_conv [dist1, dist2] else_conv
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  (Conv.rewr_conv dist3 then_conv binop_conv set_conv unfold_distinct_conv)) ct
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end
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(* simpset *)
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local
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  val antisym_le1 = mk_meta_eq @{thm order_class.antisym_conv}
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  val antisym_le2 = mk_meta_eq @{thm linorder_class.antisym_conv2}
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  val antisym_less1 = mk_meta_eq @{thm linorder_class.antisym_conv1}
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  val antisym_less2 = mk_meta_eq @{thm linorder_class.antisym_conv3}
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  fun eq_prop t thm = HOLogic.mk_Trueprop t aconv Thm.prop_of thm
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  fun dest_binop ((c as Const _) $ t $ u) = (c, t, u)
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    | dest_binop t = raise TERM ("dest_binop", [t])
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  fun prove_antisym_le ss t =
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    let
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      val (le, r, s) = dest_binop t
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      val less = Const (@{const_name less}, Term.fastype_of le)
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      val prems = Simplifier.prems_of_ss ss
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    in
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      (case find_first (eq_prop (le $ s $ r)) prems of
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        NONE =>
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          find_first (eq_prop (HOLogic.mk_not (less $ r $ s))) prems
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          |> Option.map (fn thm => thm RS antisym_less1)
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      | SOME thm => SOME (thm RS antisym_le1))
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    end
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    handle THM _ => NONE
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  fun prove_antisym_less ss t =
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    let
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      val (less, r, s) = dest_binop (HOLogic.dest_not t)
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      val le = Const (@{const_name less_eq}, Term.fastype_of less)
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      val prems = prems_of_ss ss
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    in
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      (case find_first (eq_prop (le $ r $ s)) prems of
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        NONE =>
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          find_first (eq_prop (HOLogic.mk_not (less $ s $ r))) prems
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          |> Option.map (fn thm => thm RS antisym_less2)
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      | SOME thm => SOME (thm RS antisym_le2))
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  end
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  handle THM _ => NONE
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  val basic_simpset = HOL_ss addsimps @{thms field_simps}
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    addsimps [@{thm times_divide_eq_right}, @{thm times_divide_eq_left}]
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    addsimps @{thms arith_special} addsimps @{thms less_bin_simps}
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    addsimps @{thms le_bin_simps} addsimps @{thms eq_bin_simps}
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    addsimps @{thms add_bin_simps} addsimps @{thms succ_bin_simps}
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    addsimps @{thms minus_bin_simps} addsimps @{thms pred_bin_simps}
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    addsimps @{thms mult_bin_simps} addsimps @{thms iszero_simps}
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    addsimps @{thms array_rules}
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    addsimps @{thms term_true_def} addsimps @{thms term_false_def}
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    addsimps @{thms z3div_def} addsimps @{thms z3mod_def}
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    addsimprocs [
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      Simplifier.simproc_global @{theory} "fast_int_arith" [
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        "(m::int) < n", "(m::int) <= n", "(m::int) = n"] (K Lin_Arith.simproc),
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      Simplifier.simproc_global @{theory} "antisym_le" ["(x::'a::order) <= y"]
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        (K prove_antisym_le),
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      Simplifier.simproc_global @{theory} "antisym_less" ["~ (x::'a::linorder) < y"]
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        (K prove_antisym_less)]
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  structure Simpset = Generic_Data
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  (
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    type T = simpset
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    val empty = basic_simpset
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    val extend = I
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    val merge = Simplifier.merge_ss
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  )
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in
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fun add_simproc simproc = Simpset.map (fn ss => ss addsimprocs [simproc])
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fun make_simpset ctxt rules =
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  Simplifier.context ctxt (Simpset.get (Context.Proof ctxt)) addsimps rules
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end
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end