bool pointInside(point2D a, point2D b, point2D c, point2D p){  float sign1, sign2;  if ((a.x <= p.x) && (p.x <= c.x))  {   sign2 = (p.x - a.x) * (c.y - a.y) - (p.y - a.y) * (c.x - a.x);   if ((p.x < b.x) || (b.x == c.x))    sign1 = (p.x - a.x) * (b.y - a.y) - (p.y - a.y) * (b.x - a.x);   else    sign1 = (p.y - c.y) * (b.x - c.x) - (p.x - c.x) * (b.y - c.y);      if (((sign1 >= 0) && (sign2 <= 0)) || ((sign1 <= 0) && (sign2 >= 0)))    return true;  }  return false;}