haskell - 如何使我的 Haskell 函数尽可能短？

Question

该season函数使用代数函数，但我觉得代码是重复的。

如何让它尽可能短？

data Month = Jan | Feb | Mar | Apr | May | June | July | Aug | Sept| Oct | Nov | Dec
     deriving (Eq,Ord,Show,Read)

data Seasons = Spring | Summer | Autumn | Winter
     deriving (Eq,Ord,Show,Read)

season :: Month -> Seasons
season Jan = Winter
season Feb = Winter
season Mar = Spring
season Apr = Spring
season May = Spring
season June = Summer
season July = Summer
season Aug = Summer
season Sept = Autumn
season Oct = Autumn
season Nov = Autumn
season Dec = Winter

标签： haskellalgebraic-data-types

Answer 1

您可以使用警卫，因为您创建了Month一个实例Ord：

season :: Month -> Seasons
season m | m <= Feb = Winter
         | m <= May = Spring
         | m <= Aug = Summer
         | m <= Nov = Autumn
         | otherwise = Winter