src/HOL/Tools/res_hol_clause.ML

renamed constructor RatC to Rational

(* ID: $Id$
   Author: Jia Meng, NICTA

FOL clauses translated from HOL formulae.

The combinator code needs to be deleted after the translation paper has been published.
It cannot be used with proof reconstruction because combinators are not introduced by proof.
The Turner combinators (B', C', S') yield no improvement and should be deleted.
*)

signature RES_HOL_CLAUSE =
sig
  val ext: thm
  val comb_I: thm
  val comb_K: thm
  val comb_B: thm
  val comb_C: thm
  val comb_S: thm
  datatype type_level = T_FULL | T_CONST
  val typ_level: type_level ref
  val minimize_applies: bool ref
  type axiom_name = string
  type polarity = bool
  type clause_id = int
  datatype combterm =
      CombConst of string * ResClause.fol_type * ResClause.fol_type list (*Const and Free*)
    | CombVar of string * ResClause.fol_type
    | CombApp of combterm * combterm
  datatype literal = Literal of polarity * combterm
  val strip_comb: combterm -> combterm * combterm list
  val literals_of_term: theory -> term -> literal list * (ResClause.typ_var * sort) list
  val tptp_write_file: theory -> bool -> thm list -> string ->
    (thm * (axiom_name * clause_id)) list * ResClause.classrelClause list *
      ResClause.arityClause list -> string list -> axiom_name list
  val dfg_write_file: theory -> bool -> thm list -> string ->
    (thm * (axiom_name * clause_id)) list * ResClause.classrelClause list *
      ResClause.arityClause list -> string list -> axiom_name list
end

structure ResHolClause: RES_HOL_CLAUSE =
struct

structure RC = ResClause;

(* theorems for combinators and function extensionality *)
val ext = thm "HOL.ext";
val comb_I = thm "ATP_Linkup.COMBI_def";
val comb_K = thm "ATP_Linkup.COMBK_def";
val comb_B = thm "ATP_Linkup.COMBB_def";
val comb_C = thm "ATP_Linkup.COMBC_def";
val comb_S = thm "ATP_Linkup.COMBS_def";
val comb_B' = thm "ATP_Linkup.COMBB'_def";
val comb_C' = thm "ATP_Linkup.COMBC'_def";
val comb_S' = thm "ATP_Linkup.COMBS'_def";
val fequal_imp_equal = thm "ATP_Linkup.fequal_imp_equal";
val equal_imp_fequal = thm "ATP_Linkup.equal_imp_fequal";


(*The different translations of types*)
datatype type_level = T_FULL | T_CONST;

val typ_level = ref T_CONST;

(*If true, each function will be directly applied to as many arguments as possible, avoiding
  use of the "apply" operator. Use of hBOOL is also minimized.*)
val minimize_applies = ref true;

val const_min_arity = ref (Symtab.empty : int Symtab.table);

val const_needs_hBOOL = ref (Symtab.empty : bool Symtab.table);

fun min_arity_of c = getOpt (Symtab.lookup(!const_min_arity) c, 0);

(*True if the constant ever appears outside of the top-level position in literals.
  If false, the constant always receives all of its arguments and is used as a predicate.*)
fun needs_hBOOL c = not (!minimize_applies) orelse
                    getOpt (Symtab.lookup(!const_needs_hBOOL) c, false);


(******************************************************)
(* data types for typed combinator expressions        *)
(******************************************************)

type axiom_name = string;
type polarity = bool;
type clause_id = int;

datatype combterm = CombConst of string * RC.fol_type * RC.fol_type list (*Const and Free*)
                  | CombVar of string * RC.fol_type
                  | CombApp of combterm * combterm

datatype literal = Literal of polarity * combterm;

datatype clause =
         Clause of {clause_id: clause_id,
                    axiom_name: axiom_name,
                    th: thm,
                    kind: RC.kind,
                    literals: literal list,
                    ctypes_sorts: (RC.typ_var * Term.sort) list,
                    ctvar_type_literals: RC.type_literal list,
                    ctfree_type_literals: RC.type_literal list};


