Add standard unmatchable regexp
Add `regexp-unmatchable' as a standard unmatchable regexp, defined as "\\`a\\`". Use it where such a regexp is needed, replacing slower expressions in several places. From a suggestion by Philippe Schnoebelen. * lisp/subr.el (regexp-unmatchable): New defconst. * etc/NEWS (Lisp Changes): Mention `regexp-unmatchable'. * doc/lispref/searching.texi (Regexp Functions): Document it. * lisp/emacs-lisp/regexp-opt.el (regexp-opt) * lisp/progmodes/cc-defs.el (cc-conditional-require-after-load) (c-make-keywords-re) * lisp/progmodes/cc-engine.el (c-beginning-of-statement-1) (c-forward-<>-arglist-recur, c-forward-decl-or-cast-1) (c-looking-at-decl-block) * lisp/progmodes/cc-fonts.el (c-doc-line-join-re) (c-doc-bright-comment-start-re) * lisp/progmodes/cc-langs.el (c-populate-syntax-table) (c-assignment-op-regexp) (c-block-comment-ender-regexp, c-font-lock-comment-end-skip) (c-block-comment-start-regexp, c-line-comment-start-regexp) (c-doc-comment-start-regexp, c-decl-start-colon-kwd-re) (c-type-decl-prefix-key, c-type-decl-operator-prefix-key) (c-pre-id-bracelist-key, c-enum-clause-introduction-re) (c-nonlabel-token-2-key) * lisp/progmodes/cc-mode.el (c-doc-fl-decl-start, c-doc-fl-decl-end) * lisp/progmodes/cc-vars.el (c-noise-macro-with-parens-name-re) (c-noise-macro-name-re, c-make-noise-macro-regexps) * lisp/progmodes/octave.el (octave-help-mode) * lisp/vc/vc-bzr.el (vc-bzr-log-view-mode, vc-bzr-revision-completion-table) * lisp/vc/vc-git.el (vc-git-log-view-mode) * lisp/vc/vc-hg.el (vc-hg-log-view-mode) * lisp/vc/vc-mtn.el (vc-mtn-log-view-mode): Use `regexp-unmatchable'. * lisp/textmodes/ispell.el (ispell-non-empty-string): Use `regexp-unmatchable', fixing a broken never-match regexp.
This commit is contained in:
Mattias Engdegård
parent
d0ebc389eb
commit
26f735ff19
18 changed files with 58 additions and 39 deletions
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@ -1070,6 +1070,13 @@ list of characters @var{chars}.
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@c Internal functions: regexp-opt-group
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@defvar regexp-unmatchable
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This variable contains a regexp that is guaranteed not to match any
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string at all. It is particularly useful as default value for
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variables that may be set to a pattern that actually matches
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something.
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@end defvar
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@node Regexp Search
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@section Regular Expression Searching
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@cindex regular expression searching
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4
etc/NEWS
4
etc/NEWS
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@ -1990,6 +1990,10 @@ returns a regexp that never matches anything, which is an identity for
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this operation. Previously, the empty string was returned in this
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case.
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** New constant 'regexp-unmatchable' contains a never-matching regexp.
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It is a convenient and readable way to specify a regexp that should
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not match anything, and is as fast as any such regexp can be.
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* Changes in Emacs 27.1 on Non-Free Operating Systems
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@ -144,9 +144,9 @@ usually more efficient than that of a simplified version:
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(sort (copy-sequence strings) 'string-lessp)))
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(re
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(cond
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;; No strings: return a\` which cannot match anything.
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;; No strings: return an unmatchable regexp.
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((null strings)
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(concat (or open "\\(?:") "a\\`\\)"))
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(concat (or open "\\(?:") regexp-unmatchable "\\)"))
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;; If we cannot reorder, give up all attempts at
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;; optimisation. There is room for improvement (Bug#34641).
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((and keep-order (regexp-opt--contains-prefix sorted-strings))
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@ -1989,7 +1989,7 @@ on the gateway machine to do the FTP instead."
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(make-local-variable 'comint-password-prompt-regexp)
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;; This is a regexp that can't match anything.
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;; ange-ftp has its own ways of handling passwords.
