Haskell案例中的范围检查？

Question

是否有一种在Haskell中执行以下操作的有效方法:

case n of
    0     -> doThis
    1     -> doThat
    2     -> doAnother
    3..99 -> doDefault

除了拥有97行"doDefault"之外？

Answer 1

case n of
    0     -> doThis
    1     -> doThat
    2     -> doAnother
    _     -> doDefault

如果你真的需要一个范围,

case n of
    0     -> doThis
    1     -> doThat
    2     -> doAnother
    x | 3 <= x && x < 100 -> doDefault
    _     -> reallyDoDefault

Answer 2

使用警卫!;)

Foo n 
  | n == 0 = doThis
  | n == 1 = doThat
  | n == 2 = doAnother
  | (n >= 3 ) && (n <= 99) = doDefault 

要么

  | n `elem` [3..99] =  doDefault