34 lines
1.9 KiB
Markdown
34 lines
1.9 KiB
Markdown
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# RegeXp Translator Mode
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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.
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Using pcre2el you can convert an Emacs Regexp to pcre (and back) (oh and output as rx too.)
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## Generate all matching strings (productions)
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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).
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An example in Lisp code:
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: (regexp-opt '("cat" "caterpillar" "catatonic"))
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: ;; => "\\(?:cat\\(?:atonic\\|erpillar\\)?\\)"
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: (rxt-elisp-to-strings "\\(?:cat\\(?:atonic\\|erpillar\\)?\\)")
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: ;; => '("cat" "caterpillar" "catatonic")
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##RE-Builder support
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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.
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##Use from Lisp
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Example of using the conversion functions:
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(rxt-pcre-to-elisp "(abc|def)\\w+\\d+")
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;; => "\\(\\(?:abc\\|def\\)\\)[_[:alnum:]]+[[:digit:]]+"
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## Keybindings
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pcre2el defines keybindings under `C-c /` so we'll define them under out perspective map `<SPC> R`
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