[Hs-Generics] MultiRec generic producer.

Hey guys, While playing around with MultiRec most things are pretty straightforward and most usage can be derived from the examples. The only thing that seems tricky to do, and of which I cannot find any examples, are generic producers. Any examples of generic producers that take no values as input but do produce values as output? E.g. generic parsers (read), binary get, arbitrary? I have some `SingleRec' producers that are fairly trivial to port except for the `Tag' case. Any clues? Thanks, -- Sebastiaan Visser