(perform-replace): Don't use an empty match adjacent

[bpt/emacs.git] / lispref / symbols.texi

diff --git a/lispref/symbols.texi b/lispref/symbols.texi
index 3239a9e..14f5c08 100644 (file)
--- a/lispref/symbols.texi
+++ b/lispref/symbols.texi
@@ -1,6 +1,7 @@
 @c -*-texinfo-*-
 @c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998 Free Software Foundation, Inc. 
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999
+@c   Free Software Foundation, Inc. 
 @c See the file elisp.texi for copying conditions.
 @setfilename ../info/symbols
 @node Symbols, Evaluation, Hash Tables, Top
@@ -77,6 +78,13 @@ the specified name before it creates a new one.  (In GNU Emacs Lisp,
 this lookup uses a hashing algorithm and an obarray; see @ref{Creating
 Symbols}.)
 
+  The value cell holds the symbol's value as a variable
+(@pxref{Variables}).  That is what you get if you evaluate the symbol as
+a Lisp expression (@pxref{Evaluation}).  Any Lisp object is a legitimate
+value.  Certain symbols have values that cannot be changed; these
+include @code{nil} and @code{t}, and any symbol whose name starts with
+@samp{:} (those are called @dfn{keywords}).  @xref{Constant Variables}.
+
   In normal usage, the function cell usually contains a function
 (@pxref{Functions}) or a macro (@pxref{Macros}), as that is what the
 Lisp interpreter expects to see there (@pxref{Evaluation}).  Keyboard
@@ -318,6 +326,10 @@ Therefore, you can use @code{intern-soft} to test whether a symbol with
 a given name is already interned.  If @var{obarray} is omitted, the
 value of the global variable @code{obarray} is used.
 
+The argument @var{name} may also be a symbol; in that case,
+the function returns @var{name} if @var{name} is interned
+in the specified obarray, and otherwise @code{nil}.
+
 @smallexample
 (intern-soft "frazzle")        ; @r{No such symbol exists.}
      @result{} nil
@@ -509,7 +521,7 @@ The @code{put} function returns @var{value}.
 @node Other Plists
 @subsection Property Lists Outside Symbols
 
-  These two functions are useful for manipulating property lists
+  These functions are useful for manipulating property lists
 that are stored in places other than symbols:
 
 @defun plist-get plist property
@@ -546,3 +558,12 @@ in the place where you got @var{plist}.  For example,
   (setplist symbol
             (plist-put (symbol-plist symbol) prop value)))
 @end example
+
+@defun plist-member plist property
+@tindex plist-member
+This returns non-@code{nil} if @var{plist} contains the given
+@var{property}.  Unlike @code{plist-get}, this allows you to distinguish
+between a missing property and a property with the value @code{nil}.
+The value is actually the tail of @var{plist} whose @code{car} is
+@var{property}.
+@end defun