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(Fsafe_plist_get): New defun.

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(syms_of_fns): Defsubr it.
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Kim F. Storm 2004-11-15 15:21:14 +00:00
parent 479440d29c
commit 27f604dddf
1 changed files with 30 additions and 0 deletions
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30
src/fns.c
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@ -1997,6 +1997,35 @@ one of the properties on the list. */)
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)'. */)
@ -5734,6 +5763,7 @@ used if both `use-dialog-box' and this variable are non-nil. */);
defsubr (&Sreverse);
defsubr (&Ssort);
defsubr (&Splist_get);
defsubr (&Ssafe_plist_get);
defsubr (&Sget);
defsubr (&Splist_put);
defsubr (&Sput);