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(setq comint-password-prompt-regexp "\\`a\\`")
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(setq comint-password-prompt-regexp regexp-unmatchable)
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(make-local-variable 'paragraph-start)
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(setq paragraph-start comint-prompt-regexp))
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@ -81,7 +81,7 @@
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(progn
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(require 'font-lock)
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(let (font-lock-keywords)
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(font-lock-compile-keywords '("a\\`")) ; doesn't match anything.
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(font-lock-compile-keywords (list regexp-unmatchable))
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font-lock-keywords))))
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@ -1890,8 +1890,8 @@ when it's needed. The default is the current language taken from
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;; Produce a regexp that doesn't match anything.
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(if adorn
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"\\(a\\`\\)"
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"a\\`")))
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(concat "\\(" regexp-unmatchable "\\)")
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regexp-unmatchable)))
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(put 'c-make-keywords-re 'lisp-indent-function 1)
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@ -907,7 +907,7 @@ comment at the start of cc-engine.el for more info."
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stack
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;; Regexp which matches "for", "if", etc.
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(cond-key (or c-opt-block-stmt-key
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"a\\`")) ; Doesn't match anything.
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regexp-unmatchable))
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;; Return value.
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(ret 'same)
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;; Positions of the last three sexps or bounds we've stopped at.
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@ -7646,7 +7646,9 @@ comment at the start of cc-engine.el for more info."
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(progn
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(c-forward-syntactic-ws)
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(when (or (and c-record-type-identifiers all-types)
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(not (equal c-inside-<>-type-key "\\(a\\`\\)")))
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(not (equal c-inside-<>-type-key
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(concat
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"\\(" regexp-unmatchable "\\)"))))
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(c-forward-syntactic-ws)
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(cond
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((eq (char-after) ??)
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@ -9253,7 +9255,7 @@ This function might do hidden buffer changes."
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;; Skip over type decl prefix operators. (Note similar code in
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;; `c-forward-declarator'.)
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(if (and c-recognize-typeless-decls
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(equal c-type-decl-prefix-key "a\\`")) ; Regexp which doesn't match
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(equal c-type-decl-prefix-key regexp-unmatchable))
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(when (eq (char-after) ?\()
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(progn
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(setq paren-depth (1+ paren-depth))
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@ -10886,7 +10888,7 @@ comment at the start of cc-engine.el for more info."
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;; legal because it's part of a "compound keyword" like
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;; "enum class". Of course, if c-after-brace-list-key
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;; is nil, we can skip the test.
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(or (equal c-after-brace-list-key "a\\`") ; Regexp which doesn't match
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(or (equal c-after-brace-list-key regexp-unmatchable)
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(save-match-data
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(save-excursion
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(not
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@ -2580,14 +2580,14 @@ need for `pike-font-lock-extra-types'.")
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;;; Doc comments.
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(defvar c-doc-line-join-re "a\\`")
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(defvar c-doc-line-join-re regexp-unmatchable)
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;; Matches a join of two lines in a doc comment.
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;; This should not be changed directly, but instead set by
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;; `c-setup-doc-comment-style'. This variable is used in `c-find-decl-spots'
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;; in (e.g.) autodoc style comments to bridge the gap between a "@\n" at an
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;; EOL and the token following "//!" on the next line.
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(defvar c-doc-bright-comment-start-re "a\\`")
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(defvar c-doc-bright-comment-start-re regexp-unmatchable)
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;; Matches the start of a "bright" comment, one whose contents may be
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;; fontified by, e.g., `c-font-lock-declarations'.
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@ -945,7 +945,7 @@ file name in angle brackets or quotes."
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(c-make-keywords-re 'appendable
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(c-lang-const c-cpp-include-directives))
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"[ \t]*")
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"a\\`")) ; Doesn't match anything
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regexp-unmatchable))
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(c-lang-defvar c-cpp-include-key (c-lang-const c-cpp-include-key))
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(c-lang-defconst c-opt-cpp-macro-define
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@ -1331,7 +1331,7 @@ operators."
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(c--set-difference (c-lang-const c-assignment-operators)
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'("=")
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:test 'string-equal)))
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"a\\`")) ; Doesn't match anything.
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regexp-unmatchable))
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(c-lang-defvar c-assignment-op-regexp
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(c-lang-const c-assignment-op-regexp))
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@ -1554,7 +1554,7 @@ properly."
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;; language)
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t (if (c-lang-const c-block-comment-ender)
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(regexp-quote (c-lang-const c-block-comment-ender))
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"a\\`")) ; Doesn't match anything.
