(* Title: TFL/tfl.ML
ID: $Id$
Author: Konrad Slind, Cambridge University Computer Laboratory
Copyright 1997 University of Cambridge
First part of main module.
*)
signature PRIM =
sig
val trace: bool ref
val trace_thms: string -> thm list -> unit
val trace_cterms: string -> cterm list -> unit
type pattern
val mk_functional: theory -> term list -> {functional: term, pats: pattern list}
val wfrec_definition0: theory -> string -> term -> term -> theory * thm
val post_definition: thm list -> theory * (thm * pattern list) ->
{rules: thm,
rows: int list,
TCs: term list list,
full_pats_TCs: (term * term list) list}
val wfrec_eqns: theory -> xstring -> thm list -> term list ->
{WFR: term,
SV: term list,
proto_def: term,
extracta: (thm * term list) list,
pats: pattern list}
val lazyR_def: theory -> xstring -> thm list -> term list ->
{theory: theory,
rules: thm,
R: term,
SV: term list,
full_pats_TCs: (term * term list) list,
patterns : pattern list}
val mk_induction: theory ->
{fconst: term, R: term, SV: term list, pat_TCs_list: (term * term list) list} -> thm
val postprocess: bool -> {wf_tac: tactic, terminator: tactic, simplifier: cterm -> thm}
-> theory -> {rules: thm, induction: thm, TCs: term list list}
-> {rules: thm, induction: thm, nested_tcs: thm list}
end;
structure Prim: PRIM =
struct
val trace = ref false;
structure R = Rules;
structure S = USyntax;
structure U = Utils;
fun TFL_ERR func mesg = U.ERR {module = "Tfl", func = func, mesg = mesg};
val concl = #2 o R.dest_thm;
val hyp = #1 o R.dest_thm;
val list_mk_type = U.end_itlist (curry (op -->));
fun enumerate xs = ListPair.zip(xs, 0 upto (length xs - 1));
fun front_last [] = raise TFL_ERR "front_last" "empty list"
| front_last [x] = ([],x)
| front_last (h::t) =
let val (pref,x) = front_last t
in
(h::pref,x)
end;
(*---------------------------------------------------------------------------
* The next function is common to pattern-match translation and
* proof of completeness of cases for the induction theorem.
*
* The curried function "gvvariant" returns a function to generate distinct
* variables that are guaranteed not to be in names. The names of
* the variables go u, v, ..., z, aa, ..., az, ... The returned
* function contains embedded refs!
*---------------------------------------------------------------------------*)
fun gvvariant names =
let val slist = ref names
val vname = ref "u"
fun new() =
if !vname mem_string (!slist)
then (vname := Symbol.bump_string (!vname); new())
else (slist := !vname :: !slist; !vname)
in
fn ty => Free(new(), ty)
end;
(*---------------------------------------------------------------------------
* Used in induction theorem production. This is the simple case of
* partitioning up pattern rows by the leading constructor.
*---------------------------------------------------------------------------*)
fun ipartition gv (constructors,rows) =
let fun pfail s = raise TFL_ERR "partition.part" s
fun part {constrs = [], rows = [], A} = rev A
| part {constrs = [], rows = _::_, A} = pfail"extra cases in defn"
| part {constrs = _::_, rows = [], A} = pfail"cases missing in defn"
| part {constrs = c::crst, rows, A} =
let val (c, T) = dest_Const c
val L = binder_types T
val (in_group, not_in_group) =
fold_rev (fn (row as (p::rst, rhs)) =>
fn (in_group,not_in_group) =>
let val (pc,args) = S.strip_comb p
in if (#1(dest_Const pc) = c)
then ((args@rst, rhs)::in_group, not_in_group)
else (in_group, row::not_in_group)
end) rows ([],[])
val col_types = U.take type_of (length L, #1(hd in_group))
in
part{constrs = crst, rows = not_in_group,
A = {constructor = c,
new_formals = map gv col_types,
group = in_group}::A}
end
in part{constrs = constructors, rows = rows, A = []}
end;
(*---------------------------------------------------------------------------
* Each pattern carries with it a tag (i,b) where
* i is the clause it came from and
* b=true indicates that clause was given by the user
* (or is an instantiation of a user supplied pattern)
* b=false --> i = ~1
*---------------------------------------------------------------------------*)
type pattern = term * (int * bool)
fun pattern_map f (tm,x) = (f tm, x);
fun pattern_subst theta = pattern_map (subst_free theta);
val pat_of = fst;
fun row_of_pat x = fst (snd x);
fun given x = snd (snd x);
(*---------------------------------------------------------------------------
* Produce an instance of a constructor, plus genvars for its arguments.
*---------------------------------------------------------------------------*)
fun fresh_constr ty_match colty gv c =
let val (_,Ty) = dest_Const c
val L = binder_types Ty
and ty = body_type Ty
val ty_theta = ty_match ty colty
val c' = S.inst ty_theta c
val gvars = map (S.inst ty_theta o gv) L
in (c', gvars)
end;
(*---------------------------------------------------------------------------
* Goes through a list of rows and picks out the ones beginning with a
* pattern with constructor = name.
