encoding  utf-8
layout l_u_rail

code metapost
def l_u_rail (expr P) = 
  T:=identity;
  cas := 0;
  dlzka := arclength P;
  mojkrok:=adjust_step(dlzka, 0.8u);
  pickup PenC;
  forever:
    t0 := arctime (cas) of P;
    t1 := arctime (cas + mojkrok*2/5) of P;
    t  := arctime (cas + mojkrok/2) of P;
    t4 := arctime (cas + mojkrok*3/5) of P;
    t5 := arctime (cas + mojkrok) of P;
    thdraw (subpath (t0,t1) of P);
    thdraw (subpath (t4,t5) of P);
    drawdot
       (point t of P);
    #mark_ (P,t,0.02u);
    #mark_ (P,t,-0.02u);
     #f := (P,t,0.2u);
     #draw f;
    cas := cas + mojkrok;
    exitif cas > dlzka - (2*mojkrok/3); % for rounding errors
  endfor;
enddef;


initsymbol("l_u_rail")
#text en line u:rail "Railing"
endcode

endlayout