Revision: [email protected]/emacs--cvs-trunk--0--patch-248

src/lisp.h (CYCLE_CHECK): Macro moved from xfaces.c

1 files changed, 26 insertions, 0 deletions

diff --git a/src/lisp.h b/src/lisp.h
index aa1e0cb8e4..ce5a5c5917 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -3185,6 +3185,32 @@ extern Lisp_Object Vdirectory_sep_char;
     ? make_float (val) \
     : make_number ((EMACS_INT)(val)))
 
+
+/* Checks the `cycle check' variable CHECK to see if it indicates that
+   EL is part of a cycle; CHECK must be either Qnil or a value returned
+   by an earlier use of CYCLE_CHECK.  SUSPICIOUS is the number of
+   elements after which a cycle might be suspected; after that many
+   elements, this macro begins consing in order to keep more precise
+   track of elements.
+
+   Returns nil if a cycle was detected, otherwise a new value for CHECK
+   that includes EL.
+
+   CHECK is evaluated multiple times, EL and SUSPICIOUS 0 or 1 times, so
+   the caller should make sure that's ok.  */
+
+#define CYCLE_CHECK(check, el, suspicious)	\
+  (NILP (check)					\
+   ? make_number (0)				\
+   : (INTEGERP (check)				\
+      ? (XFASTINT (check) < (suspicious)	\
+	 ? make_number (XFASTINT (check) + 1)	\
+	 : Fcons (el, Qnil))			\
+      : (!NILP (Fmemq ((el), (check)))		\
+	 ? Qnil					\
+	 : Fcons ((el), (check)))))
+
+
 #endif /* EMACS_LISP_H */
 
 /* arch-tag: 9b2ed020-70eb-47ac-94ee-e1c2a5107d5e