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regexp-unmatchable))
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(c-lang-defvar c-block-comment-ender-regexp
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(c-lang-const c-block-comment-ender-regexp))
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@ -1565,7 +1565,7 @@ properly."
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;; `font-lock-comment-delimiter-face'.
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t (if (c-lang-const c-block-comment-ender)
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(concat "[ \t]*" (c-lang-const c-block-comment-ender-regexp))
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"a\\`")) ; Doesn't match anything.
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regexp-unmatchable))
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(c-lang-setvar font-lock-comment-end-skip
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(c-lang-const c-font-lock-comment-end-skip))
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@ -1584,7 +1584,7 @@ properly."
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;; language)
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t (if (c-lang-const c-block-comment-starter)
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(regexp-quote (c-lang-const c-block-comment-starter))
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"a\\`")) ; Doesn't match anything.
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regexp-unmatchable))
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(c-lang-defvar c-block-comment-start-regexp
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(c-lang-const c-block-comment-start-regexp))
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@ -1593,7 +1593,7 @@ properly."
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;; language; it does in all 7 CC Mode languages).
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t (if (c-lang-const c-line-comment-starter)
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(regexp-quote (c-lang-const c-line-comment-starter))
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"a\\`")) ; Doesn't match anything.
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regexp-unmatchable))
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(c-lang-defvar c-line-comment-start-regexp
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(c-lang-const c-line-comment-start-regexp))
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@ -1628,7 +1628,7 @@ starter."
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(c-lang-defconst c-doc-comment-start-regexp
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"Regexp to match the start of documentation comments."
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t "a\\`" ; Doesn't match anything.
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t regexp-unmatchable
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;; From font-lock.el: `doxygen' uses /*! while others use /**.
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(c c++ objc) "/\\*[*!]"
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java "/\\*\\*"
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@ -3112,7 +3112,7 @@ Note that Java specific rules are currently applied to tell this from
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"Regexp matching a keyword that is followed by a colon, where
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the whole construct can precede a declaration.
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E.g. \"public:\" in C++."
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t "a\\`" ; Doesn't match anything.
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t regexp-unmatchable
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c++ (c-make-keywords-re t (c-lang-const c-protection-kwds)))
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(c-lang-defvar c-decl-start-colon-kwd-re
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(c-lang-const c-decl-start-colon-kwd-re))
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@ -3309,7 +3309,7 @@ Identifier syntax is in effect when this is matched \(see
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t (if (c-lang-const c-type-modifier-kwds)
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(concat (regexp-opt (c-lang-const c-type-modifier-kwds) t) "\\>")
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;; Default to a regexp that never matches.
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"a\\`")
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regexp-unmatchable)
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;; Check that there's no "=" afterwards to avoid matching tokens
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;; like "*=".
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(c objc) (concat "\\("
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@ -3347,7 +3347,7 @@ that might precede the identifier in a declaration, e.g. the
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as the end of the operator. Identifier syntax is in effect when
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this is matched \(see `c-identifier-syntax-table')."
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t ;; Default to a regexp that never matches.
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"a\\`"
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regexp-unmatchable
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;; Check that there's no "=" afterwards to avoid matching tokens
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;; like "*=".
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(c objc) (concat "\\(\\*\\)"
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@ -3506,7 +3506,7 @@ list."
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(c-lang-defconst c-pre-id-bracelist-key
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"A regexp matching tokens which, preceding an identifier, signify a bracelist.
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"
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t "a\\`" ; Doesn't match anything.
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t regexp-unmatchable
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c++ "new\\([^[:alnum:]_$]\\|$\\)\\|&&?\\(\\S.\\|$\\)")
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(c-lang-defvar c-pre-id-bracelist-key (c-lang-const c-pre-id-bracelist-key))
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@ -3562,7 +3562,7 @@ the invalidity of the putative template construct."
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;; before the '{' of the enum list, to avoid searching too far.
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"[^][{};/#=]*"
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"{")
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"a\\`")) ; Doesn't match anything.
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regexp-unmatchable))
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(c-lang-defvar c-enum-clause-introduction-re
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(c-lang-const c-enum-clause-introduction-re))
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@ -3703,7 +3703,7 @@ Only used if `c-recognize-colon-labels' is set."
