从字符串解析纬度和经度对

Question

我有一个包含纬度/经度对的字符串：

"50.0814253N, 14.4876106E"

我想将其解析为Maybe (Float, Float)。我可以轻松地到达[Just 50.0814253, Just 14.4876106]或类似的东西，但是获得最终的Maybe (Float, Float)非常混乱。有一种从List (Maybe Float)到Maybe (Float, Float)的好方法吗？

Answer 1

如果您已经有[Just 50.0814253, Just 14.4876106]并想要Maybe (Float, Float)，则可以使用case ... of的简单模式匹配：

let list = [Just 50.0814253, Just 14.4876106]
in
case list of
  [Just a, Just b] ->
    Just (a, b)
  _ ->
    None