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Functions and Similar Entities

This section describes the commands for describing functions and similar entities:

@deffn category name arguments...

The @deffn command is the general definition command for functions, interactive commands, and similar entities that may take arguments. You must choose a term to describe the category of entity being defined; for example, "Function" could be used if the entity is a function. The @deffn command is written at the beginning of a line and is followed on the same line by the category of entity being described, the name of this particular entity, and its arguments, if any. Terminate the definition with @end deffn on a line of its own.

For example, here is a definition:

@deffn Command forward-char nchars
Move point forward @var{nchars} characters.
@end deffn

This shows a rather terse definition for a "command" named forward-char with one argument, nchars.

@deffn prints argument names such as nchars in italics or upper case, as if @var had been used, because we think of these names as metasyntactic variables--they stand for the actual argument values. Within the text of the description, write an argument name explicitly with @var to refer to the value of the argument. In the example above, we used @var{nchars} in this way.

The template for @deffn is:

@deffn category name arguments...
body-of-definition
@end deffn

@defun name arguments...

The @defun command is the definition command for functions. @defun is equivalent to @deffn Function ....

For example,

@defun set symbol new-value
Change the value of the symbol @var{symbol}
to @var{new-value}.
@end defun

shows a rather terse definition for a function set whose arguments are symbol and new-value. The argument names on the @defun line automatically appear in italics or upper case as if they were enclosed in @var. Terminate the definition with @end defun on a line of its own.

The template is:

@defun function-name arguments...
body-of-definition
@end defun

@defun creates an entry in the index of functions.

@defmac name arguments...

The @defmac command is the definition command for macros. @defmac is equivalent to @deffn Macro ... and works like @defun.

@defspec name arguments...

The @defspec command is the definition command for special forms. (In Lisp, a special form is an entity much like a function, see Special Forms.) @defspec is equivalent to @deffn {Special Form} ... and works like @defun.