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* doc/lispref/syntax.texi (Syntax Flags): Document new `c' flag.

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Stefan Monnier 2010-09-11 15:58:57 +02:00
parent 9250002f81
commit 7cf78aac59
3 changed files with 65 additions and 59 deletions
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4
doc/lispref/ChangeLog
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@ -1,3 +1,7 @@
2010-09-11 Stefan Monnier <monnier@iro.umontreal.ca>
* syntax.texi (Syntax Flags): Document new `c' flag.
2010-09-09 Glenn Morris <rgm@gnu.org>
* display.texi (ImageMagick Images): General cleanup.

119
doc/lispref/syntax.texi
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@ -292,19 +292,21 @@ identifying them as generic string delimiters.
@cindex syntax flags
In addition to the classes, entries for characters in a syntax table
can specify flags. There are seven possible flags, represented by the
characters @samp{1}, @samp{2}, @samp{3}, @samp{4}, @samp{b}, @samp{n},
and @samp{p}.
can specify flags. There are eight possible flags, represented by the
characters @samp{1}, @samp{2}, @samp{3}, @samp{4}, @samp{b}, @samp{c},
@samp{n}, and @samp{p}.
All the flags except @samp{n} and @samp{p} are used to describe
multi-character comment delimiters. The digit flags indicate that a
character can @emph{also} be part of a comment sequence, in addition to
the syntactic properties associated with its character class. The flags
are independent of the class and each other for the sake of characters
such as @samp{*} in C mode, which is a punctuation character, @emph{and}
the second character of a start-of-comment sequence (@samp{/*}),
@emph{and} the first character of an end-of-comment sequence
(@samp{*/}).
All the flags except @samp{p} are used to describe comment
delimiters. The digit flags are used for comment delimiters made up
of 2 characters. They indicate that a character can @emph{also} be
part of a comment sequence, in addition to the syntactic properties
associated with its character class. The flags are independent of the
class and each other for the sake of characters such as @samp{*} in
C mode, which is a punctuation character, @emph{and} the second
character of a start-of-comment sequence (@samp{/*}), @emph{and} the
first character of an end-of-comment sequence (@samp{*/}). The flags
@samp{b}, @samp{c}, and @samp{n} are used to qualify the corresponding
comment delimiter.
Here is a table of the possible flags for a character @var{c},
and what they mean:
@ -325,55 +327,15 @@ sequence.
@samp{4} means @var{c} is the second character of such a sequence.
@item
@c Emacs 19 feature
@samp{b} means that @var{c} as a comment delimiter belongs to the
alternative ``b'' comment style.
alternative ``b'' comment style. For a two-character comment starter,
this flag is only significant on the second char, and for a 2-character
comment ender it is only significant on the first char.
Emacs supports two comment styles simultaneously in any one syntax
table. This is for the sake of C++. Each style of comment syntax has
its own comment-start sequence and its own comment-end sequence. Each
comment must stick to one style or the other; thus, if it starts with
the comment-start sequence of style ``b,'' it must also end with the
comment-end sequence of style ``b.''
The two comment-start sequences must begin with the same character; only
the second character may differ. Mark the second character of the
``b''-style comment-start sequence with the @samp{b} flag.
A comment-end sequence (one or two characters) applies to the ``b''
style if its first character has the @samp{b} flag set; otherwise, it
applies to the ``a'' style.
The appropriate comment syntax settings for C++ are as follows:
@table @asis
@item @samp{/}
@samp{124b}
@item @samp{*}
@samp{23}
@item newline
@samp{>b}
@end table
This defines four comment-delimiting sequences:
@table @asis
@item @samp{/*}
This is a comment-start sequence for ``a'' style because the
second character, @samp{*}, does not have the @samp{b} flag.
@item @samp{//}
This is a comment-start sequence for ``b'' style because the second
character, @samp{/}, does have the @samp{b} flag.
@item @samp{*/}
This is a comment-end sequence for ``a'' style because the first
character, @samp{*}, does not have the @samp{b} flag.
@item newline
This is a comment-end sequence for ``b'' style, because the newline
character has the @samp{b} flag.
@end table
@item
@samp{c} means that @var{c} as a comment delimiter belongs to the
alternative ``c'' comment style. For a two-character comment
delimiter, @samp{c} on either character makes it of style ``c''.
@item
@samp{n} on a comment delimiter character specifies
@ -381,6 +343,45 @@ that this kind of comment can be nested. For a two-character
comment delimiter, @samp{n} on either character makes it
nestable.
Emacs supports several comment styles simultaneously in any one syntax
table. A comment style is a set of flags @samp{b}, @samp{c}, and
@samp{n}, so there can be up to 8 different comment styles.
Each comment delimiter has a style and only matches comment delimiters
of the same style. Thus if a comment starts with the comment-start
sequence of style ``bn'', it will extend until the next matching
comment-end sequence of style ``bn''.
The appropriate comment syntax settings for C++ can be as follows:
@table @asis
@item @samp{/}
@samp{124}
@item @samp{*}
@samp{23b}
@item newline
@samp{>}
@end table
This defines four comment-delimiting sequences:
@table @asis
@item @samp{/*}
This is a comment-start sequence for ``b'' style because the
second character, @samp{*}, has the @samp{b} flag.
@item @samp{//}
This is a comment-start sequence for ``a'' style because the second
character, @samp{/}, does not have the @samp{b} flag.
@item @samp{*/}
This is a comment-end sequence for ``b'' style because the first
character, @samp{*}, does have the @samp{b} flag.
@item newline
This is a comment-end sequence for ``a'' style, because the newline
character does not have the @samp{b} flag.
@end table
@item
@c Emacs 19 feature
@samp{p} identifies an additional ``prefix character'' for Lisp syntax.

1
etc/NEWS
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@ -492,6 +492,7 @@ syntactic rules.
** New hook post-self-insert-hook run at the end of self-insert-command.
+++
** Syntax tables support a new "comment style c" additionally to style b.
** frame-local variables cannot be let-bound any more.
** prog-mode is a new major-mode meant to be the parent of programming mode.