diff --git a/C/c_interface.c b/C/c_interface.c
index e3804ba4a..8cdb88fa2 100644
--- a/C/c_interface.c
+++ b/C/c_interface.c
@@ -1065,6 +1065,18 @@ YAP_PutInSlot(long slot, Term t)
 }
 
 
+typedef enum
+{ FRG_FIRST_CALL = 0,		/* Initial call */
+  FRG_CUTTED     = 1,		/* Context was cutted */
+  FRG_REDO	 = 2		/* Normal redo */
+} frg_code;
+
+typedef  struct context
+    { int *		context;	/* context value */
+      frg_code		control;	/* FRG_* action */
+      struct PL_local_data *engine;		/* invoking engine */
+} scontext ;
+
 typedef Int (*CPredicate1)(long);
 typedef Int (*CPredicate2)(long,long);
 typedef Int (*CPredicate3)(long,long,long);
@@ -1073,10 +1085,17 @@ typedef Int (*CPredicate5)(long,long,long,long,long);
 typedef Int (*CPredicate6)(long,long,long,long,long,long);
 typedef Int (*CPredicate7)(long,long,long,long,long,long,long);
 typedef Int (*CPredicate8)(long,long,long,long,long,long,long,long);
+typedef Int (*CPredicateV)(Int,Int,struct context *);
 
 Int
 YAP_Execute(PredEntry *pe, CPredicate exec_code)
 {
+  if (pe->PredFlags & CArgsPredFlag) {
+    CPredicateV codev = exec_code;
+    struct context ctx;
+
+    return ((codev)((&ARG1)-LCL0,0,&ctx));
+  }
   if (pe->PredFlags & CArgsPredFlag) {
     switch (pe->ArityOfPE) {
     case 0:
diff --git a/C/init.c b/C/init.c
index cb4ffbc12..a168b50c9 100644
--- a/C/init.c
+++ b/C/init.c
@@ -1317,6 +1317,7 @@ InitCodes(void)
   Yap_heap_regs->functor_clist = Yap_MkFunctor(Yap_FullLookupAtom("$when"), 4);
   Yap_heap_regs->functor_comma = Yap_MkFunctor(AtomComma, 2);
   Yap_heap_regs->functor_csult = Yap_MkFunctor(AtomCsult, 1);
+  Yap_heap_regs->functor_dot = Yap_MkFunctor(AtomDot, 2);
   Yap_heap_regs->functor_eq = Yap_MkFunctor(AtomEq, 2);
   Yap_heap_regs->functor_execute_in_mod = Yap_MkFunctor(Yap_FullLookupAtom("$execute_in_mod"), 2);
   Yap_heap_regs->functor_execute2_in_mod = Yap_MkFunctor(Yap_FullLookupAtom("$execute_wo_mod"), 2);
diff --git a/C/tracer.c b/C/tracer.c
index 6898ae555..17391359e 100644
--- a/C/tracer.c
+++ b/C/tracer.c
@@ -396,7 +396,6 @@ volatile int vsc_wait;
 
 static Int p_vsc_wait(void)
 {
-  fprintf(stderr,"attach %d\n",(int)getpid());
   while (!vsc_wait);
   vsc_wait=1;
   return(TRUE);
diff --git a/H/Heap.h b/H/Heap.h
index e15c1559c..b8fe722e8 100644
--- a/H/Heap.h
+++ b/H/Heap.h
@@ -463,6 +463,7 @@ typedef struct various_codes {
     functor_creep,
     functor_csult,
     functor_cut_by,
+    functor_dot,
     functor_eq,
     functor_execute_in_mod,
     functor_execute2_in_mod,
@@ -778,6 +779,7 @@ extern struct various_codes *Yap_heap_regs;
 #define  FunctorCreep             Yap_heap_regs->functor_creep
 #define  FunctorCsult             Yap_heap_regs->functor_csult
 #define  FunctorCutBy             Yap_heap_regs->functor_cut_by
+#define  FunctorDot               Yap_heap_regs->functor_dot
 #define  FunctorEq                Yap_heap_regs->functor_eq
 #define  FunctorExecuteInMod      Yap_heap_regs->functor_execute_in_mod
 #define  FunctorExecute2InMod     Yap_heap_regs->functor_execute2_in_mod
diff --git a/H/Yatom.h b/H/Yatom.h
index 29bdafcc4..e630b541d 100644
--- a/H/Yatom.h
+++ b/H/Yatom.h
@@ -665,6 +665,7 @@ typedef enum
   ProfiledPredFlag = 0x00000010L,	/* pred is being profiled   */
   MyddasPredFlag = 0x00000008L,	/* Myddas Imported pred  */
   ModuleTransparentPredFlag = 0x00000004L,	/* ModuleTransparent pred  */
+  SWIEnvPredFlag = 0x00000002L	/* new SWI interface */
 } pred_flag;
 
