Question

我刚开始使用LISP，来自C的背景。到目前为止它很有趣，虽然有一个令人难以置信的学习曲线（我也是一个emacs新手）。

无论如何，我对以下代码有一个愚蠢的问题来解析来自c source的include语句 - 如果有人可以对此发表评论并建议解决方案，那将会有很大帮助。

(defun include-start ( line )
    (search "#include " line))

(defun get-include( line )
  (let ((s (include-start line)))
    (if (not (eq NIL s))
      (subseq line s (length line)))))

(get-include "#include <stdio.h>")

我希望最后一行返回

"<stdio.h>"

然而实际结果是

"#include <stdio.h>"

有什么想法吗？

Answer 1

(defun include-start (line)
  "returns the string position after the '#include ' directive or nil if none"
  (let ((search-string "#include "))
    (when (search search-string line)
      (length search-string))))

(defun get-include (line)
  (let ((s (include-start line)))
    (when s
      (subseq line s))))

Answer 2

我发现replace-in-string更容易。

(replace-in-string "#include <stdio.h>" "#include +" "")
    => "<stdio.h>"

对于您的代码，include-start会返回匹配的开头，顾名思义。您正在寻找可能include-end

的(+ (include-start ....) (length ....))

Answer 3

(defun get-include (s)
   (subseq s (mismatch "#include " s)))

subseq（LISP）的简单问题

3 个答案: