Haskell 数据类型范围

Question

我定义了自己的数据类型。

data Row = A | B | C deriving (Show,Eq,Ord)

问题是，是否有比这更优雅的方式来定义我的范围？

instance Ix Row where
  range (A,A) = [A]
  range (A,B) = [A,B]
  range (A,C) = [A,B,C]
  range (B,B) = [B]
  range (B,C) = [B,C]
  range (C,C) = [C]
  range _     = []

Answer 1

有:导出Enum并定义

range (x, y) = [x .. y]