(*********************************************************************)
(* convert a clause with type Term.term to a clause with type clause *)
(*********************************************************************)

fun isFalse (Literal(pol, CombConst(c,_,_))) =
      (pol andalso c = "c_False") orelse
      (not pol andalso c = "c_True")
  | isFalse _ = false;

fun isTrue (Literal (pol, CombConst(c,_,_))) =
      (pol andalso c = "c_True") orelse
      (not pol andalso c = "c_False")
  | isTrue _ = false;

fun isTaut (Clause {literals,...}) = exists isTrue literals;

fun type_of (Type (a, Ts)) =
      let val (folTypes,ts) = types_of Ts
      in  (RC.Comp(RC.make_fixed_type_const a, folTypes), ts)  end
  | type_of (tp as (TFree(a,s))) =
      (RC.AtomF (RC.make_fixed_type_var a), [RC.mk_typ_var_sort tp])
  | type_of (tp as (TVar(v,s))) =
      (RC.AtomV (RC.make_schematic_type_var v), [RC.mk_typ_var_sort tp])
and types_of Ts =
      let val (folTyps,ts) = ListPair.unzip (map type_of Ts)
      in  (folTyps, RC.union_all ts)  end;

(* same as above, but no gathering of sort information *)
fun simp_type_of (Type (a, Ts)) =
      RC.Comp(RC.make_fixed_type_const a, map simp_type_of Ts)
  | simp_type_of (TFree (a,s)) = RC.AtomF(RC.make_fixed_type_var a)
  | simp_type_of (TVar (v,s)) = RC.AtomV(RC.make_schematic_type_var v);


fun const_type_of thy (c,t) =
      let val (tp,ts) = type_of t
      in  (tp, ts, map simp_type_of (Sign.const_typargs thy (c,t))) end;

(* convert a Term.term (with combinators) into a combterm, also accummulate sort info *)
fun combterm_of thy (Const(c,t)) =
      let val (tp,ts,tvar_list) = const_type_of thy (c,t)
          val c' = CombConst(RC.make_fixed_const c, tp, tvar_list)
      in  (c',ts)  end
  | combterm_of thy (Free(v,t)) =
      let val (tp,ts) = type_of t
          val v' = if RC.isMeta v then CombVar(RC.make_schematic_var(v,0),tp)
                   else CombConst(RC.make_fixed_var v, tp, [])
      in  (v',ts)  end
  | combterm_of thy (Var(v,t)) =
      let val (tp,ts) = type_of t
          val v' = CombVar(RC.make_schematic_var v,tp)
      in  (v',ts)  end
  | combterm_of thy (P $ Q) =
      let val (P',tsP) = combterm_of thy P
          val (Q',tsQ) = combterm_of thy Q
      in  (CombApp(P',Q'), tsP union tsQ)  end
  | combterm_of thy (t as Abs _) = raise RC.CLAUSE("HOL CLAUSE",t);

fun predicate_of thy ((Const("Not",_) $ P), polarity) = predicate_of thy (P, not polarity)
  | predicate_of thy (t,polarity) = (combterm_of thy t, polarity);

fun literals_of_term1 thy args (Const("Trueprop",_) $ P) = literals_of_term1 thy args P
  | literals_of_term1 thy args (Const("op |",_) $ P $ Q) =
      literals_of_term1 thy (literals_of_term1 thy args P) Q
  | literals_of_term1 thy (lits,ts) P =
      let val ((pred,ts'),pol) = predicate_of thy (P,true)
      in
          (Literal(pol,pred)::lits, ts union ts')
      end;

fun literals_of_term thy P = literals_of_term1 thy ([],[]) P;

(* making axiom and conjecture clauses *)
fun make_clause thy (clause_id,axiom_name,kind,th) =
    let val (lits,ctypes_sorts) = literals_of_term thy (prop_of th)
        val (ctvar_lits,ctfree_lits) = RC.add_typs_aux ctypes_sorts
    in
        if forall isFalse lits
        then error "Problem too trivial for resolution (empty clause)"
        else
            Clause {clause_id = clause_id, axiom_name = axiom_name, th = th, kind = kind,
                    literals = lits, ctypes_sorts = ctypes_sorts,
                    ctvar_type_literals = ctvar_lits,
                    ctfree_type_literals = ctfree_lits}
    end;


fun add_axiom_clause thy ((th,(name,id)), pairs) =
  let val cls = make_clause thy (id, name, RC.Axiom, th)
  in
      if isTaut cls then pairs else (name,cls)::pairs
  end;

fun make_axiom_clauses thy = foldl (add_axiom_clause thy) [];

fun make_conjecture_clauses_aux _ _ [] = []
  | make_conjecture_clauses_aux thy n (th::ths) =
      make_clause thy (n,"conjecture", RC.Conjecture, th) ::
      make_conjecture_clauses_aux thy (n+1) ths;

fun make_conjecture_clauses thy = make_conjecture_clauses_aux thy 0;


