app package:rhine

Some arrows allow application of arrow inputs to other inputs. Instances should satisfy the following laws:

• first (arr (\x -> arr (\y ->
  (x,y)))) >>> app = id

• first (arr (g >>>)) >>>
  app = second g >>> app

• first (arr (>>> h)) >>>
  app = app >>> h

Such arrows are equivalent to monads (see ArrowMonad).

Any instance of ArrowApply can be made into an instance of ArrowChoice by defining left = leftApp.

Like accumulateWith, with mappend as the accumulation function.

Like mappendFrom, initialised at mempty.