@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
-@c Free Software Foundation, Inc.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2000, 2002,
+@c 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/variables
@node Variables, Functions, Control Structures, Top
* Buffer-Local Variables:: Variable values in effect only in one buffer.
* Frame-Local Variables:: Variable values in effect only in one frame.
* Future Local Variables:: New kinds of local values we might add some day.
-* Variable Aliases:: Variables that are aliases for other variables.
* File Local Variables:: Handling local variable lists in files.
+* Variable Aliases:: Variables that are aliases for other variables.
+* Variables with Restricted Values:: Non-constant variables whose value can
+ @emph{not} be an arbitrary Lisp object.
@end menu
@node Global Variables
All of the @var{value-form}s in @var{bindings} are evaluated in the
order they appear and @emph{before} binding any of the symbols to them.
-Here is an example of this: @code{Z} is bound to the old value of
-@code{Y}, which is 2, not the new value of @code{Y}, which is 1.
+Here is an example of this: @code{z} is bound to the old value of
+@code{y}, which is 2, not the new value of @code{y}, which is 1.
@example
@group
-(setq Y 2)
+(setq y 2)
@result{} 2
@end group
@group
-(let ((Y 1)
- (Z Y))
- (list Y Z))
+(let ((y 1)
+ (z y))
+ (list y z))
@result{} (1 2)
@end group
@end example
@example
@group
-(setq Y 2)
+(setq y 2)
@result{} 2
@end group
@group
-(let* ((Y 1)
- (Z Y)) ; @r{Use the just-established value of @code{Y}.}
- (list Y Z))
+(let* ((y 1)
+ (z y)) ; @r{Use the just-established value of @code{y}.}
+ (list y z))
@result{} (1 1)
@end group
@end example
localized in time.
@defvar max-specpdl-size
+@anchor{Definition of max-specpdl-size}
@cindex variable limit error
@cindex evaluation error
@cindex infinite recursion
This variable defines the limit on the total number of local variable
-bindings and @code{unwind-protect} cleanups (@pxref{Nonlocal Exits})
-that are allowed before signaling an error (with data @code{"Variable
-binding depth exceeds max-specpdl-size"}).
+bindings and @code{unwind-protect} cleanups (@pxref{Cleanups,,
+Cleaning Up from Nonlocal Exits}) that are allowed before signaling an
+error (with data @code{"Variable binding depth exceeds
+max-specpdl-size"}).
This limit, with the associated error when it is exceeded, is one way
that Lisp avoids infinite recursion on an ill-defined function.
@code{max-lisp-eval-depth} provides another limit on depth of nesting.
-@xref{Eval}.
+@xref{Definition of max-lisp-eval-depth,, Eval}.
-The default value is 600. Entry to the Lisp debugger increases the
+The default value is 1000. Entry to the Lisp debugger increases the
value, if there is little room left, to make sure the debugger itself
has room to execute.
@end defvar
at top level in a file where its value does not matter.
@end defspec
-@defspec defconst symbol [value [doc-string]]
+@defspec defconst symbol value [doc-string]
This special form defines @var{symbol} as a value and initializes it.
It informs a person reading your code that @var{symbol} has a standard
global value, established here, that should not be changed by the user
symbol to be defined must appear explicitly in the @code{defconst}.
@code{defconst} always evaluates @var{value}, and sets the value of
-@var{symbol} to the result if @var{value} is given. If @var{symbol}
-does have a buffer-local binding in the current buffer, @code{defconst}
-sets the default value, not the buffer-local value. (But you should not
-be making buffer-local bindings for a symbol that is defined with
+@var{symbol} to the result. If @var{symbol} does have a buffer-local
+binding in the current buffer, @code{defconst} sets the default value,
+not the buffer-local value. (But you should not be making
+buffer-local bindings for a symbol that is defined with
@code{defconst}.)
Here, @code{pi} is a constant that presumably ought not to be changed
declared equivalently in @file{cus-start.el}.} or by the first character
of their @code{variable-documentation} property. If the property exists
and is a string, and its first character is @samp{*}, then the variable
-is a user option.
+is a user option. Aliases of user options are also user options.
@end defun
@kindex variable-interactive
(@pxref{Customization}).
@strong{Warning:} If the @code{defconst} and @code{defvar} special
-forms are used while the variable has a local binding, they set the
-local binding's value; the global binding is not changed. This is not
-what you usually want. To prevent it, use these special forms at top
-level in a file, where normally no local binding is in effect, and make
-sure to load the file before making a local binding for the variable.
