src/HOL/ex/reflection.ML
author wenzelm
Wed Dec 31 15:30:10 2008 +0100 (2008-12-31)
changeset 29269 5c25a2012975
parent 24630 351a308ab58d
child 29273 285c00993bc2
permissions -rw-r--r--
moved term order operations to structure TermOrd (cf. Pure/term_ord.ML);
tuned signature of structure Term;
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(*  Author:     Amine Chaieb, TU Muenchen
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A trial for automatical reification.
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*)
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signature REFLECTION =
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sig
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  val genreify_tac: Proof.context -> thm list -> term option -> int -> tactic
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  val reflection_tac: Proof.context -> thm list -> thm list -> term option -> int -> tactic
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  val gen_reflection_tac: Proof.context -> (cterm -> thm)
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    -> thm list -> thm list -> term option -> int -> tactic
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end;
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structure Reflection : REFLECTION =
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struct
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val ext2 = thm "ext2";
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val nth_Cons_0 = thm "nth_Cons_0";
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val nth_Cons_Suc = thm "nth_Cons_Suc";
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  (* Make a congruence rule out of a defining equation for the interpretation *)
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  (* th is one defining equation of f, i.e.
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     th is "f (Cp ?t1 ... ?tn) = P(f ?t1, .., f ?tn)" *)
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  (* Cp is a constructor pattern and P is a pattern *)
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  (* The result is:
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      [|?A1 = f ?t1 ; .. ; ?An= f ?tn |] ==> P (?A1, .., ?An) = f (Cp ?t1 .. ?tn) *)
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  (*  + the a list of names of the A1 .. An, Those are fresh in the ctxt*)
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fun mk_congeq ctxt fs th = 
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  let 
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   val (f as Const(fN,fT)) = th |> prop_of |> HOLogic.dest_Trueprop |> HOLogic.dest_eq 
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				|> fst |> strip_comb |> fst
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   val thy = ProofContext.theory_of ctxt
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   val cert = Thm.cterm_of thy
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   val (((_,_),[th']), ctxt') = Variable.import_thms true [th] ctxt
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   val (lhs, rhs) = HOLogic.dest_eq (HOLogic.dest_Trueprop (Thm.prop_of th'))
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   fun add_fterms (t as t1 $ t2) = 
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       if exists (fn f => Term.could_unify (t |> strip_comb |> fst, f)) fs then insert (op aconv) t
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       else add_fterms t1 #> add_fterms t2
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     | add_fterms (t as Abs(xn,xT,t')) = 
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       if (fN mem (term_consts t)) then (fn _ => [t]) else (fn _ => [])
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     | add_fterms _ = I
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   val fterms = add_fterms rhs []
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   val (xs, ctxt'') = Variable.variant_fixes (replicate (length fterms) "x") ctxt'
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   val tys = map fastype_of fterms
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   val vs = map Free (xs ~~ tys)
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   val env = fterms ~~ vs
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		    (* FIXME!!!!*)	
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   fun replace_fterms (t as t1 $ t2) =
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       (case AList.lookup (op aconv) env t of
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	    SOME v => v
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	  | NONE => replace_fterms t1 $ replace_fterms t2)
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     | replace_fterms t = (case AList.lookup (op aconv) env t of
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			       SOME v => v
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			     | NONE => t)
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   fun mk_def (Abs(x,xT,t),v) = HOLogic.mk_Trueprop ((HOLogic.all_const xT)$ Abs(x,xT,HOLogic.mk_eq(v$(Bound 0), t)))
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     | mk_def (t, v) = HOLogic.mk_Trueprop (HOLogic.mk_eq (v, t))
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   fun tryext x = (x RS ext2 handle THM _ =>  x)
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   val cong = (Goal.prove ctxt'' [] (map mk_def env)
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			  (HOLogic.mk_Trueprop (HOLogic.mk_eq (lhs, replace_fterms rhs)))
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			  (fn x => LocalDefs.unfold_tac (#context x) (map tryext (#prems x)) 
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							THEN rtac th' 1)) RS sym
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   val (cong' :: vars') = 
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       Variable.export ctxt'' ctxt (cong :: map (Drule.mk_term o cert) vs)
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   val vs' = map (fst o fst o Term.dest_Var o Thm.term_of o Drule.dest_term) vars'
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  in  (vs', cong') end; 
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 (* congs is a list of pairs (P,th) where th is a theorem for *)
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        (* [| f p1 = A1; ...; f pn = An|] ==> f (C p1 .. pn) = P *)
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val FWD = curry (op OF);
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 (* da is the decomposition for atoms, ie. it returns ([],g) where g
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 returns the right instance f (AtC n) = t , where AtC is the Atoms
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 constructor and n is the number of the atom corresponding to t *)
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(* Generic decomp for reification : matches the actual term with the
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rhs of one cong rule. The result of the matching guides the
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proof synthesis: The matches of the introduced Variables A1 .. An are
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processed recursively
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 The rest is instantiated in the cong rule,i.e. no reification is needed *)
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exception REIF of string;
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val bds = ref ([]: (typ * ((term list) * (term list))) list);
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fun index_of t = 
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 let 
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  val tt = HOLogic.listT (fastype_of t)
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 in 
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  (case AList.lookup Type.could_unify (!bds) tt of
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    NONE => error "index_of : type not found in environements!"
