通过Emacs评估ghci或拥抱中的缓冲区 [英] Evaluate buffer in ghci or hugs via Emacs

问题描述

在Emacs中使用sml模式我已经能够使用 C-c C-b 将缓冲区内容直接发送到较差的SML进程。现在我只想和Haskell做同样的事情。 Haskell模式似乎不支持这一点，所以我想知道：Emacs和Haskell的正确方法是什么？

学习SML时，我一直使用 Cc Cb 几乎不停地轻松地评估我的程序，当我走，立即看到分配值的结果等等。但是如果我在包含两行的保存文件中的haskell模式中使用 Cc Cl ， let foo = foo和 let bar =bar - 我得到解析错误（可能不正确的缩进）

解决方案

我认为你正在做一个常见的菜鸟错误，混淆你可以在ghci的副本中写什么以及您在haskell源文件中写的内容。

所有的sml解释器都是以这样一种方式进行的，您可以将任何顶级声明写入repl中，换句话说：任何您可以在sml文件中写入你可以写入sml解释器。因此，您可以将 val foo =bar写入文件，并使用 Cc Cb 加载文件，您可以将 val foo =bar放入解释器。

另一方面，由于haskell的工作原理，您可以将 let foo = 42 写入ghci，但它不是有效的顶级声明，因此这不能在一个haskell源文件（通过它自己）。另一方面，您可以在haskell源文件中使用 id n = n ，并使用 Cc Cl 加载文件，但是您不能直接将其写入ghci（您将收到错误：1：6：输入'='时的解析错误）。这样做的原因是ghci中的repl在IO monad中运行，因此，您写入ghci的内容必须使用符号来完成。我只能建议您从提供的互动评估中查看使用GHCi用户指南。

cc Cb 在sml模式是完全相同的 Cc Cl 在haskell模式，至少在概念上。我不太了解haskell模式的内部，但是在sml模式中，code> Cc Cb 在解释器中执行一些sml代码，通常是使用（...）函数。在haskell模式下，似乎只是排除了：load... ghci命令

Using sml-mode in Emacs I have been able to send my buffer contents directly to an inferior SML process using C-c C-b. Now I want to do the same thing only with Haskell. Haskell-mode does not seem to support this, so I'm wondering: What is the right way to go about this with Emacs and Haskell?

While learning SML I've been using C-c C-b almost non-stop to easily evaluate my program as I go, instantly seeing the results of assigning values etc. But if I use C-c C-l in haskell-mode on a saved file containing two lines, let foo = "foo" and let bar = "bar" - I get "parse error (possibly incorrect indentation)"

解决方案

I think you are making a common rookie mistake, confusing what you can write inside the repl of ghci and what you write in a haskell source file.

All sml interpreters are made in such a way that you can write any top level declaration into the repl, or put in other words: anything you can write in an sml file, you can write into the sml interpreter. Thus you are allowed to write val foo = "bar" into a file and use C-c C-b to load the file and you are allowed to just put in val foo = "bar" into the interpreter.

On the other hand, because of how haskell work, you can write let foo = 42 into ghci, however it is not a valid top level declaration and thus this can't be in a haskell source file (by it self). On the other hand you can have id n = n in a haskell source file and use C-c C-l to load the file, however you can't write this directly into ghci (you will get an error: :1:6: parse error on input '='). The reason for this is that the repl in ghci runs in the IO monad, and thus what ever you write into ghci must be done using the do notation. I can only recommend that you read Interactive evaluation at the prompt from the Using GHCi user guide.

C-c C-b in sml-mode is the exact same thing as C-c C-l in haskell-mode, well atleast conceptually. I don't know that much about the internals of haskell-mode, but in sml-mode C-c C-b executes some sml code in the interpreter, normally the use(...) function. In haskell-mode it seems to just excute the :load "..." ghci command

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