【摘要】fmap :: (T -> R) -> Functor<T> -> Functor<R> lifts a function of type T -> R into a function of type Functor<T> -> Functor<R>; flatMap :: (T -> Monad<R>) -> Monad<T> -> Monad<R> lifts a function of type T -> Monad<R> into a function of type Monad<T> -> Monad<R>. 阅读全文