+forms are used while the variable has a local binding (made with
+@code{let}, or a function argument), they set the local-binding's
+value; the top-level binding is not changed. This is not what you
+usually want. To prevent it, use these special forms at top level in
+a file, where normally no local binding is in effect, and make sure to
+load the file before making a local binding for the variable.
@node Tips for Defining
@section Tips for Defining Variables Robustly
x ; @r{@code{x} now has a global value.}
@result{} 3
@group
-(let ((x 5))
+(let ((x 5))
(setq x 6) ; @r{The local binding of @code{x} is set.}
x)
@result{} 6
@group
(setq x 10 ; @r{Notice that @code{x} is set before}
y (1+ x)) ; @r{the value of @code{y} is computed.}
- @result{} 11
+ @result{} 11
@end group
@end example
@end defspec
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
+@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
(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
@cindex scope
@cindex extent
@cindex dynamic scoping
+@cindex lexical scoping
Local bindings in Emacs Lisp have @dfn{indefinite scope} and
@dfn{dynamic extent}. @dfn{Scope} refers to @emph{where} textually in
the source code the binding can be accessed. ``Indefinite scope'' means
be changed with @code{setq} in any buffer; the only way to change it is
with @code{setq-default}.
- @strong{Warning:} When a variable has buffer-local values in one or
-more buffers, you can get Emacs very confused by binding the variable
-with @code{let}, changing to a different current buffer in which a
-different binding is in effect, and then exiting the @code{let}. This
-can scramble the values of the buffer-local and default bindings.
-
- To preserve your sanity, avoid using a variable in that way. If you
-use @code{save-excursion} around each piece of code that changes to a
-different current buffer, you will not have this problem
-(@pxref{Excursions}). Here is an example of what to avoid:
+ @strong{Warning:} When a variable has buffer-local or frame-local
+bindings in one or more buffers, @code{let} rebinds the binding that's
+currently in effect. For instance, if the current buffer has a
+buffer-local value, @code{let} temporarily rebinds that. If no
+buffer-local or frame-local bindings are in effect, @code{let} rebinds
+the default value. If inside the @code{let} you then change to a
+different current buffer in which a different binding is in effect,
+you won't see the @code{let} binding any more. And if you exit the
+@code{let} while still in the other buffer, you won't see the
+unbinding occur (though it will occur properly). Here is an example
+to illustrate:
@example
@group
-(setq foo 'b)
+(setq foo 'g)
(set-buffer "a")
(make-local-variable 'foo)
@end group
(setq foo 'a)
(let ((foo 'temp))
+ ;; foo @result{} 'temp ; @r{let binding in buffer @samp{a}}
(set-buffer "b")
+ ;; foo @result{} 'g ; @r{the global value since foo is not local in @samp{b}}
@var{body}@dots{})
@group
-foo @result{} 'a ; @r{The old buffer-local value from buffer @samp{a}}
- ; @r{is now the default value.}
-@end group
-@group
-(set-buffer "a")
-foo @result{} 'temp ; @r{The local @code{let} value that should be gone}
- ; @r{is now the buffer-local value in buffer @samp{a}.}
+foo @result{} 'g ; @r{exiting restored the local value in buffer @samp{a},}
+ ; @r{but we don't see that in buffer @samp{b}}
@end group
-@end example
-
-@noindent
-But @code{save-excursion} as shown here avoids the problem:
-
-@example
@group
-(let ((foo 'temp))
- (save-excursion
- (set-buffer "b")
- @var{body}@dots{}))
+(set-buffer "a") ; @r{verify the local value was restored}
+foo @result{} 'a
@end group
@end example
variables cannot have buffer-local bindings as well. @xref{Multiple
Displays}.
-@strong{Note:} Do not use @code{make-local-variable} for a hook
-variable. The hook variables are automatically made buffer-local
-as needed if you use the @var{local} argument to @code{add-hook} or
+@strong{Warning:} do not use @code{make-local-variable} for a hook
+variable. The hook variables are automatically made buffer-local as
+needed if you use the @var{local} argument to @code{add-hook} or
@code{remove-hook}.
@end deffn
A peculiar wrinkle of this feature is that binding the variable (with
@code{let} or other binding constructs) does not create a buffer-local
binding for it. Only setting the variable (with @code{set} or
-@code{setq}) does so.
