(*  Author: Jia Meng, Cambridge University Computer Laboratory

    ID: $Id$

    Copyright 2004 University of Cambridge

ML data structure for storing/printing FOL clauses and arity clauses.

Typed equality is treated differently.

*)

signature RES_CLAUSE =

  sig

    exception ARCLAUSE of string

    exception CLAUSE of string

    type arityClause 

    type classrelClause

    val classrelClauses_of : string * string list -> classrelClause list

    type clause

    val init : theory -> unit

    val keep_types : bool ref

    val make_axiom_arity_clause :

       string * (string * string list list) -> arityClause

    val make_axiom_classrelClause :

       string * string option -> classrelClause

    val make_axiom_clause : Term.term -> string * int -> clause

    val make_conjecture_clause : Term.term -> clause

    val make_conjecture_clause_thm : Thm.thm -> clause

    val make_hypothesis_clause : Term.term -> clause

    val special_equal : bool ref

    val tptp_arity_clause : arityClause -> string

    val tptp_classrelClause : classrelClause -> string

    val tptp_clause : clause -> string list

    val clause_info : clause ->  string * string

    val tptp_clauses2str : string list -> string

    val typed : unit -> unit

    val untyped : unit -> unit

    val clause2tptp : clause -> string * string list

    val tfree_clause : string -> string

    val schematic_var_prefix : string

    val fixed_var_prefix : string

    val tvar_prefix : string

    val tfree_prefix : string

    val clause_prefix : string 

    val arclause_prefix : string

    val const_prefix : string

    val tconst_prefix : string 

    val class_prefix : string 

  end;

structure ResClause : RES_CLAUSE =

struct

(* Added for typed equality *)

val special_equal = ref false; (* by default,equality does not carry type information *)

val eq_typ_wrapper = "typeinfo"; (* default string *)

val schematic_var_prefix = "V_";

val fixed_var_prefix = "v_";

val tvar_prefix = "T_";

val tfree_prefix = "t_";

val clause_prefix = "cls_"; 

val arclause_prefix = "arcls_" 

val const_prefix = "c_";

val tconst_prefix = "tc_"; 

val class_prefix = "class_"; 

(**** some useful functions ****)

val const_trans_table =

      Symtab.make [("op =", "equal"),

	  	   ("op <=", "lessequals"),

		   ("op <", "less"),

		   ("op &", "and"),

		   ("op |", "or"),

		   ("op -->", "implies"),

		   ("op :", "in"),

		   ("op Un", "union"),

		   ("op Int", "inter")];

val type_const_trans_table =

      Symtab.make [("*", "t_prod"),

	  	   ("+", "t_sum"),

		   ("~=>", "t_map")];

(*Escaping of special characters.

  Alphanumeric characters are left unchanged.

  The character _ goes to __

  Characters in the range ASCII space to / go to _A to _P, respectively.

  Other printing characters go to _NNN where NNN is the decimal ASCII code.*)

local

val A_minus_space = Char.ord #"A" - Char.ord #" ";

fun ascii_of_c c =

  if Char.isAlphaNum c then String.str c

  else if c = #"_" then "__"

  else if #" " <= c andalso c <= #"/" 

       then "_" ^ String.str (Char.chr (Char.ord c + A_minus_space))

  else if Char.isPrint c then ("_" ^ Int.toString (Char.ord c))

  else ""

in

val ascii_of = String.translate ascii_of_c;

end;

(*Remove the initial ' character from a type variable, if it is present*)

fun trim_type_var s =

  if s <> "" andalso String.sub(s,0) = #"'" then String.extract(s,1,NONE)

  else error ("trim_type: Malformed type variable encountered: " ^ s);

fun ascii_of_indexname (v,0) = ascii_of v

  | ascii_of_indexname (v,i) = ascii_of v ^ "_" ^ string_of_int i;

fun make_schematic_var v = schematic_var_prefix ^ (ascii_of_indexname v);

fun make_fixed_var x = fixed_var_prefix ^ (ascii_of x);

(*Type variables contain _H because the character ' translates to that.*)

fun make_schematic_type_var (x,i) = 

      tvar_prefix ^ (ascii_of_indexname (trim_type_var x,i));

fun make_fixed_type_var x = tfree_prefix ^ (ascii_of (trim_type_var x));

fun make_fixed_const c =

    case Symtab.lookup (const_trans_table,c) of

        SOME c' => c'

      | NONE =>  const_prefix ^ (ascii_of c);

fun make_fixed_type_const c = 

    case Symtab.lookup (type_const_trans_table,c) of

        SOME c' => c'

      | NONE =>  tconst_prefix ^ (ascii_of c);

fun make_type_class clas = class_prefix ^ (ascii_of clas);

