code: public static Function<? super ReactiveSeq<Double>, ? extends ReactiveSeq<Double>> mapDoubles(DoubleUnaryOperator b){
  
          return a->a.doubles(i->i,s->s.map(b));
      }
docs: /*
  Fluent transform operation using primitive types
  e.g.
  <pre>
  {@code
  import static cyclops.ReactiveSeq.mapDoubles;
  
  ReactiveSeq.ofDoubles(1d,2d,3d)
  .to(mapDoubles(i->i*2));
  
  //[2d,4d,6d]
  }
  </pre>