usepackage("esvect");
usepackage("fourier","upright");
import graph;
unitsize(0.75cm);
real u0=-1, r=3;
int n=4;
object objtemp, ui[];
pair   z[];
for(int k=0; k<=n; ++k){
  z.push(u0+k*r);
  objtemp = draw(Label(format("$u_%i$",k),align=N),ellipse,z[k],nullpen);
  ui.push(objtemp);
  label(format("$M_%i$",k),z[k],4S);
}
// Du "deferred drawing" pour le tracé des flèches entre les "objects".
add(new void(picture pic, transform t) {
     for(int k=0; k<n; ++k) 
         draw(pic,Label("$+r$",align=LeftSide),
                  point(ui[k],NE,t){NE}..{S}point(ui[k+1],N,t),
                  Arrow);
});
xaxis(Ticks("%",Step=1,step=1,Size=1mm));
draw("$\vec{i}$",(0,0)--(1,0),1.5bp+red,Arrow(SimpleHead,size=8));
label("$O$",0,S,red);
real abs[]={5,11};
for(real x:abs) labelx(string(x),x,realEpsilon*S);