(***** definitions and functions for FOL clauses, prepared for conversion into TPTP format or SPASS format. *****)

val keep_types = ref true; (* default is true *)

fun untyped () = (keep_types := false);

fun typed () = (keep_types := true);

datatype kind = Axiom | Hypothesis | Conjecture;

fun name_of_kind Axiom = "axiom"

  | name_of_kind Hypothesis = "hypothesis"

  | name_of_kind Conjecture = "conjecture";

type clause_id = int;

type axiom_name = string;

type polarity = bool;

type indexname = Term.indexname;

(* "tag" is used for vampire specific syntax  *)

type tag = bool; 

val id_ref = ref 0;

fun generate_id () = 

    let val id = !id_ref

    in id_ref := id + 1; id end;

(**** Isabelle FOL clauses ****)

(* by default it is false *)

val tagged = ref false;

type pred_name = string;

type sort = Term.sort;

type fol_type = string;

datatype type_literal = LTVar of string | LTFree of string;

datatype folTerm = UVar of string * fol_type| Fun of string * fol_type * folTerm list;

datatype predicate = Predicate of pred_name * fol_type * folTerm list;

datatype literal = Literal of polarity * predicate * tag;

datatype typ_var = FOLTVar of indexname | FOLTFree of string;

(* ML datatype used to repsent one single clause: disjunction of literals. *)

datatype clause = 

	 Clause of {clause_id: clause_id,

		    axiom_name: axiom_name,

		    kind: kind,

		    literals: literal list,

		    types_sorts: (typ_var * sort) list, 

                    tvar_type_literals: type_literal list, 

                    tfree_type_literals: type_literal list };

exception CLAUSE of string;

(*** make clauses ***)

fun make_clause (clause_id,axiom_name,kind,literals,

                 types_sorts,tvar_type_literals,

                 tfree_type_literals) =

     Clause {clause_id = clause_id, axiom_name = axiom_name, kind = kind, 

             literals = literals, types_sorts = types_sorts,

             tvar_type_literals = tvar_type_literals,

             tfree_type_literals = tfree_type_literals};

(*Definitions of the current theory--to allow suppressing types.*)

val curr_defs = ref Defs.empty;

(*Initialize the type suppression mechanism with the current theory before

    producing any clauses!*)

fun init thy = (curr_defs := Theory.defs_of thy);

(*Types aren't needed if the constant has at most one definition and is monomorphic*)

fun no_types_needed s =

  (case Defs.fast_overloading_info (!curr_defs) s of

      NONE => true

    | SOME (T,len,_) => len <= 1 andalso null (typ_tvars T))

(*Flatten a type to a string while accumulating sort constraints on the TFress and

  TVars it contains.*)    

fun type_of (Type (a, [])) = (make_fixed_type_const a,[]) 

  | type_of (Type (a, Ts)) = 

      let val foltyps_ts = map type_of Ts

	  val (folTyps,ts) = ListPair.unzip foltyps_ts

	  val ts' = ResLib.flat_noDup ts

      in    

	  (((make_fixed_type_const a) ^ (ResLib.list_to_string folTyps)), ts') 

      end

  | type_of (TFree (a, s)) = (make_fixed_type_var a, [((FOLTFree a),s)])

  | type_of (TVar (v, s))  = (make_schematic_type_var v, [((FOLTVar v),s)]);

fun maybe_type_of c T =

 if no_types_needed c then ("",[]) else type_of T;

(* Any variables created via the METAHYPS tactical should be treated as

   universal vars, although it is represented as "Free(...)" by Isabelle *)

val isMeta = String.isPrefix "METAHYP1_"

fun pred_name_type (Const(c,T)) = (make_fixed_const c, maybe_type_of c T)

  | pred_name_type (Free(x,T))  = 

      if isMeta x then raise CLAUSE("Predicate Not First Order") 

      else (make_fixed_var x, type_of T)

  | pred_name_type (Var(_,_))   = raise CLAUSE("Predicate Not First Order")

  | pred_name_type _          = raise CLAUSE("Predicate input unexpected");

(* For type equality *)

(* here "arg_typ" is the type of "="'s argument's type, not the type of the equality *)

(* Find type of equality arg *)

fun eq_arg_type (Type("fun",[T,_])) = 

    let val (folT,_) = type_of T;

    in

	folT

    end;

fun fun_name_type (Const(c,T)) = (make_fixed_const c, maybe_type_of c T)

  | fun_name_type (Free(x,T)) = (make_fixed_var x,type_of T)

  | fun_name_type _ = raise CLAUSE("Function Not First Order");

(* FIX - add in funcs and stuff to this *)

fun term_of (Var(ind_nm,T)) = 

      let val (folType,ts) = type_of T

      in

	  (UVar(make_schematic_var ind_nm, folType), ts)

      end

  | term_of (Free(x,T)) = 

      let val (folType,ts) = type_of T

      in

	  if isMeta x then (UVar(make_schematic_var(x,0), folType), ts)

	  else (Fun(make_fixed_var x,folType,[]), ts)

      end

  | term_of (Const(c,T)) =  (* impossible to be equality *)

      let val (folType,ts) = type_of T

      in

	  (Fun(make_fixed_const c,folType,[]), ts)

      end    

  | term_of (app as (t $ a)) = 

      let val (f,args) = strip_comb app

	  fun term_of_aux () = 

	      let val (funName,(funType,ts1)) = fun_name_type f

		   val (args',ts2) = ListPair.unzip (map term_of args)

		   val ts3 = ResLib.flat_noDup (ts1::ts2)

	      in

		  (Fun(funName,funType,args'),ts3)

	      end

	  fun term_of_eq ((Const ("op =", typ)),args) =

	      let val arg_typ = eq_arg_type typ

		  val (args',ts) = ListPair.unzip (map term_of args)

		  val equal_name = make_fixed_const ("op =")

	      in

		  (Fun(equal_name,arg_typ,args'),ResLib.flat_noDup ts)

	      end

      in

	  case f of Const ("op =", typ) => term_of_eq (f,args)

		  | Const(_,_) => term_of_aux ()

		  | Free(s,_)  => if isMeta s 

		                  then raise CLAUSE("Function Not First Order") 

		                  else term_of_aux()

		  | _          => raise CLAUSE("Function Not First Order")

      end

  | term_of _ = raise CLAUSE("Function Not First Order"); 

fun pred_of_eq ((Const ("op =", typ)),args) =

    let val arg_typ = eq_arg_type typ 

	val (args',ts) = ListPair.unzip (map term_of args)

	val equal_name = make_fixed_const "op ="

    in

	(Predicate(equal_name,arg_typ,args'),ResLib.flat_noDup ts)

    end;

(* changed for non-equality predicate *)

(* The input "pred" cannot be an equality *)

fun pred_of_nonEq (pred,args) = 

    let val (predName,(predType,ts1)) = pred_name_type pred

	val (args',ts2) = ListPair.unzip (map term_of args)

	val ts3 = ResLib.flat_noDup (ts1::ts2)

    in

	(Predicate(predName,predType,args'),ts3)

    end;

(* Changed for typed equality *)

(* First check if the predicate is an equality or not, then call different functions for equality and non-equalities *)

fun predicate_of term =

    let val (pred,args) = strip_comb term

    in

	case pred of (Const ("op =", _)) => pred_of_eq (pred,args)

		   | _ => pred_of_nonEq (pred,args)

    end;

fun literals_of_term ((Const("Trueprop",_) $ P),lits_ts) = literals_of_term (P,lits_ts)

  | literals_of_term ((Const("op |",_) $ P $ Q),(lits,ts)) = 

      let val (lits',ts') = literals_of_term (P,(lits,ts))

      in

	  literals_of_term (Q, (lits',ts'))

      end

  | literals_of_term ((Const("Not",_) $ P),(lits,ts)) = 

      let val (pred,ts') = predicate_of P

	  val lits' = Literal(false,pred,false) :: lits

	  val ts'' = ResLib.no_rep_app ts ts'

      in

	  (lits',ts'')

      end

  | literals_of_term (P,(lits,ts)) = 

      let val (pred,ts') = predicate_of P

	  val lits' = Literal(true,pred,false) :: lits

	  val ts'' = ResLib.no_rep_app ts ts' 

      in

	  (lits',ts'')

      end;

fun literals_of_thm thm = literals_of_term (prop_of thm, ([],[]));

