Составить новый дек, записывая в него элементы исходного дека, изымая их поочередно слева и справа - Turbo Pascal

Unit IDeck;
Interface
type
 TUnsignedInt = word;
 TSignedInt = integer;
 tShortUnsignedInt = byte;
 TIndex1 = TUnsignedInt;
 TIndex2 = TUnsignedInt;
 TElem = char;
 
 pDec = ^cDec;
 cDec = Object
 
Private
 nmax:TSignedInt;
 head,tail:TUnsignedInt;
 p:pointer;
 ERRORCODE:tShortUnsignedInt;
 z:integer;
 
Public
 Constructor Init(n:TSignedInt);
 Constructor Copy(pq:Pdec);
 Destructor Done;
 Procedure makeEmpty;
 Function IsEmpty:boolean;
 function isFull:boolean;
 procedure Addl(x:Telem);
 procedure Addr(x:Telem);
 procedure RemoveL(var x:Telem);
 procedure RemoveR(var x:Telem);
 procedure SeeHead(var x:Telem);
 procedure SeeRight(var x:Telem);
 procedure ChangeHead(x:telem);
 procedure ChangeRight(x:telem);
 procedure writeDec(n:TSignedInt; var x:telem);
 procedure DelHead;
 procedure DelRight;
// procedure Delete;
end;
 
Implementation
{$Q+} {$R-}
 
uses
CRT;
type
 
        tArr = array [0..0] of Telem;
        Parr = ^tArr;
        PBlock=^Tblock;
        Tblock = Record
                data:Telem;
                next:Pblock;
        end;
Const
 SElem = sizeof (TElem) ;
 SegmentSize = 65520;
 
Constructor cDec.Init(n:TSignedInt);
var need:longInt;  x:telem;
begin
        need:=longint(n+2)*sizeOf(tElem);
        getmem(p,need);
        nmax:=n+1;
        head:=0;
        tail:=0;
       // x:= Pkey^[head];
        //x:=pblock(p)^.data;
end;
 
Constructor cdec.Copy(pq:Pdec);
var need:longint; i:integer;
begin
need:=longint (pq^.nmax+1) * sizeof(Telem);
getmem(p, need);
nmax:=pq^.nmax;
head:=pq^.head;
tail:=pq^.tail;
i:=head;
while i<>tail do
begin
        parr(p)^[i]:=parr(pq^.p)^[i];
        i:=(i+1) mod nmax;
end;
end;
 
Destructor cDec.done;
var need:longint;
begin
        need:=longint(nmax)*sizeof(Telem);
        freemem(p,need);
end;
 
Procedure cDec.makeEmpty;
begin
        head:=0;
        tail:=0;
end;
 
Function cDec.IsEmpty:boolean;
begin
        isEmpty:=(head=tail);
end;
 
Function cDec.IsFull:boolean;
begin
        isFull:=(head=(tail+1) mod nmax);
end;
 
procedure cDec.addl(x:Telem);
begin
        if isFull then ErrorCode:= 2
        else
        begin
                ERRORCODE := 0;
                head:=((head-1)+nmax) mod nmax;
                Parr(p)^[head]:=x;
        end;
end;
 
procedure cDec.addr(x:Telem);
begin
        if isFull then ErrorCode:= 2
        else
        begin
                ERRORCODE := 0;
                Parr(p)^[tail]:=x;
                tail:=(tail+1) mod nmax;
        end;
end;
 
procedure cDec.RemoveL(var x:tElem);
begin
        if isEmpty then ErrorCode:=2
        else
        begin
                ErrorCode:=0;
                x:=parr(p)^[head];
                head:=(head+1) mod nmax;
        end;
end;
 
procedure cDec.RemoveR(var x:tElem);
begin
        if isEmpty then ErrorCode:=2
        else
        begin
                ErrorCode:=0;
                x:=parr(p)^[tail-1];
                tail:=(tail-1) mod nmax;
        end;
end;
 
procedure cDec.SeeHead(var x:Telem);
begin
        if isEmpty then ErrorCode:=2
        else
        begin
                ErrorCode:=0;
                x:=parr(p)^[head];
        end;
end;
 
procedure cDec.SeeRight(var x:Telem);
begin
        if isEmpty then ErrorCode:=2
        else
        begin
                ErrorCode:=0;
                x:=parr(p)^[tail];
        end;
end;
 
procedure cDec.ChangeHead(x:Telem);
begin
      if isEmpty then ErrorCode:=2
        else
        begin
                ErrorCode:=0;
                parr(p)^[head]:=x;
        end
end;
 
procedure cDec.ChangeRight(x:Telem);
begin
      if isEmpty then ErrorCode:=2
        else
        begin
                ErrorCode:=0;
                parr(p)^[tail]:=x;
        end
end;
 
procedure cDec.DelHead;
begin
      if isEmpty then ErrorCode:=2
        else
        begin
                ErrorCode:=0;
                head:=(head+1) mod nmax;
        end
end;
 
procedure cDec.DelRight;
begin
      if isEmpty then ErrorCode:=2
        else
        begin
                ErrorCode:=0;
                tail:=(tail-1) mod nmax;
        end;
end;
 
procedure cDec.writeDec(n:TSignedInt; var x:telem);
begin
      if isEmpty then ErrorCode:=2
        else
        begin
                ErrorCode:=0;
                x:=parr(p)^[tail-n];
        end;
end;
 
End.