Here is a table of syntax classes, the characters that stand for them, their meanings, and examples of their use.
- Syntax class: whitespace character
"Whitespace characters" (designated with ` ' or `-') 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 almost always
classified as whitespace.
- Syntax class: word constituent
"Word constituents" (designated with `w') are parts of normal
English words and are typically used in variable and command names
in programs. All upper- and lower-case letters, and the digits,
are typically word constituents.
- Syntax class: symbol constituent
"Symbol constituents" (designated with `_') are the extra
characters that are used in variable and command names along with
word constituents. For example, the symbol constituents class is
used in Lisp mode to indicate that certain characters may be part
of symbol names even though they are not part of English words.
These characters are `$&*+-_<>'. In standard C, the only
non-word-constituent character that is valid in symbols is
underscore (`_').
- Syntax class: punctuation character
"Punctuation characters" (`.') are those characters that are used
as punctuation in English, or are used in some way in a programming
language to separate symbols from one another. Most programming
language modes, including Emacs Lisp mode, have no characters in
this class since the few characters that are not symbol or word
constituents all have other uses.
- Syntax class: open parenthesis character
- Syntax class: close parenthesis character
Open and close "parenthesis characters" are characters used in
dissimilar pairs to surround sentences or expressions. Such a
grouping is begun with an open parenthesis character and
terminated with a close. Each open parenthesis character matches
a particular close parenthesis character, and vice versa.
Normally, XEmacs indicates momentarily the matching open
parenthesis when you insert a close parenthesis. Blinking
The class of open parentheses is designated with `(', and that of close parentheses with `)'.
In English text, and in C code, the parenthesis pairs are `()',
`[]', and `{}'. In XEmacs Lisp, the delimiters for lists and
vectors (`()' and `[]') are classified as parenthesis characters.
- Syntax class: string quote
"String quote characters" (designated with `"') are used in many
languages, including Lisp and C, to delimit string constants. The
same string quote character appears at the beginning and the end
of a string. Such quoted strings do not nest.
The parsing facilities of XEmacs consider a string as a single token. The usual syntactic meanings of the characters in the string are suppressed.
The Lisp modes have two string quote characters: double-quote (`"') and vertical bar (`|'). `|' is not used in XEmacs Lisp, but it is used in Common Lisp. C also has two string quote characters: double-quote for strings, and single-quote (`'') for character constants.
English text has no string quote characters because English is not a programming language. Although quotation marks are used in English, we do not want them to turn off the usual syntactic properties of other characters in the quotation.
- Syntax class: escape
An "escape character" (designated with `\') starts an escape
sequence such as is used in C string and character constants. The
character `\' belongs to this class in both C and Lisp. (In C, it
is used thus only inside strings, but it turns out to cause no
trouble to treat it this way throughout C code.)
Characters in this class count as part of words if
`words-include-escapes' is non-`nil'. Word Motion
- Syntax class: character quote
A "character quote character" (designated with `/') quotes the
following character so that it loses its normal syntactic meaning.
This differs from an escape character in that only the character
immediately following is ever affected.
Characters in this class count as part of words if
`words-include-escapes' is non-`nil'. Word Motion
This class is used for backslash in TeX mode.
- Syntax class: paired delimiter
"Paired delimiter characters" (designated with `$') are like
string quote characters except that the syntactic properties of the
characters between the delimiters are not suppressed. Only TeX
mode uses a paired delimiter presently--the `$' that both enters
and leaves math mode.
- Syntax class: expression prefix
An "expression prefix operator" (designated with `'') is used for
syntactic operators that are part of an expression if they appear
next to one. These characters in Lisp include the apostrophe, `''
(used for quoting), the comma, `,' (used in macros), and `#' (used
in the read syntax for certain data types).
- Syntax class: comment starter
- Syntax class: comment ender
The "comment starter" and "comment ender" characters are used in
various languages to delimit comments. These classes are
designated with `<' and `>', respectively.
English text has no comment characters. In Lisp, the semicolon (`;') starts a comment and a newline or formfeed ends one.
- Syntax class: inherit
This syntax class does not specify a syntax. It says to look in
the standard syntax table to find the syntax of this character.
The designator for this syntax code is `@'.