(*Make literals for sorted type variables*) 

fun sorts_on_typs (_, []) = []

  | sorts_on_typs (v, "HOL.type" :: s) =

      sorts_on_typs (v,s)   (*Ignore sort "type"*)

  | sorts_on_typs ((FOLTVar(indx)), (s::ss)) =

      LTVar((make_type_class s) ^ 

        "(" ^ (make_schematic_type_var indx) ^ ")") :: 

      (sorts_on_typs ((FOLTVar(indx)), ss))

  | sorts_on_typs ((FOLTFree(x)), (s::ss)) =

      LTFree((make_type_class s) ^ "(" ^ (make_fixed_type_var(x)) ^ ")") :: 

      (sorts_on_typs ((FOLTFree(x)), ss));

(*Given a list of sorted type variables, return two separate lists.

  The first is for TVars, the second for TFrees.*)

fun add_typs_aux [] = ([],[])

  | add_typs_aux ((FOLTVar(indx),s)::tss) = 

      let val vs = sorts_on_typs (FOLTVar(indx), s)

	  val (vss,fss) = add_typs_aux tss

      in

	  (ResLib.no_rep_app vs vss, fss)

      end

  | add_typs_aux ((FOLTFree(x),s)::tss) =

      let val fs = sorts_on_typs (FOLTFree(x), s)

	  val (vss,fss) = add_typs_aux tss

      in

	  (vss, ResLib.no_rep_app fs fss)

      end;

fun add_typs (Clause cls) = add_typs_aux (#types_sorts cls)

(** make axiom clauses, hypothesis clauses and conjecture clauses. **)

fun make_conjecture_clause_thm thm =

    let val (lits,types_sorts) = literals_of_thm thm

	val cls_id = generate_id()

	val (tvar_lits,tfree_lits) = add_typs_aux types_sorts

    in

	make_clause(cls_id,"",Conjecture,lits,types_sorts,tvar_lits,tfree_lits)

    end;

fun make_axiom_clause term (axname,cls_id) =

    let val (lits,types_sorts) = literals_of_term (term,([],[]))

	val (tvar_lits,tfree_lits) = add_typs_aux types_sorts

    in 

	make_clause(cls_id,axname,Axiom,lits,types_sorts,tvar_lits,tfree_lits)

    end;

fun make_hypothesis_clause term =

    let val (lits,types_sorts) = literals_of_term (term,([],[]))

	val cls_id = generate_id()

	val (tvar_lits,tfree_lits) = add_typs_aux types_sorts

    in

	make_clause(cls_id,"",Hypothesis,lits,types_sorts,tvar_lits,tfree_lits)

    end;

fun make_conjecture_clause term =

    let val (lits,types_sorts) = literals_of_term (term,([],[]))

	val cls_id = generate_id()

	val (tvar_lits,tfree_lits) = add_typs_aux types_sorts

    in

	make_clause(cls_id,"",Conjecture,lits,types_sorts,tvar_lits,tfree_lits)

    end;

(**** Isabelle arities ****)

exception ARCLAUSE of string;

type class = string; 

type tcons = string; 

datatype arLit = TConsLit of bool * (class * tcons * string list) | TVarLit of bool * (class * string);

datatype arityClause =  

	 ArityClause of {clause_id: clause_id,

			 kind: kind,

			 conclLit: arLit,

			 premLits: arLit list};

fun get_TVars 0 = []

  | get_TVars n = ("T_" ^ (string_of_int n)) :: get_TVars (n-1);

fun pack_sort(_,[])  = raise ARCLAUSE("Empty Sort Found") 

  | pack_sort(tvar, [cls]) = [(make_type_class cls, tvar)] 

  | pack_sort(tvar, cls::srt) =  (make_type_class cls,tvar) :: (pack_sort(tvar, srt));

fun make_TVarLit (b,(cls,str)) = TVarLit(b,(cls,str));

fun make_TConsLit (b,(cls,tcons,tvars)) = TConsLit(b,(make_type_class cls,make_fixed_type_const tcons,tvars));

fun make_arity_clause (clause_id,kind,conclLit,premLits) =

    ArityClause {clause_id = clause_id, kind = kind, conclLit = conclLit, premLits = premLits};

fun make_axiom_arity_clause (tcons,(res,args)) =

     let val cls_id = generate_id()

	 val nargs = length args

	 val tvars = get_TVars nargs

	 val conclLit = make_TConsLit(true,(res,tcons,tvars))

         val tvars_srts = ListPair.zip (tvars,args)

	 val tvars_srts' = ResLib.flat_noDup(map pack_sort tvars_srts)

         val false_tvars_srts' = ResLib.pair_ins false tvars_srts'

	 val premLits = map make_TVarLit false_tvars_srts'

     in

	 make_arity_clause (cls_id,Axiom,conclLit,premLits)

     end;

