fcn addItem(old,[(nm,w,v,c)]){  // old:list:(cost of:,(name,#,...))
   [1..c].reduce(fcn(list,i,nm,w,v,old){
      wi,left,right:=w*i,list[0,wi],list[wi,*];
      new:=old.apply('wrap([(val,itms)]){ T(val + v*i,itms.append(nm,i)) });
      left.extend(right.zipWith(  // inc
	    fcn([(v1,_)]a,[(v2,_)]b){ v1>v2 and a or b  },new));
   },old,nm,w,v,old);
}//--> new list