%-----判斷線段是否相交函數-------------------------------------------
function result=line_cross(x1,y1,x2,y2,x3,y3,x4,y4) %x1,y1,x2,y2為L1線段端點坐標

result = false;
if max(x2,x1)>=min(x3,x4) && max(x3,x4)>=min(x1,x2) &&...
     max(y2,y1)>=min(y3,y4) && max(y3,y4)>=min(y1,y2) &&...
     det([x3-x1,y3-y1;x2-x1,y2-y1])*det([x4-x1,y4-y1;x2-x1,y2-y1])<=0 &&...
     det([x1-x3,y1-y3;x3-x4,y3-y4])*det([x2-x3,y2-y3;x3-x4,y3-y4])<=0
 result = true;
end