+@code{setq}), while the variable does not have a @code{let}-style
+binding that was made in the current buffer, does so.
+
+If @var{variable} does not have a default value, then calling this
+command will give it a default value of @code{nil}. If @var{variable}
+already has a default value, that value remains unchanged.
+Subsequently calling @code{makunbound} on @var{variable} will result
+in a void buffer-local value and leave the default value unaffected.
The value returned is @var{variable}.
@code{nil}.
@end defun
+@defun local-variable-if-set-p variable &optional buffer
+This returns @code{t} if @var{variable} will become buffer-local in
+buffer @var{buffer} (which defaults to the current buffer) if it is
+set there.
+@end defun
+
+@defun buffer-local-value variable buffer
+This function returns the buffer-local binding of @var{variable} (a
+symbol) in buffer @var{buffer}. If @var{variable} does not have a
+buffer-local binding in buffer @var{buffer}, it returns the default
+value (@pxref{Default Value}) of @var{variable} instead.
+@end defun
+
@defun buffer-local-variables &optional buffer
This function returns a list describing the buffer-local variables in
buffer @var{buffer}. (If @var{buffer} is omitted, the current buffer is
(mode-name . "Fundamental")
@dots{}
@group
- ;; @r{Next, non-built-in buffer-local variables.}
+ ;; @r{Next, non-built-in buffer-local variables.}
;; @r{This one is buffer-local and void:}
foobar
;; @r{This one is buffer-local and nonvoid:}
list does @emph{not} change the buffer-local values of the variables.
@end defun
-@defun buffer-local-value variable buffer
-This function returns the buffer-local binding of @var{variable} (a
-symbol) in buffer @var{buffer}. If @var{variable} does not have a
-buffer-local binding in buffer @var{buffer}, it returns the default
-value (@pxref{Default Value}) of @var{variable} instead.
-@end defun
-
@deffn Command kill-local-variable variable
This function deletes the buffer-local binding (if any) for
@var{variable} (a symbol) in the current buffer. As a result, the
The function @code{kill-all-local-variables} runs this normal hook
before it does anything else. This gives major modes a way to arrange
for something special to be done if the user switches to a different
-major mode. For best results, make this variable buffer-local, so that
-it will disappear after doing its job and will not interfere with the
+major mode. It is also useful for buffer-specific minor modes
+that should be forgotten if the user changes the major mode.
+
+For best results, make this variable buffer-local, so that it will
+disappear after doing its job and will not interfere with the
subsequent major mode. @xref{Hooks}.
@end defvar
if some frame already has a value for @var{variable} as a frame
parameter, that value automatically becomes a frame-local binding.
+If @var{variable} does not have a default value, then calling this
+command will give it a default value of @code{nil}. If @var{variable}
+already has a default value, that value remains unchanged.
+
If the variable is terminal-local, this function signals an error,
because such variables cannot have frame-local bindings as well.
@xref{Multiple Displays}. A few variables that are implemented
-specially in Emacs can be (and usually are) buffer-local, but can never
-be frame-local.
+specially in Emacs can be buffer-local, but can never be frame-local.
+
+This command returns @var{variable}.
@end deffn
Buffer-local bindings take precedence over frame-local bindings. Thus,
If sufficient application is found for either of these two kinds of
local bindings, we will provide it in a subsequent Emacs version.
+@node File Local Variables
+@section File Local Variables
+
+ This section describes the functions and variables that affect
+processing of file local variables. @xref{File variables, ,
+Local Variables in Files, emacs, The GNU Emacs Manual}, for basic
+information about 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}.
+@end defopt
+
+@defun hack-local-variables &optional mode-only
+This function parses, and binds or evaluates as appropriate, any local
+variables specified by the contents of the current buffer. The variable
+@code{enable-local-variables} has its effect here. However, this
+function does not look for the @samp{mode:} local variable in the
+@w{@samp{-*-}} line. @code{set-auto-mode} does that, also taking
+@code{enable-local-variables} into account (@pxref{Auto Major Mode}).
+
+If the optional argument @var{mode-only} is non-@code{nil}, then all
+this function does is return @code{t} if the @w{@samp{-*-}} line or
+the local variables list specifies a mode and @code{nil} otherwise.
+It does not set the mode nor any other file local variable.
+@end defun
+
+ If a file local variable could specify a function that would
+be called later, or an expression that would be executed later, simply
+visiting a file could take over your Emacs. Emacs takes several
+measures to prevent this.
