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The character ‘@’ is used to start all Texinfo commands. (It has the same meaning that ‘\’ has in plain TeX.) Texinfo has four types of @-command:
These commands consist of an @ followed by a punctuation mark or
other character that is not part of the Latin alphabet. Non-alphabetic
commands are almost always part of the text within a paragraph. The
non-alphabetic commands include @@
, @{
, @}
,
@.
, @SPACE
, most of the accent commands, and
many more.
These commands start with @ followed by a word followed by a
left and right- brace. These commands insert special symbols in
the document; they do not take arguments. Some examples:
@dots{}
⇒ ‘…’, @equiv{}
⇒ ‘≡’, @TeX{}
⇒ ‘TeX’, and
@bullet{}
⇒ ‘•’.
These commands start with @ followed by a letter or a word, followed by an
argument within braces. For example, the command @dfn
indicates
the introductory or defining use of a term; it is used as follows: ‘In
Texinfo, @@-commands are @dfn{mark-up} commands.’
These commands occupy an entire line. The line starts with @,
followed by the name of the command (a word); for example, @center
or @cindex
. If no argument is needed, the word is followed by
the end of the line. If there is an argument, it is separated from
the command name by a space. Braces are not used.
Whitespace following an @-command name are optional and (usually)
ignored if present. The exceptions are contexts whee whitespace is
significant, e.g., an @example
environment.
Thus, the alphabetic commands fall into classes that have different argument syntaxes. You cannot tell to which class a command belongs by the appearance of its name, but you can tell by the command’s meaning: if the command stands for a glyph, it is in class 2 and does not require an argument; if it makes sense to use the command among other text as part of a paragraph, the command is in class 3 and must be followed by an argument in braces; otherwise, it is in class 4 and uses the rest of the line as its argument.
The purpose of having a different syntax for commands of classes 3
and 4 is to make Texinfo files easier to read, and also to help
the GNU Emacs paragraph and filling commands work properly. There is
only one exception to this rule: the command @refill
, which is
always used at the end of a paragraph immediately following the final
period or other punctuation character. @refill
takes no
argument and does not require braces. @refill
never
confuses the Emacs paragraph commands because it cannot appear at the
beginning of a line. It is also no longer needed, since all
formatters now refill paragraphs automatically.
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