*---------------------------------------------------------------------------*)
fun mk_group name rows =
fold_rev (fn (row as ((prfx, p::rst), rhs)) =>
fn (in_group,not_in_group) =>
let val (pc,args) = S.strip_comb p
in if ((#1 (Term.dest_Const pc) = name) handle TERM _ => false)
then (((prfx,args@rst), rhs)::in_group, not_in_group)
else (in_group, row::not_in_group) end)
rows ([],[]);
(*---------------------------------------------------------------------------
* Partition the rows. Not efficient: we should use hashing.
*---------------------------------------------------------------------------*)
fun partition _ _ (_,_,_,[]) = raise TFL_ERR "partition" "no rows"
| partition gv ty_match
(constructors, colty, res_ty, rows as (((prfx,_),_)::_)) =
let val fresh = fresh_constr ty_match colty gv
fun part {constrs = [], rows, A} = rev A
| part {constrs = c::crst, rows, A} =
let val (c',gvars) = fresh c
val (in_group, not_in_group) = mk_group (#1 (dest_Const c')) rows
val in_group' =
if (null in_group) (* Constructor not given *)
then [((prfx, #2(fresh c)), (S.ARB res_ty, (~1,false)))]
else in_group
in
part{constrs = crst,
rows = not_in_group,
A = {constructor = c',
new_formals = gvars,
group = in_group'}::A}
end
in part{constrs=constructors, rows=rows, A=[]}
end;
(*---------------------------------------------------------------------------
* Misc. routines used in mk_case
*---------------------------------------------------------------------------*)
fun mk_pat (c,l) =
let val L = length (binder_types (type_of c))
fun build (prfx,tag,plist) =
let val args = Library.take (L,plist)
and plist' = Library.drop(L,plist)
in (prfx,tag,list_comb(c,args)::plist') end
in map build l end;
fun v_to_prfx (prfx, v::pats) = (v::prfx,pats)
| v_to_prfx _ = raise TFL_ERR "mk_case" "v_to_prfx";
fun v_to_pats (v::prfx,tag, pats) = (prfx, tag, v::pats)
| v_to_pats _ = raise TFL_ERR "mk_case" "v_to_pats";
(*----------------------------------------------------------------------------
* Translation of pattern terms into nested case expressions.
*
* This performs the translation and also builds the full set of patterns.
* Thus it supports the construction of induction theorems even when an
* incomplete set of patterns is given.
*---------------------------------------------------------------------------*)
fun mk_case ty_info ty_match usednames range_ty =
let
fun mk_case_fail s = raise TFL_ERR "mk_case" s
val fresh_var = gvvariant usednames
val divide = partition fresh_var ty_match
fun expand constructors ty ((_,[]), _) = mk_case_fail"expand_var_row"
| expand constructors ty (row as ((prfx, p::rst), rhs)) =
if (is_Free p)
then let val fresh = fresh_constr ty_match ty fresh_var
fun expnd (c,gvs) =
let val capp = list_comb(c,gvs)
in ((prfx, capp::rst), pattern_subst[(p,capp)] rhs)
end
in map expnd (map fresh constructors) end
else [row]
fun mk{rows=[],...} = mk_case_fail"no rows"
| mk{path=[], rows = ((prfx, []), (tm,tag))::_} = (* Done *)
([(prfx,tag,[])], tm)
| mk{path=[], rows = _::_} = mk_case_fail"blunder"
| mk{path as u::rstp, rows as ((prfx, []), rhs)::rst} =
mk{path = path,
rows = ((prfx, [fresh_var(type_of u)]), rhs)::rst}
| mk{path = u::rstp, rows as ((_, p::_), _)::_} =
let val (pat_rectangle,rights) = ListPair.unzip rows
val col0 = map(hd o #2) pat_rectangle
in
if (forall is_Free col0)
then let val rights' = map (fn(v,e) => pattern_subst[(v,u)] e)
(ListPair.zip (col0, rights))
val pat_rectangle' = map v_to_prfx pat_rectangle
val (pref_patl,tm) = mk{path = rstp,
rows = ListPair.zip (pat_rectangle',
rights')}
in (map v_to_pats pref_patl, tm)
end
else
let val pty as Type (ty_name,_) = type_of p
in
case (ty_info ty_name)
of NONE => mk_case_fail("Not a known datatype: "^ty_name)
| SOME{case_const,constructors} =>
let
val case_const_name = #1(dest_Const case_const)
val nrows = List.concat (map (expand constructors pty) rows)
val subproblems = divide(constructors, pty, range_ty, nrows)
val groups = map #group subproblems
and new_formals = map #new_formals subproblems
and constructors' = map #constructor subproblems
val news = map (fn (nf,rows) => {path = nf@rstp, rows=rows})
(ListPair.zip (new_formals, groups))
val rec_calls = map mk news
val (pat_rect,dtrees) = ListPair.unzip rec_calls
val case_functions = map S.list_mk_abs
(ListPair.zip (new_formals, dtrees))
val types = map type_of (case_functions@[u]) @ [range_ty]
val case_const' = Const(case_const_name, list_mk_type types)
val tree = list_comb(case_const', case_functions@[u])
val pat_rect1 = List.concat
(ListPair.map mk_pat (constructors', pat_rect))
in (pat_rect1,tree)
end
end end
