Haskell 不能'；t匹配预期类型'；整数->；t'；实际类型_Haskell_Functional Programming

Haskell 不能'；t匹配预期类型'；整数->；t'；实际类型

haskell functional-programming

Haskell 不能'；t匹配预期类型'；整数->；t'；实际类型,haskell,functional-programming,Haskell,Functional Programming,我正在尝试运行这个教科书示例，但不断出现以下错误： * Couldn't match expected type `Integer -> t' with actual type `[Char]' * The function `showPerson' is applied to two arguments, but its type `People -> [Char]' has only one In the expression: showPer

我正在尝试运行这个教科书示例，但不断出现以下错误：

* Couldn't match expected type `Integer -> t'
              with actual type `[Char]'
* The function `showPerson' is applied to two arguments,
  but its type `People -> [Char]' has only one
  In the expression: showPerson "charles" 18
  In an equation for `it': it = showPerson "charles" 18
* Relevant bindings include it :: t (bound at <interactive>:38:1)

声明的

showPerson

函数只有一个参数。此参数的类型为

People

但是，从您引用的错误判断，您试图用两个参数调用此函数-

“charles”

和

。第一个参数的类型为

String

，第二个参数的类型为

Int

这就是编译器试图告诉您的内容，它说：

The function `showPerson' is applied to two arguments, 
but its type `People -> [Char]' has only one

要正确调用函数，您需要首先创建一个

People

类型的值，然后将该值作为参数传递给函数：

p = Person "charles" 18
showPerson p

或者一行中的相同内容：

showPerson (Person "charles" 18)

声明的

showPerson