unit veremu;

interface

Type TelemTip=char;
     TveremElemMut=^TveremElem;
     TveremElem=Record ertek:TelemTip;
                           kov:TveremElemMut end;
     Tverem=Object
               private
                    teto:TveremElemMut;
                    hiba:boolean;
                public
                    Procedure ures;
                    Function ures_e:boolean;
                    Procedure verembe(e:TelemTip);
                    Procedure verembol(var e:Telemtip);
                    Function tetejere:Telemtip;
                    Function tele_e:boolean;
                    Function hibas_e:boolean;
                  end;
implementation

Procedure Tverem.ures;
begin
teto:=nil; hiba:=false;
end;

Function Tverem.ures_e:boolean;
begin
  ures_e:=(teto=nil);
end;

procedure Tverem.verembe(e:TelemTip);
var sv:TveremElemMut;
begin
if tele_e then hiba:=true
 else begin
   new(sv);
   sv^.ertek:=e;
   sv^.kov:=teto;
   teto:=sv; end;
end;

Procedure Tverem.verembol(var e:Telemtip);
var sv:TveremElemMut;
begin
  if ures_e then hiba:=true
   else begin
    sv:=teto;
    e:=sv^.ertek;
    teto:=sv^.kov;
    dispose(sv); end;
end;

Function Tverem.tetejere:Telemtip;
begin
  if ures_e then hiba:=true
   else tetejere:=teto^.ertek;
end;

Function Tverem.tele_e:boolean;
begin
  if maxavail<sizeof(TveremElem) then tele_e:=true
    else tele_e:=false;
end;

Function Tverem.hibas_e:boolean;
begin
  hibas_e:=hiba;
  hiba:=false;
end;

end.