in mk
end;
(* Repeated variable occurrences in a pattern are not allowed. *)
fun FV_multiset tm =
case (S.dest_term tm)
of S.VAR{Name = c, Ty = T} => [Free(c, T)]
| S.CONST _ => []
| S.COMB{Rator, Rand} => FV_multiset Rator @ FV_multiset Rand
| S.LAMB _ => raise TFL_ERR "FV_multiset" "lambda";
fun no_repeat_vars thy pat =
let fun check [] = true
| check (v::rst) =
if mem_term (v,rst) then
raise TFL_ERR "no_repeat_vars"
(quote (#1 (dest_Free v)) ^
" occurs repeatedly in the pattern " ^
quote (string_of_cterm (Thry.typecheck thy pat)))
else check rst
in check (FV_multiset pat)
end;
fun dest_atom (Free p) = p
| dest_atom (Const p) = p
| dest_atom _ = raise TFL_ERR "dest_atom" "function name not an identifier";
fun same_name (p,q) = #1(dest_atom p) = #1(dest_atom q);
local fun mk_functional_err s = raise TFL_ERR "mk_functional" s
fun single [_$_] =
mk_functional_err "recdef does not allow currying"
| single [f] = f
| single fs =
(*multiple function names?*)
if length (distinct same_name fs) < length fs
then mk_functional_err
"The function being declared appears with multiple types"
else mk_functional_err
(Int.toString (length fs) ^
" distinct function names being declared")
in
fun mk_functional thy clauses =
let val (L,R) = ListPair.unzip (map HOLogic.dest_eq clauses
handle TERM _ => raise TFL_ERR "mk_functional"
"recursion equations must use the = relation")
val (funcs,pats) = ListPair.unzip (map (fn (t$u) =>(t,u)) L)
val atom = single (distinct (op aconv) funcs)
val (fname,ftype) = dest_atom atom
val dummy = map (no_repeat_vars thy) pats
val rows = ListPair.zip (map (fn x => ([]:term list,[x])) pats,
map (fn (t,i) => (t,(i,true))) (enumerate R))
val names = foldr add_term_names [] R
val atype = type_of(hd pats)
and aname = variant names "a"
val a = Free(aname,atype)
val ty_info = Thry.match_info thy
val ty_match = Thry.match_type thy
val range_ty = type_of (hd R)
val (patts, case_tm) = mk_case ty_info ty_match (aname::names) range_ty
{path=[a], rows=rows}
val patts1 = map (fn (_,tag,[pat]) => (pat,tag)) patts
handle Match => mk_functional_err "error in pattern-match translation"
val patts2 = Library.sort (Library.int_ord o Library.pairself row_of_pat) patts1
val finals = map row_of_pat patts2
val originals = map (row_of_pat o #2) rows
val dummy = case (originals\\finals)
of [] => ()
| L => mk_functional_err
("The following clauses are redundant (covered by preceding clauses): " ^
commas (map (fn i => Int.toString (i + 1)) L))
in {functional = Abs(Sign.base_name fname, ftype,
abstract_over (atom,
absfree(aname,atype, case_tm))),
pats = patts2}
end end;
(*----------------------------------------------------------------------------
*
* PRINCIPLES OF DEFINITION
*
*---------------------------------------------------------------------------*)
(*For Isabelle, the lhs of a definition must be a constant.*)
fun mk_const_def sign (c, Ty, rhs) =
Sign.infer_types (Sign.pp sign) sign (Sign.consts_of sign) (K NONE) (K NONE) [] false
([Const("==",dummyT) $ Const(c,Ty) $ rhs], propT)
|> #1;
(*Make all TVars available for instantiation by adding a ? to the front*)
fun poly_tvars (Type(a,Ts)) = Type(a, map (poly_tvars) Ts)
| poly_tvars (TFree (a,sort)) = TVar (("?" ^ a, 0), sort)
| poly_tvars (TVar ((a,i),sort)) = TVar (("?" ^ a, i+1), sort);
local val f_eq_wfrec_R_M =
#ant(S.dest_imp(#2(S.strip_forall (concl Thms.WFREC_COROLLARY))))
val {lhs=f, rhs} = S.dest_eq f_eq_wfrec_R_M
val (fname,_) = dest_Free f
val (wfrec,_) = S.strip_comb rhs
in
fun wfrec_definition0 thy fid R (functional as Abs(x, Ty, _)) =
let val def_name = if x<>fid then
raise TFL_ERR "wfrec_definition0"
("Expected a definition of " ^
quote fid ^ " but found one of " ^
quote x)
else x ^ "_def"
val wfrec_R_M = map_term_types poly_tvars
(wfrec $ map_term_types poly_tvars R)
$ functional
val def_term = mk_const_def (Theory.sign_of thy) (x, Ty, wfrec_R_M)
val ([def], thy') = PureThy.add_defs_i false [Thm.no_attributes (def_name, def_term)] thy
in (thy', def) end;
end;
(*---------------------------------------------------------------------------
* This structure keeps track of congruence rules that aren't derived
* from a datatype definition.
*---------------------------------------------------------------------------*)
fun extraction_thms thy =
let val {case_rewrites,case_congs} = Thry.extract_info thy
in (case_rewrites, case_congs)
end;
(*---------------------------------------------------------------------------
* Pair patterns with termination conditions. The full list of patterns for
* a definition is merged with the TCs arising from the user-given clauses.
