check if time is in hh:mm:ss format

task2.pas

procedure Check(d: string; var res: boolean; var hms: vec);
var
  i, r: integer;
begin
  res := length(d) = 8;
  if not res then exit;
  res := (d[3] = ':') AND (d[6] = ':');
  if not res then exit;
  for i:=1 to 3 do
  begin
    val(copy(d, 1+(i-1)*3, 2), hms[i], r);
    res := r = 0;
    if not res then exit;
  end;
  res := (hms[1] <= 24) AND (hms[2] <= 60) and (hms[3] <= 60);
end;