length(y_):= nint(sqrt(1+d(y,x)^2),x,0,1);
length(y_,x_):= nint(sqrt(1+d(y,x)^2),x,0,1);

length(y1_,y2_,y3_,x_,a_,b_):= nint(sqrt(d(y1,x)^2+d(y2,x)^2+d(y3,x)^2),x,a,b);
length(y1_,y2_,x_,a_,b_):= nint(sqrt(d(y1,x)^2+d(y2,x)^2),x,a,b);
length(y_,x_,a_,b_):= nint(sqrt(1+d(y,x)^2),x,a,b);
length(y1_ and y2_,x_,a_,b_):= nint(sqrt(1+d(y1,x)^2)+sqrt(1+d(y2,x)^2),x,a,b);
length(y_,a_,b_):= nint(sqrt(1+d(y,x)^2),x,a,b);
length(x=y1_,y=y2_):= nint(sqrt(d(y1,t)^2+d(y2,t)^2),t,0,6.28);
length(y1_ and y2_):= nint(sqrt(1+d(y1,x)^2)+sqrt(1+d(y2,x)^2),x,0,1);

length(vector(a_,b_)):= if(isconstant(a,b),abs(a,b) );
length(vector(a_,b_,c_)):=if(isconstant(a,b,c),abs(a,b,c) );
length(complex(x_,y_)) := abs(x,y);
length(circles(r_)):=pi*r;
length(squres(l_)):=4l;
length(x^2+y^2=r2_):=pi*sqrt(r2);