* There can be fewer clauses than the full list, if the user omitted some
* cases. This routine is used to prepare input for mk_induction.
*---------------------------------------------------------------------------*)
fun merge full_pats TCs =
let fun insert (p,TCs) =
let fun insrt ((x as (h,[]))::rst) =
if (p aconv h) then (p,TCs)::rst else x::insrt rst
| insrt (x::rst) = x::insrt rst
| insrt[] = raise TFL_ERR "merge.insert" "pattern not found"
in insrt end
fun pass ([],ptcl_final) = ptcl_final
| pass (ptcs::tcl, ptcl) = pass(tcl, insert ptcs ptcl)
in
pass (TCs, map (fn p => (p,[])) full_pats)
end;
fun givens pats = map pat_of (List.filter given pats);
fun post_definition meta_tflCongs (theory, (def, pats)) =
let val tych = Thry.typecheck theory
val f = #lhs(S.dest_eq(concl def))
val corollary = R.MATCH_MP Thms.WFREC_COROLLARY def
val pats' = List.filter given pats
val given_pats = map pat_of pats'
val rows = map row_of_pat pats'
val WFR = #ant(S.dest_imp(concl corollary))
val R = #Rand(S.dest_comb WFR)
val corollary' = R.UNDISCH corollary (* put WF R on assums *)
val corollaries = map (fn pat => R.SPEC (tych pat) corollary')
given_pats
val (case_rewrites,context_congs) = extraction_thms theory
(*case_ss causes minimal simplification: bodies of case expressions are
not simplified. Otherwise large examples (Red-Black trees) are too
slow.*)
val case_ss = Simplifier.theory_context theory
(HOL_basic_ss addcongs
(map (#weak_case_cong o snd) o Symtab.dest o DatatypePackage.get_datatypes) theory addsimps case_rewrites)
val corollaries' = map (Simplifier.simplify case_ss) corollaries
val extract = R.CONTEXT_REWRITE_RULE
(f, [R], cut_apply, meta_tflCongs@context_congs)
val (rules, TCs) = ListPair.unzip (map extract corollaries')
val rules0 = map (rewrite_rule [Thms.CUT_DEF]) rules
val mk_cond_rule = R.FILTER_DISCH_ALL(not o curry (op aconv) WFR)
val rules1 = R.LIST_CONJ(map mk_cond_rule rules0)
in
{rules = rules1,
rows = rows,
full_pats_TCs = merge (map pat_of pats) (ListPair.zip (given_pats, TCs)),
TCs = TCs}
end;
(*---------------------------------------------------------------------------
* Perform the extraction without making the definition. Definition and
* extraction commute for the non-nested case. (Deferred recdefs)
*
* The purpose of wfrec_eqns is merely to instantiate the recursion theorem
* and extract termination conditions: no definition is made.
*---------------------------------------------------------------------------*)
fun wfrec_eqns thy fid tflCongs eqns =
let val {lhs,rhs} = S.dest_eq (hd eqns)
val (f,args) = S.strip_comb lhs
val (fname,fty) = dest_atom f
val (SV,a) = front_last args (* SV = schematic variables *)
val g = list_comb(f,SV)
val h = Free(fname,type_of g)
val eqns1 = map (subst_free[(g,h)]) eqns
val {functional as Abs(x, Ty, _), pats} = mk_functional thy eqns1
val given_pats = givens pats
(* val f = Free(x,Ty) *)
val Type("fun", [f_dty, f_rty]) = Ty
val dummy = if x<>fid then
raise TFL_ERR "wfrec_eqns"
("Expected a definition of " ^
quote fid ^ " but found one of " ^
quote x)
else ()
val (case_rewrites,context_congs) = extraction_thms thy
val tych = Thry.typecheck thy
val WFREC_THM0 = R.ISPEC (tych functional) Thms.WFREC_COROLLARY
val Const("All",_) $ Abs(Rname,Rtype,_) = concl WFREC_THM0
val R = Free (variant (foldr add_term_names [] eqns) Rname,
Rtype)
val WFREC_THM = R.ISPECL [tych R, tych g] WFREC_THM0
val ([proto_def, WFR],_) = S.strip_imp(concl WFREC_THM)
val dummy =
if !trace then
writeln ("ORIGINAL PROTO_DEF: " ^
Sign.string_of_term (Theory.sign_of thy) proto_def)
else ()
val R1 = S.rand WFR
val corollary' = R.UNDISCH(R.UNDISCH WFREC_THM)
val corollaries = map (fn pat => R.SPEC (tych pat) corollary') given_pats
val corollaries' = map (rewrite_rule case_rewrites) corollaries
fun extract X = R.CONTEXT_REWRITE_RULE
(f, R1::SV, cut_apply, tflCongs@context_congs) X
in {proto_def = proto_def,
SV=SV,
WFR=WFR,
pats=pats,
extracta = map extract corollaries'}
end;
(*---------------------------------------------------------------------------
* Define the constant after extracting the termination conditions. The
* wellfounded relation used in the definition is computed by using the
* choice operator on the extracted conditions (plus the condition that
* such a relation must be wellfounded).
