我承认对喜欢有明显的偏见PCRE regexps 比 emacs 好得多，如果没有其他原因，当我输入 '(' 我几乎总是想要一个分组运算符。当然，\w 和类似的比其他等价物方便得多。
但是，当然，期望改变 emacs 的内部结构是很疯狂的。但是我认为应该可以从 PCRE experssion 转换为 emacs 表达式，并进行所有需要的转换，以便我可以写:
(defun my-super-regexp-function ...
(search-forward (pcre-convert "__\\w: \d+")))
(或类似)。
有人知道可以做到这一点的elisp库吗？
编辑:从下面的答案中选择一个回复...
哇，我喜欢从 4 天的假期回来寻找大量有趣的答案来整理!我喜欢这两种类型的解决方案的工作。
最后，看起来解决方案的 exec-a-script 和直接 elisp 版本都可以工作，但是从纯粹的速度和“正确性”方法来看，elisp 版本肯定是人们更喜欢的版本(包括我自己) .
请您参考如下方法:
https://github.com/joddie/pcre2el是这个答案的最新版本。
pcre2elorrxt(RegeXp Translator or RegeXp Tools) is a utility for working with regular expressions in Emacs, based on a recursive-descent parser for regexp syntax. In addition to converting (a subset of) PCRE syntax into its Emacs equivalent, it can do the following:
- convert Emacs syntax to PCRE
- convert either syntax to
rx, an S-expression based regexp syntax- untangle complex regexps by showing the parse tree in
rxform and highlighting the corresponding chunks of code- show the complete list of strings (productions) matching a regexp, provided the list is finite
- provide live font-locking of regexp syntax (so far only for Elisp buffers – other modes on the TODO list)
原始答案的文本如下......
这是一个 quick and ugly Emacs lisp solution (编辑:现在更永久地位于 here )。它主要基于
pcrepattern 中的描述手册页，并逐个标记地工作，仅转换以下结构:
( .. ) | {M,N} \Q .. \E \a , \c , \e , \f , \n , \r , \t , \x , 和 \ + 八进制数字 \d , \D , \h , \H , \s , \S , \v , \V \w和 \W保持原样(使用 Emacs 自己的单词和非单词字符的想法)它不会对更复杂的 PCRE 断言做任何事情，但它会尝试在字符类中转换转义符。在字符类包括类似
\D 的情况下，这是通过转换为具有交替的非捕获组来完成的。
它通过了我为它编写的测试，但肯定存在错误，并且逐个 token 扫描的方法可能很慢。换句话说，没有保修。但也许出于某些目的，它可以完成工作中更简单的部分。欢迎有兴趣的人士改进它;-)
(eval-when-compile (require 'cl))
(defvar pcre-horizontal-whitespace-chars
(mapconcat 'char-to-string
'(#x0009 #x0020 #x00A0 #x1680 #x180E #x2000 #x2001 #x2002 #x2003
#x2004 #x2005 #x2006 #x2007 #x2008 #x2009 #x200A #x202F
#x205F #x3000)
""))
(defvar pcre-vertical-whitespace-chars
(mapconcat 'char-to-string
'(#x000A #x000B #x000C #x000D #x0085 #x2028 #x2029) ""))
(defvar pcre-whitespace-chars
(mapconcat 'char-to-string '(9 10 12 13 32) ""))
(defvar pcre-horizontal-whitespace
(concat "[" pcre-horizontal-whitespace-chars "]"))
(defvar pcre-non-horizontal-whitespace
(concat "[^" pcre-horizontal-whitespace-chars "]"))
(defvar pcre-vertical-whitespace
(concat "[" pcre-vertical-whitespace-chars "]"))
(defvar pcre-non-vertical-whitespace
(concat "[^" pcre-vertical-whitespace-chars "]"))
(defvar pcre-whitespace (concat "[" pcre-whitespace-chars "]"))
(defvar pcre-non-whitespace (concat "[^" pcre-whitespace-chars "]"))
(eval-when-compile
(defmacro pcre-token-case (&rest cases)
"Consume a token at point and evaluate corresponding forms.
CASES is a list of `cond'-like clauses, (REGEXP FORMS
...). Considering CASES in order, if the text at point matches
REGEXP then moves point over the matched string and returns the
value of FORMS. Returns `nil' if none of the CASES matches."
(declare (debug (&rest (sexp &rest form))))
`(cond
,@(mapcar
(lambda (case)
(let ((token (car case))
(action (cdr case)))
`((looking-at ,token)
(goto-char (match-end 0))
,@action)))
cases)
(t nil))))
(defun pcre-to-elisp (pcre)
"Convert PCRE, a regexp in PCRE notation, into Elisp string form."
(with-temp-buffer
(insert pcre)
(goto-char (point-min))
(let ((capture-count 0) (accum '())
(case-fold-search nil))
(while (not (eobp))
(let ((translated
(or
;; Handle tokens that are treated the same in
;; character classes
(pcre-re-or-class-token-to-elisp)
;; Other tokens
(pcre-token-case
("|" "\\|")
("(" (incf capture-count) "\\(")
(")" "\\)")
("{" "\\{")
("}" "\\}")
;; Character class
("\\[" (pcre-char-class-to-elisp))
;; Backslash + digits => backreference or octal char?
