Haskell 错误:“缺少随附的绑定"和“不在范围内" [英] Haskell errors: "lacks an accompanying binding" and "not in scope"

问题描述

我已经创建了一段代码:

I have created a piece of code this:

intToDigit :: Char -> Int
ord :: Char -> Int
intToDigit c = ord c - ord 'a'

但是，当我运行它时，我收到此错误消息:

However, when I run it I get this error message:

ChangeVowels.hs:2:1:`ord' 的类型签名缺少伴随的绑定

ChangeVowels.hs:2:1: The type signature for `ord' lacks an accompanying binding

ChangeVowels.hs:4:16: 不在范围内:`ord'

ChangeVowels.hs:4:16: Not in scope: `ord'

ChangeVowels.hs:4:24:不在范围内:`ord'

ChangeVowels.hs:4:24: Not in scope: `ord'

我用 Import data.char 试过了，但也不管用.

I tried it with Import data.char but that doesnt work either.

推荐答案

您需要为 ord 函数提供一个实现.在这里，您已经为 ord 提供了一个签名，但没有实现.

You need to provide an implementation for the function ord. Here, you have given a signature for ord, but no implementation.

或者你可以使用Haskell自带的ord函数，即Char.ord.

Or you can use Haskell's own ord function, that is Char.ord.

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