/*preparer(x,y)->rule(notes(x,y,z),nil)
		assert(noteutile(x,y,z),nil)
		fail; */

preparer(x,y)-> notes(x,y,z)
		asserta(noteutile(x,y,z),nil)
		fail;
preparer(x,y)->;


somme(x,y,s,n)-> retract (noteutile(x,y,z),nil) 
                 !
		 somme(x,y,s1,n1)
		 val(add(s1,z),s)
		 val(add(n1,1),n);
somme(x,y,0,0)->;


calculer(x,y,m)->somme(x,y,s,n)
		val(div(s,n),m);


effacer->retract(noteutile(x,y,z),nil)
		fail;
effacer->;

moyenne(x,y,m)->effacer
		preparer(x,y)
	   	calculer(x,y,m);