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What is this?
This contrib layer sets up pcre2el or rxt (RegeXp Translator or RegeXp Tools) which is a utility for working with regular expressions in Emacs, to parse, convert, and font-lock PCRE, Emacs and rx regexps.
Using pcre2el you can convert an Emacs Regexp to pcre (and back) (oh and output as rx too.)
Generate all matching strings (productions)
Occasionally you come across a regexp which is designed to match a finite set of
strings, e.g. a set of keywords, and it would be useful to recover the original
set. (In Emacs you can generate such regexps using regexp-opt). The commands
rxt-convert-to-strings (C-c /′), rxt-pcre-to-strings (C-c / p ′) or
rxt-elisp-to-strings (C-c / e ′) accomplish this by generating all the
matching strings ("productions") of a regexp. (The productions are copied to the
kill ring as a Lisp list).
An example in Lisp code:
(regexp-opt =("cat" "caterpillar" "catatonic"))
;; => "\\(?:cat\\(?:atonic\\|erpillar\\)?\\)"
(rxt-elisp-to-strings "\\(?:cat\\(?:atonic\\|erpillar\\)?\\)")
;; => =("cat" "caterpillar" "catatonic")RE-Builder support
The Emacs RE-Builder is a useful visual tool which allows using several
different built-in syntaxes via reb-change-syntax (C-c TAB). It supports
Elisp read and literal syntax and rx, but it can only convert from the
symbolic forms to Elisp, not the other way. This package hacks the RE-Builder to
also work with emulated PCRE syntax, and to convert transparently between Elisp,
PCRE and rx syntaxes. PCRE mode reads a delimited Perl-like literal of the form
/ ... /, and it should correctly support using the x and s flags.
Use from Lisp
Example of using the conversion functions:
(rxt-pcre-to-elisp "(abc|def)\\w+\\d+")
;; => "\\(\\(?:abc\\|def\\)\\)[_[:alnum:]]+[[:digit:]]+"Keybindings
pcre2el defines keybindings under C-c / so we'll define them under <SPC> R.