local fn IsInCarpet( x as NSUInteger, y as NSUInteger ) as BOOL
  while ( x != 0 && y != 0 )
    if ( x % 3 == 1 && y % 3 == 1 ) then return NO
    y /= 3 : x /= 3
  wend
end fn = YES

void local fn SierpinskiCarpet( n as NSUInteger )
  NSUInteger i, j, k = fn pow(3,n) - 1
  pen -1
  for i = 0 to k
    for j = 0 to k
      ColorRef col = fn ColorOrange
      if ( fn IsInCarpet(i,j) )
        col = fn ColorRed
      end if
      rect fill (i * 10, j * 10, 10, 10 ), col
    next
  next
end fn

window 1, @"Sierpinski Carpet", (0,0,270,270), NSWindowStyleMaskTitled
fn SierpinskiCarpet(3)

HandleEvents