 /* profile data */
diff --git a/H/rheap.h b/H/rheap.h
index 0048c2310..b339b757c 100644
--- a/H/rheap.h
+++ b/H/rheap.h
@@ -904,6 +904,7 @@ restore_codes(void)
   Yap_heap_regs->functor_comma = FuncAdjust(Yap_heap_regs->functor_comma);
   Yap_heap_regs->functor_creep = FuncAdjust(Yap_heap_regs->functor_creep);
   Yap_heap_regs->functor_csult = FuncAdjust(Yap_heap_regs->functor_csult);
+  Yap_heap_regs->functor_dot = FuncAdjust(Yap_heap_regs->functor_dot);
   Yap_heap_regs->functor_eq = FuncAdjust(Yap_heap_regs->functor_eq);
   Yap_heap_regs->functor_execute_in_mod = FuncAdjust(Yap_heap_regs->functor_execute_in_mod);
   Yap_heap_regs->functor_execute2_in_mod = FuncAdjust(Yap_heap_regs->functor_execute2_in_mod);
diff --git a/Makefile.in b/Makefile.in
index 702995e84..59a257b0f 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -572,6 +572,7 @@ mycb: $(srcdir)/mycb.c
 	$(CC) $(CFLAGS) $(srcdir)/mycb.c -o mycb
 
 all: startup
+	(cd LGPL/PLStream; $(MAKE))
 	@INSTALL_DLLS@ (cd library/random; $(MAKE))
 	@INSTALL_DLLS@ (cd library/regex; $(MAKE))
 	@INSTALL_DLLS@ (cd library/rltree; $(MAKE))
diff --git a/config.h.in b/config.h.in
index 271e4fc22..1cbd4889a 100644
--- a/config.h.in
+++ b/config.h.in
@@ -61,6 +61,7 @@
 #undef  HAVE_IEEEFP_H
 #undef  HAVE_IO_H
 #undef  HAVE_LIMITS_H
+#undef  HAVE_LOCALE_H
 #undef  HAVE_MACH_O_DYLD_H
 #undef  HAVE_MALLOC_H
 #undef  HAVE_MATH_H
@@ -70,6 +71,7 @@
 #undef  HAVE_NETDB_H
 #undef  HAVE_NETINET_IN_H
 #undef  HAVE_PTHREAD_H
+#undef  HAVE_PWD_H
 #undef  HAVE_READLINE_READLINE_H
 #undef  HAVE_REGEX_H
 #undef  HAVE_SIGINFO_H
@@ -91,6 +93,7 @@
 #undef  HAVE_SYS_TYPES_H
 #undef  HAVE_SYS_UCONTEXT_H
 #undef  HAVE_SYS_UN_H
+#undef  HAVE_SYS_WAIT_H
 #undef  HAVE_TIME_H
 #undef  HAVE_UNISTD_H
 #undef  HAVE_WCTYPE_H
@@ -156,6 +159,7 @@
 #undef  HAVE_FETESTEXCEPT
 #undef  HAVE_FGETPOS
 #undef  HAVE_FINITE
+#undef  HAVE_FTIME
 #undef  HAVE_GETCWD
 #undef  HAVE_GETENV
 #undef  HAVE_GETHOSTBYNAME
diff --git a/configure b/configure
index c48ebaafb..acc4789f0 100755
--- a/configure
+++ b/configure
@@ -8284,7 +8284,8 @@ done
 