+
+@cindex safe local variable
+ You can specify safe values for a variable with a
+@code{safe-local-variable} property. The property has to be
+a function of one argument; any value is safe if the function
+returns non-@code{nil} given that value. Many commonly encountered
+file variables standardly have @code{safe-local-variable} properties,
+including @code{fill-column}, @code{fill-prefix}, and
+@code{indent-tabs-mode}. For boolean-valued variables that are safe,
+use @code{booleanp} as the property value.
+
+@defopt safe-local-variable-values
+This variable provides another way to mark some variable values as
+safe. It is a list of cons cells @code{(@var{var} . @var{val})},
+where @var{var} is a variable name and @var{val} is a value which is
+safe for that variable.
+
+When Emacs asks the user whether or not to obey a set of file local
+variable specifications, the user can choose to mark them as safe.
+Doing so adds those variable/value pairs to
+@code{safe-local-variable-values}, and saves it to the user's custom
+file.
+@end defopt
+
+@defun safe-local-variable-p sym val
+This function returns non-@code{nil} if it is safe to give @var{sym}
+the value @var{val}, based on the above criteria.
+@end defun
+
+@cindex 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},
+@samp{-forms}, @samp{-map}, @samp{-map-alist}, @samp{-mode-alist},
+@samp{-program}, or @samp{-predicate} is considered risky. The
+variables @samp{font-lock-keywords}, @samp{font-lock-keywords}
+followed by a digit, and @samp{font-lock-syntactic-keywords} are also
+considered risky. Finally, any variable whose name has a
+non-@code{nil} @code{risky-local-variable} property is considered
+risky.
+
+@defun risky-local-variable-p sym
+This function returns non-@code{nil} if @var{sym} is a risky variable,
+based on the above criteria.
+@end defun
+
+ If a variable is risky, it will not be entered automatically into
+@code{safe-local-variable-values} as described above. Therefore,
+Emacs will always query before setting a risky variable, unless the
+user explicitly allows the setting by customizing
+@code{safe-local-variable-values} directly.
+
+@defvar ignored-local-variables
+This variable holds a list of variables that should not be given local
+values by files. Any value specified for one of these variables is
+completely ignored.
+@end defvar
+
+ The @samp{Eval:} ``variable'' is also a potential loophole, so Emacs
+normally asks for confirmation before handling it.
+
+@defopt enable-local-eval
+This variable controls processing of @samp{Eval:} in @samp{-*-} lines
+or local variables
+lists in files being visited. A value of @code{t} means process them
+unconditionally; @code{nil} means ignore them; anything else means ask
+the user what to do for each file. The default value is @code{maybe}.
+@end defopt
+
+ Text properties are also potential loopholes, since their values
+could include functions to call. So Emacs discards all text
+properties from string values specified for file local variables.
+
@node Variable Aliases
@section Variable Aliases
to keep the old name as an @emph{alias} of the new one for
compatibility. You can do this with @code{defvaralias}.
-@defmac defvaralias alias-var base-var
-This function defines the symbol @var{alias-var} as a variable alias
-for symbol @var{base-var}. This means that retrieving the value of
-@var{alias-var} returns the value of @var{base-var}, and changing the
-value of @var{alias-var} changes the value of @var{base-var}.
+@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}.
+
+If the @var{docstring} argument is non-@code{nil}, it specifies the
+documentation for @var{new-alias}; otherwise, the alias gets the same
+documentation as @var{base-variable} has, if any, unless
+@var{base-variable} is itself an alias, in which case @var{new-alias} gets
+the documentation of the variable at the end of the chain of aliases.
+
+This function returns @var{base-variable}.
+@end defun
+
+ Variable aliases are convenient for replacing an old name for a
+variable with a new name. @code{make-obsolete-variable} declares that
+the old name is obsolete and therefore that it may be removed at some
+stage in the future.
+
+@defun make-obsolete-variable obsolete-name current-name &optional when
+This function makes the byte-compiler warn that the variable
+@var{obsolete-name} is obsolete. If @var{current-name} is a symbol, it is
+the variable's new name; then the warning message says to use
+@var{current-name} instead of @var{obsolete-name}. If @var{current-name}
+is a string, this is the message and there is no replacement variable.
+
+If provided, @var{when} should be a string indicating when the
+variable was first made obsolete---for example, a date or a release
+number.
+@end defun
+
+ You can make two variables synonyms and declare one obsolete at the
+same time using the macro @code{define-obsolete-variable-alias}.
+
+@defmac define-obsolete-variable-alias obsolete-name current-name &optional when docstring
+This macro marks the variable @var{obsolete-name} as obsolete and also
+makes it an alias for the variable @var{current-name}. It is
+equivalent to the following:
+
+@example
+(defvaralias @var{obsolete-name} @var{current-name} @var{docstring})
+(make-obsolete-variable @var{obsolete-name} @var{current-name} @var{when})
+@end example
@end defmac
@defun indirect-variable variable
This function returns the variable at the end of the chain of aliases
of @var{variable}. If @var{variable} is not a symbol, or if @var{variable} is
not defined as an alias, the function returns @var{variable}.
+
+This function signals a @code{cyclic-variable-indirection} error if
+there is a loop in the chain of symbols.
@end defun
@example
(setq bar 2)
bar
@result{} 2
+@group
foo
@result{} 2
+@end group
(setq foo 0)
bar
@result{} 0
@result{} 0
@end example
-@node File Local Variables
-@section File Local Variables
-
- This section describes the functions and variables that affect
-processing of local variables lists in files.
-
-@defopt enable-local-variables
-This variable controls whether to process file local variables lists. A
-value of @code{t} means process the local variables lists
-unconditionally; @code{nil} means ignore them; anything else means ask
-the user what to do for each file. The default value is @code{t}.
-@end defopt
-
-@defun hack-local-variables &optional force
-This function parses, and binds or evaluates as appropriate, any local
-variables specified by the contents of the current buffer. The variable
-@code{enable-local-variables} has its effect here.
-
-The argument @var{force} usually comes from the argument @var{find-file}
-given to @code{normal-mode}.
-@end defun
+@node Variables with Restricted Values
+@section Variables with Restricted Values
- If a file local variable list could specify the a function that will
-be called later, or an expression that will be executed later, simply
-visiting a file could take over your Emacs. To prevent this, Emacs
-takes care not to allow local variable lists to set such variables.
+ Ordinary Lisp variables can be assigned any value that is a valid
+Lisp object. However, certain Lisp variables are not defined in Lisp,
+but in C. Most of these variables are defined in the C code using
+@code{DEFVAR_LISP}. Like variables defined in Lisp, these can take on
+any value. However, some variables are defined using
+@code{DEFVAR_INT} or @code{DEFVAR_BOOL}. @xref{Defining Lisp
+variables in C,, Writing Emacs Primitives}, in particular the
+description of functions of the type @code{syms_of_@var{filename}},
+for a brief discussion of the C implementation.
- For one thing, any variable whose name ends in @samp{-function},
-@samp{-functions}, @samp{-hook}, @samp{-hooks}, @samp{-form},
-@samp{-forms}, @samp{-program}, @samp{-command} or @samp{-predicate}
-cannot be set in a local variable list. In general, you should use such
-a name whenever it is appropriate for the variable's meaning.
+ Variables of type @code{DEFVAR_BOOL} can only take on the values
+@code{nil} or @code{t}. Attempting to assign them any other value
+will set them to @code{t}:
- In addition, any variable whose name has a non-@code{nil}
-@code{risky-local-variable} property is also ignored. So are
-all variables listed in @code{ignored-local-variables}:
+@example
+(let ((display-hourglass 5))
+ display-hourglass)
+ @result{} t
+@end example
-@defvar ignored-local-variables
-This variable holds a list of variables that should not be
-set by a file's local variables list. Any value specified
-for one of these variables is ignored.
+@defvar byte-boolean-vars
+This variable holds a list of all variables of type @code{DEFVAR_BOOL}.
@end defvar
- The @samp{Eval:} ``variable'' is also a potential loophole, so Emacs
-normally asks for confirmation before handling it.
+ Variables of type @code{DEFVAR_INT} can only take on integer values.
+Attempting to assign them any other value will result in an error:
-@defopt enable-local-eval
-This variable controls processing of @samp{Eval:} in local variables
-lists in files being visited. A value of @code{t} means process them
-unconditionally; @code{nil} means ignore them; anything else means ask
-the user what to do for each file. The default value is @code{maybe}.
-@end defopt
+@example
+(setq window-min-height 5.0)
+@error{} Wrong type argument: integerp, 5.0
+@end example
+
+@ignore
+ arch-tag: 5ff62c44-2b51-47bb-99d4-fea5aeec5d3e
+@end ignore