*---------------------------------------------------------------------------*)
fun lazyR_def thy fid tflCongs eqns =
let val {proto_def,WFR,pats,extracta,SV} =
wfrec_eqns thy fid tflCongs eqns
val R1 = S.rand WFR
val f = #lhs(S.dest_eq proto_def)
val (extractants,TCl) = ListPair.unzip extracta
val dummy = if !trace
then (writeln "Extractants = ";
prths extractants;
())
else ()
val TCs = foldr (gen_union (op aconv)) [] TCl
val full_rqt = WFR::TCs
val R' = S.mk_select{Bvar=R1, Body=S.list_mk_conj full_rqt}
val R'abs = S.rand R'
val proto_def' = subst_free[(R1,R')] proto_def
val dummy = if !trace then writeln ("proto_def' = " ^
Sign.string_of_term
(Theory.sign_of thy) proto_def')
else ()
val {lhs,rhs} = S.dest_eq proto_def'
val (c,args) = S.strip_comb lhs
val (name,Ty) = dest_atom c
val defn = mk_const_def (Theory.sign_of thy)
(name, Ty, S.list_mk_abs (args,rhs))
val ([def0], theory) =
thy
|> PureThy.add_defs_i false
[Thm.no_attributes (fid ^ "_def", defn)]
val def = Thm.freezeT def0;
val dummy = if !trace then writeln ("DEF = " ^ string_of_thm def)
else ()
(* val fconst = #lhs(S.dest_eq(concl def)) *)
val tych = Thry.typecheck theory
val full_rqt_prop = map (Dcterm.mk_prop o tych) full_rqt
(*lcp: a lot of object-logic inference to remove*)
val baz = R.DISCH_ALL
(fold_rev R.DISCH full_rqt_prop
(R.LIST_CONJ extractants))
val dum = if !trace then writeln ("baz = " ^ string_of_thm baz)
else ()
val f_free = Free (fid, fastype_of f) (*'cos f is a Const*)
val SV' = map tych SV;
val SVrefls = map reflexive SV'
val def0 = (fold (fn x => fn th => R.rbeta(combination th x))
SVrefls def)
RS meta_eq_to_obj_eq
val def' = R.MP (R.SPEC (tych R') (R.GEN (tych R1) baz)) def0
val body_th = R.LIST_CONJ (map R.ASSUME full_rqt_prop)
val SELECT_AX = (*in this way we hope to avoid a STATIC dependence upon
theory Hilbert_Choice*)
thm "Hilbert_Choice.tfl_some"
handle ERROR msg => cat_error msg
"defer_recdef requires theory Main or at least Hilbert_Choice as parent"
val bar = R.MP (R.ISPECL[tych R'abs, tych R1] SELECT_AX) body_th
in {theory = theory, R=R1, SV=SV,
rules = fold (U.C R.MP) (R.CONJUNCTS bar) def',
full_pats_TCs = merge (map pat_of pats) (ListPair.zip (givens pats, TCl)),
patterns = pats}
end;
(*----------------------------------------------------------------------------
*
* INDUCTION THEOREM
*
*---------------------------------------------------------------------------*)
(*------------------------ Miscellaneous function --------------------------
*
* [x_1,...,x_n] ?v_1...v_n. M[v_1,...,v_n]
* -----------------------------------------------------------
* ( M[x_1,...,x_n], [(x_i,?v_1...v_n. M[v_1,...,v_n]),
* ...
* (x_j,?v_n. M[x_1,...,x_(n-1),v_n])] )
*
* This function is totally ad hoc. Used in the production of the induction
* theorem. The nchotomy theorem can have clauses that look like
*
* ?v1..vn. z = C vn..v1
*
* in which the order of quantification is not the order of occurrence of the
* quantified variables as arguments to C. Since we have no control over this
* aspect of the nchotomy theorem, we make the correspondence explicit by
* pairing the incoming new variable with the term it gets beta-reduced into.