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"Regexp matching things that can't occur two symbols before a colon in
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a label construct. This catches C++'s inheritance construct \"class foo
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: bar\". Only used if `c-recognize-colon-labels' is set."
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t "a\\`" ; Doesn't match anything.
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t regexp-unmatchable
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c++ (c-make-keywords-re t '("class")))
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(c-lang-defvar c-nonlabel-token-2-key (c-lang-const c-nonlabel-token-2-key))
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@ -1825,7 +1825,7 @@ Note that this is a strict tail, so won't match, e.g. \"0x....\".")
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;; by `c-doc-line-join-re'), return the position of the first line of the
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;; sequence. Otherwise, return nil. Point has no significance at entry to
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;; and exit from this function.
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(when (not (equal c-doc-line-join-re "a\\`"))
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(when (not (equal c-doc-line-join-re regexp-unmatchable))
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(goto-char pos)
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(back-to-indentation)
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(and (or (looking-at c-comment-start-regexp)
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@ -1842,7 +1842,7 @@ Note that this is a strict tail, so won't match, e.g. \"0x....\".")
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;; marker (as defined by `c-doc-line-join-re), return the position of
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;; the BOL at the end of the sequence. Otherwise, return nil. Point has no
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;; significance at entry to and exit from this function.
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(when (not (equal c-doc-line-join-re "a\\`"))
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(when (not (equal c-doc-line-join-re regexp-unmatchable))
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(goto-char pos)
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(back-to-indentation)
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(let ((here (point)))
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@ -1648,9 +1648,9 @@ white space either before or after the operator, but not both."
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:group 'c)
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;; Initialize the next two to a regexp which never matches.
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(defvar c-noise-macro-with-parens-name-re "a\\`")
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(defvar c-noise-macro-with-parens-name-re regexp-unmatchable)
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(make-variable-buffer-local 'c-noise-macro-with-parens-name-re)
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(defvar c-noise-macro-name-re "a\\`")
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(defvar c-noise-macro-name-re regexp-unmatchable)
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(make-variable-buffer-local 'c-noise-macro-name-re)
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(defcustom c-noise-macro-names nil
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@ -1682,7 +1682,7 @@ These are recognized by CC Mode only in declarations."
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;; Convert `c-noise-macro-names' and `c-noise-macro-with-parens-names' into
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;; `c-noise-macro-name-re' and `c-noise-macro-with-parens-name-re'.
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(setq c-noise-macro-with-parens-name-re
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(cond ((null c-noise-macro-with-parens-names) "a\\`") ; Never matches.
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(cond ((null c-noise-macro-with-parens-names) regexp-unmatchable)
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((consp c-noise-macro-with-parens-names)
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(concat (regexp-opt c-noise-macro-with-parens-names t)
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"\\([^[:alnum:]_$]\\|$\\)"))
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@ -1691,7 +1691,7 @@ These are recognized by CC Mode only in declarations."
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(t (error "c-make-noise-macro-regexps: \
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c-noise-macro-with-parens-names is invalid: %s" c-noise-macro-with-parens-names))))
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(setq c-noise-macro-name-re
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(cond ((null c-noise-macro-names) "a\\`") ; Never matches anything.
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(cond ((null c-noise-macro-names) regexp-unmatchable)
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((consp c-noise-macro-names)
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(concat (regexp-opt c-noise-macro-names t)
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"\\([^[:alnum:]_$]\\|$\\)"))
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@ -837,7 +837,8 @@ This function is called from `compilation-filter-hook'."
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grep-mode-line-matches)
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;; compilation-directory-matcher can't be nil, so we set it to a regexp that
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;; can never match.
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(set (make-local-variable 'compilation-directory-matcher) '("\\`a\\`"))
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(set (make-local-variable 'compilation-directory-matcher)
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(list regexp-unmatchable))
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(set (make-local-variable 'compilation-process-setup-function)
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'grep-process-setup)
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(set (make-local-variable 'compilation-disable-input) t)
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@ -1691,7 +1691,7 @@ code line."
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(eval-and-compile (require 'help-mode))
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;; Don't highlight `EXAMPLE' as elisp symbols by using a regexp that
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;; can never match.
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(setq-local help-xref-symbol-regexp "x\\`"))
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(setq-local help-xref-symbol-regexp regexp-unmatchable))
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(defun octave-help (fn)
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"Display the documentation of FN."
