问题
在从Haskell书中记笔记时，此代码示例应该返回： Left [NameEmpty, AgeTooLow] ，但它只返回第一个案例 Left [NameEmpty] . 然后，当我将函数 mkPerson2 结果传递给它应返回 Right Person _ _ 时，我得到一个“非详尽模式```错误 . 我已经查看了这段代码很长一段时间了，但它对我来说是正确的 . 我在这里错过了什么？关于这个问题的任何解释都将非常感谢，谢谢！
代码
module EqCaseGuard where
type Name = String
type Age = Integer
type ValidatePerson a = Either [PersonInvalid] a
data Person = Person Name Age deriving Show
data PersonInvalid = NameEmpty
| AgeTooLow
deriving Eq
ageOkay :: Age -> Either [PersonInvalid] Age
ageOkay age = case age >= 0 of
True -> Right age
False -> Left [AgeTooLow]
nameOkay :: Name -> Either [PersonInvalid] Name
nameOkay name = case name /= "" of
True -> Right name
False -> Left [NameEmpty]
mkPerson2 :: Name -> Age -> ValidatePerson Person
mkPerson2 name age = mkPerson2' (nameOkay name) (ageOkay age)
mkPerson2' :: ValidatePerson Name -> ValidatePerson Age -> ValidatePerson Person
mKPerson2' (Right nameOk) (Right ageOk) = Right (Person nameOk ageOk)
mKPerson2' (Left badName) (Left badAge) = Left (badName ++ badAge)
mkPerson2' (Left badName) _ = Left badName
mkPerson2' _ (Left badAge) = Left badAge
错误
*EqCaseGuard> mkPerson2 "jack" 22
*** Exception: eqCaseGuard.hs:(54,1)-(55,53): Non-exhaustive patterns in function mkPerson2'
*EqCaseGuard> mkPerson2 "" (-1)
Left [NameEmpty]
*EqCaseGuard>
1 回答
您在前两个定义中使用了大写字母K：