将IO [a - > b]应用于类型a的单个参数

我有

functions :: IO[a -> b]   -- IO List of functions
param :: IO[a]            -- Single parameter

而且我想得到

result :: IO[b]
result = IO[*first function* <$> param, *second function* <$> param, ...]

我不知何故可以获得类型的结果IO[IO b],但我想要IO[b]

通过"单个参数"我假设你的意思是一个元素列表.如果是这样,那么这就是它的完成方式:

result :: IO [b]
result = do
    fs <- functions    -- fs :: [a -> b]
    xs <- param        -- xs :: [a]
    let ys = fs <*> xs -- ys :: [b]
    return ys

import Control.Applicative (liftA2)

result :: IO [b]
result = liftA2 (<*>) functions param