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@ -5544,4 +5544,8 @@ returned list are in the same order as in TREE.
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;; for discoverability:
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(defalias 'flatten-list 'flatten-tree)
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;; The initial anchoring is for better performance in searching matches.
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(defconst regexp-unmatchable "\\`a\\`"
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"Standard regexp guaranteed not to match any string at all.")
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;;; subr.el ends here
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@ -4016,7 +4016,7 @@ You can bind this to the key C-c i in GNUS or mail by adding to
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(defun ispell-non-empty-string (string)
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(if (or (not string) (string-equal string ""))
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"\\'\\`" ; An unmatchable string if string is null.
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regexp-unmatchable
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(regexp-quote string)))
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@ -702,7 +702,7 @@ or a superior directory.")
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(remove-hook 'log-view-mode-hook 'vc-bzr-log-view-mode) ;Deactivate the hack.
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||||
(require 'add-log)
|
||||
(set (make-local-variable 'log-view-per-file-logs) nil)
|
||||
(set (make-local-variable 'log-view-file-re) "\\`a\\`")
|
||||
(set (make-local-variable 'log-view-file-re) regexp-unmatchable)
|
||||
(set (make-local-variable 'log-view-message-re)
|
||||
(if (eq vc-log-view-type 'short)
|
||||
"^ *\\([0-9.]+\\): \\(.*?\\)[ \t]+\\([0-9]\\{4\\}-[0-9]\\{2\\}-[0-9]\\{2\\}\\)\\( \\[merge\\]\\)?"
|
||||
|
|
@ -1319,7 +1319,8 @@ stream. Standard error output is discarded."
|
|||
((string-match "\\`annotate:" string)
|
||||
(completion-table-with-context
|
||||
(substring string 0 (match-end 0))
|
||||
(apply-partially #'completion-table-with-terminator '(":" . "\\`a\\`")
|
||||
(apply-partially #'completion-table-with-terminator
|
||||
(cons ":" regexp-unmatchable)
|
||||
#'completion-file-name-table)
|
||||
(substring string (match-end 0)) pred action))
|
||||
|
||||
|
|
|
|||
|
|
@ -1087,7 +1087,7 @@ If LIMIT is a revision string, use it as an end-revision."
|
|||
(define-derived-mode vc-git-log-view-mode log-view-mode "Git-Log-View"
|
||||
(require 'add-log) ;; We need the faces add-log.
|
||||
;; Don't have file markers, so use impossible regexp.
|
||||
(set (make-local-variable 'log-view-file-re) "\\`a\\`")
|
||||
(set (make-local-variable 'log-view-file-re) regexp-unmatchable)
|
||||
(set (make-local-variable 'log-view-per-file-logs) nil)
|
||||
(set (make-local-variable 'log-view-message-re)
|
||||
(if (not (eq vc-log-view-type 'long))
|
||||
|
|
|
|||
|
|
@ -444,7 +444,7 @@ If LIMIT is non-nil, show no more than this many entries."
|
|||
|
||||
(define-derived-mode vc-hg-log-view-mode log-view-mode "Hg-Log-View"
|
||||
(require 'add-log) ;; we need the add-log faces
|
||||
(set (make-local-variable 'log-view-file-re) "\\`a\\`")
|
||||
(set (make-local-variable 'log-view-file-re) regexp-unmatchable)
|
||||
(set (make-local-variable 'log-view-per-file-logs) nil)
|
||||
(set (make-local-variable 'log-view-message-re)
|
||||
(if (eq vc-log-view-type 'short)
|
||||
|
|
|
|||
|
|
@ -240,7 +240,7 @@ If LIMIT is non-nil, show no more than this many entries."
|
|||
|
||||
(define-derived-mode vc-mtn-log-view-mode log-view-mode "Mtn-Log-View"
|
||||
;; Don't match anything.
|
||||
(set (make-local-variable 'log-view-file-re) "\\`a\\`")
|
||||
(set (make-local-variable 'log-view-file-re) regexp-unmatchable)
|
||||
(set (make-local-variable 'log-view-per-file-logs) nil)
|
||||
;; TODO: Use a more precise regexp than "[ |/]+" to avoid false positives
|
||||
;; in the ChangeLog text.
|
||||
|
|
|
|||
Loading…
Add table
Reference in a new issue