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

您可以使用reads：

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

然而，返回Maybe Int会更加个性化：

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

Answer 2

您可以使用readMaybe中的Text.Read并获得Maybe Int代替：

import Text.Read

tryParse :: String -> Maybe Int
tryParse = readMaybe

在Haskell中实现FSharp的Int32.TryParse

2 个答案: