src/HOL/ex/reflection.ML
 author chaieb Sun, 08 Jul 2007 19:01:28 +0200 changeset 23648 bccbf6138c30 parent 23643 32ee4111d1bc child 23791 e105381d4140 permissions -rw-r--r--
Try several correctness theorems for reflection; rearrange cong rules to avoid the absoption cases;
```
(*
ID:         \$Id\$
Author:     Amine Chaieb, TU Muenchen

A trial for automatical reification.
*)

signature REFLECTION = sig
val genreify_tac: Proof.context -> thm list -> term option -> int -> tactic
val reflection_tac: Proof.context -> thm list -> thm list -> term option -> int -> tactic
val gen_reflection_tac: Proof.context -> (cterm -> thm)
-> thm list -> thm list -> term option -> int -> tactic
end;

structure Reflection : REFLECTION
= struct

val ext2 = thm "ext2";
val nth_Cons_0 = thm "nth_Cons_0";
val nth_Cons_Suc = thm "nth_Cons_Suc";

(* Make a congruence rule out of a defining equation for the interpretation *)
(* th is one defining equation of f, i.e.
th is "f (Cp ?t1 ... ?tn) = P(f ?t1, .., f ?tn)" *)
(* Cp is a constructor pattern and P is a pattern *)

(* The result is:
[|?A1 = f ?t1 ; .. ; ?An= f ?tn |] ==> P (?A1, .., ?An) = f (Cp ?t1 .. ?tn) *)
(*  + the a list of names of the A1 .. An, Those are fresh in the ctxt*)

fun mk_congeq ctxt fs th =
let
val (f as Const(fN,fT)) = th |> prop_of |> HOLogic.dest_Trueprop |> HOLogic.dest_eq
|> fst |> strip_comb |> fst
val thy = ProofContext.theory_of ctxt
val cert = Thm.cterm_of thy
val (((_,_),[th']), ctxt') = Variable.import_thms true [th] ctxt
val (lhs, rhs) = HOLogic.dest_eq (HOLogic.dest_Trueprop (Thm.prop_of th'))
fun add_fterms (t as t1 \$ t2) =
if exists (fn f => could_unify (t |> strip_comb |> fst, f)) fs then insert (op aconv) t
| add_fterms (t as Abs(xn,xT,t')) =
if (fN mem (term_consts t)) then (fn _ => [t]) else (fn _ => [])
val fterms = add_fterms rhs []
val (xs, ctxt'') = Variable.variant_fixes (replicate (length fterms) "x") ctxt'
val tys = map fastype_of fterms
val vs = map Free (xs ~~ tys)
val env = fterms ~~ vs
(* FIXME!!!!*)
fun replace_fterms (t as t1 \$ t2) =
(case AList.lookup (op aconv) env t of
SOME v => v
| NONE => replace_fterms t1 \$ replace_fterms t2)
| replace_fterms t = (case AList.lookup (op aconv) env t of
SOME v => v
| NONE => t)

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)))
| mk_def (t, v) = HOLogic.mk_Trueprop (HOLogic.mk_eq (v, t))
fun tryext x = (x RS ext2 handle THM _ =>  x)
val cong = (Goal.prove ctxt'' [] (map mk_def env)
(HOLogic.mk_Trueprop (HOLogic.mk_eq (lhs, replace_fterms rhs)))
(fn x => LocalDefs.unfold_tac (#context x) (map tryext (#prems x))
THEN rtac th' 1)) RS sym

val (cong' :: vars') =
Variable.export ctxt'' ctxt (cong :: map (Drule.mk_term o cert) vs)
val vs' = map (fst o fst o Term.dest_Var o Thm.term_of o Drule.dest_term) vars'

in  (vs', cong') end;
(* congs is a list of pairs (P,th) where th is a theorem for *)
(* [| f p1 = A1; ...; f pn = An|] ==> f (C p1 .. pn) = P *)
val FWD = curry (op OF);

(* da is the decomposition for atoms, ie. it returns ([],g) where g
returns the right instance f (AtC n) = t , where AtC is the Atoms
constructor and n is the number of the atom corresponding to t *)

(* Generic decomp for reification : matches the actual term with the
rhs of one cong rule. The result of the matching guides the
proof synthesis: The matches of the introduced Variables A1 .. An are
processed recursively
The rest is instantiated in the cong rule,i.e. no reification is needed *)

exception REIF of string;

val bds = ref ([]: (typ * ((term list) * (term list))) list);

fun index_of t =
let
val tt = HOLogic.listT (fastype_of t)
in
(case AList.lookup Type.could_unify (!bds) tt of
| SOME (tbs,tats) =>
let
val i = find_index_eq t tats
val j = find_index_eq t tbs
in (if j= ~1 then
if i= ~1
