%@AUTEUR: Christophe Poulain (4 février 2003)

vardef hachurage(expr chemin, angle, ecart, trace)suffix couleur =
  save $;
  picture $;
  path support;
  support=(((-37cm,0))--((37cm,0))) rotated angle;
  if trace=1:
    drawoptions(dashed evenly);
  elseif trace=2:
    drawoptions(dashed dashpattern(on12bp off6bp on3bp off6bp));
  fi;
  $ = image(
    for j=-200 upto 200:
     if ((support shifted (ecart*j*(1,0))) intersectiontimes chemin)<>(-1,-1):
       draw support shifted (ecart*j*(1,0)) 
           withcolor if str couleur="":(0,0,0) else:couleur fi;
     fi
    endfor;
  );
  clip $ to chemin;
  drawoptions();
  $
enddef;

color rouge;
rouge = (1,0,0);

beginfig(1);
  path p,q;
  p = fullcircle scaled 3cm;
  draw hachurage(p,45,2mm,0)rouge;
  draw p;
  q = (p scaled 0.5) shifted (4cm,2cm);
  draw hachurage(q,30,4mm,1);
  draw q;
endfig;

def dessine(expr p,a,e,t,s)(text couleurs)  =
    save co,n;
    color co[];
    numeric n;
    n := 0; forsuffixes c = couleurs: co[incr n] = c; endfor;
    if n = 1: co2 = co1; fi;
    draw hachurage(p,a,e,t) co1;
    draw p withpen pencircle scaled s withcolor co2;
enddef;
    
beginfig(2);
 path carre,cercle;
 cercle = fullcircle scaled 2cm;
 carre = ((0,0)--(3cm,0)--(3cm,3cm)--(0,3cm)--cycle) shifted (3cm,-1cm);
 dessine(((3cm,1cm)..(4cm,3cm)..(1cm,2cm)..cycle),30,4mm,3,1pt,black);
 dessine(cercle,60,3mm,0,2pt,green);
 dessine(carre,45,5mm,2,1pt,blue,red);
endfig;
end