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

问题描述

我试图在Haskell中使用Maybe类型。我查找了返回Maybe的关键值数组。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。 另外你可以匹配模式：

  case $V $ $ b $值只是价值 - > ... 
无 - > ... 
  

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.

解决方案

Alternatively you can pattern match:

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

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