在 Haskell 中使用 Maybe 类型 [英] Using Maybe type in Haskell

问题描述

我正在尝试使用 Haskell 中的 Maybe 类型.我有一个键值元组的查找返回一个Maybe.如何访问由Maybe包装的数据?例如我想将Maybe包含的整数与另一个整数相加.

I'm trying to utilize the Maybe type in Haskell. I have a lookup for key, value tuples that returns a Maybe. How do I access the data that was wrapped by Maybe? For example I want to add the integer contained by Maybe with another integer.

推荐答案

或者你可以模式匹配:

case maybeValue of
  Just value -> ...
  Nothing    -> ...

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