(Type Predicates): Add links for booleanp and string-or-null-p.

[gnu-emacs] / lispref / variables.texi

diff --git a/lispref/variables.texi b/lispref/variables.texi
index 6040a4c09ae4bc4f2de28607ab2e6a9c2d67516c..c2abdf0563ddd2da985270df1e4af14614ca5073 100644 (file)
--- a/lispref/variables.texi
+++ b/lispref/variables.texi
@@ -1,8 +1,7 @@
 @c -*-texinfo-*-
 @c This is part of the GNU Emacs Lisp Reference Manual.
 @c -*-texinfo-*-
 @c This is part of the GNU Emacs Lisp Reference Manual.

-@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999,
-@c 2000, 2003, 2004
-@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
 @c See the file elisp.texi for copying conditions.
 @setfilename ../info/variables
 @node Variables, Functions, Control Structures, Top


@@ -42,8 +41,8 @@ variable.
 * 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.
 * 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.
 * 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
 * Variables with Restricted Values::  Non-constant variables whose value can
                                         @emph{not} be an arbitrary Lisp object.
 @end menu


@@ -277,7 +276,7 @@ that Lisp avoids infinite recursion on an ill-defined function.
 @code{max-lisp-eval-depth} provides another limit on depth of nesting.
 @xref{Definition of max-lisp-eval-depth,, Eval}.
 
 @code{max-lisp-eval-depth} provides another limit on depth of nesting.
 @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
 value, if there is little room left, to make sure the debugger itself
 has room to execute.
 @end defvar


@@ -569,7 +568,7 @@ though being declared using @code{defcustom}@footnote{They may also be
 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
 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
 @end defun
 
 @kindex variable-interactive


@@ -903,6 +902,62 @@ foo                       ;; @r{@code{foo} was changed.}
     (setq @var{var} (cons @var{value} @var{var})))
 @end example
 
     (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 Variable Scoping
 @section Scoping Rules for Variable Bindings
 


@@ -1589,8 +1644,7 @@ 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
 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
 
 This command returns @var{variable}.
 @end deffn


@@ -1688,6 +1742,111 @@ bindings offer a way to handle these situations more robustly.
   If sufficient application is found for either of these two kinds of
 local bindings, we will provide it in a subsequent Emacs version.
 
   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}.
+
+@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
 
 @node Variable Aliases
 @section Variable Aliases
 


@@ -1699,19 +1858,19 @@ chosen, or because its meaning has partly changed---it can be useful
 to keep the old name as an @emph{alias} of the new one for
 compatibility.  You can do this with @code{defvaralias}.
 
 to keep the old name as an @emph{alias} of the new one for
 compatibility.  You can do this with @code{defvaralias}.
 

-@defun defvaralias alias-var base-var &optional docstring
-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
 
 If the @var{docstring} argument is non-@code{nil}, it specifies the

-documentation for @var{alias-var}; otherwise, the alias gets the same
-documentation as @var{base-var} has, if any, unless @var{base-var} is
-itself an alias, in which case @var{alias-var} gets the documentation
-of the variable at the end of the chain of aliases.
+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-var}.
+This function returns @var{base-variable}.

 @end defun
 
   Variable aliases are convenient for replacing an old name for a
 @end defun
 
   Variable aliases are convenient for replacing an old name for a


@@ -1719,12 +1878,12 @@ 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.
 
 the old name is obsolete and therefore that it may be removed at some
 stage in the future.
 

-@defun make-obsolete-variable variable new &optional when
+@defun make-obsolete-variable obsolete-name current-name &optional when

 This function makes the byte-compiler warn that the variable
 This function makes the byte-compiler warn that the variable

-@var{variable} is obsolete.  If @var{new} is a symbol, it is the
-variable's new name; then the warning message says to use @var{new}
-instead of @var{variable}.  If @var{new} is a string, this is the
-message and there is no replacement 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
 
 If provided, @var{when} should be a string indicating when the
 variable was first made obsolete---for example, a date or a release


@@ -1734,20 +1893,14 @@ number.
   You can make two variables synonyms and declare one obsolete at the
 same time using the macro @code{define-obsolete-variable-alias}.
 
   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 variable new &optional when docstring
-This macro marks the variable @var{variable} as obsolete and also
-makes it an alias for the variable @var{new}.  A typical call has the form:
-
-@example
-(define-obsolete-variable-alias 'old-var 'new-var "22.1" "Doc.")
-@end example
-
-@noindent
-which is equivalent to the following two lines of code:
+@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
 
 @example

-(defvaralias 'oldvar 'newvar "Doc.")
-(make-obsolete-variable 'old-var 'new-var "22.1")
+(defvaralias @var{obsolete-name} @var{current-name} @var{docstring})
+(make-obsolete-variable @var{obsolete-name} @var{current-name} @var{when})

 @end example
 @end defmac
 
 @end example
 @end defmac
 


@@ -1780,92 +1933,6 @@ foo
      @result{} 0
 @end example
 
      @result{} 0
 @end example
 

-@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 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{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.  To prevent this, Emacs
-takes care not to allow to set such file local variables.
-
-  For one thing, any variable whose name ends in @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} cannot be given a file local value.  In general,
-you should use such a name whenever it is appropriate for the
-variable's meaning.  The variables @samp{font-lock-keywords},
-@samp{font-lock-keywords-[0-9]}, and
-@samp{font-lock-syntactic-keywords} cannot be given file local values either.
-These rules can be overridden by giving the variable's
-name a non-@code{nil} @code{safe-local-variable} property.  If one
-gives it a @code{safe-local-variable} property of @code{t}, then one
-can give the variable any file local value.  One can also give any
-symbol, including the above, a @code{safe-local-variable} property
-that is a function taking exactly one argument.  In that case, giving
-a variable with that name a file local value is only allowed if the
-function returns non-@code{nil} when called with that value as
-argument.
-
-  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}:
-
-@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
-ignored.
-@end defvar
-
-@defun risky-local-variable-p sym &optional val
-If @var{val} is non-@code{nil}, returns non-@code{nil} if giving
-@var{sym} a file local value of @var{val} would be risky, for any of
-the reasons stated above.  If @var{val} is @code{nil} or omitted, only
-returns @code{nil} if @var{sym} can be safely assigned any file local
-value whatsoever.
-@end defun
-
-  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 Variables with Restricted Values
 @section Variables with Restricted Values
 
 @node Variables with Restricted Values
 @section Variables with Restricted Values