The class you're looking for is Applicative. The (<*>) operator handles application of "effectful" things to "effectful" things, whereas (<$>) handles the application of non-"effectful" things to "effectful" things. This situation is interesting because it highlights the fact that there is a distinction between the meaning of whitespace between function and argument vs the meaning of whitespace between argument and argument.
`Applicative` is not enough for monads. `Applicative` is like functor only for functions with many arguments. It's good for patterns: (a -> b -> c -> d) -> (m a -> m b -> m c -> m d) Monads are good for patterns (a -> b -> c -> m d) -> (m a -> m b -> m c -> m d) So I can not express it with `Applicative`. My analogy really breaks down on functions with several arguments, since as you have pointed out there are two white spaces. But I like the idea of using one sign for normal and monadic and maybe applicative applications. Anton
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