*---------------------------------------------------------------------------*)
fun alpha_ex_unroll (xlist, tm) =
let val (qvars,body) = S.strip_exists tm
val vlist = #2(S.strip_comb (S.rhs body))
val plist = ListPair.zip (vlist, xlist)
val args = map (the o AList.lookup (op aconv) plist) qvars
handle Option => sys_error
"TFL fault [alpha_ex_unroll]: no correspondence"
fun build ex [] = []
| build (_$rex) (v::rst) =
let val ex1 = Term.betapply(rex, v)
in ex1 :: build ex1 rst
end
val (nex::exl) = rev (tm::build tm args)
in
(nex, ListPair.zip (args, rev exl))
end;
(*----------------------------------------------------------------------------
*
* PROVING COMPLETENESS OF PATTERNS
*
*---------------------------------------------------------------------------*)
fun mk_case ty_info usednames thy =
let
val divide = ipartition (gvvariant usednames)
val tych = Thry.typecheck thy
fun tych_binding(x,y) = (tych x, tych y)
fun fail s = raise TFL_ERR "mk_case" s
fun mk{rows=[],...} = fail"no rows"
| mk{path=[], rows = [([], (thm, bindings))]} =
R.IT_EXISTS (map tych_binding bindings) thm
| mk{path = u::rstp, rows as (p::_, _)::_} =
let val (pat_rectangle,rights) = ListPair.unzip rows
val col0 = map hd pat_rectangle
val pat_rectangle' = map tl pat_rectangle
in
if (forall is_Free col0) (* column 0 is all variables *)
then let val rights' = map (fn ((thm,theta),v) => (thm,theta@[(u,v)]))
(ListPair.zip (rights, col0))
in mk{path = rstp, rows = ListPair.zip (pat_rectangle', rights')}
end
else (* column 0 is all constructors *)
let val Type (ty_name,_) = type_of p
in
case (ty_info ty_name)
of NONE => fail("Not a known datatype: "^ty_name)
| SOME{constructors,nchotomy} =>
let val thm' = R.ISPEC (tych u) nchotomy
val disjuncts = S.strip_disj (concl thm')
val subproblems = divide(constructors, rows)
val groups = map #group subproblems
and new_formals = map #new_formals subproblems
val existentials = ListPair.map alpha_ex_unroll
(new_formals, disjuncts)
val constraints = map #1 existentials
val vexl = map #2 existentials
fun expnd tm (pats,(th,b)) = (pats,(R.SUBS[R.ASSUME(tych tm)]th,b))
val news = map (fn (nf,rows,c) => {path = nf@rstp,
rows = map (expnd c) rows})
(U.zip3 new_formals groups constraints)
val recursive_thms = map mk news
val build_exists = Library.foldr
(fn((x,t), th) =>
R.CHOOSE (tych x, R.ASSUME (tych t)) th)
val thms' = ListPair.map build_exists (vexl, recursive_thms)
val same_concls = R.EVEN_ORS thms'
in R.DISJ_CASESL thm' same_concls
end
end end
in mk
end;
fun complete_cases thy =
let val tych = Thry.typecheck thy
val ty_info = Thry.induct_info thy
in fn pats =>
let val names = foldr add_term_names [] pats
val T = type_of (hd pats)
val aname = Term.variant names "a"
val vname = Term.variant (aname::names) "v"
val a = Free (aname, T)
val v = Free (vname, T)
val a_eq_v = HOLogic.mk_eq(a,v)
val ex_th0 = R.EXISTS (tych (S.mk_exists{Bvar=v,Body=a_eq_v}), tych a)
(R.REFL (tych a))
val th0 = R.ASSUME (tych a_eq_v)
val rows = map (fn x => ([x], (th0,[]))) pats
in
R.GEN (tych a)
(R.RIGHT_ASSOC
(R.CHOOSE(tych v, ex_th0)
(mk_case ty_info (vname::aname::names)
thy {path=[v], rows=rows})))
end end;
(*---------------------------------------------------------------------------
* Constructing induction hypotheses: one for each recursive call.
*
* Note. R will never occur as a variable in the ind_clause, because
* to do so, it would have to be from a nested definition, and we don't
* allow nested defns to have R variable.
*
* Note. When the context is empty, there can be no local variables.
*---------------------------------------------------------------------------*)
(*
local infix 5 ==>
fun (tm1 ==> tm2) = S.mk_imp{ant = tm1, conseq = tm2}
in
fun build_ih f P (pat,TCs) =
let val globals = S.free_vars_lr pat
fun nested tm = isSome (S.find_term (curry (op aconv) f) tm)
fun dest_TC tm =
let val (cntxt,R_y_pat) = S.strip_imp(#2(S.strip_forall tm))
val (R,y,_) = S.dest_relation R_y_pat
val P_y = if (nested tm) then R_y_pat ==> P$y else P$y
in case cntxt
of [] => (P_y, (tm,[]))
| _ => let
val imp = S.list_mk_conj cntxt ==> P_y
val lvs = gen_rems (op aconv) (S.free_vars_lr imp, globals)
val locals = #2(U.pluck (curry (op aconv) P) lvs) handle U.ERR _ => lvs
in (S.list_mk_forall(locals,imp), (tm,locals)) end
end
in case TCs
of [] => (S.list_mk_forall(globals, P$pat), [])
| _ => let val (ihs, TCs_locals) = ListPair.unzip(map dest_TC TCs)
val ind_clause = S.list_mk_conj ihs ==> P$pat
in (S.list_mk_forall(globals,ind_clause), TCs_locals)
end
end
end;
*)
local infix 5 ==>
fun (tm1 ==> tm2) = S.mk_imp{ant = tm1, conseq = tm2}
in
fun build_ih f (P,SV) (pat,TCs) =
let val pat_vars = S.free_vars_lr pat
val globals = pat_vars@SV
fun nested tm = isSome (S.find_term (curry (op aconv) f) tm)
fun dest_TC tm =
let val (cntxt,R_y_pat) = S.strip_imp(#2(S.strip_forall tm))
val (R,y,_) = S.dest_relation R_y_pat
val P_y = if (nested tm) then R_y_pat ==> P$y else P$y
in case cntxt
of [] => (P_y, (tm,[]))
| _ => let
val imp = S.list_mk_conj cntxt ==> P_y
val lvs = gen_rems (op aconv) (S.free_vars_lr imp, globals)
val locals = #2(U.pluck (curry (op aconv) P) lvs) handle U.ERR _ => lvs
in (S.list_mk_forall(locals,imp), (tm,locals)) end
end
in case TCs
of [] => (S.list_mk_forall(pat_vars, P$pat), [])
| _ => let val (ihs, TCs_locals) = ListPair.unzip(map dest_TC TCs)
val ind_clause = S.list_mk_conj ihs ==> P$pat
in (S.list_mk_forall(pat_vars,ind_clause), TCs_locals)
end
end
end;
(*---------------------------------------------------------------------------
* This function makes good on the promise made in "build_ih".
