Branch imports for masters.

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diff --git a/mps/code/ring.c b/mps/code/ring.c
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+++ b/mps/code/ring.c
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+/* impl.c.ring: RING IMPLEMENTATION
+ *
+ * $HopeName$
+ * Copyright (C) 1995 Harlequin Limited.  All rights reserved.
+ *
+ * .intro: This is a portable implementation of Rings.
+ *
+ * .purpose: Rings are used to manage potentially unbounded collections
+ * of things.
+ *
+ * .sources: design.mps.ring,
+ *   item 6 of mail.richard_brooksby.1996-03-25.16-02
+ */
+
+#include "ring.h"
+#include "check.h"
+#include "misc.h"
+
+
+SRCID(ring, "$HopeName: MMsrc!ring.c(trunk.7) $");
+
+
+/* RingCheck, RingCheckSingle -- check the validity of a ring node
+ *
+ * RingCheck performs a consistency check on the ring node. 
+ * RingCheckSingle performs the same check, but also checks that
+ * the ring node is a singleton (design.mps.ring.def.singleton).
+ */
+
+Bool RingCheck(Ring ring)
+{
+  CHECKL(ring != NULL);
+  CHECKL(ring->next != NULL);
+  CHECKL(ring->next->prev == ring);
+  CHECKL(ring->prev != NULL);
+  CHECKL(ring->prev->next == ring);
+  UNUSED(ring); /* impl.c.mpm.check.unused */
+  return TRUE;
+}
+
+Bool RingCheckSingle(Ring ring)
+{
+  CHECKL(RingCheck(ring));
+  CHECKL(ring->next == ring);
+  CHECKL(ring->prev == ring);
+  UNUSED(ring); /* impl.c.mpm.check.unused */
+  return TRUE;
+}
+
+Bool RingIsSingle(Ring ring)
+{
+  AVERT(Ring, ring);
+  return (ring->next == ring);
+}
+
+
+/* RingInit -- initialize a ring node
+ */
+
+void (RingInit)(Ring ring)
+{
+  RingInit(ring);                       /* impl.h.mpm.ring.init */
+}
+
+
+/* RingFinish -- finish a ring node
+ */
+ 
+void (RingFinish)(Ring ring)
+{
+  RingFinish(ring);                     /* impl.h.mpm.ring.finish */
+}
+
+
+/* RingAppend -- add a ring node to the end of a ring
+ */
+
+void (RingAppend)(Ring ring, Ring new)
+{
+  RingAppend(ring, new);                /* impl.h.mpm.ring.append */
+}
+
+
+/* RingInsert -- add a ring node to the start of a ring
+ */
+
+void (RingInsert)(Ring ring, Ring new)
+{
+  RingInsert(ring, new);                /* impl.h.mpm.ring.insert */
+}
+
+
+/* RingRemove -- remove a node from a ring
+ */
+
+void (RingRemove)(Ring old)
+{
+  RingRemove(old);                      /* impl.h.mpm.ring.remove */
+}
+
+
+/* RingNext -- get the next element of a ring
+ */
+
+Ring (RingNext)(Ring ring)
+{
+  return RingNext(ring);                /* impl.h.mpm.ring.next */
+}
+
+
+/* RING_ELT -- get the ring element structure
+ *
+ * RING_ELT has no function (as it does not have function-like
+ * behaviour), and is defined in impl.h.mpm.ring.elt.
+ */
+
+
+/* RING_FOR -- ring iterator construct
+ *
+ * RING_FOR has no function (as it does not have function-like
+ * behaviour), and is defined in impl.h.mpm.ring.for.
+ */