Question

我已从以下网址的“实用的Haskell：编程的真实世界指南”中复制了这段代码1：1。 Alejandro Serrano Mena，但由于某些原因，它无法正确输入信息。

module Chapter2.Datatypes2 where

    data Person = Person String String Gender
                deriving Show
    data Gender = Male | Female | Unknown
                deriving Show

    data Client = GovOrg     String
                | Company    String Integer Person String
                | Individual Person Bool
                deriving Show

    clientName :: Client -> String
    clientName client = case client of
                          GovOrg  name                -> name
                          Company name _ _ _ -> name
                          Individual person ads       ->
                              case person of
                                Person fNm lNm gender -> fNm ++ " " ++ lNm

编译可以正常进行，但是当我使用(Individual [Person "Jack" "Smith" Male]) False输入函数时，它会从解释器中收到以下错误：

<interactive>:27:1: error:
    * Couldn't match expected type `Bool -> t'
                  with actual type `[Char]'
    * The function `clientName' is applied to two arguments,
      but its type `Client -> [Char]' has only one
      In the expression:
        clientName (Individual [Person "Jack" "Smith" Male]) False
      In an equation for `it':
          it = clientName (Individual [Person "Jack" "Smith" Male]) False
    * Relevant bindings include it :: t (bound at <interactive>:27:1)

<interactive>:27:13: error:
    * Couldn't match expected type `Client'
                  with actual type `Bool -> Client'
    * Probable cause: `Individual' is applied to too few arguments
      In the first argument of `clientName', namely
        `(Individual [Person "Jack" "Smith" Male])'
      In the expression:
        clientName (Individual [Person "Jack" "Smith" Male]) False
      In an equation for `it':
          it = clientName (Individual [Person "Jack" "Smith" Male]) False

<interactive>:27:24: error:
    * Couldn't match expected type `Person' with actual type `[Person]'
    * In the first argument of `Individual', namely
        `[Person "Jack" "Smith" Male]'
      In the first argument of `clientName', namely
        `(Individual [Person "Jack" "Smith" Male])'
      In the expression:
        clientName (Individual [Person "Jack" "Smith" Male]) False

Answer 1

for T in range(100):
    x = x_list[T]
    y = y_list[T]
    
    plt.scatter(x, y, label="T{}".format(T))

模式匹配期间无法匹配Haskell中的预期类型

1 个答案: