Simplify use of FOR_EACH_TAIL

* src/data.c (circular_list): New function.
* src/lisp.h (FOR_EACH_TAIL): Use Brent’s algorithm and C99 for-loop
decl, to eliminate the need for the args TAIL, TORTOISE and N, and
to speed things up a bit on typical hosts with optimization.
All uses changed (Bug#25605).

1 files changed, 6 insertions, 0 deletions

diff --git a/src/data.c b/src/data.c
index 8e07bf01b44..12dc2df0bac 100644
--- a/src/data.c
+++ b/src/data.c
@@ -170,6 +170,12 @@ args_out_of_range_3 (Lisp_Object a1, Lisp_Object a2, Lisp_Object a3)
   xsignal3 (Qargs_out_of_range, a1, a2, a3);
 }
 
+void
+circular_list (Lisp_Object list)
+{
+  xsignal1 (Qcircular_list, list);
+}
+
 
 /* Data type predicates.  */