public function isConvex()
{
$lines = $this->getLines();
$lines[] = $lines[0];
// to loop on every angles
for ($i = 1, $imax = count($lines); $i < $imax; $i++) {
$angle = Line::getAntiClockWiseAngleBetweenLines($lines[$i], $lines[$i - 1]);
if (abs($angle) > 180) {
return false;
}
}
return true;
}