(**********************************************************************)
(* convert clause into ATP specific formats:                          *)
(* TPTP used by Vampire and E                                         *)
(* DFG used by SPASS                                                  *)
(**********************************************************************)

(*Result of a function type; no need to check that the argument type matches.*)
fun result_type (RC.Comp ("tc_fun", [_, tp2])) = tp2
  | result_type _ = raise ERROR "result_type"

fun type_of_combterm (CombConst(c,tp,_)) = tp
  | type_of_combterm (CombVar(v,tp)) = tp
  | type_of_combterm (CombApp(t1,t2)) = result_type (type_of_combterm t1);

(*gets the head of a combinator application, along with the list of arguments*)
fun strip_comb u =
    let fun stripc (CombApp(t,u), ts) = stripc (t, u::ts)
        |   stripc  x =  x
    in  stripc(u,[])  end;

val type_wrapper = "ti";

fun head_needs_hBOOL (CombConst(c,_,_)) = needs_hBOOL c
  | head_needs_hBOOL _ = true;

fun wrap_type (s, tp) =
  if !typ_level=T_FULL then
      type_wrapper ^ RC.paren_pack [s, RC.string_of_fol_type tp]
  else s;

fun apply ss = "hAPP" ^ RC.paren_pack ss;

fun rev_apply (v, []) = v
  | rev_apply (v, arg::args) = apply [rev_apply (v, args), arg];

fun string_apply (v, args) = rev_apply (v, rev args);

(*Apply an operator to the argument strings, using either the "apply" operator or
  direct function application.*)
fun string_of_applic (CombConst(c,tp,tvars), args) =
      let val c = if c = "equal" then "c_fequal" else c
          val nargs = min_arity_of c
          val args1 = List.take(args, nargs)
            handle Subscript => raise ERROR ("string_of_applic: " ^ c ^ " has arity " ^
                                             Int.toString nargs ^ " but is applied to " ^
                                             space_implode ", " args)
          val args2 = List.drop(args, nargs)
          val targs = if !typ_level = T_CONST then map RC.string_of_fol_type tvars
                      else []
      in
          string_apply (c ^ RC.paren_pack (args1@targs), args2)
      end
  | string_of_applic (CombVar(v,tp), args) = string_apply (v, args)
  | string_of_applic _ = raise ERROR "string_of_applic";

fun wrap_type_if (head, s, tp) = if head_needs_hBOOL head then wrap_type (s, tp) else s;

fun string_of_combterm t =
  let val (head, args) = strip_comb t
  in  wrap_type_if (head,
                    string_of_applic (head, map string_of_combterm args),
                    type_of_combterm t)
  end;

(*Boolean-valued terms are here converted to literals.*)
fun boolify t = "hBOOL" ^ RC.paren_pack [string_of_combterm t];

fun string_of_predicate t =
  case t of
      (CombApp(CombApp(CombConst("equal",_,_), t1), t2)) =>
          (*DFG only: new TPTP prefers infix equality*)
          ("equal" ^ RC.paren_pack [string_of_combterm t1, string_of_combterm t2])
    | _ =>
          case #1 (strip_comb t) of
              CombConst(c,_,_) => if needs_hBOOL c then boolify t else string_of_combterm t
            | _ => boolify t;

fun string_of_clausename (cls_id,ax_name) =
    RC.clause_prefix ^ RC.ascii_of ax_name ^ "_" ^ Int.toString cls_id;

fun string_of_type_clsname (cls_id,ax_name,idx) =
    string_of_clausename (cls_id,ax_name) ^ "_tcs" ^ (Int.toString idx);


(*** tptp format ***)

fun tptp_of_equality pol (t1,t2) =
  let val eqop = if pol then " = " else " != "
  in  string_of_combterm t1 ^ eqop ^ string_of_combterm t2  end;

fun tptp_literal (Literal(pol, CombApp(CombApp(CombConst("equal",_,_), t1), t2))) =
      tptp_of_equality pol (t1,t2)
  | tptp_literal (Literal(pol,pred)) =
      RC.tptp_sign pol (string_of_predicate pred);

