@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2001,
-@c 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
+@c Copyright (C) 1990-1995, 1998-1999, 2001-2012
+@c Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../../info/syntax
@node Syntax Tables, Abbrevs, Searching and Matching, Top
* Desc: Syntax Descriptors. How characters are classified.
* Syntax Table Functions:: How to create, examine and alter syntax tables.
* Syntax Properties:: Overriding syntax with text properties.
-* Motion and Syntax:: Moving over characters with certain syntaxes.
+* Motion and Syntax:: Moving over characters with certain syntaxes.
* Parsing Expressions:: Parsing balanced expressions
using the syntax table.
* Standard Syntax Tables:: Syntax tables used by various major modes.
character or flags are needed, one character is sufficient.
For example, the syntax descriptor for the character @samp{*} in C
-mode is @samp{@w{. 23}} (i.e., punctuation, matching character slot
+mode is @code{". 23"} (i.e., punctuation, matching character slot
unused, second character of a comment-starter, first character of a
comment-ender), and the entry for @samp{/} is @samp{@w{. 14}} (i.e.,
punctuation, matching character slot unused, first character of a
@deffn {Syntax class} @w{whitespace character}
@dfn{Whitespace characters} (designated by @w{@samp{@ }} or @samp{-})
separate symbols and words from each other. Typically, whitespace
-characters have no other syntactic significance, and multiple whitespace
-characters are syntactically equivalent to a single one. Space, tab,
-newline and formfeed are classified as whitespace in almost all major
-modes.
+characters have no other syntactic significance, and multiple
+whitespace characters are syntactically equivalent to a single one.
+Space, tab, and formfeed are classified as whitespace in almost all
+major modes.
@end deffn
@deffn {Syntax class} @w{word constituent}
@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}.
-
- 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{*/}).
+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{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:
@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.''
+@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''.
-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.
+@item
+@samp{n} on a comment delimiter character specifies
+that this kind of comment can be nested. For a two-character
+comment delimiter, @samp{n} on either character makes it
+nestable.
-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.
+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++ are as follows:
+The appropriate comment syntax settings for C++ can be as follows:
@table @asis
@item @samp{/}
-@samp{124b}
+@samp{124}
@item @samp{*}
-@samp{23}
+@samp{23b}
@item newline
-@samp{>b}
+@samp{>}
@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.
+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 ``b'' style because the second
-character, @samp{/}, does have the @samp{b} flag.
+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 ``a'' style because the first
-character, @samp{*}, does not have the @samp{b} flag.
+This is a comment-end sequence for ``b'' style because the first
+character, @samp{*}, has the @samp{b} flag.
@item newline
-This is a comment-end sequence for ``b'' style, because the newline
-character has the @samp{b} flag.
+This is a comment-end sequence for ``a'' style, because the newline
+character does not have the @samp{b} flag.
@end table
-@item
-@samp{n} on a comment delimiter character specifies
-that this kind of comment can be nested. For a two-character
-comment delimiter, @samp{n} on either character makes it
-nestable.
-
@item
@c Emacs 19 feature
@samp{p} identifies an additional ``prefix character'' for Lisp syntax.
@section Parsing Expressions
This section describes functions for parsing and scanning balanced
-expressions, also known as @dfn{sexps}. Basically, a sexp is either a
-balanced parenthetical grouping, a string, or a symbol name (a
-sequence of characters whose syntax is either word constituent or
-symbol constituent). However, characters whose syntax is expression
-prefix are treated as part of the sexp if they appear next to it.
+expressions. We will refer to such expressions as @dfn{sexps},
+following the terminology of Lisp, even though these functions can act
+on languages other than Lisp. Basically, a sexp is either a balanced
+parenthetical grouping, a string, or a ``symbol'' (i.e.@: a sequence
+of characters whose syntax is either word constituent or symbol
+constituent). However, characters whose syntax is expression prefix
+are treated as part of the sexp if they appear next to it.
The syntax table controls the interpretation of characters, so these
functions can be used for Lisp expressions when in Lisp mode and for C
arrived at a top level position.
@end defun
- We have provided this access function rather than document how the
-data is represented in the state, because we plan to change the
-representation in the future.
-
@node Low-Level Parsing
@subsection Low-Level Parsing
@defun define-category char docstring &optional table
This function defines a new category, with name @var{char} and
documentation @var{docstring}, for the category table @var{table}.
+
+Here's an example of defining a new category for characters that have
+strong right-to-left directionality (@pxref{Bidirectional Display})
+and using it in a special category table:
+
+@example
+(defvar special-category-table-for-bidi
+ (let ((category-table (make-category-table))
+ (uniprop-table (unicode-property-table-internal 'bidi-class)))
+ (define-category ?R "Characters of bidi-class R, AL, or RLO"
+ category-table)
+ (map-char-table
+ #'(lambda (key val)
+ (if (memq val '(R AL RLO))
+ (modify-category-entry key ?R category-table)))
+ uniprop-table)
+ category-table))
+@end example
@end defun
@defun category-docstring category &optional table
displays that buffer. If @var{buffer-or-name} is non-@code{nil}, it
describes the category table of that buffer instead.
@end deffn
-
-@ignore
- arch-tag: 4d914e96-0283-445c-9233-75d33662908c
-@end ignore