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  | SOME (tbs,tats) =>
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    let
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     val i = find_index_eq t tats
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     val j = find_index_eq t tbs 
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    in (if j= ~1 then 
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	    if i= ~1 
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	    then (bds := AList.update Type.could_unify (tt,(tbs,tats@[t])) (!bds) ; 
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		  length tbs + length tats) 
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	    else i else j)
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    end)
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 end;
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fun dest_listT (Type ("List.list", [T])) = T;
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fun decomp_genreif da cgns (t,ctxt) =
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 let 
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  val thy = ProofContext.theory_of ctxt 
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  val cert = cterm_of thy
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  fun tryabsdecomp (s,ctxt) = 
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   (case s of 
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     Abs(xn,xT,ta) => 
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     (let
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       val ([xn],ctxt') = Variable.variant_fixes ["x"] ctxt
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       val (xn,ta) = variant_abs (xn,xT,ta)
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       val x = Free(xn,xT)
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       val _ = (case AList.lookup Type.could_unify (!bds) (HOLogic.listT xT)
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		 of NONE => error "tryabsdecomp: Type not found in the Environement"
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		  | SOME (bsT,atsT) => 
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		    (bds := AList.update Type.could_unify (HOLogic.listT xT, ((x::bsT), atsT)) (!bds)))
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      in ([(ta, ctxt')] , 
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	  fn [th] => ((let val (bsT,asT) = the(AList.lookup Type.could_unify (!bds) (HOLogic.listT xT))
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		       in (bds := AList.update Type.could_unify (HOLogic.listT xT,(tl bsT,asT)) (!bds))
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		       end) ; 
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		      hd (Variable.export ctxt' ctxt [(forall_intr (cert x) th) COMP allI])))
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	end)
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    | _ => da (s,ctxt))
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  in 
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  (case cgns of 
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    [] => tryabsdecomp (t,ctxt)
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  | ((vns,cong)::congs) => ((let
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        val cert = cterm_of thy
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	val certy = ctyp_of thy
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        val (tyenv, tmenv) =
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        Pattern.match thy
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        ((fst o HOLogic.dest_eq o HOLogic.dest_Trueprop) (concl_of cong), t)
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        (Envir.type_env (Envir.empty 0), Vartab.empty)
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        val (fnvs,invs) = List.partition (fn ((vn,_),_) => vn mem vns) (Vartab.dest tmenv)
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        val (fts,its) = 
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	    (map (snd o snd) fnvs,
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             map (fn ((vn,vi),(tT,t)) => (cert(Var ((vn,vi),tT)), cert t)) invs)
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	val ctyenv = map (fn ((vn,vi),(s,ty)) => (certy (TVar((vn,vi),s)), certy ty)) (Vartab.dest tyenv)
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    in (fts ~~ (replicate (length fts) ctxt), FWD (instantiate (ctyenv, its) cong))
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    end)
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      handle MATCH => decomp_genreif da congs (t,ctxt)))
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  end;
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 (* looks for the atoms equation and instantiates it with the right number *)
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fun mk_decompatom eqs (t,ctxt) =
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let 
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 val tT = fastype_of t
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 fun isat eq = 
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  let 
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   val rhs = eq |> prop_of |> HOLogic.dest_Trueprop |> HOLogic.dest_eq |> snd
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   in exists_Const 
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	  (fn (n,ty) => n="List.nth" 
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			andalso 
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			AList.defined Type.could_unify (!bds) (domain_type ty)) rhs 
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	  andalso Type.could_unify (fastype_of rhs, tT)
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   end
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 fun get_nths t acc = 
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  case t of
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    Const("List.nth",_)$vs$n => insert (fn ((a,_),(b,_)) => a aconv b) (t,(vs,n)) acc
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  | t1$t2 => get_nths t1 (get_nths t2 acc)