 
 
-for ac_header in malloc.h math.h memory.h mpi.h
+
+for ac_header in locale.h malloc.h math.h memory.h mpi.h
 do
 as_ac_Header=`echo "ac_cv_header_$ac_header" | $as_tr_sh`
 if { as_var=$as_ac_Header; eval "test \"\${$as_var+set}\" = set"; }; then
@@ -8426,7 +8427,8 @@ done
 
 
 
-for ac_header in netdb.h netinet/in.h regex.h
+
+for ac_header in netdb.h netinet/in.h pwd.h regex.h
 do
 as_ac_Header=`echo "ac_cv_header_$ac_header" | $as_tr_sh`
 if { as_var=$as_ac_Header; eval "test \"\${$as_var+set}\" = set"; }; then
@@ -9279,7 +9281,8 @@ done
 
 
 
-for ac_header in sys/ucontext.h sys/un.h
+
+for ac_header in sys/ucontext.h sys/un.h sys/wait.h
 do
 as_ac_Header=`echo "ac_cv_header_$ac_header" | $as_tr_sh`
 if { as_var=$as_ac_Header; eval "test \"\${$as_var+set}\" = set"; }; then
@@ -14257,7 +14260,8 @@ done
 
 
 
-for ac_func in fesettrapenable fgetpos finite getcwd getenv
+
+for ac_func in fesettrapenable fgetpos finite ftime getcwd getenv
 do
 as_ac_var=`echo "ac_cv_func_$ac_func" | $as_tr_sh`
 { echo "$as_me:$LINENO: checking for $ac_func" >&5
@@ -16209,12 +16213,13 @@ mkdir -p  LGPL/JPL/src
 mkdir -p  LGPL/clp
 mkdir -p  LGPL/chr
 mkdir -p  LGPL/swi_console
+mkdir -p  LGPL/PLStream
 mkdir -p  GPL
 mkdir -p  GPL/clpqr
 mkdir -p  GPL/http
 mkdir -p  cplint
 
-ac_config_files="$ac_config_files Makefile library/matrix/Makefile library/matlab/Makefile library/regex/Makefile library/system/Makefile library/random/Makefile library/yap2swi/Makefile library/mpi/Makefile .depend library/Makefile LGPL/Makefile LGPL/chr/Makefile CLPBN/Makefile LGPL/clp/Makefile GPL/clpqr/Makefile library/lammpi/Makefile library/tries/Makefile library/rltree/Makefile LGPL/swi_console/Makefile LGPL/JPL/Makefile LGPL/JPL/src/Makefile LGPL/JPL/java/Makefile LGPL/JPL/jpl_paths.yap GPL/http/Makefile GPL/Makefile cplint/Makefile"
+ac_config_files="$ac_config_files Makefile library/matrix/Makefile library/matlab/Makefile library/regex/Makefile library/system/Makefile library/random/Makefile library/yap2swi/Makefile library/mpi/Makefile .depend library/Makefile LGPL/Makefile LGPL/chr/Makefile CLPBN/Makefile LGPL/clp/Makefile GPL/clpqr/Makefile library/lammpi/Makefile library/tries/Makefile library/rltree/Makefile LGPL/swi_console/Makefile LGPL/JPL/Makefile LGPL/JPL/src/Makefile LGPL/JPL/java/Makefile LGPL/JPL/jpl_paths.yap GPL/http/Makefile GPL/Makefile cplint/Makefile LGPL/PLStream/Makefile"
 
 cat >confcache <<\_ACEOF
 # This file is a shell script that caches the results of configure
@@ -16796,6 +16801,7 @@ do
     "GPL/http/Makefile") CONFIG_FILES="$CONFIG_FILES GPL/http/Makefile" ;;
     "GPL/Makefile") CONFIG_FILES="$CONFIG_FILES GPL/Makefile" ;;
     "cplint/Makefile") CONFIG_FILES="$CONFIG_FILES cplint/Makefile" ;;
+    "LGPL/PLStream/Makefile") CONFIG_FILES="$CONFIG_FILES LGPL/PLStream/Makefile" ;;
 
