haskell - 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

七行解析一个 Int？!有没有更短的方法？

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)

返回 Maybe Int 会更加惯用然而:

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