[PAS] Sprawdzanie nawiasowanie na stosie

program Project1;

uses
    crt, DOS;
type
  listPtr = ^list;

  list = record
       next: listPtr;
       previous: listPtr;
       x: String;
  end;

procedure push(var listStart: listPtr; var listEnd: listPtr; y: String);
var
   newElement: listPtr;
begin
     clrScr;
     if listEnd = NIL then
     begin
          newElement := listStart;
          new(newElement);

          newElement^.x := y;
          newElement^.next := NIL;
          newElement^.previous := NIL;
          listEnd := newElement;
          listStart := newElement;
     end else
     begin
          newElement := listEnd;
          New(newElement^.next);
          newElement := newElement^.next;
          newElement^.x := y;

          newElement^.next := NIL;
          newElement^.previous := listEnd;
          listEnd := newElement;
     end;
end;


function pop(var listStart: listPtr; var listEnd: listPtr): String;
var
   pointer: listPtr;
begin
     if listStart^.next = NIL then
     begin
          pointer := listStart;
          pop := pointer^.x;
          dispose(pointer);
          listStart := NIL;
          listEnd := NIL;
     end else
     begin
          pointer := listEnd;
          listEnd := pointer^.previous;
          listEnd^.next := NIL;
          pop := pointer^.x;
          dispose(pointer);
     end;
end;


function isEmpty(var listStart: listPtr): Boolean;
begin
     clrScr;
     if listStart = NIL then
         isEmpty := True
     else
         isEmpty := False;
end;



function readBracket(var listStart: listPtr; var listEnd: listPtr): Boolean;
var
   line: String;
begin
     readBracket := True;
     writeLn('Wprowadz nawias lub 0, aby zakonczyc: ');
     ReadLn(line);

     if (line = '{') or (line = '(') then
     begin
          push(listStart, listEnd, line);
     end else if (line = ')') then
     begin
          if not isEmpty(listStart) then
          begin
               if pop(listStart, listEnd) = '(' then
               begin
                    writeLn('Nawias pasuje!');
                    delay(500);
               end else
               begin
                    readBracket := False;
                    writeLn('Nawias NIE pasuje!');
                    delay(500);
               end;
          end else
          begin
               writeLn('Brak nawiasow na stosie!');
               delay(500);
          end;
     end else if (line = '}') then
     begin
          if not isEmpty(listStart) then
          begin
               if pop(listStart, listEnd) = '{' then
               begin
                    writeLn('Nawias pasuje!');
                    delay(500);
               end else
               begin
                    readBracket := False;
                    writeLn('Nawias NIE pasuje!');
                    delay(500);
               end;
          end else
          begin
               writeLn('Brak nawiasow na stosie!');
               delay(500);
          end;
     end else if (line = '0') then
     begin
          readBracket := False;
          if isEmpty(listStart) then
              begin
                   writeLn('Nawiasowanie poprawne!');
              end else
              begin
                   writeLn('Nawiasowanie bledne!');
              end;
          delay(500);
     end else
     begin
          writeLn('Bledne dane wejsciowe, wpisz jeszcze raz!');
          delay(500);
     end;
end;

var
   listStart, listEnd: listPtr;
   go: Boolean;
begin
     listEnd:= NIL;
     listStart := NIL;

     go := True;

     clrScr;
     while go do
     begin
          clrScr;
          go := readBracket(listStart, listEnd);
     end;

     writeLn('Nacisnij dowolny klawisz aby wyjsc...');
     ReadKey;

end.