The Template for a Definition

The @deffn command is used for definitions of entities that resemble functions. To write a definition using the @deffn command, write the @deffn command at the beginning of a line and follow it on the same line by the category of the entity, the name of the entity itself, and its arguments (if any). Then write the body of the definition on succeeding lines. (You may embed examples in the body.) Finally, end the definition with an @end deffn command written on a line of its own. (The other definition commands follow the same format.)

The template for a definition looks like this:

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

For example,

     @deffn Command forward-word count
     This command moves point forward @var{count} words
     (or backward if @var{count} is negative). ...
     @end deffn
     

produces

forward-word count

Command

This function moves point forward count words (or backward if count is negative). ...

Capitalize the category name like a title. If the name of the category contains spaces, as in the phrase `Interactive Command', write braces around it. For example:

     @deffn {Interactive Command} isearch-forward
     ...
     @end deffn
     

Otherwise, the second word will be mistaken for the name of the entity.

Some of the definition commands are more general than others. The @deffn command, for example, is the general definition command for functions and the like--for entities that may take arguments. When you use this command, you specify the category to which the entity belongs. The @deffn command possesses three predefined, specialized variations, @defun, @defmac, and @defspec, that specify the category for you: "Function", "Macro", and "Special Form" respectively. (In Lisp, a special form is an entity much like a function.) The @defvr command also is accompanied by several predefined, specialized variations for describing particular kinds of variables.

The template for a specialized definition, such as @defun, is similar to the template for a generalized definition, except that you do not need to specify the category:

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

Thus,

     @defun buffer-end flag
     This function returns @code{(point-min)} if @var{flag}
     is less than 1, @code{(point-max)} otherwise.
     ...
     @end defun
     

produces

buffer-end flag

Function

This function returns (point-min) if flag is less than 1, (point-max) otherwise. ...

See Sample Function Definition, for a more detailed example of a function definition, including the use of @example inside the definition.

The other specialized commands work like @defun.

Note that, due to implementation difficulties, macros are not expanded in @deffn and all the other definition commands.