function l=overlapLength(x1,y1,x2,y2)

    l=0;
    if length(x1) == 1 
        
        max1 = max(x1,y1);
        min1 = min(x1,y1);
        max2 = max(x2,y2);
        min2 = min(x2,y2);
        
        if (min1 >= max2) || (min2 >= max1)  %case1
            l=0;
        elseif (max2 > min1 && min1 > min2) %case2
            l= max2-min1;
        elseif max2 > min1 && min2 >= min1 && max2 <= max1 %case4
            l = max2 - min2;
        elseif max1 > min2 && min1 >= min2 && max1 <= max2 % case5
            l= max1-min1;
        elseif max2 >= max1 && min1 < min2 %case3
            l = max1 - min2;
        end
        
        return;
        
    else
        
        if x1(1) == x1(2) && x2(1) == x2(2) && x1(1) == x2(1)
            l=overlapLength(y1(1),y1(2),y2(1),y2(2));
            return;
        elseif y1(1) == y1(2) && y2(1) == y2(2) && y1(1) == y2(1)
            l=overlapLength(x1(1),x1(2),x2(1),x2(2));
            return;
        elseif x1(1) ~= x1(2) && x2(1) ~= x2(2)
            
            m(1) = (y1(2)-y1(1))/(x1(2)-x1(1));
            b(1) = y1(1) - m(1)*x1(1);
            m(2) = (y1(2)-y1(1))/(x1(2)-x1(1));
            b(2) = y2(1) - m(2)*x2(1);
            
            m= round(m.*10^7)./10^7;
            b= round(b.*10^7)./10^7;
            
            
            if (m(1) == m(2) && b(1) == b(2))
                
                x0 = -b(1)/m(1);
                
                hyp1(1) = sqrt( y1(1)^2 + (x1(1)-x0)^2);
                hyp1(2) = sqrt( y1(2)^2 + (x1(2)-x0)^2);
                hyp2(1) = sqrt( y2(1)^2 + (x2(1)-x0)^2);
                hyp2(2) = sqrt( y2(2)^2 + (x2(2)-x0)^2);
                
                l = overlapLength(hyp1(1),hyp1(2),hyp2(1),hyp2(2));
                return;
            end
        end
        
    
    end
        
end