code: public static Function<? super ReactiveSeq<Double>, ? extends ReactiveSeq<Double>> filterLongs(DoublePredicate b){
  
          return a->a.doubles(i->i,s->s.filter(b));
      }
docs: /*
  Fluent filter operation using primitive types
  e.g.
  <pre>
  {@code
  import static cyclops.ReactiveSeq.filterDoubles;
  
  ReactiveSeq.ofDoubles(1d,2d,3d)
  .to(filterDoubles(i->i>2));
  
  //[3d]
  }
  </pre>