@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2000, 2002,
-@c 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2000,
+@c 2001, 2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/variables
@node Variables, Functions, Control Structures, Top
@node Constant Variables
@section Variables that Never Change
-@vindex nil
-@vindex t
@kindex setting-constant
@cindex keyword symbol
+@cindex variable with constant value
+@cindex constant variables
+@cindex symbol that evaluates to itself
+@cindex symbol with constant value
In Emacs Lisp, certain symbols normally evaluate to themselves. These
include @code{nil} and @code{t}, as well as any symbol whose name starts
@item @dots{}-command
The value is a whole shell command.
-@item @samp{}-switches
+@item @dots{}-switches
The value specifies options for a command.
@end table
@end group
@group
-;; @r{Here the value of @code{abracadabra},}
+;; @r{Here, the value of @code{abracadabra},}
;; @r{which is @code{foo},}
;; @r{is the symbol whose value is examined.}
(let ((abracadabra 'foo))
@end quotation
@end defun
- One other function for setting a variable is designed to add
-an element to a list if it is not already present in the list.
-
-@defun add-to-list symbol element &optional append
-This function sets the variable @var{symbol} by consing @var{element}
-onto the old value, if @var{element} is not already a member of that
-value. It returns the resulting list, whether updated or not. The
-value of @var{symbol} had better be a list already before the call.
-Membership is tested using @code{equal}.
-
-Normally, if @var{element} is added, it is added to the front of
-@var{symbol}, but if the optional argument @var{append} is
-non-@code{nil}, it is added at the end.
-
-The argument @var{symbol} is not implicitly quoted; @code{add-to-list}
-is an ordinary function, like @code{set} and unlike @code{setq}. Quote
-the argument yourself if that is what you want.
-@end defun
-
-Here's a scenario showing how to use @code{add-to-list}:
-
-@example
-(setq foo '(a b))
- @result{} (a b)
-
-(add-to-list 'foo 'c) ;; @r{Add @code{c}.}
- @result{} (c a b)
-
-(add-to-list 'foo 'b) ;; @r{No effect.}
- @result{} (c a b)
-
-foo ;; @r{@code{foo} was changed.}
- @result{} (c a b)
-@end example
-
- An equivalent expression for @code{(add-to-list '@var{var}
-@var{value})} is this:
-
-@example
-(or (member @var{value} @var{var})
- (setq @var{var} (cons @var{value} @var{var})))
-@end example
-
-@defun add-to-ordered-list symbol element &optional order
-This function sets the variable @var{symbol} by inserting
-@var{element} into the old value, which must be a list, at the
-position specified by @var{order}. If @var{element} is already a
-member of the list, its position in the list is adjusted according
-to @var{order}. Membership is tested using @code{eq}.
-This function returns the resulting list, whether updated or not.
-
-The @var{order} is typically a number (integer or float), and the
-elements of the list are sorted in non-decreasing numerical order.
-
-@var{order} may also be omitted or @code{nil}. Then the numeric order
-of @var{element} stays unchanged if it already has one; otherwise,
-@var{element} has no numeric order. Elements without a numeric list
-order are placed at the end of the list, in no particular order.
-
-Any other value for @var{order} removes the numeric order of @var{element}
-if it already has one; otherwise, it is equivalent to @code{nil}.
-
-The argument @var{symbol} is not implicitly quoted;
-@code{add-to-ordered-list} is an ordinary function, like @code{set}
-and unlike @code{setq}. Quote the argument yourself if that is what
-you want.
-
-The ordering information is stored in a hash table on @var{symbol}'s
-@code{list-order} property.
-@end defun
-
-Here's a scenario showing how to use @code{add-to-ordered-list}:
-
-@example
-(setq foo '())
- @result{} nil
-
-(add-to-ordered-list 'foo 'a 1) ;; @r{Add @code{a}.}
- @result{} (a)
-
-(add-to-ordered-list 'foo 'c 3) ;; @r{Add @code{c}.}
- @result{} (a c)
-
-(add-to-ordered-list 'foo 'b 2) ;; @r{Add @code{b}.}
- @result{} (a b c)
-
-(add-to-ordered-list 'foo 'b 4) ;; @r{Move @code{b}.}
- @result{} (a c b)
-
-(add-to-ordered-list 'foo 'd) ;; @r{Append @code{d}.}
- @result{} (a c b d)
-
-(add-to-ordered-list 'foo 'e) ;; @r{Add @code{e}}.
- @result{} (a c b e d)
-
-foo ;; @r{@code{foo} was changed.}
- @result{} (a c b e d)
-@end example
-
@node Variable Scoping
@section Scoping Rules for Variable Bindings
@node Buffer-Local Variables
@section Buffer-Local Variables
-@cindex variables, buffer-local
+@cindex variable, buffer-local
@cindex buffer-local variables
Global and local variable bindings are found in most programming
@node Frame-Local Variables
@section Frame-Local Variables
+@cindex frame-local variables
Just as variables can have buffer-local bindings, they can also have
frame-local bindings. These bindings belong to one frame, and are in
@node File Local Variables
@section File Local Variables
+@cindex file local variables
A file can specify local variable values; Emacs uses these to create
buffer-local bindings for those variables in the buffer visiting that
processing of file local variables.
@defopt enable-local-variables
-This variable controls whether to process file local variables. A
-value of @code{t} means to process them, querying the user if unsafe
-variables are encountered; @code{nil} means ignore them; anything else
-means to query the user for each file. The default value is @code{t}.
+This variable controls whether to process file local variables.
+The possible values are:
+
+@table @asis
+@item @code{t} (the default)
+Set the safe variables, and query (once) about any unsafe variables.
+@item @code{:safe}
+Set only the safe variables and do not query.
+@item @code{:all}
+Set all the variables and do not query.
+@item @code{nil}
+Don't set any variables.
+@item anything else
+Query (once) about all the variables.
+@end table
@end defopt
@defun hack-local-variables &optional mode-only
the value @var{val}, based on the above criteria.
@end defun
-@cindex risky local variable
+@c @cindex risky local variable Duplicates risky-local-variable
Some variables are considered @dfn{risky}. A variable whose name
ends in any of @samp{-command}, @samp{-frame-alist}, @samp{-function},
@samp{-functions}, @samp{-hook}, @samp{-hooks}, @samp{-form},
@node Variable Aliases
@section Variable Aliases
+@cindex variable aliases
It is sometimes useful to make two variables synonyms, so that both
variables always have the same value, and changing either one also
@defun defvaralias new-alias base-variable &optional docstring
This function defines the symbol @var{new-alias} as a variable alias
-for symbol @var{base-variable}. This means that retrieving the value of
-@var{new-alias} returns the value of @var{base-variable}, and changing the
-value of @var{new-alias} changes the value of @var{base-variable}.
+for symbol @var{base-variable}. This means that retrieving the value
+of @var{new-alias} returns the value of @var{base-variable}, and
+changing the value of @var{new-alias} changes the value of
+@var{base-variable}. The two aliased variable names always share the
+same value and the same bindings.
If the @var{docstring} argument is non-@code{nil}, it specifies the
documentation for @var{new-alias}; otherwise, the alias gets the same