ObjectSieve.borg

{
`creeert zeef-objecten
`illustrates how the behavior of an object can be changed
`the data method it's behavior changes to check the prime
`after the arrival of the first unknown number
createsieve(next,collector)::
    {
    prime:0;
    data(num):
        {collector.prime(prime:=num);
        data:=checker};
    checker(num):
        if( (!((num\\prime)=0)), next.data(num));
    clone()
    };

`start de zeef met 500 filters
startsieve()::
{
  numcounter:0;
  prime(p)::
    {if ((numcounter\\10)=0,display(eoln));
    display("  "+text(p));
    numcounter:=numcounter+1};
  data(p)::void;
  col:beg:clone();
  for(i:547,i>0,i:=i-1, beg:=createsieve(beg,col));
  for(i:2,i<547,i:=i+1, beg.data(i));
  eoln
};

display("startsieve()")
}