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[Emacs-diffs] Changes to emacs/src/fns.c


From: Kim F . Storm
Subject: [Emacs-diffs] Changes to emacs/src/fns.c
Date: Mon, 15 Nov 2004 10:35:18 -0500

Index: emacs/src/fns.c
diff -c emacs/src/fns.c:1.375 emacs/src/fns.c:1.376
*** emacs/src/fns.c:1.375       Sat Nov  6 17:01:27 2004
--- emacs/src/fns.c     Mon Nov 15 15:21:14 2004
***************
*** 1997,2002 ****
--- 1997,2031 ----
    return Qnil;
  }
  
+ DEFUN ("safe-plist-get", Fsafe_plist_get, Ssafe_plist_get, 2, 2, 0,
+        doc: /* Extract a value from a property list.
+ PLIST is a property list, which is a list of the form
+ \(PROP1 VALUE1 PROP2 VALUE2...).  This function returns the value
+ corresponding to the given PROP, or nil if PROP is not
+ one of the properties on the list.
+ This function never signals an error.  */)
+      (plist, prop)
+      Lisp_Object plist;
+      Lisp_Object prop;
+ {
+   Lisp_Object tail, halftail;
+ 
+   /* halftail is used to detect circular lists.  */
+   tail = halftail = plist;
+   while (CONSP (tail) && CONSP (XCDR (tail)))
+     {
+       if (EQ (prop, XCAR (tail)))
+       return XCAR (XCDR (tail));
+ 
+       tail = XCDR (XCDR (tail));
+       halftail = XCDR (halftail);
+       if (EQ (tail, halftail))
+       break;
+     }
+ 
+   return Qnil;
+ }
+ 
  DEFUN ("get", Fget, Sget, 2, 2, 0,
         doc: /* Return the value of SYMBOL's PROPNAME property.
  This is the last value stored with `(put SYMBOL PROPNAME VALUE)'.  */)
***************
*** 5734,5739 ****
--- 5763,5769 ----
    defsubr (&Sreverse);
    defsubr (&Ssort);
    defsubr (&Splist_get);
+   defsubr (&Ssafe_plist_get);
    defsubr (&Sget);
    defsubr (&Splist_put);
    defsubr (&Sput);




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