Has anyone developed a typeclass model for (Control.Monad.mapM) and related functions for arrows? I've a preliminary model, using Adam Megacz's Generalized Arrows, of the form: class (GArrowDrop a (**) u) => GArrowMap_ a (**) u c where mapA_ :: a d u -> a (c d) u class (GArrow a (**) u c) => GArrowMap a (**) u c where mapA :: a d r -> a (c d) (c r) class (GArrowMap a (**) u c) => GArrowJoin a (**) u c where join :: a d (c r) -> a (c d) (c r) class (GArrow a (**) u) => GArrowUnion a (**) u c where union :: a ((c r) ** (c r)) (c r) class (GArrowMap a (**) u c, GArrow a (++) v) => GArrowPartition a (**) u (++) v c where partition :: a d (q ++ r) -> a (c d) ((c q) ** (c r)) Motivations: regular arrows (including GArrows) expose simple products for behavior, but those have a static 'width' and don't seem suitable for processing large values. ArrowApply would give me a dynamic amount of processing, but seems excessively expressive. In my own case, 'c' might be representing an asynchronous or distributed, reactive collection, so the ability to restrict expressiveness is important for performance. I'm wondering if you know of any other work along the same lines. Thank you, Dave