在Haskell中实现FSharp的Int32.TryParse

Question

我喜欢F#中的Int32.TryParse函数,我想在Haskell中创建自己的函数:

import qualified Control.Exception as CE
handler:: CE.ErrorCall -> IO (Bool,Int)
handler e = return (False,0)
s2Int :: String->Int
s2Int s = read s
tryParse :: String -> IO (Bool,Int)
tryParse s = CE.catch (s2Int s `seq` return (True,read s)) handler

解析Int的七行？!有更短的方式吗？

谢谢...

Answer 1

你可以使用reads:

tryParse :: String -> (Bool, Int)
tryParse s =
    case reads s of
        [(i, "")] -> (True, i)
        _ -> (False, 0)

Maybe Int然而,返回a会更加个性化:

tryParse :: String -> Maybe Int
tryParse s =
    case reads s of
        [(i, "")] -> Just i
        _ -> Nothing

Answer 2

你可以使用readMaybe从Text.Read,并得到一个Maybe Int相反:

import Text.Read

tryParse :: String -> Maybe Int
tryParse = readMaybe