elm - 从字符串中解析纬度和经度对

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) 。我可以轻松调用[Just 50.0814253, Just 14.4876106]或类似的东西，但得到最终的 Maybe (Float, Float)相当困惑。有没有好的方法可以从 List (Maybe Float) 获取至Maybe (Float, Float) ？

Answer 1

如果您已经有[Just 50.0814253, Just 14.4876106]并且想要Maybe (Float, Float)，您可以使用简单的模式匹配与case .. . of:

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