master 94d8eeeff4a 3/3: Call them “bracket expressions” more consistently

[Paul Eggert]

branch: master
commit 94d8eeeff4ae99cb12718dab7cf7fdc52de77b6e
Author: Paul Eggert <eggert@cs.ucla.edu>
Commit: Paul Eggert <eggert@cs.ucla.edu>

    Call them “bracket expressions” more consistently
    
    Emacs comments and doc were inconsistent about the name used for
    regexps like [a-z].  Sometimes it called them “character
    alternatives”, sometimes “character sets”, sometimes “bracket
    expressions”.  Prefer “bracket expressions” as it is less confusing:
    POSIX and most other programs’ doc uses “bracket expressions”,
    “alternative” is also used in the Emacs documentation to talk about
    ...\|... in regexps, and “character set” normally has a different
    meaning in Emacs.
---
 doc/emacs/search.texi        | 12 +++----
 doc/lispref/searching.texi   | 74 ++++++++++++++++++++++----------------------
 lisp/emacs-lisp/lisp-mode.el |  2 +-
 lisp/textmodes/picture.el    |  2 +-
 4 files changed, 45 insertions(+), 45 deletions(-)

diff --git a/doc/emacs/search.texi b/doc/emacs/search.texi
index 45378d95f65..2a816221235 100644
--- a/doc/emacs/search.texi
+++ b/doc/emacs/search.texi
@@ -950,8 +950,8 @@ features used mainly in Lisp programs.
 @dfn{special constructs} and the rest are @dfn{ordinary}.  An ordinary
 character matches that same character and nothing else.  The special
 characters are @samp{$^.*+?[\}.  The character @samp{]} is special if
-it ends a character alternative (see below).  The character @samp{-}
-is special inside a character alternative.  Any other character
+it ends a bracket expression (see below).  The character @samp{-}
+is special inside a bracket expression.  Any other character
 appearing in a regular expression is ordinary, unless a @samp{\}
 precedes it.  (When you use regular expressions in a Lisp program,
 each @samp{\} must be doubled, see the example near the end of this
@@ -1033,11 +1033,11 @@ you search for @samp{a.*?$} against the text 
@samp{abbab} followed by
 a newline, it matches the whole string.  Since it @emph{can} match
 starting at the first @samp{a}, it does.
 
+@cindex bracket expression
 @cindex set of alternative characters, in regular expressions
 @cindex character set, in regular expressions
 @item @kbd{[ @dots{} ]}
-is a @dfn{set of alternative characters}, or a @dfn{character set},
-beginning with @samp{[} and terminated by @samp{]}.
+is a @dfn{bracket expression}, which matches one of a set of characters.
 
 In the simplest case, the characters between the two brackets are what
 this set can match.  Thus, @samp{[ad]} matches either one @samp{a} or
@@ -1057,7 +1057,7 @@ Greek letters.
 @cindex character classes, in regular expressions
 You can also include certain special @dfn{character classes} in a
 character set.  A @samp{[:} and balancing @samp{:]} enclose a
-character class inside a set of alternative characters.  For instance,
+character class inside a bracket expression.  For instance,
 @samp{[[:alnum:]]} matches any letter or digit.  @xref{Char Classes,,,
 elisp, The Emacs Lisp Reference Manual}, for a list of character
 classes.
@@ -1125,7 +1125,7 @@ no preceding expression on which the @samp{*} can act.  
It is poor practice
 to depend on this behavior; it is better to quote the special character anyway,
 regardless of where it appears.
 
-As a @samp{\} is not special inside a set of alternative characters, it can
+As a @samp{\} is not special inside a bracket expression, it can
 never remove the special meaning of @samp{-}, @samp{^} or @samp{]}.
 You should not quote these characters when they have no special
 meaning.  This would not clarify anything, since backslashes
diff --git a/doc/lispref/searching.texi b/doc/lispref/searching.texi
index 608abae762c..28230cea643 100644
--- a/doc/lispref/searching.texi
+++ b/doc/lispref/searching.texi
@@ -278,10 +278,10 @@ character is a simple regular expression that matches 
that character
 and nothing else.  The special characters are @samp{.}, @samp{*},
 @samp{+}, @samp{?}, @samp{[}, @samp{^}, @samp{$}, and @samp{\}; no new
 special characters will be defined in the future.  The character
-@samp{]} is special if it ends a character alternative (see later).
-The character @samp{-} is special inside a character alternative.  A
+@samp{]} is special if it ends a bracket expression (see later).
+The character @samp{-} is special inside a bracket expression.  A
 @samp{[:} and balancing @samp{:]} enclose a character class inside a
-character alternative.  Any other character appearing in a regular
+bracket expression.  Any other character appearing in a regular
 expression is ordinary, unless a @samp{\} precedes it.
 
   For example, @samp{f} is not a special character, so it is ordinary, and
@@ -374,19 +374,19 @@ expression @samp{c[ad]*?a}, applied to that same string, 
matches just
 permits the whole expression to match is @samp{d}.)
 
 @item @samp{[ @dots{} ]}
-@cindex character alternative (in regexp)
+@cindex bracket expression (in regexp)
 @cindex @samp{[} in regexp
 @cindex @samp{]} in regexp
-is a @dfn{character alternative}, which begins with @samp{[} and is
+is a @dfn{bracket expression}, which begins with @samp{[} and is
 terminated by @samp{]}.  In the simplest case, the characters between
-the two brackets are what this character alternative can match.
+the two brackets are what this bracket expression can match.
 
 Thus, @samp{[ad]} matches either one @samp{a} or one @samp{d}, and
 @samp{[ad]*} matches any string composed of just @samp{a}s and @samp{d}s
 (including the empty string).  It follows that @samp{c[ad]*r}
 matches @samp{cr}, @samp{car}, @samp{cdr}, @samp{caddaar}, etc.
 
-You can also include character ranges in a character alternative, by
+You can also include character ranges in a bracket expression, by
 writing the starting and ending characters with a @samp{-} between them.
 Thus, @samp{[a-z]} matches any lower-case @acronym{ASCII} letter.
 Ranges may be intermixed freely with individual characters, as in
@@ -395,7 +395,7 @@ or @samp{$}, @samp{%} or period.  However, the ending 
character of one
 range should not be the starting point of another one; for example,
 @samp{[a-m-z]} should be avoided.
 
-A character alternative can also specify named character classes
+A bracket expression can also specify named character classes
 (@pxref{Char Classes}).  For example, @samp{[[:ascii:]]} matches any
 @acronym{ASCII} character.  Using a character class is equivalent to
 mentioning each of the characters in that class; but the latter is not
@@ -404,9 +404,9 @@ different characters.  A character class should not appear 
as the
 lower or upper bound of a range.
 
 The usual regexp special characters are not special inside a
-character alternative.  A completely different set of characters is
+bracket expression.  A completely different set of characters is
 special: @samp{]}, @samp{-} and @samp{^}.
-To include @samp{]} in a character alternative, put it at the
+To include @samp{]} in a bracket expression, put it at the
 beginning.  To include @samp{^}, put it anywhere but at the beginning.
 To include @samp{-}, put it at the end.  Thus, @samp{[]^-]} matches
 all three of these special characters.  You cannot use @samp{\} to
@@ -444,7 +444,7 @@ characters and raw 8-bit bytes, but not non-ASCII 
characters.  This
 feature is intended for searching text in unibyte buffers and strings.
 @end enumerate
 
-Some kinds of character alternatives are not the best style even
+Some kinds of bracket expressions are not the best style even
 though they have a well-defined meaning in Emacs.  They include:
 
 @enumerate
@@ -458,7 +458,7 @@ Unicode character escapes can help here; for example, for 
most programmers
 @samp{[ก-ฺ฿-๛]} is less clear than @samp{[\u0E01-\u0E3A\u0E3F-\u0E5B]}.
 
 @item
-Although a character alternative can include duplicates, it is better
+Although a bracket expression can include duplicates, it is better
 style to avoid them.  For example, @samp{[XYa-yYb-zX]} is less clear
 than @samp{[XYa-z]}.
 
@@ -469,30 +469,30 @@ is simpler to list the characters.  For example,
 than @samp{[ij]}, and @samp{[i-k]} is less clear than @samp{[ijk]}.
 
 @item
-Although a @samp{-} can appear at the beginning of a character
-alternative or as the upper bound of a range, it is better style to
-put @samp{-} by itself at the end of a character alternative.  For
+Although a @samp{-} can appear at the beginning of a bracket
+expression or as the upper bound of a range, it is better style to
+put @samp{-} by itself at the end of a bracket expression.  For
 example, although @samp{[-a-z]} is valid, @samp{[a-z-]} is better
 style; and although @samp{[*--]} is valid, @samp{[*+,-]} is clearer.
 @end enumerate
 
 @item @samp{[^ @dots{} ]}
 @cindex @samp{^} in regexp
-@samp{[^} begins a @dfn{complemented character alternative}.  This
+@samp{[^} begins a @dfn{complemented bracket expression}.  This
 matches any character except the ones specified.  Thus,
 @samp{[^a-z0-9A-Z]} matches all characters @emph{except} ASCII letters and
 digits.
 
-@samp{^} is not special in a character alternative unless it is the first
+@samp{^} is not special in a bracket expression unless it is the first
 character.  The character following the @samp{^} is treated as if it
 were first (in other words, @samp{-} and @samp{]} are not special there).
 
-A complemented character alternative can match a newline, unless newline is
+A complemented bracket expression can match a newline, unless newline is
 mentioned as one of the characters not to match.  This is in contrast to
 the handling of regexps in programs such as @code{grep}.
 
-You can specify named character classes, just like in character
-alternatives.  For instance, @samp{[^[:ascii:]]} matches any
+You can specify named character classes, just like in bracket
+expressions.  For instance, @samp{[^[:ascii:]]} matches any
 non-@acronym{ASCII} character.  @xref{Char Classes}.
 
 @item @samp{^}
@@ -556,7 +556,7 @@ that matches only empty strings, as Emacs has bugs in this 
area.
 For example, it is unwise to use @samp{\b*}, which can be omitted
 without changing the documented meaning of the regular expression.
 
-As a @samp{\} is not special inside a character alternative, it can
+As a @samp{\} is not special inside a bracket expression, it can
 never remove the special meaning of @samp{-}, @samp{^} or @samp{]}.
 You should not quote these characters when they have no special
 meaning.  This would not clarify anything, since backslashes
@@ -565,23 +565,23 @@ special meaning, as in @samp{[^\]} (@code{"[^\\]"} for 
Lisp string
 syntax), which matches any single character except a backslash.
 
 In practice, most @samp{]} that occur in regular expressions close a
-character alternative and hence are special.  However, occasionally a
+bracket expression and hence are special.  However, occasionally a
 regular expression may try to match a complex pattern of literal
 @samp{[} and @samp{]}.  In such situations, it sometimes may be
 necessary to carefully parse the regexp from the start to determine
-which square brackets enclose a character alternative.  For example,
-@samp{[^][]]} consists of the complemented character alternative
+which square brackets enclose a bracket expression.  For example,
+@samp{[^][]]} consists of the complemented bracket expression
 @samp{[^][]} (which matches any single character that is not a square
 bracket), followed by a literal @samp{]}.
 
 The exact rules are that at the beginning of a regexp, @samp{[} is
 special and @samp{]} not.  This lasts until the first unquoted
-@samp{[}, after which we are in a character alternative; @samp{[} is
+@samp{[}, after which we are in a bracket expression; @samp{[} is
 no longer special (except when it starts a character class) but @samp{]}
 is special, unless it immediately follows the special @samp{[} or that
 @samp{[} followed by a @samp{^}.  This lasts until the next special
-@samp{]} that does not end a character class.  This ends the character
-alternative and restores the ordinary syntax of regular expressions;
+@samp{]} that does not end a character class.  This ends the bracket
+expression and restores the ordinary syntax of regular expressions;
 an unquoted @samp{[} is special again and a @samp{]} not.
 
 @node Char Classes
@@ -592,8 +592,8 @@ an unquoted @samp{[} is special again and a @samp{]} not.
 @cindex alpha character class, regexp
 @cindex xdigit character class, regexp
 
-  Below is a table of the classes you can use in a character
-alternative, and what they mean.  Note that the @samp{[} and @samp{]}
+  Below is a table of the classes you can use in a bracket
+expression, and what they mean.  Note that the @samp{[} and @samp{]}
 characters that enclose the class name are part of the name, so a
 regular expression using these classes needs one more pair of
 brackets.  For example, a regular expression matching a sequence of
@@ -920,7 +920,7 @@ with a symbol-constituent character.
 
