我想實現應用型實例這樣的類型: newtype State s a = State {runState :: s -> (a, s)}
我有(< *>)功能有些不同的想法。實現它 的一種方式。這使我的心是 (<*>) :: State s (a -> b) -> State s a -> State s b
State f <*> State s = State $ do
(fa,
嗨,我有以下Scala代碼與cats庫 results = patrons.map(p => {
(verifyCardId(p.cardId), verifyAddress(p.address)).map2(
(maybeValidCard, maybeValidAddress) => {
val result = for {
idCheck <- may
在Haskell我們可以寫這樣的代碼: 如何做同樣的事情在F#? 我試着寫代碼這樣的事情,但它不是同一 let (<*>) f v =
match v with
| Some v' ->
match f with
| Some f' -> Some (f' v')
| _ -> None
| _ -> None
let cnst
這是一個後續行動,我以前question: 假設我想用Applicative應用功能A => B => C到List[A]和List[B]。 我相信它看起來像在Haskell: pure f <*> as <*> bs // apply f to List[A] and List[B]
或 f <$> as <*> bs
是否cats提供這樣的語法?你如何用cats來寫?
我讀格雷厄姆·赫頓在Haskell書編程和我有一些問題了解<*>和部分應用程序如何被用來解析字符串。 我知道pure (+1) <*> Just 2 產生Just 3 因爲pure (+1)產生Just (+1),然後Just (+1) <*> Just 2 產生Just (2+1)然後Just 3 但在更復雜的情況是這樣的: -- Define a new type containing a p
我擡頭實施,它更神祕: -- | Sequence actions, discarding the value of the first argument.
(*>) :: f a -> f b -> f b
a1 *> a2 = (id <$ a1) <*> a2
-- This is essentially the same as liftA2 (flip const), but if