int isParallel(TLine &l1, TLine &l2) { float dx1 = (*l1.getp2()).getx()-(*l1.getp1()).getx(); float dy1 = (*l1.getp2()).gety()-(*l1.getp1()).gety(); float dx2 = (*l2.getp2()).getx()-(*l2.getp1()).getx(); float dy2 = (*l2.getp2()).gety()-(*l2.getp1()).gety(); if((dx1==0) || (dx2==0)) if(dx1==dx2) return 1; else return 0; else { float k1 = dy1/dx1; float k2 = dy2/dx2; if(k1==k2) return 1; else return 0; } }