# 13.2 Lambda 表达式（WORKING）

lambda 表达式是由Lisp编写的函数对象。

这里有一个例子：

```
(lambda (x)
  "Return the hyperbolic cosine of X."
  (* 0.5 (+ (exp x) (exp (- x)))))
```

在Emacs Lisp中，这个列表是一个合法表达式，求值后返回一个函数对象。

lambda表达式本身没有名称；而是匿名函数。lambda表达式可以以这种形式使用（详情查阅匿名函数），但更通用的做法，是绑定一个符号来指代函数（详情查阅函数命名）。在深入这些细节之前，余下的几个字章节将会组成lambda表达式的组成部分，以及它们的作用。


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