fcn vogel(costs,supply,demand){
   // a Dictionary can be created via a list of (k,v) pairs
   res:= Dictionary(costs.pump(List,fcn([(k,_)]){ return(k,D()) }));
   g  := Dictionary(); // cross index costs and make writable
   supply.pump(Void,'wrap([(k,_)]){ g[k] =
      costs[k].keys.sort('wrap(a,b){ costs[k][a]<costs[k][b] }).copy() });
   demand.pump(Void,'wrap([(k,_)]){ g[k] =
      costs.keys.sort('wrap(a,b){ costs[a][k]<costs[b][k] }).copy() });

   while(g){
      d:=Dictionary(demand.pump(List,'wrap([(k,_)]){ return(k,
	 g[k][0,2].apply('wrap(gk){ costs[gk][k] }).reverse().reduce('-)) }));
      s:=Dictionary(supply.pump(List,'wrap([(k,_)]){ return(k,
	 g[k][0,2].apply('wrap(gk){ costs[k][gk] }).reverse().reduce('-)) }));
      f:=(0).max(d.values); f=d.filter('wrap([(_,v)]){ v==f })[-1][0];
      t:=(0).max(s.values); t=s.filter('wrap([(_,v)]){ v==t })[-1][0];
      t,f=(if(d[f]>s[t]) T(f,g[f][0]) else T(g[t][0],t));
      v:=supply[f].min(demand[t]);
      res[f].appendV(t,v);  // create t:(v) or append v to t:(...)
      if(0 == (demand[t]-=v)){
	 supply.pump(Void,'wrap([(k,n)]){ if(n!=0) g[k].remove(t) });
	 g.del(t); demand.del(t);
      }
      if(0 == (supply[f]-=v)){
	 demand.pump(Void,'wrap([(k,n)]){ if(n!=0) g[k].remove(f) });
	 g.del(f); supply.del(f);
      }
   }//while
   res
}