由于语法错误，我无法在Haskell上执行任何操作 [英] I can't do anything on Haskell due to syntax errors

问题描述

我可以执行简单的操作，例如

I can execute simply operations, like

Hugs> 2+2

例如

.或其他任何操作.

for instance. Or any operation, for that matter.

但是在实际尝试定义函数时，例如:

But when it comes to actually trying to define a function, e.g:

occurs :: Eq a => a -> [a] -> Bool 
occurs x l = x `elem` l

然后我收到消息:

ERROR - Syntax error in input (unexpected `=')

在其他情况下，我也得到unexpected `::'.我正在使用WinHugs.

I also get unexpected `::' in other cases. I'm using WinHugs.

推荐答案

由于提示仅接受表达式，因此您需要将函数保存在文件(* .hs)中并通过:load <filename>加载.

You need to save the function in a file (*.hs) and load it via :load <filename>, since the prompt accepts only expressions.

8.5.如何输入函数定义?

拥抱"提示仅接受用于求值的表达式.您可以创建一个包含Haskell模块的文件，然后加载该文件(请参见第2.2节以获取详细信息).

The Hugs prompt only accepts expressions for evaluation. You can create a file containing a Haskell module, and load that (see Section 2.2 for details).

如果要在REPL环境中尝试使用函数定义，建议您改用GHCi.

If you want to experiment with function definitions in a REPL environment, I recommend you to use GHCi instead.

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