(*Given a clause, returns its literals paired with a list of literals concerning TFrees;
  the latter should only occur in conjecture clauses.*)
fun tptp_type_lits (Clause cls) =
    let val lits = map tptp_literal (#literals cls)
        val ctvar_lits_strs = map RC.tptp_of_typeLit (#ctvar_type_literals cls)
        val ctfree_lits = map RC.tptp_of_typeLit (#ctfree_type_literals cls)
    in
        (ctvar_lits_strs @ lits, ctfree_lits)
    end;

fun clause2tptp (cls as Clause{axiom_name,clause_id,kind,ctypes_sorts,...}) =
    let val (lits,ctfree_lits) = tptp_type_lits cls
        val cls_str = RC.gen_tptp_cls(clause_id,axiom_name,kind,lits)
    in
        (cls_str,ctfree_lits)
    end;


(*** dfg format ***)

fun dfg_literal (Literal(pol,pred)) = RC.dfg_sign pol (string_of_predicate pred);

fun dfg_clause_aux (Clause{literals, ctypes_sorts, ...}) =
  let val lits = map dfg_literal literals
      val (tvar_lits,tfree_lits) = RC.add_typs_aux ctypes_sorts
      val tvar_lits_strs = map RC.dfg_of_typeLit tvar_lits
      val tfree_lits = map RC.dfg_of_typeLit tfree_lits
  in
      (tvar_lits_strs @ lits, tfree_lits)
  end;

fun get_uvars (CombConst _) vars = vars
  | get_uvars (CombVar(v,_)) vars = (v::vars)
  | get_uvars (CombApp(P,Q)) vars = get_uvars P (get_uvars Q vars);

fun get_uvars_l (Literal(_,c)) = get_uvars c [];

fun dfg_vars (Clause {literals,...}) = RC.union_all (map get_uvars_l literals);

fun clause2dfg (cls as Clause{axiom_name,clause_id,kind,ctypes_sorts,...}) =
    let val (lits,tfree_lits) = dfg_clause_aux cls
        val vars = dfg_vars cls
        val tvars = RC.get_tvar_strs ctypes_sorts
        val knd = RC.name_of_kind kind
        val lits_str = commas lits
        val cls_str = RC.gen_dfg_cls(clause_id, axiom_name, knd, lits_str, tvars@vars)
    in (cls_str, tfree_lits) end;

(** For DFG format: accumulate function and predicate declarations **)

fun addtypes tvars tab = foldl RC.add_foltype_funcs tab tvars;

fun add_decls (CombConst(c,tp,tvars), (funcs,preds)) =
      if c = "equal" then (addtypes tvars funcs, preds)
      else
	let val arity = min_arity_of c
	    val ntys = if !typ_level = T_CONST then length tvars else 0
	    val addit = Symtab.update(c, arity+ntys)
	in
	    if needs_hBOOL c then (addtypes tvars (addit funcs), preds)
	    else (addtypes tvars funcs, addit preds)
	end
  | add_decls (CombVar(_,ctp), (funcs,preds)) =
      (RC.add_foltype_funcs (ctp,funcs), preds)
  | add_decls (CombApp(P,Q),decls) = add_decls(P,add_decls (Q,decls));

fun add_literal_decls (Literal(_,c), decls) = add_decls (c,decls);

fun add_clause_decls (Clause {literals, ...}, decls) =
    foldl add_literal_decls decls literals
    handle Symtab.DUP a => raise ERROR ("function " ^ a ^ " has multiple arities")

fun decls_of_clauses clauses arity_clauses =
  let val init_functab = Symtab.update (type_wrapper,2) (Symtab.update ("hAPP",2) RC.init_functab)
      val init_predtab = Symtab.update ("hBOOL",1) Symtab.empty
      val (functab,predtab) = (foldl add_clause_decls (init_functab, init_predtab) clauses)
  in
      (Symtab.dest (foldl RC.add_arityClause_funcs functab arity_clauses),
       Symtab.dest predtab)
  end;

fun add_clause_preds (Clause {ctypes_sorts, ...}, preds) =
  foldl RC.add_type_sort_preds preds ctypes_sorts
  handle Symtab.DUP a => raise ERROR ("predicate " ^ a ^ " has multiple arities")