then (bds := AList.update Type.could_unify (tt,(tbs,tats@[t])) (!bds) ;
length tbs + length tats)
else i else j)
end)
end;

fun dest_listT (Type ("List.list", [T])) = T;

fun decomp_genreif da cgns (t,ctxt) =
let
val thy = ProofContext.theory_of ctxt
val cert = cterm_of thy
fun tryabsdecomp (s,ctxt) =
(case s of
Abs(xn,xT,ta) =>
(let
val ([xn],ctxt') = Variable.variant_fixes ["x"] ctxt
val (xn,ta) = variant_abs (xn,xT,ta)
val x = Free(xn,xT)
val _ = (case AList.lookup Type.could_unify (!bds) (HOLogic.listT xT)
| SOME (bsT,atsT) =>
(bds := AList.update Type.could_unify (HOLogic.listT xT, ((x::bsT), atsT)) (!bds)))
in ([(ta, ctxt')] ,
fn [th] => ((let val (bsT,asT) = the(AList.lookup Type.could_unify (!bds) (HOLogic.listT xT))
in (bds := AList.update Type.could_unify (HOLogic.listT xT,(tl bsT,asT)) (!bds))
end) ;
hd (Variable.export ctxt' ctxt [(forall_intr (cert x) th) COMP allI])))
end)
| _ => da (s,ctxt))
in
(case cgns of
[] => tryabsdecomp (t,ctxt)
| ((vns,cong)::congs) => ((let
val cert = cterm_of thy
val certy = ctyp_of thy
val (tyenv, tmenv) =
Pattern.match thy
((fst o HOLogic.dest_eq o HOLogic.dest_Trueprop) (concl_of cong), t)
(Envir.type_env (Envir.empty 0),Term.Vartab.empty)
val (fnvs,invs) = List.partition (fn ((vn,_),_) => vn mem vns) (Vartab.dest tmenv)
val (fts,its) =
(map (snd o snd) fnvs,
map (fn ((vn,vi),(tT,t)) => (cert(Var ((vn,vi),tT)), cert t)) invs)
val ctyenv = map (fn ((vn,vi),(s,ty)) => (certy (TVar((vn,vi),s)), certy ty)) (Vartab.dest tyenv)
in (fts ~~ (replicate (length fts) ctxt), FWD (instantiate (ctyenv, its) cong))
end)
handle MATCH => decomp_genreif da congs (t,ctxt)))
end;

(* looks for the atoms equation and instantiates it with the right number *)

fun mk_decompatom eqs (t,ctxt) =
let
val tT = fastype_of t
fun isat eq =
let
val rhs = eq |> prop_of |> HOLogic.dest_Trueprop |> HOLogic.dest_eq |> snd
in exists_Const
(fn (n,ty) => n="List.nth"
andalso
AList.defined Type.could_unify (!bds) (domain_type ty)) rhs
andalso Type.could_unify (fastype_of rhs, tT)
end
fun get_nths t acc =
case t of
Const("List.nth",_)\$vs\$n => insert (fn ((a,_),(b,_)) => a aconv b) (t,(vs,n)) acc
| t1\$t2 => get_nths t1 (get_nths t2 acc)
| Abs(_,_,t') => get_nths t'  acc
| _ => acc

fun
tryeqs [] = error "Can not find the atoms equation"
| tryeqs (eq::eqs) = ((
let
val rhs = eq |> prop_of |> HOLogic.dest_Trueprop  |> HOLogic.dest_eq |> snd
val nths = get_nths rhs []
val (vss,ns) = fold_rev (fn (_,(vs,n)) => fn (vss,ns) =>
(insert (op aconv) vs vss, insert (op aconv) n ns)) nths ([],[])
val (vsns, ctxt') = Variable.variant_fixes (replicate (length vss) "vs") ctxt
val (xns, ctxt'') = Variable.variant_fixes (replicate (length nths) "x") ctxt'
val thy = ProofContext.theory_of ctxt''
val cert = cterm_of thy
val certT = ctyp_of thy
val vsns_map = vss ~~ vsns
val xns_map = (fst (split_list nths)) ~~ xns
val subst = map (fn (nt, xn) => (nt, Var ((xn,0), fastype_of nt))) xns_map
val rhs_P = subst_free subst rhs
val (tyenv, tmenv) = Pattern.match
thy (rhs_P, t)
(Envir.type_env (Envir.empty 0),Term.Vartab.empty)
val sbst = Envir.subst_vars (tyenv, tmenv)
val sbsT = Envir.typ_subst_TVars tyenv
val subst_ty = map (fn (n,(s,t)) => (certT (TVar (n, s)), certT t))
(Vartab.dest tyenv)
val tml = Vartab.dest tmenv
val t's = map (fn xn => snd (valOf (AList.lookup (op =) tml (xn,0)))) xns (* FIXME : Express with sbst*)
val subst_ns = map (fn (Const _ \$ vs \$ n, Var (xn0,T)) =>
(cert n, snd (valOf (AList.lookup (op =) tml xn0))
|> (index_of #> IntInf.fromInt #> HOLogic.mk_nat #> cert)))
subst
val subst_vs =
let
fun ty (Const _ \$ (vs as Var (vsn,lT)) \$ n, Var (xn0,T)) = (certT T, certT (sbsT T))
fun h (Const _ \$ (vs as Var (vsn,lT)) \$ n, Var (xn0,T)) =
let
val cns = sbst (Const("List.list.Cons", T --> lT --> lT))
val lT' = sbsT lT
val (bsT,asT) = the (AList.lookup Type.could_unify (!bds) lT)