*
* Input is tm = "(!y. R y pat ==> P y) ==> P pat",
* TCs = TC_1[pat] ... TC_n[pat]
* thm = ih1 /\ ... /\ ih_n |- ih[pat]
*---------------------------------------------------------------------------*)
fun prove_case f thy (tm,TCs_locals,thm) =
let val tych = Thry.typecheck thy
val antc = tych(#ant(S.dest_imp tm))
val thm' = R.SPEC_ALL thm
fun nested tm = isSome (S.find_term (curry (op aconv) f) tm)
fun get_cntxt TC = tych(#ant(S.dest_imp(#2(S.strip_forall(concl TC)))))
fun mk_ih ((TC,locals),th2,nested) =
R.GENL (map tych locals)
(if nested then R.DISCH (get_cntxt TC) th2 handle U.ERR _ => th2
else if S.is_imp (concl TC) then R.IMP_TRANS TC th2
else R.MP th2 TC)
in
R.DISCH antc
(if S.is_imp(concl thm') (* recursive calls in this clause *)
then let val th1 = R.ASSUME antc
val TCs = map #1 TCs_locals
val ylist = map (#2 o S.dest_relation o #2 o S.strip_imp o
#2 o S.strip_forall) TCs
val TClist = map (fn(TC,lvs) => (R.SPEC_ALL(R.ASSUME(tych TC)),lvs))
TCs_locals
val th2list = map (U.C R.SPEC th1 o tych) ylist
val nlist = map nested TCs
val triples = U.zip3 TClist th2list nlist
val Pylist = map mk_ih triples
in R.MP thm' (R.LIST_CONJ Pylist) end
else thm')
end;
(*---------------------------------------------------------------------------
*
* x = (v1,...,vn) |- M[x]
* ---------------------------------------------
* ?v1 ... vn. x = (v1,...,vn) |- M[x]
*
*---------------------------------------------------------------------------*)
fun LEFT_ABS_VSTRUCT tych thm =
let fun CHOOSER v (tm,thm) =
let val ex_tm = S.mk_exists{Bvar=v,Body=tm}
in (ex_tm, R.CHOOSE(tych v, R.ASSUME (tych ex_tm)) thm)
end
val [veq] = List.filter (can S.dest_eq) (#1 (R.dest_thm thm))
val {lhs,rhs} = S.dest_eq veq
val L = S.free_vars_lr rhs
in #2 (fold_rev CHOOSER L (veq,thm)) end;
(*----------------------------------------------------------------------------
* Input : f, R, and [(pat1,TCs1),..., (patn,TCsn)]
*
* Instantiates WF_INDUCTION_THM, getting Sinduct and then tries to prove
* recursion induction (Rinduct) by proving the antecedent of Sinduct from
* the antecedent of Rinduct.
*---------------------------------------------------------------------------*)
fun mk_induction thy {fconst, R, SV, pat_TCs_list} =
let val tych = Thry.typecheck thy
val Sinduction = R.UNDISCH (R.ISPEC (tych R) Thms.WF_INDUCTION_THM)
val (pats,TCsl) = ListPair.unzip pat_TCs_list
val case_thm = complete_cases thy pats
val domain = (type_of o hd) pats
val Pname = Term.variant (foldr (Library.foldr add_term_names)
[] (pats::TCsl)) "P"
val P = Free(Pname, domain --> HOLogic.boolT)
val Sinduct = R.SPEC (tych P) Sinduction
val Sinduct_assumf = S.rand ((#ant o S.dest_imp o concl) Sinduct)
val Rassums_TCl' = map (build_ih fconst (P,SV)) pat_TCs_list
val (Rassums,TCl') = ListPair.unzip Rassums_TCl'
val Rinduct_assum = R.ASSUME (tych (S.list_mk_conj Rassums))
val cases = map (fn pat => Term.betapply (Sinduct_assumf, pat)) pats
val tasks = U.zip3 cases TCl' (R.CONJUNCTS Rinduct_assum)
val proved_cases = map (prove_case fconst thy) tasks
val v = Free (variant (foldr add_term_names [] (map concl proved_cases))
"v",
domain)
val vtyped = tych v
val substs = map (R.SYM o R.ASSUME o tych o (curry HOLogic.mk_eq v)) pats
val proved_cases1 = ListPair.map (fn (th,th') => R.SUBS[th]th')
(substs, proved_cases)
val abs_cases = map (LEFT_ABS_VSTRUCT tych) proved_cases1
val dant = R.GEN vtyped (R.DISJ_CASESL (R.ISPEC vtyped case_thm) abs_cases)
val dc = R.MP Sinduct dant
val Parg_ty = type_of(#Bvar(S.dest_forall(concl dc)))
val vars = map (gvvariant[Pname]) (S.strip_prod_type Parg_ty)
val dc' = fold_rev (R.GEN o tych) vars
(R.SPEC (tych(S.mk_vstruct Parg_ty vars)) dc)
in
R.GEN (tych P) (R.DISCH (tych(concl Rinduct_assum)) dc')
end
handle U.ERR _ => raise TFL_ERR "mk_induction" "failed derivation";
(*---------------------------------------------------------------------------
*
* POST PROCESSING
*
*---------------------------------------------------------------------------*)
fun simplify_induction thy hth ind =
let val tych = Thry.typecheck thy
val (asl,_) = R.dest_thm ind
val (_,tc_eq_tc') = R.dest_thm hth
val tc = S.lhs tc_eq_tc'
fun loop [] = ind
| loop (asm::rst) =
if (can (Thry.match_term thy asm) tc)
then R.UNDISCH
(R.MATCH_MP
(R.MATCH_MP Thms.simp_thm (R.DISCH (tych asm) ind))
hth)
else loop rst
in loop asl
end;
(*---------------------------------------------------------------------------
* The termination condition is an antecedent to the rule, and an
* assumption to the theorem.
