IsPrime

// by warpie, modified by Janilabo
function IsPrime(n: Integer): Boolean;
var
  i: Integer;
  h: Single;
begin
  Result := (n = 2);
  if not (Result or (n < 2)) then
    if not ((n mod 2) = 0) then
    begin
      h := (Sqrt(n) + 1);
      i := 3;
      while (i <= h) do
        if ((n mod i) = 0) then
          Exit
        else
          i := (i + 2);
      Result := True;
    end;
end;

function PrimeTest(x: Integer): string;
var
  i: Integer;
begin
  for i := -1000 to x do
    if IsPrime(i) then
      Result := (Result + IntToStr(i) + ', ');
end;

begin
  WriteLn(PrimeTest(1000));
end.