haskell - Haskell: Algebraic data type from List?

Question

Assume I have a list [A, B, C]. Is there any way I can declare an algebraic data type based on that list with the following semantics:

data V = A | B | C

Thanks!

Answer 1

您想要的是动态生成的抽象数据类型，这在任何带有 ADT 的语言中听起来都相当不标准。

您可以做的是拥有一个具有单个构造函数的数据类型，然后是一个所谓的smart-constructor，它对可以传递给构造函数的值施加了一些逻辑。

data PermList a = PermList ([a] -> Bool) [a]

permList :: ([a] -> Bool) -> [a] -> PermList a
permList f xs | f xs      = PermList f xs
              | otherwise = undefined