Slice

program new;

function Slice(arr:TIntegerArray; start,stop:Int64; step:Int32=1): TIntegerArray;
var
  len:Int32;
  P,R:^Int32;
  L:PtrUInt;
begin
  len := Length(arr);
  if len = 0 then Exit();

  if (step > 0) and (stop >= len)  then
    stop  := len;   //not inclusive
  if (step < 0) and (start >= len) then
    start := len-1; //inclusive
  if ((stop  < 0) and ((abs(stop) > abs(start)) or (step > 0))) then
    stop  := len+stop;
  if (start < 0) then
    start := len+start;

  SetLength(Result, Max(0, Ceil((stop-start) / step)));
  if Length(Result) = 0 then Exit();

  //WriteLn('>>> ', [start, stop, step]);

  P := @arr[start];
  R := @Result[0];
  L := PtrUInt(@Result[High(Result)]);
  while PtrUInt(R) <= L do
  begin
    R^ := P^;
    Inc(R);
    Inc(P, step);
  end;
end;

function Equal(Left, Right: TIntegerArray): Boolean;
begin
//WriteLn([Left, Right]);
  if Length(Left) <> Length(Right) then Exit(False);
  If (Length(Left) = Length(Right)) and (Length(Left) = 0) then Exit(True);
  Result := CompareMem(Left[0], Right[0], SizeOf(Int32)*Length(Left));
end;

var
  x: TIntegerArray = [0,1,2,3,4,5,6,7,8,9];
begin
  WriteLn Equal(Slice(x, 0,High(Int32),1),   [0, 1, 2, 3, 4, 5, 6, 7, 8,9]);
  WriteLn Equal(Slice(x, High(Int32),0,-1),  [9, 8, 7, 6, 5, 4, 3, 2, 1]);
  WriteLn Equal(Slice(x, 0,-1,1),   [0, 1, 2, 3, 4, 5, 6, 7, 8]);
  WriteLn Equal(Slice(x, 6,0,-1),   [6, 5, 4, 3, 2, 1]);
  WriteLn Equal(Slice(x, 0,6,1),    [0, 1, 2, 3, 4, 5]);
  WriteLn Equal(Slice(x, 0,10,1),   [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
  WriteLn Equal(Slice(x, 0,7,3),    [0, 3, 6]);
  WriteLn Equal(Slice(x, 5,9,1),    [5, 6, 7, 8]);
  WriteLn Equal(Slice(x, -1,0,-1),  [9, 8, 7, 6, 5, 4, 3, 2, 1]);
  WriteLn Equal(Slice(x, -1,-1,-1), [9, 8, 7, 6, 5, 4, 3, 2, 1, 0]);
  WriteLn Equal(Slice(x, -3,-1, 1), [7, 8]);
  WriteLn Equal(Slice(x, -1,-1, 1), []);
  WriteLn Equal(Slice(x, 5,0, 1),   []);
  WriteLn Equal(Slice(x, 0,5,-1),   []);
  WriteLn Equal(Slice(x, 7,2,-3),   [7,4]);
  WriteLn Equal(Slice(x, 7,2,-100), [7]);
  WriteLn Equal(Slice(x, -4,-1, 1), [6,7,8]);
  WriteLn Equal(Slice(x, -1,-4,-1), [9,8,7]);
  WriteLn Equal(Slice(x, -1, 3,-1), [9, 8, 7, 6, 5, 4]);
end.