 @kindex invalid-regexp
   Not every string is a valid regular expression.  For example, a string
-that ends inside a character alternative without a terminating @samp{]}
+that ends inside a bracket expression without a terminating @samp{]}
 is invalid, and so is a string that ends with a single @samp{\}.  If
 an invalid regular expression is passed to any of the search functions,
 an @code{invalid-regexp} error is signaled.
@@ -957,7 +957,7 @@ deciphered as follows:
 
 @table @code
 @item [.?!]
-The first part of the pattern is a character alternative that matches
+The first part of the pattern is a bracket expression that matches
 any one of three characters: period, question mark, and exclamation
 mark.  The match must begin with one of these three characters.  (This
 is one point where the new default regexp used by Emacs differs from
@@ -969,7 +969,7 @@ The second part of the pattern matches any closing braces 
and quotation
 marks, zero or more of them, that may follow the period, question mark
 or exclamation mark.  The @code{\"} is Lisp syntax for a double-quote in
 a string.  The @samp{*} at the end indicates that the immediately
-preceding regular expression (a character alternative, in this case) may be
+preceding regular expression (a bracket expression, in this case) may be
 repeated zero or more times.
 
 @item \\($\\|@ $\\|\t\\|@ @ \\)
@@ -1920,7 +1920,7 @@ attempts.  Other zero-width assertions may also bring 
benefits by
 causing a match to fail early.
 
 @item
-Avoid or-patterns in favor of character alternatives: write
+Avoid or-patterns in favor of bracket expressions: write
 @samp{[ab]} instead of @samp{a\|b}.  Recall that @samp{\s-} and @samp{\sw}
 are equivalent to @samp{[[:space:]]} and @samp{[[:word:]]}, respectively.
 
@@ -3012,7 +3012,7 @@ but does not support all the Emacs escapes.
 @item
 In POSIX BREs, it is an implementation option whether @samp{^} is special
 after @samp{\(}; GNU @command{grep} treats it like Emacs does.
-In POSIX EREs, @samp{^} is always special outside of character alternatives,
+In POSIX EREs, @samp{^} is always special outside of bracket expressions,
 which means the ERE @samp{x^} never matches.
 In Emacs regular expressions, @samp{^} is special only at the
 beginning of the regular expression, or after @samp{\(}, @samp{\(?:}
@@ -3021,7 +3021,7 @@ or @samp{\|}.
 @item
 In POSIX BREs, it is an implementation option whether @samp{$} is special
 before @samp{\)}; GNU @command{grep} treats it like Emacs does.
-In POSIX EREs, @samp{$} is always special outside of character alternatives,
+In POSIX EREs, @samp{$} is always special outside of bracket expressions,
 which means the ERE @samp{$x} never matches.
 In Emacs regular expressions, @samp{$} is special only at the
 end of the regular expression, or before @samp{\)} or @samp{\|}.
@@ -3049,8 +3049,8 @@ character classes @samp{[:ascii:]}, @samp{[:multibyte:]},
 @samp{[:nonascii:]}, @samp{[:unibyte:]}, and @samp{[:word:]}.
 
 @item
-BRE and ERE alternatives can contain collating symbols and equivalence
-class expressions, e.g., @samp{[[.ch.]d[=a=]]}.
+BREs and EREs can contain collating symbols and equivalence
+class expressions within bracket expressions, e.g., @samp{[[.ch.]d[=a=]]}.
 Emacs regular expressions do not support this.
 
 @item
diff --git a/lisp/emacs-lisp/lisp-mode.el b/lisp/emacs-lisp/lisp-mode.el
index 9914ededb85..1990630608d 100644
--- a/lisp/emacs-lisp/lisp-mode.el
+++ b/lisp/emacs-lisp/lisp-mode.el
@@ -1453,7 +1453,7 @@ and initial semicolons."
       ;; are buffer-local, but we avoid changing them so that they can be set
       ;; to make `forward-paragraph' and friends do something the user wants.
       ;;
-      ;; `paragraph-start': The `(' in the character alternative and the
+      ;; `paragraph-start': The `(' in the bracket expression and the
       ;; left-singlequote plus `(' sequence after the \\| alternative prevent
       ;; sexps and backquoted sexps that follow a docstring from being filled
       ;; with the docstring.  This setting has the consequence of inhibiting
diff --git a/lisp/textmodes/picture.el b/lisp/textmodes/picture.el
index 9aa9b72c513..f98c3963b6f 100644
--- a/lisp/textmodes/picture.el
+++ b/lisp/textmodes/picture.el
@@ -383,7 +383,7 @@ Interactively, ARG is the numeric argument, and defaults to 
1."
 The syntax for this variable is like the syntax used inside of `[...]'
 in a regular expression--but without the `[' and the `]'.
 It is NOT a regular expression, and should follow the usual
-rules for the contents of a character alternative.
+rules for the contents of a bracket expression.
 It defines a set of \"interesting characters\" to look for when setting
 \(or searching for) tab stops, initially \"!-~\" (all printing characters).
 For example, suppose that you are editing a table which is formatted thus: