GHCi中的多行命令 [英] Multi-line commands in GHCi
问题描述
我在输入ghci中的多行命令时遇到问题。
以下两行代码可以从文件中找到:
addTwo :: Int - > Int - > Int
addTwo xy = x + y
但是当我输入ghci时, 。我也尝试将代码放入:{...:}
中,但它们对于此示例也不起作用,因为这只是将行附加到一行中,不应该是这样。
我使用WinGHCi,版本2011.2.0.1
Prelude>让addTwo xy = x + y
如果您确实需要使用类型签名或您的定义跨越多行,你可以在ghci中做到这一点:
Prelude> :{
Prelude |让addTwo :: Int - > Int - > Int
Prelude | addTwo x y = x + y
Prelude | :}
前奏> addTwo 4 7
11
请注意,您也可以将它压缩到一行: p>
Prelude>让addTwo :: Int - > Int - > Int; addTwo xy = x + y
你可以在文档提示符中的交互式评估。
I am having problem in entering multi-line commands in ghci. The following 2-line code works from a file:
addTwo :: Int -> Int -> Int
addTwo x y = x + y
But when I enter in ghci, I get errors. I also tried putting the code inside :{ ... :}
, but they are also not working for this example, because this is just appending the lines into one line, which should not be the case.
I am using WinGHCi, version 2011.2.0.1
Most of the time, you can rely on type inference to work out a signature for you. In your example, the following is sufficient:
Prelude> let addTwo x y = x + y
If you really want a definition with a type signature, or your definition spans over multiple lines, you can do this in ghci:
Prelude> :{
Prelude| let addTwo :: Int -> Int -> Int
Prelude| addTwo x y = x + y
Prelude| :}
Prelude> addTwo 4 7
11
Note that you can also squeeze this onto one line:
Prelude> let addTwo :: Int -> Int -> Int ; addTwo x y = x + y
You can find out more about interacting with ghci on the Interactive evaluation at the prompt section of the documentation.
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