如何检查Emacs下的功能（例如服务器运行-p）是否可用？ [英] How to check if a function (e.g. server-running-p) is available under Emacs?

问题描述

我正在尝试检查我的.emacs文件中是否提供了 server-running-p 。我已经有以下内容：

I'm trying to check if server-running-p is available in my .emacs file before calling it. I already have the following:

(if (not (server-running-p))
    (server-start))

但是在使用Emacs的某些电脑上，调用（server- running-p）给出错误，因为所述呼叫不可用。所以我想在调用之前检查 server-running-p 是否可用。我认为 boundp 会尝试，但调用（boundp'server-running-p） return nil 即使（server-running-p）调用成功。检查调用 server-running-p 的正确方法将不会失败...或者至少在所述调用失败时抑制错误。 （还有什么样的奇怪对象是 server-running-p 无论如何 boundp 返回 nil ，但是调用成功？）

But on some computers where I use Emacs, calling (server-running-p) gives an error because said call is not available. So I want to check if server-running-p is available before calling it. I thought boundp would do the try, but calling (boundp 'server-running-p) return nil even though the (server-running-p) call succeeds. What's the right way to check that calling server-running-p won't fail... or at least to suppress the error if said call fails. (And what kind of weird object is server-running-p anyway that boundp returns nil, but calling it succeeds?)

这是在Emacs 23.2.1上，如果有任何区别。

This is on Emacs 23.2.1, if it makes any difference.

其实找到答案。由于某种原因，您必须使用 fboundp 而不是 boundp 。

Actually found the answer. You have to use fboundp for this instead of boundp, for some reason.

推荐答案

boundp 检查是否绑定了一个变量。由于 server-running-p 是一个函数，您将需要使用 fboundp 。像这样：

boundp checks to see if a variable is bound. Since server-running-p is a function you'll want to use fboundp. Like so:

(if (and (fboundp 'server-running-p) 
         (not (server-running-p)))
   (server-start))

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