If a user option variable records a true-or-false condition, give it a
name that ends in @samp{-flag}.
+@item
+If the purpose of a variable is to store a single function, give it a
+name that ends in @samp{-function}. If the purpose of a variable is
+to store a list of functions (i.e., the variable is a hook), please
+follow the naming conventions for hooks. @xref{Hooks}.
+
@item
@cindex reserved keys
@cindex keys, reserved
that simply loading it has no visible effect---that should not enable
the feature.@footnote{Consider that the package may be loaded
arbitrarily by Custom for instance.} Users will request the feature by
-invoking the command.
+invoking the command. It is a good idea to define this command
+as a minor mode.
+
+@cindex unloading packages
+If loading the file adds functions to hooks, define a function
+@code{@var{feature}-unload-hook}, where @var{feature} is the name of
+the feature the package provides, and make it undo any such changes.
+Using @code{unload-feature} to unload the file will run this function.
+@xref{Unloading}.
@item
It is a bad idea to define aliases for the Emacs primitives. Use the
say which functions are replaced, and how the behavior of the
replacements differs from that of the originals.
+@item
+Avoid using macros that define functions and variables with names that
+are constructed. It is best for maintenance when the name of the
+function or variable being defined is given explicitly in the source
+code, as the second element of the list---as it is when you use
+@code{defun}, @code{defalias}, @code{defvar} and @code{defcustom}.
+
@item
Please keep the names of your Emacs Lisp source files to 13 characters
or less. This way, if the files are compiled, the compiled files' names
@item
Try to avoid compiler warnings about undefined free variables, by adding
-@code{defvar} definitions for these variables.
+dummy @code{defvar} definitions for these variables, like this:
+
+@example
+(defvar foo)
+@end example
+
+Such a definition has no effect except to tell the compiler
+not to warn about uses of the variable @code{foo} in this file.
-Sometimes adding a @code{require} for another package is useful to avoid
-compilation warnings for variables and functions defined in that
-package. If you do this, often it is better if the @code{require} acts
-only at compile time. Here's how to do that:
+@item
+If you use many functions and variables from a certain file, you can
+add a @code{require} for that package to avoid compilation warnings
+for them. It is better if the @code{require} acts only at compile
+time. Here's how to do this:
@example
(eval-when-compile
- (require 'foo)
- (defvar bar-baz))
+ (require 'foo))
@end example
-If you bind a variable in one function, and use it or set it in another
-function, the compiler warns about the latter function unless the
-variable has a definition. But often these variables have short names,
-and it is not clean for Lisp packages to define such variable names.
-Therefore, you should rename the variable to start with the name prefix
-used for the other functions and variables in your package.
+@item
+If you bind a variable in one function, and use it or set it in
+another function, the compiler warns about the latter function unless
+the variable has a definition. But adding a definition would be
+unclean if the variable has a short name, since Lisp packages should
+not define short variable names. The right thing to do is to rename
+this variable to start with the name prefix used for the other
+functions and variables in your package.
@item
Indent each function with @kbd{C-M-q} (@code{indent-sexp}) using the
@item
For consistency, phrase the verb in the first sentence of a function's
-documentation string as an imperative--for instance, use ``Return the
+documentation string as an imperative---for instance, use ``Return the
cons of A and B.'' in preference to ``Returns the cons of A and B@.''
Usually it looks good to do likewise for the rest of the first
paragraph. Subsequent paragraphs usually look better if each sentence
This prevents the open-parenthesis from being treated as the start of a
defun (@pxref{Defuns,, Defuns, emacs, The GNU Emacs Manual}).
+@anchor{Docstring hyperlinks}
@item
@iftex
When a documentation string refers to a Lisp symbol, write it as it
does not make a hyperlink to the documentation, irrelevant here, of the
function @code{list}.
+Normally, no hyperlink is made for a variable without variable
+documentation. You can force a hyperlink for such variables by
+preceding them with one of the words @samp{variable} or
+@samp{option}.
+
+Hyperlinks for faces are only made if the face name is preceded or
+followed by the word @samp{face}. In that case, only the face
+documentation will be shown, even if the symbol is also defined as a
+variable or as a function.
+
To make a hyperlink to Info documentation, write the name of the Info
-node in single quotes, preceded by @samp{info node} or @samp{Info
-node}. The Info file name defaults to @samp{emacs}. For example,
+node (or anchor) in single quotes, preceded by @samp{info node},
+@samp{Info node}, @samp{info anchor} or @samp{Info anchor}. The Info
+file name defaults to @samp{emacs}. For example,
@smallexample
See Info node `Font Lock' and Info node `(elisp)Font Lock Basics'.
the left margin. These are used, occasionally, for comments within
functions that should start at the margin. We also use them sometimes
for comments that are between functions---whether to use two or three
-semicolons there is a matter of style.
+semicolons depends on whether the comment should be considered a
+``heading'' by Outline minor mode. By default, comments starting with
+at least three semicolons (followed by a single space and a
+non-whitespace character) are considered headings, comments starting
+with two or less are not.
Another use for triple-semicolon comments is for commenting out lines
within a function. We use three semicolons for this precisely so that
-they remain at the left margin.
+they remain at the left margin. By default, Outline minor mode does
+not consider a comment to be a heading (even if it starts with at
+least three semicolons) if the semicolons are followed by at least two
+spaces. Thus, if you add an introductory comment to the commented out
+code, make sure to indent it by at least two spaces after the three
+semicolons.
@smallexample
(defun foo (a)
-;;; This is no longer necessary.
+;;; This is no longer necessary.
;;; (force-mode-line-update)
(message "Finished with %s" a))
@end smallexample
+When commenting out entire functions, use two semicolons.
+
@item ;;;;
Comments that start with four semicolons, @samp{;;;;}, should be aligned
to the left margin and are used for headings of major sections of a
text is used by the Finder package, so it should make sense in that
context.
-@item ;;; Documentation
-This has been used in some files in place of @samp{;;; Commentary:},
-but @samp{;;; Commentary:} is preferred.
+@item ;;; Documentation:
+This was used in some files in place of @samp{;;; Commentary:},
+but it is deprecated.
@item ;;; Change Log:
This begins change log information stored in the library file (if you