Some of these are explanable from mathematical conventions. In abstract algebra it's common to surround an operator in a circle to denote a "generic" or "lifted

Some of these are explanable from mathematical conventions. In abstract algebra it's common to surround an operator in a circle to denote a "generic" or "lifted" operator. So <$> denotes a "lifted application", i.e. ($) :: (a → b) → a → b (<$>) :: Functor f => (a → b) → f a → f b