(**** Isabelle class relations ****)

datatype classrelClause = 

	 ClassrelClause of {clause_id: clause_id,

			    subclass: class,

			    superclass: class option};

fun make_classrelClause (clause_id,subclass,superclass) =

    ClassrelClause {clause_id = clause_id,subclass = subclass, superclass = superclass};

fun make_axiom_classrelClause (subclass,superclass) =

    let val cls_id = generate_id()

	val sub = make_type_class subclass

	val sup = case superclass of NONE => NONE 

				   | SOME s => SOME (make_type_class s)

    in

	make_classrelClause(cls_id,sub,sup)

    end;

fun classrelClauses_of_aux (sub,[]) = []

  | classrelClauses_of_aux (sub,(sup::sups)) = make_axiom_classrelClause(sub,SOME sup) :: (classrelClauses_of_aux (sub,sups));

fun classrelClauses_of (sub,sups) = 

    case sups of [] => [make_axiom_classrelClause (sub,NONE)]

	       | _ => classrelClauses_of_aux (sub, sups);

(***** convert clauses to tptp format *****)

fun string_of_clauseID (Clause cls) = 

    clause_prefix ^ string_of_int (#clause_id cls);

fun string_of_kind (Clause cls) = name_of_kind (#kind cls);

fun string_of_axiomName (Clause cls) = #axiom_name cls;

(****!!!! Changed for typed equality !!!!****)

fun wrap_eq_type typ t = eq_typ_wrapper ^"(" ^ t ^ "," ^ typ ^ ")";

(****!!!! Changed for typed equality !!!!****)

(* Only need to wrap equality's arguments with "typeinfo" if the output clauses are typed && if we specifically ask for types to be included.   *)

fun string_of_equality (typ,terms) =

    let val [tstr1,tstr2] = map string_of_term terms

    in

	if ((!keep_types) andalso (!special_equal)) then 

	    "equal(" ^ (wrap_eq_type typ tstr1) ^ "," ^ (wrap_eq_type typ tstr2) ^ ")"

	else

	    "equal(" ^ tstr1 ^ "," ^ tstr2 ^ ")"

    end

and

    string_of_term (UVar(x,_)) = x

  | string_of_term (Fun("equal",typ,terms)) = string_of_equality(typ,terms)

  | string_of_term (Fun (name,typ,[])) = name

  | string_of_term (Fun (name,typ,terms)) = 

    let val terms' = map string_of_term terms

    in

        if !keep_types andalso typ<>"" then name ^ (ResLib.list_to_string (terms' @ [typ]))

        else name ^ (ResLib.list_to_string terms')

    end;

(* Changed for typed equality *)

(* before output the string of the predicate, check if the predicate corresponds to an equality or not. *)

fun string_of_predicate (Predicate("equal",typ,terms)) = 

       string_of_equality(typ,terms)

  | string_of_predicate (Predicate(name,_,[])) = name 

  | string_of_predicate (Predicate(name,typ,terms)) = 

      let val terms_as_strings = map string_of_term terms

      in

	  if !keep_types andalso typ<>""

	  then name ^ (ResLib.list_to_string  (terms_as_strings @ [typ]))

	  else name ^ (ResLib.list_to_string terms_as_strings) 

      end;

fun tptp_literal (Literal(pol,pred,tag)) =

    let val pred_string = string_of_predicate pred

	val tagged_pol = 

	      if (tag andalso !tagged) then (if pol then "+++" else "---")

	      else (if pol then "++" else "--")

     in

	tagged_pol ^ pred_string

    end;

fun tptp_of_typeLit (LTVar x) = "--" ^ x

  | tptp_of_typeLit (LTFree x) = "++" ^ x;

fun gen_tptp_cls (cls_id,ax_name,knd,lits) = 

    let val ax_str = (if ax_name = "" then "" else ("_" ^ ascii_of ax_name))

    in

	"input_clause(" ^ cls_id ^ ax_str ^ "," ^ knd ^ "," ^ lits ^ ")."

