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{ a helper hides an existing enumerator }
program tchlp53;
{$ifdef fpc}
{$mode delphi}
{$endif}
{$apptype console}
type
TContainerEnum = class;
TContainer = class
Contents: array[0..5] of Integer;
function GetEnumerator: TContainerEnum;
constructor Create;
end;
TContainerEnum = class
private
fIndex: Integer;
fContainer: TContainer;
fForward: Boolean;
public
constructor Create(aContainer: TContainer; aForward: Boolean);
function GetCurrent: Integer;
function MoveNext: Boolean;
property Current: Integer read GetCurrent;
end;
TContainerHelper = class helper for TContainer
function GetEnumerator: TContainerEnum;
end;
{ TContainer }
constructor TContainer.Create;
var
i: Integer;
begin
for i := Low(Contents) to High(Contents) do
Contents[i] := i;
end;
function TContainer.GetEnumerator: TContainerEnum;
begin
Result := TContainerEnum.Create(Self, True);
end;
{ TContainerHelper }
function TContainerHelper.GetEnumerator: TContainerEnum;
begin
Result := TContainerEnum.Create(Self, False);
end;
{ TContainerEnum }
constructor TContainerEnum.Create(aContainer: TContainer; aForward: Boolean);
begin
fContainer := aContainer;
fForward := aForward;
if fForward then
fIndex := Low(fContainer.Contents) - 1
else
fIndex := High(fContainer.Contents) + 1;
end;
function TContainerEnum.GetCurrent: Integer;
begin
Result := fContainer.Contents[fIndex];
end;
function TContainerEnum.MoveNext: Boolean;
begin
if fForward then begin
Inc(fIndex);
Result := fIndex <= High(fContainer.Contents);
end else begin
Dec(fIndex);
Result := fIndex >= Low(fContainer.Contents);
end;
end;
var
cont: TContainer;
i, c: Integer;
begin
cont := TContainer.Create;
c := 5;
for i in cont do begin
if c <> i then
Halt(1);
Writeln(i);
Dec(c);
end;
Writeln('ok');
end.
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