(*Higher-order clauses have only the predicates hBOOL and type classes.*)
fun preds_of_clauses clauses clsrel_clauses arity_clauses =
    Symtab.dest
        (foldl RC.add_classrelClause_preds
               (foldl RC.add_arityClause_preds
                      (foldl add_clause_preds Symtab.empty clauses)
                      arity_clauses)
               clsrel_clauses)


(**********************************************************************)
(* write clauses to files                                             *)
(**********************************************************************)

val init_counters =
    Symtab.make [("c_COMBI", 0), ("c_COMBK", 0),
                 ("c_COMBB", 0), ("c_COMBC", 0),
                 ("c_COMBS", 0), ("c_COMBB_e", 0),
                 ("c_COMBC_e", 0), ("c_COMBS_e", 0)];

fun count_combterm (CombConst(c,tp,_), ct) =
     (case Symtab.lookup ct c of NONE => ct  (*no counter*)
                               | SOME n => Symtab.update (c,n+1) ct)
  | count_combterm (CombVar(v,tp), ct) = ct
  | count_combterm (CombApp(t1,t2), ct) = count_combterm(t1, count_combterm(t2, ct));

fun count_literal (Literal(_,t), ct) = count_combterm(t,ct);

fun count_clause (Clause{literals,...}, ct) = foldl count_literal ct literals;

fun count_user_clause user_lemmas (Clause{axiom_name,literals,...}, ct) =
  if axiom_name mem_string user_lemmas then foldl count_literal ct literals
  else ct;

val cnf_helper_thms = ResAxioms.cnf_rules_pairs o (map ResAxioms.pairname)

fun get_helper_clauses thy isFO (conjectures, axclauses, user_lemmas) =
  if isFO then []  (*first-order*)
  else
    let val ct0 = foldl count_clause init_counters conjectures
        val ct = foldl (count_user_clause user_lemmas) ct0 axclauses
        fun needed c = valOf (Symtab.lookup ct c) > 0
        val IK = if needed "c_COMBI" orelse needed "c_COMBK"
                 then (Output.debug (fn () => "Include combinator I K"); cnf_helper_thms [comb_I,comb_K])
                 else []
        val BC = if needed "c_COMBB" orelse needed "c_COMBC"
                 then (Output.debug (fn () => "Include combinator B C"); cnf_helper_thms [comb_B,comb_C])
                 else []
        val S = if needed "c_COMBS"
                then (Output.debug (fn () => "Include combinator S"); cnf_helper_thms [comb_S])
                else []
        val B'C' = if needed "c_COMBB_e" orelse needed "c_COMBC_e"
                   then (Output.debug (fn () => "Include combinator B' C'"); cnf_helper_thms [comb_B', comb_C'])
                   else []
        val S' = if needed "c_COMBS_e"
                 then (Output.debug (fn () => "Include combinator S'"); cnf_helper_thms [comb_S'])
                 else []
        val other = cnf_helper_thms [ext,fequal_imp_equal,equal_imp_fequal]
    in
        map #2 (make_axiom_clauses thy (other @ IK @ BC @ S @ B'C' @ S'))
    end;

(*Find the minimal arity of each function mentioned in the term. Also, note which uses
  are not at top level, to see if hBOOL is needed.*)
fun count_constants_term toplev t =
  let val (head, args) = strip_comb t
      val n = length args
      val _ = List.app (count_constants_term false) args
  in
      case head of
          CombConst (a,_,_) => (*predicate or function version of "equal"?*)
            let val a = if a="equal" andalso not toplev then "c_fequal" else a
            in
              const_min_arity := Symtab.map_default (a,n) (curry Int.min n) (!const_min_arity);
              if toplev then ()
              else const_needs_hBOOL := Symtab.update (a,true) (!const_needs_hBOOL)
            end
        | ts => ()
  end;

(*A literal is a top-level term*)
fun count_constants_lit (Literal (_,t)) = count_constants_term true t;

fun count_constants_clause (Clause{literals,...}) = List.app count_constants_lit literals;

fun display_arity (c,n) =
  Output.debug (fn () => "Constant: " ^ c ^ " arity:\t" ^ Int.toString n ^
                (if needs_hBOOL c then " needs hBOOL" else ""));

fun count_constants (conjectures, axclauses, helper_clauses) =
  if !minimize_applies then
    (const_min_arity := Symtab.empty;
     const_needs_hBOOL := Symtab.empty;
     List.app count_constants_clause conjectures;
     List.app count_constants_clause axclauses;
     List.app count_constants_clause helper_clauses;
     List.app display_arity (Symtab.dest (!const_min_arity)))
  else ();

