is should not require a prism — a fold should be fine.

[kindaro]

This is the function in question. It has type signature is :: APrism s t a b -> s -> Bool. It seems to me that fmap isJust . preview would do the same but have a more general type MonadReader s m => Getting (First a) s a -> m (Maybe a). Can we have this definition for is?

[phadej]

There is has :: Getting Any s a -> s -> Bool

[kindaro]

Alright, so why is is not has? Do they agree on the optics for which both are defined? Can we document this?