("\\\\\\([0-9]+\\)"
(let* ((digits (match-string 1))
(dec (string-to-number digits)))
;; from "man pcrepattern": If the number is
;; less than 10, or if there have been at
;; least that many previous capturing left
;; parentheses in the expression, the entire
;; sequence is taken as a back reference.
(cond ((< dec 10) (concat "\\" digits))
((>= capture-count dec)
(error "backreference \\%s can't be used in Emacs regexps"
digits))
(t
;; from "man pcrepattern": if the
;; decimal number is greater than 9 and
;; there have not been that many
;; capturing subpatterns, PCRE re-reads
;; up to three octal digits following
;; the backslash, and uses them to
;; generate a data character. Any
;; subsequent digits stand for
;; themselves.
(goto-char (match-beginning 1))
(re-search-forward "[0-7]\\{0,3\\}")
(char-to-string (string-to-number (match-string 0) 8))))))
;; Regexp quoting.
("\\\\Q"
(let ((beginning (point)))
(search-forward "\\E")
(regexp-quote (buffer-substring beginning (match-beginning 0)))))
;; Various character classes
("\\\\d" "[0-9]")
("\\\\D" "[^0-9]")
("\\\\h" pcre-horizontal-whitespace)
("\\\\H" pcre-non-horizontal-whitespace)
("\\\\s" pcre-whitespace)
("\\\\S" pcre-non-whitespace)
("\\\\v" pcre-vertical-whitespace)
("\\\\V" pcre-non-vertical-whitespace)
;; Use Emacs' native notion of word characters
("\\\\[Ww]" (match-string 0))
;; Any other escaped character
("\\\\\\(.\\)" (regexp-quote (match-string 1)))
;; Any normal character
("." (match-string 0))))))
(push translated accum)))
(apply 'concat (reverse accum)))))
(defun pcre-re-or-class-token-to-elisp ()
"Consume the PCRE token at point and return its Elisp equivalent.
Handles only tokens which have the same meaning in character
classes as outside them."
(pcre-token-case
("\\\\a" (char-to-string #x07)) ; bell
("\\\\c\\(.\\)" ; control character
(char-to-string
(- (string-to-char (upcase (match-string 1))) 64)))
("\\\\e" (char-to-string #x1b)) ; escape
("\\\\f" (char-to-string #x0c)) ; formfeed
("\\\\n" (char-to-string #x0a)) ; linefeed
("\\\\r" (char-to-string #x0d)) ; carriage return
("\\\\t" (char-to-string #x09)) ; tab
("\\\\x\\([A-Za-z0-9]\\{2\\}\\)"
(char-to-string (string-to-number (match-string 1) 16)))
("\\\\x{\\([A-Za-z0-9]*\\)}"
(char-to-string (string-to-number (match-string 1) 16)))))
(defun pcre-char-class-to-elisp ()
"Consume the remaining PCRE character class at point and return its Elisp equivalent.
Point should be after the opening \"[\" when this is called, and
will be just after the closing \"]\" when it returns."
(let ((accum '("["))
(pcre-char-class-alternatives '())
(negated nil))
(when (looking-at "\\^")
(setq negated t)
(push "^" accum)
(forward-char))
(when (looking-at "\\]") (push "]" accum) (forward-char))
(while (not (looking-at "\\]"))
(let ((translated
(or
(pcre-re-or-class-token-to-elisp)
(pcre-token-case
;; Backslash + digits => always an octal char
("\\\\\\([0-7]\\{1,3\\}\\)"
(char-to-string (string-to-number (match-string 1) 8)))
;; Various character classes. To implement negative char classes,
;; we cons them onto the list `pcre-char-class-alternatives' and
;; transform the char class into a shy group with alternation
("\\\\d" "0-9")
("\\\\D" (push (if negated "[0-9]" "[^0-9]")
pcre-char-class-alternatives) "")
("\\\\h" pcre-horizontal-whitespace-chars)
("\\\\H" (push (if negated
pcre-horizontal-whitespace
pcre-non-horizontal-whitespace)
pcre-char-class-alternatives) "")
("\\\\s" pcre-whitespace-chars)
("\\\\S" (push (if negated
pcre-whitespace
pcre-non-whitespace)
pcre-char-class-alternatives) "")
("\\\\v" pcre-vertical-whitespace-chars)
("\\\\V" (push (if negated
pcre-vertical-whitespace
pcre-non-vertical-whitespace)
pcre-char-class-alternatives) "")
("\\\\w" (push (if negated "\\W" "\\w")
pcre-char-class-alternatives) "")
("\\\\W" (push (if negated "\\w" "\\W")
pcre-char-class-alternatives) "")
;; Leave POSIX syntax unchanged
("\\[:[a-z]*:\\]" (match-string 0))
;; Ignore other escapes
("\\\\\\(.\\)" (match-string 0))
;; Copy everything else
("." (match-string 0))))))
(push translated accum)))
(push "]" accum)
(forward-char)
(let ((class
(apply 'concat (reverse accum))))
(when (or (equal class "[]")
(equal class "[^]"))
(setq class ""))
(if (not pcre-char-class-alternatives)
class
(concat "\\(?:"
class "\\|"
(mapconcat 'identity
pcre-char-class-alternatives
"\\|")
"\\)")))))
