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VC/include/corout_utils.h

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+/*************************************************************************
+*									 *
+*	 YAP Prolog 							 *
+*									 *
+*	Yap Prolog was developed at NCCUP - Universidade do Porto	 *
+*									 *
+* Copyright L.Damas, V.S.Costa and Universidade do Porto 1985-1997	 *
+*									 *
+**************************************************************************
+*									 *
+* File:		corout_utils.h						 *
+* Last rev:								 *
+* mods:									 *
+* comments:	Co-routining from within YAP				 *
+*									 *
+*************************************************************************/
+
+STATIC_PROTO (Term SDeref, (Term));
+STATIC_PROTO (Term SDerefa, (CELL *));
+STATIC_PROTO (sus_tag * deref_susp_chain, (sus_tag *));
+
+static inline Term
+SDeref (Term a)
+{
+  while (IsVarTerm (a))
+    {
+      Term *b = (Term *) a;
+      a = *b;
+#if SBA
+      if (a == (0))
+	return (CELL) b;
+#else
+      if (a == ((Term) b))
+	return a;
+#endif
+    }
+  return (a);
+}
+
+static inline Term
+SDerefa (CELL * b)
+{
+  Term a = *b;
+  while (IsVarTerm (a))
+    {
+#if SBA
+      if (a == (0))
+	return (CELL) b;
+#else
+      if (a == ((Term) b))
+	return a;
+#endif
+      b = (Term *) a;
+      a = *b;
+    }
+  return (a);
+}
+
+static inline CELL *
+SADerefa (CELL * b)
+{
+  Term a = *b;
+  while (IsVarTerm (a))
+    {
+#if SBA
+      if (a == (0))
+	return b;
+#else
+      if (a == ((Term) b))
+	return b;
+#endif
+      b = (Term *) a;
+      a = *b;
+    }
+  return (b);
+}
+
+
+
+inline EXTERN Term SArgOfTerm (int i, Term t);
+
+inline EXTERN Term
+SArgOfTerm (int i, Term t)
+{
+  return (Term) (SDerefa (RepAppl (t) + (i)));
+}
+
+
+
+inline EXTERN Term SHeadOfTerm (Term);
+
+inline EXTERN Term
+SHeadOfTerm (Term t)
+{
+  return (Term) (SDerefa (RepPair (t)));
+}
+
+
+
+inline EXTERN Term STailOfTerm (Term);
+
+inline EXTERN Term
+STailOfTerm (Term t)
+{
+  return (Term) (SDerefa (RepPair (t) + 1));
+}
+
+
+
+static inline sus_tag *
+deref_susp_chain (sus_tag * susp)
+{
+  /* we may have bound several suspension chains together. Follow the
+     reference chain
+   */
+  while (IsVarTerm (susp->ActiveSus)
+	 && susp->ActiveSus != (CELL) & susp->ActiveSus)
+    susp =
+      (sus_tag *) (susp->ActiveSus - (Int) (&(((sus_tag *) (0))->ActiveSus)));
+  return (susp);
+}