如何在 Common Lisp 中内联函数

Question

有人可以告诉我如何在 Common Lisp 中内联一个函数吗？我有很多小函数一直在调用，所以最好节省这些函数调用的成本。

例如，如何将 "standalone" 函数内联到 "caller" 函数中？

(defun standalone ()
 (* 2 5))

(defun caller ()
 (standalone))

Answer 1

(declaim (inline standalone))

(defun standalone ()
 (* 2 5))

(defun caller ()
 (standalone))

文档是 here。

（但请记住，定义一个总是 returns 数字文字 10 的函数没有多大意义...）

Answer 2

查看食谱：https://lispcookbook.github.io/cl-cookbook/performance.html#code-inline

如果编译器支持，内联声明将函数调用替换为函数体。它将节省函数调用的成本，但可能会增加代码大小。使用内联的最佳情况可能是那些小但经常使用的函数。以下片段展示了如何鼓励和禁止内联代码。

;; The globally defined function DISPATCH should be open-coded,
;; if the implementation supports inlining, unless a NOTINLINE 
;; declaration overrides this effect.
(declaim (inline dispatch))
(defun dispatch (x) (funcall (get (car x) 'dispatch) x))

;; Here is an example where inlining would be encouraged.
;; Because function DISPATCH was defined as INLINE, the code 
;; inlining will be encouraged by default.
(defun use-dispatch-inline-by-default () 
  (dispatch (read-command)))

;; Here is an example where inlining would be prohibited.
;; The NOTINLINE here only affects this function.
(defun use-dispatch-with-declare-notinline  ()
  (declare (notinline dispatch))
  (dispatch (read-command)))

;; Here is an example where inlining would be prohibited.
;; The NOTINLINE here affects all following code.
(declaim (notinline dispatch))
(defun use-dispatch-with-declaim-noinline () 
  (dispatch (read-command)))

;; Inlining would be encouraged becuase you specified it.
;; The INLINE here only affects this function.
(defun use-dispatch-with-inline () 
  (declare (inline dispatch))
  (dispatch (read-command)))

Answer 3

一些实现，例如 Allegro CL 编译器 ignore inline declarations。

Compiler macros 由 define-compiler-macro 创建（不同于 defmacro！）也可以用来代替内联代码。

如何在 Common Lisp 中内联函数

How to inline functions in Common Lisp

inline

common-lisp