*---------------------------------------------------------------------------*)
fun elim_tc tcthm (rule,induction) =
(R.MP rule tcthm, R.PROVE_HYP tcthm induction)
fun trace_thms s L =
if !trace then writeln (cat_lines (s :: map string_of_thm L))
else ();
fun trace_cterms s L =
if !trace then writeln (cat_lines (s :: map string_of_cterm L))
else ();;
fun postprocess strict {wf_tac, terminator, simplifier} theory {rules,induction,TCs} =
let val tych = Thry.typecheck theory
val prove = R.prove strict;
(*---------------------------------------------------------------------
* Attempt to eliminate WF condition. It's the only assumption of rules
*---------------------------------------------------------------------*)
val (rules1,induction1) =
let val thm = prove(tych(HOLogic.mk_Trueprop
(hd(#1(R.dest_thm rules)))),
wf_tac)
in (R.PROVE_HYP thm rules, R.PROVE_HYP thm induction)
end handle U.ERR _ => (rules,induction);
(*----------------------------------------------------------------------
* The termination condition (tc) is simplified to |- tc = tc' (there
* might not be a change!) and then 3 attempts are made:
*
* 1. if |- tc = T, then eliminate it with eqT; otherwise,
* 2. apply the terminator to tc'. If |- tc' = T then eliminate; else
* 3. replace tc by tc' in both the rules and the induction theorem.
*---------------------------------------------------------------------*)
fun simplify_tc tc (r,ind) =
let val tc1 = tych tc
val _ = trace_cterms "TC before simplification: " [tc1]
val tc_eq = simplifier tc1
val _ = trace_thms "result: " [tc_eq]
in
elim_tc (R.MATCH_MP Thms.eqT tc_eq) (r,ind)
handle U.ERR _ =>
(elim_tc (R.MATCH_MP(R.MATCH_MP Thms.rev_eq_mp tc_eq)
(prove(tych(HOLogic.mk_Trueprop(S.rhs(concl tc_eq))),
terminator)))
(r,ind)
handle U.ERR _ =>
(R.UNDISCH(R.MATCH_MP (R.MATCH_MP Thms.simp_thm r) tc_eq),
simplify_induction theory tc_eq ind))
end
(*----------------------------------------------------------------------
* Nested termination conditions are harder to get at, since they are
* left embedded in the body of the function (and in induction
* theorem hypotheses). Our "solution" is to simplify them, and try to
* prove termination, but leave the application of the resulting theorem
* to a higher level. So things go much as in "simplify_tc": the
* termination condition (tc) is simplified to |- tc = tc' (there might
* not be a change) and then 2 attempts are made:
*
* 1. if |- tc = T, then return |- tc; otherwise,
* 2. apply the terminator to tc'. If |- tc' = T then return |- tc; else
* 3. return |- tc = tc'
*---------------------------------------------------------------------*)
fun simplify_nested_tc tc =
let val tc_eq = simplifier (tych (#2 (S.strip_forall tc)))
in
R.GEN_ALL
(R.MATCH_MP Thms.eqT tc_eq
handle U.ERR _ =>
(R.MATCH_MP(R.MATCH_MP Thms.rev_eq_mp tc_eq)
(prove(tych(HOLogic.mk_Trueprop (S.rhs(concl tc_eq))),
terminator))
handle U.ERR _ => tc_eq))
end
(*-------------------------------------------------------------------
* Attempt to simplify the termination conditions in each rule and
* in the induction theorem.
*-------------------------------------------------------------------*)
fun strip_imp tm = if S.is_neg tm then ([],tm) else S.strip_imp tm
fun loop ([],extras,R,ind) = (rev R, ind, extras)
| loop ((r,ftcs)::rst, nthms, R, ind) =
let val tcs = #1(strip_imp (concl r))
val extra_tcs = gen_rems (op aconv) (ftcs, tcs)
val extra_tc_thms = map simplify_nested_tc extra_tcs
val (r1,ind1) = fold simplify_tc tcs (r,ind)
val r2 = R.FILTER_DISCH_ALL(not o S.is_WFR) r1
in loop(rst, nthms@extra_tc_thms, r2::R, ind1)
end
val rules_tcs = ListPair.zip (R.CONJUNCTS rules1, TCs)
val (rules2,ind2,extras) = loop(rules_tcs,[],[],induction1)
in
{induction = ind2, rules = R.LIST_CONJ rules2, nested_tcs = extras}
end;
end;