    end;

fun gen_tptp_type_cls (cls_id,knd,tfree_lit,idx) = 

    "input_clause(" ^ cls_id ^ "_tcs" ^ (string_of_int idx) ^ "," ^ 

    knd ^ ",[" ^ tfree_lit ^ "]).";

fun tptp_clause_aux (Clause cls) = 

    let val lits = map tptp_literal (#literals cls)

	val tvar_lits_strs =

	      if (!keep_types) 

	      then (map tptp_of_typeLit (#tvar_type_literals cls)) 

	      else []

	val tfree_lits = 

	      if (!keep_types) 

	      then (map tptp_of_typeLit (#tfree_type_literals cls)) 

	      else []

    in

	(tvar_lits_strs @ lits,tfree_lits)

    end; 

fun tptp_clause cls =

    let val (lits,tfree_lits) = tptp_clause_aux cls (*"lits" includes the typing assumptions (TVars)*)

	val cls_id = string_of_clauseID cls

	val ax_name = string_of_axiomName cls

	val knd = string_of_kind cls

	val lits_str = ResLib.list_to_string' lits

	val cls_str = gen_tptp_cls(cls_id,ax_name,knd,lits_str) 			fun typ_clss k [] = []

          | typ_clss k (tfree :: tfrees) = 

            (gen_tptp_type_cls(cls_id,knd,tfree,k)) ::  (typ_clss (k+1) tfrees)

    in 

	cls_str :: (typ_clss 0 tfree_lits)

    end;

fun clause_info cls = (string_of_axiomName cls, string_of_clauseID cls);

fun clause2tptp cls =

    let val (lits,tfree_lits) = tptp_clause_aux cls (*"lits" includes the typing assumptions (TVars)*)

	val cls_id = string_of_clauseID cls

	val ax_name = string_of_axiomName cls

	val knd = string_of_kind cls

	val lits_str = ResLib.list_to_string' lits

	val cls_str = gen_tptp_cls(cls_id,ax_name,knd,lits_str) 

    in

	(cls_str,tfree_lits) 

    end;

fun tfree_clause tfree_lit =

    "input_clause(" ^ "tfree_tcs," ^ "conjecture" ^ ",[" ^ tfree_lit ^ "]).";

val delim = "\n";

val tptp_clauses2str = ResLib.list2str_sep delim; 

fun string_of_arClauseID (ArityClause arcls) = arclause_prefix ^ string_of_int(#clause_id arcls);

fun string_of_arLit (TConsLit(b,(c,t,args))) =

    let val pol = if b then "++" else "--"

	val  arg_strs = (case args of [] => "" | _ => ResLib.list_to_string args)

    in 

	pol ^ c ^ "(" ^ t ^ arg_strs ^ ")"

    end

  | string_of_arLit (TVarLit(b,(c,str))) =

    let val pol = if b then "++" else "--"

    in

	pol ^ c ^ "(" ^ str ^ ")"

    end;

fun string_of_conclLit (ArityClause arcls) = string_of_arLit (#conclLit arcls);

fun strings_of_premLits (ArityClause arcls) = map string_of_arLit (#premLits arcls);

fun string_of_arKind (ArityClause arcls) = name_of_kind(#kind arcls);

fun tptp_arity_clause arcls = 

    let val arcls_id = string_of_arClauseID arcls

	val concl_lit = string_of_conclLit arcls

	val prems_lits = strings_of_premLits arcls

	val knd = string_of_arKind arcls

	val all_lits = concl_lit :: prems_lits

    in

	"input_clause(" ^ arcls_id ^ "," ^ knd ^ "," ^ (ResLib.list_to_string' all_lits) ^ ")."

    end;

val clrelclause_prefix = "relcls_";

fun tptp_classrelLits sub sup = 

    let val tvar = "(T)"

    in 

	case sup of NONE => "[++" ^ sub ^ tvar ^ "]"

		  | (SOME supcls) =>  "[--" ^ sub ^ tvar ^ ",++" ^ supcls ^ tvar ^ "]"

    end;

fun tptp_classrelClause (ClassrelClause cls) =

    let val relcls_id = clrelclause_prefix ^ string_of_int(#clause_id cls)

	val sub = #subclass cls

	val sup = #superclass cls

	val lits = tptp_classrelLits sub sup

    in

	"input_clause(" ^ relcls_id ^ ",axiom," ^ lits ^ ")."

    end; 

end;