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  | Abs(_,_,t') => get_nths t'  acc
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  | _ => acc
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 fun 
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   tryeqs [] = error "Can not find the atoms equation"
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 | tryeqs (eq::eqs) = ((
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  let 
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   val rhs = eq |> prop_of |> HOLogic.dest_Trueprop  |> HOLogic.dest_eq |> snd
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   val nths = get_nths rhs []
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   val (vss,ns) = fold_rev (fn (_,(vs,n)) => fn (vss,ns) => 
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                             (insert (op aconv) vs vss, insert (op aconv) n ns)) nths ([],[]) 
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   val (vsns, ctxt') = Variable.variant_fixes (replicate (length vss) "vs") ctxt
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   val (xns, ctxt'') = Variable.variant_fixes (replicate (length nths) "x") ctxt' 
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   val thy = ProofContext.theory_of ctxt''
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   val cert = cterm_of thy
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   val certT = ctyp_of thy
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   val vsns_map = vss ~~ vsns
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   val xns_map = (fst (split_list nths)) ~~ xns
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   val subst = map (fn (nt, xn) => (nt, Var ((xn,0), fastype_of nt))) xns_map
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   val rhs_P = subst_free subst rhs
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   val (tyenv, tmenv) = Pattern.match 
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	                    thy (rhs_P, t)
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	                    (Envir.type_env (Envir.empty 0), Vartab.empty)
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   val sbst = Envir.subst_vars (tyenv, tmenv)
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   val sbsT = Envir.typ_subst_TVars tyenv
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   val subst_ty = map (fn (n,(s,t)) => (certT (TVar (n, s)), certT t)) 
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                      (Vartab.dest tyenv)
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   val tml = Vartab.dest tmenv
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   val t's = map (fn xn => snd (valOf (AList.lookup (op =) tml (xn,0)))) xns (* FIXME : Express with sbst*)
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   val subst_ns = map (fn (Const _ $ vs $ n, Var (xn0,T)) => 
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                          (cert n, snd (valOf (AList.lookup (op =) tml xn0)) 
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                             |> (index_of #> HOLogic.mk_nat #> cert))) 
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                      subst
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   val subst_vs = 
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    let 
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     fun ty (Const _ $ (vs as Var (vsn,lT)) $ n, Var (xn0,T)) = (certT T, certT (sbsT T))
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     fun h (Const _ $ (vs as Var (vsn,lT)) $ n, Var (xn0,T)) = 
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      let 
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       val cns = sbst (Const("List.list.Cons", T --> lT --> lT))
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       val lT' = sbsT lT
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       val (bsT,asT) = the (AList.lookup Type.could_unify (!bds) lT)
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       val vsn = valOf (AList.lookup (op =) vsns_map vs)
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       val cvs = cert (fold_rev (fn x => fn xs => cns$x$xs) bsT (Free (vsn, lT')))
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      in (cert vs, cvs) end
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    in map h subst end
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   val cts = map (fn ((vn,vi),(tT,t)) => (cert(Var ((vn,vi),tT)), cert t)) 
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                 (fold (AList.delete (fn (((a: string),_),(b,_)) => a = b)) 
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                       (map (fn n => (n,0)) xns) tml)
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   val substt = 
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    let val ih = Drule.cterm_rule (Thm.instantiate (subst_ty,[]))
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    in map (fn (v,t) => (ih v, ih t)) (subst_ns@subst_vs@cts)  end
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   val th = (instantiate (subst_ty, substt)  eq) RS sym
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  in  hd (Variable.export ctxt'' ctxt [th]) end)
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 handle MATCH => tryeqs eqs)
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in ([], fn _ => tryeqs (filter isat eqs))
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end;
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  (* Generic reification procedure: *)
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  (* creates all needed cong rules and then just uses the theorem synthesis *)
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  fun mk_congs ctxt raw_eqs = 
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 let
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  val fs = fold_rev (fn eq =>
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		     insert (op =) (eq |> prop_of |> HOLogic.dest_Trueprop 
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			 |> HOLogic.dest_eq |> fst |> strip_comb 
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			 |> fst)) raw_eqs []
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  val tys = fold_rev (fn f => fn ts => (f |> fastype_of |> binder_types |> tl) 
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				    union ts) fs []
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  val _ = bds := AList.make (fn _ => ([],[])) tys
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  val (vs, ctxt') = Variable.variant_fixes (replicate (length tys) "vs") ctxt
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  val thy = ProofContext.theory_of ctxt'
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  val cert = cterm_of thy
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  val vstys = map (fn (t,v) => (t,SOME (cert (Free(v,t))))) 
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		  (tys ~~ vs)
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  val is_Var = can dest_Var
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  fun insteq eq vs = 
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   let
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     val subst = map (fn (v as Var(n,t)) => (cert v, (valOf o valOf) (AList.lookup (op =) vstys t)))  
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  (filter is_Var vs)
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   in Thm.instantiate ([],subst) eq
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   end
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  val eqs = map (fn eq => eq |> prop_of |> HOLogic.dest_Trueprop 
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			     |> HOLogic.dest_eq |> fst |> strip_comb |> snd |> tl
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			     |> (insteq eq)) raw_eqs
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  val (ps,congs) = split_list (map (mk_congeq ctxt' fs) eqs)
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in ps ~~ (Variable.export ctxt' ctxt congs)
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end
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fun partition P [] = ([],[])
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  | partition P (x::xs) = 
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     let val (yes,no) = partition P xs
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     in if P x then (x::yes,no) else (yes, x::no) end
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fun rearrange congs = 
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let 
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 fun P (_, th) = 
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  let val @{term "Trueprop"}$(Const ("op =",_) $l$_) = concl_of th
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  in can dest_Var l end
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 val (yes,no) = partition P congs 
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 in no @ yes end
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fun genreif ctxt raw_eqs t =
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 let 
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  val congs = rearrange (mk_congs ctxt raw_eqs)
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  val th = divide_and_conquer (decomp_genreif (mk_decompatom raw_eqs) congs) (t,ctxt)
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  fun is_listVar (Var (_,t)) = can dest_listT t
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       | is_listVar _ = false
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  val vars = th |> prop_of |> HOLogic.dest_Trueprop |> HOLogic.dest_eq |> snd
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	       |> strip_comb |> snd |> filter is_listVar
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  val cert = cterm_of (ProofContext.theory_of ctxt)
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  val cvs = map (fn (v as Var(n,t)) => (cert v, the (AList.lookup Type.could_unify (!bds) t) |> snd |> HOLogic.mk_list (dest_listT t) |> cert)) vars
chaieb@23624
   284
  val th' = instantiate ([], cvs) th
chaieb@20564
   285
  val t' = (fst o HOLogic.dest_eq o HOLogic.dest_Trueprop o prop_of) th'
chaieb@23643
   286
  val th'' = Goal.prove ctxt [] [] (HOLogic.mk_Trueprop (HOLogic.mk_eq (t, t')))
wenzelm@24044
   287
			(fn _ => simp_tac (local_simpset_of ctxt) 1)
chaieb@20564
   288
  val _ = bds := []
chaieb@23624
   289
in FWD trans [th'',th']
chaieb@23624
   290
end
wenzelm@20319
   291
chaieb@23648
   292
chaieb@23648
   293
fun genreflect ctxt conv corr_thms raw_eqs t =
chaieb@23648
   294
let 
chaieb@23648
   295
  val reifth = genreif ctxt raw_eqs t
chaieb@23648
   296
  fun trytrans [] = error "No suitable correctness theorem found"
chaieb@23648
   297
    | trytrans (th::ths) = 
chaieb@23648
   298
         (FWD trans [reifth, th RS sym] handle THM _ => trytrans ths)
chaieb@23648
   299
  val th = trytrans corr_thms
chaieb@23648
   300
  val ft = (Thm.dest_arg1 o Thm.dest_arg o Thm.dest_arg o cprop_of) th
chaieb@23648
   301
  val rth = conv ft
chaieb@23648
   302
in simplify (HOL_basic_ss addsimps raw_eqs addsimps [nth_Cons_0, nth_Cons_Suc])
chaieb@23648
   303
           (simplify (HOL_basic_ss addsimps [rth]) th)
chaieb@23648
   304
end
wenzelm@20319
   305
wenzelm@20319
   306
fun genreify_tac ctxt eqs to i = (fn st =>
wenzelm@20319
   307
  let
wenzelm@20319
   308
    val P = HOLogic.dest_Trueprop (List.nth (prems_of st, i - 1))
wenzelm@20319
   309
    val t = (case to of NONE => P | SOME x => x)
wenzelm@20319
   310
    val th = (genreif ctxt eqs t) RS ssubst
wenzelm@20319
   311
  in rtac th i st
wenzelm@20319
   312
  end);
wenzelm@20319
   313
wenzelm@20319
   314
    (* Reflection calls reification and uses the correctness *)
wenzelm@20319
   315
        (* theorem assumed to be the dead of the list *)
chaieb@23648
   316
fun gen_reflection_tac ctxt conv corr_thms raw_eqs to i = (fn st =>
haftmann@21878
   317
  let
haftmann@21878
   318
    val P = HOLogic.dest_Trueprop (nth (prems_of st) (i - 1));
haftmann@21878
   319
    val t = the_default P to;
chaieb@23648
   320
    val th = genreflect ctxt conv corr_thms raw_eqs t
haftmann@21878
   321
      RS ssubst;
nipkow@23791
   322
  in (rtac th i THEN TRY(rtac TrueI i)) st end);
haftmann@21878
   323
nipkow@23791
   324
fun reflection_tac ctxt = gen_reflection_tac ctxt Codegen.evaluation_conv;
wenzelm@20797
   325
end