Accepting parallel collections in a library...

well...

two methods, one for sequencial, one for parallel?

Am 23.12.2011 02:12, schrieb William Uther:
> Hi all,
>
> I'm writing a simple library. e.g.
>
> import scala.collection.immutable.Set;
>
> def myMax(s: Set[Int]) = s.max
>
> But that only allows serial collections. I want to allow serial or parallel collections (and actually use the parallel implementation for parallel collections), and I will be writing everything assuming immutable collections.
>
> If I switch to ParSet then I only get parallel collections. If I stick with s.c.i.Set and add a '.par' then I can accept either serial or parallel collections (with the caller having to call '.seq' sometimes), but sometimes I'll pay a performance hit to copy a serial collection into the parallel collection.
>
> If I use GenSet then I can use either serial or parallel collections, but I've lost the restriction to immutable collections. This may not be so bad - using a mutable collection as an immutable collection will be inefficient, but not incorrect, right? Is there any way to add the immutable restriction back in?
>
> It is a pity that the parallel immutable collections do not appear to implement the scala.Immutable trait, otherwise I could use 'GenSet with Immutable'. Is this deliberate or an oversight? (The parallel mutable collections are missing the scala.Mutable trait, so it is symmetric.)
>
> Thanks,
>
> Will :-}
>
>

On Thu, Dec 22, 2011 at 23:12, William Uther
wrote:
> Hi all,
>
> I'm writing a simple library.  e.g.
>
>  import scala.collection.immutable.Set;
>
>  def myMax(s: Set[Int]) = s.max
>
> But that only allows serial collections.  I want to allow serial or parallel collections (and actually use the parallel implementation for parallel collections), and I will be writing everything assuming immutable collections.
>
>  If I switch to ParSet then I only get parallel collections.  If I stick with s.c.i.Set and add a '.par' then I can accept either serial or parallel collections (with the caller having to call '.seq' sometimes), but sometimes I'll pay a performance hit to copy a serial collection into the parallel collection.
>
>  If I use GenSet then I can use either serial or parallel collections, but I've lost the restriction to immutable collections.  This may not be so bad - using a mutable collection as an immutable collection will be inefficient, but not incorrect, right?  Is there any way to add the immutable restriction back in?
>
>  It is a pity that the parallel immutable collections do not appear to implement the scala.Immutable trait, otherwise I could use 'GenSet with Immutable'.  Is this deliberate or an oversight?  (The parallel mutable collections are missing the scala.Mutable trait, so it is symmetric.)

I think it's an oversight. I suggest you open an enhancement ticket
about this with the information above.