(* tptp format *)

(* write TPTP format to a single file *)
fun tptp_write_file thy isFO thms filename (ax_tuples,classrel_clauses,arity_clauses) user_lemmas =
    let val _ = Output.debug (fn () => ("Preparing to write the TPTP file " ^ filename))
        val _ = RC.dfg_format := false
        val conjectures = make_conjecture_clauses thy thms
        val (clnames,axclauses) = ListPair.unzip (make_axiom_clauses thy ax_tuples)
        val helper_clauses = get_helper_clauses thy isFO (conjectures, axclauses, user_lemmas)
        val _ = count_constants (conjectures, axclauses, helper_clauses);
        val (tptp_clss,tfree_litss) = ListPair.unzip (map clause2tptp conjectures)
        val tfree_clss = map RC.tptp_tfree_clause (foldl (op union_string) [] tfree_litss)
        val out = TextIO.openOut filename
    in
        List.app (curry TextIO.output out o #1 o clause2tptp) axclauses;
        RC.writeln_strs out tfree_clss;
        RC.writeln_strs out tptp_clss;
        List.app (curry TextIO.output out o RC.tptp_classrelClause) classrel_clauses;
        List.app (curry TextIO.output out o RC.tptp_arity_clause) arity_clauses;
        List.app (curry TextIO.output out o #1 o clause2tptp) helper_clauses;
        TextIO.closeOut out;
        clnames
    end;



(* dfg format *)

fun dfg_write_file thy isFO thms filename (ax_tuples,classrel_clauses,arity_clauses) user_lemmas =
    let val _ = Output.debug (fn () => ("Preparing to write the DFG file " ^ filename))
        val _ = RC.dfg_format := true
        val conjectures = make_conjecture_clauses thy thms
        val (clnames,axclauses) = ListPair.unzip (make_axiom_clauses thy ax_tuples)
        val helper_clauses = get_helper_clauses thy isFO (conjectures, axclauses, user_lemmas)
        val _ = count_constants (conjectures, axclauses, helper_clauses);
        val (dfg_clss, tfree_litss) = ListPair.unzip (map clause2dfg conjectures)
        and probname = Path.implode (Path.base (Path.explode filename))
        val axstrs = map (#1 o clause2dfg) axclauses
        val tfree_clss = map RC.dfg_tfree_clause (RC.union_all tfree_litss)
        val out = TextIO.openOut filename
        val helper_clauses_strs = map (#1 o clause2dfg) helper_clauses
        val (funcs,cl_preds) = decls_of_clauses (helper_clauses @ conjectures @ axclauses) arity_clauses
        and ty_preds = preds_of_clauses axclauses classrel_clauses arity_clauses
    in
        TextIO.output (out, RC.string_of_start probname);
        TextIO.output (out, RC.string_of_descrip probname);
        TextIO.output (out, RC.string_of_symbols
                              (RC.string_of_funcs funcs)
                              (RC.string_of_preds (cl_preds @ ty_preds)));
        TextIO.output (out, "list_of_clauses(axioms,cnf).\n");
        RC.writeln_strs out axstrs;
        List.app (curry TextIO.output out o RC.dfg_classrelClause) classrel_clauses;
        List.app (curry TextIO.output out o RC.dfg_arity_clause) arity_clauses;
        RC.writeln_strs out helper_clauses_strs;
        TextIO.output (out, "end_of_list.\n\nlist_of_clauses(conjectures,cnf).\n");
        RC.writeln_strs out tfree_clss;
        RC.writeln_strs out dfg_clss;
        TextIO.output (out, "end_of_list.\n\n");
        (*VarWeight=3 helps the HO problems, probably by counteracting the presence of hAPP*)
        TextIO.output (out, "list_of_settings(SPASS).\n{*\nset_flag(VarWeight,3).\n*}\nend_of_list.\n\n");
        TextIO.output (out, "end_problem.\n");
        TextIO.closeOut out;
        clnames
    end;

end