抓住错误抛出“错误”？

Question

有一些stdlib函数会在无效输入上抛出错误。例如：

Prelude> read "1o2" :: Int
*** Exception: Prelude.read: no parse

我想将其换行以返回Either e a。我怎么能这样做？

Answer 1

There is no spoon.你没有听到我的声音。

但是，对于此特定示例，您应该使用reads代替。

Answer 2

我更喜欢将错误转换为值：

 maybeRead :: Read a => String -> Maybe a
 maybeRead s = case reads s of
      [(x, "")] -> Just x
      _         -> Nothing