val vsn = valOf (AList.lookup (op =) vsns_map vs)
val cvs = cert (fold_rev (fn x => fn xs => cns\$x\$xs) bsT (Free (vsn, lT')))
in (cert vs, cvs) end
in map h subst end
val cts = map (fn ((vn,vi),(tT,t)) => (cert(Var ((vn,vi),tT)), cert t))
(fold (AList.delete (fn (((a: string),_),(b,_)) => a = b))
(map (fn n => (n,0)) xns) tml)
val substt =
let val ih = Drule.cterm_rule (Thm.instantiate (subst_ty,[]))
in map (fn (v,t) => (ih v, ih t)) (subst_ns@subst_vs@cts)  end
val th = (instantiate (subst_ty, substt)  eq) RS sym
in  hd (Variable.export ctxt'' ctxt [th]) end)
handle MATCH => tryeqs eqs)
in ([], fn _ => tryeqs (filter isat eqs))
end;

(* Generic reification procedure: *)
(* creates all needed cong rules and then just uses the theorem synthesis *)

fun mk_congs ctxt raw_eqs =
let
val fs = fold_rev (fn eq =>
insert (op =) (eq |> prop_of |> HOLogic.dest_Trueprop
|> HOLogic.dest_eq |> fst |> strip_comb
|> fst)) raw_eqs []
val tys = fold_rev (fn f => fn ts => (f |> fastype_of |> binder_types |> tl)
union ts) fs []
val _ = bds := AList.make (fn _ => ([],[])) tys
val (vs, ctxt') = Variable.variant_fixes (replicate (length tys) "vs") ctxt
val thy = ProofContext.theory_of ctxt'
val cert = cterm_of thy
val vstys = map (fn (t,v) => (t,SOME (cert (Free(v,t)))))
(tys ~~ vs)
val is_Var = can dest_Var
fun insteq eq vs =
let
val subst = map (fn (v as Var(n,t)) => (cert v, (valOf o valOf) (AList.lookup (op =) vstys t)))
(filter is_Var vs)
in Thm.instantiate ([],subst) eq
end
val eqs = map (fn eq => eq |> prop_of |> HOLogic.dest_Trueprop
|> HOLogic.dest_eq |> fst |> strip_comb |> snd |> tl
|> (insteq eq)) raw_eqs
val (ps,congs) = split_list (map (mk_congeq ctxt' fs) eqs)
in ps ~~ (Variable.export ctxt' ctxt congs)
end

fun partition P [] = ([],[])
| partition P (x::xs) =
let val (yes,no) = partition P xs
in if P x then (x::yes,no) else (yes, x::no) end

fun rearrange congs =
let
fun P (_, th) =
let val @{term "Trueprop"}\$(Const ("op =",_) \$l\$_) = concl_of th
in can dest_Var l end
val (yes,no) = partition P congs
in no @ yes end

fun genreif ctxt raw_eqs t =
let
val congs = rearrange (mk_congs ctxt raw_eqs)
val th = divide_and_conquer (decomp_genreif (mk_decompatom raw_eqs) congs) (t,ctxt)
fun is_listVar (Var (_,t)) = can dest_listT t
| is_listVar _ = false
val vars = th |> prop_of |> HOLogic.dest_Trueprop |> HOLogic.dest_eq |> snd
|> strip_comb |> snd |> filter is_listVar
val cert = cterm_of (ProofContext.theory_of ctxt)
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
val th' = instantiate ([], cvs) th
val t' = (fst o HOLogic.dest_eq o HOLogic.dest_Trueprop o prop_of) th'
val th'' = Goal.prove ctxt [] [] (HOLogic.mk_Trueprop (HOLogic.mk_eq (t, t')))
(fn _ => Simp_tac 1)
val _ = bds := []
in FWD trans [th'',th']
end

fun genreflect ctxt conv corr_thms raw_eqs t =
let
val reifth = genreif ctxt raw_eqs t
fun trytrans [] = error "No suitable correctness theorem found"
| trytrans (th::ths) =
(FWD trans [reifth, th RS sym] handle THM _ => trytrans ths)
val th = trytrans corr_thms
val ft = (Thm.dest_arg1 o Thm.dest_arg o Thm.dest_arg o cprop_of) th
val rth = conv ft
end

fun genreify_tac ctxt eqs to i = (fn st =>
let
val P = HOLogic.dest_Trueprop (List.nth (prems_of st, i - 1))
val t = (case to of NONE => P | SOME x => x)
val th = (genreif ctxt eqs t) RS ssubst
in rtac th i st
end);

(* Reflection calls reification and uses the correctness *)
(* theorem assumed to be the dead of the list *)
fun gen_reflection_tac ctxt conv corr_thms raw_eqs to i = (fn st =>
let
val P = HOLogic.dest_Trueprop (nth (prems_of st) (i - 1));
val t = the_default P to;
val th = genreflect ctxt conv corr_thms raw_eqs t
RS ssubst;
in rtac th i st end);

fun reflection_tac ctxt = gen_reflection_tac ctxt NBE.normalization_conv;
end
```