   *) { { echo "$as_me:$LINENO: error: invalid argument: $ac_config_target" >&5
 echo "$as_me: error: invalid argument: $ac_config_target" >&2;}
@@ -17449,4 +17455,4 @@ fi
 
 
 make depend
-
+(cd LGPL/PLStream; make depend; cd ../..)
diff --git a/configure.in b/configure.in
index 8989011b3..23808f44b 100644
--- a/configure.in
+++ b/configure.in
@@ -1020,14 +1020,14 @@ AC_HEADER_SYS_WAIT
 AC_CHECK_HEADERS(arpa/inet.h ctype.h direct.h dirent.h dlfcn.h)
 AC_CHECK_HEADERS(errno.h fcntl.h)
 AC_CHECK_HEADERS(fenv.h fpu_control.h ieeefp.h io.h limits.h)
-AC_CHECK_HEADERS(malloc.h math.h memory.h mpi.h)
-AC_CHECK_HEADERS(netdb.h netinet/in.h regex.h)
+AC_CHECK_HEADERS(locale.h malloc.h math.h memory.h mpi.h)
+AC_CHECK_HEADERS(netdb.h netinet/in.h pwd.h regex.h)
 AC_CHECK_HEADERS(siginfo.h signal.h stdarg.h string.h stropts.h)
 AC_CHECK_HEADERS(sys/conf.h sys/file.h)
 AC_CHECK_HEADERS(sys/mman.h sys/param.h sys/resource.h sys/select.h)
 AC_CHECK_HEADERS(sys/shm.h sys/socket.h sys/stat.h)
 AC_CHECK_HEADERS(sys/time.h sys/times.h sys/types.h)
-AC_CHECK_HEADERS(sys/ucontext.h sys/un.h)
+AC_CHECK_HEADERS(sys/ucontext.h sys/un.h sys/wait.h)
 AC_CHECK_HEADERS(time.h unistd.h wctype.h winsock.h winsock2.h)
 AC_CHECK_HEADERS(mach-o/dyld.h)
 if test "$yap_cv_gmp" != "no"
@@ -1290,7 +1290,7 @@ fi
 dnl Checks for library functions.
 AC_TYPE_SIGNAL
 AC_CHECK_FUNCS(acosh asinh atanh chdir ctime dlopen dup2)
-AC_CHECK_FUNCS(fesettrapenable fgetpos finite getcwd getenv)
+AC_CHECK_FUNCS(fesettrapenable fgetpos finite ftime getcwd getenv)
 AC_CHECK_FUNCS(gethostbyname gethostid gethostname)
 AC_CHECK_FUNCS(gethrtime getpwnam getrusage gettimeofday getwd)
 AC_CHECK_FUNCS(isatty isnan kill labs link lgamma)
@@ -1450,12 +1450,13 @@ mkdir -p  LGPL/JPL/src
 mkdir -p  LGPL/clp
 mkdir -p  LGPL/chr
 mkdir -p  LGPL/swi_console
+mkdir -p  LGPL/PLStream
 mkdir -p  GPL
 mkdir -p  GPL/clpqr
 mkdir -p  GPL/http
 mkdir -p  cplint
 
-AC_OUTPUT(Makefile library/matrix/Makefile library/matlab/Makefile library/regex/Makefile library/system/Makefile library/random/Makefile library/yap2swi/Makefile library/mpi/Makefile .depend library/Makefile LGPL/Makefile LGPL/chr/Makefile CLPBN/Makefile LGPL/clp/Makefile GPL/clpqr/Makefile library/lammpi/Makefile library/tries/Makefile library/rltree/Makefile LGPL/swi_console/Makefile  LGPL/JPL/Makefile LGPL/JPL/src/Makefile LGPL/JPL/java/Makefile  LGPL/JPL/jpl_paths.yap GPL/http/Makefile GPL/Makefile  cplint/Makefile)
+AC_OUTPUT(Makefile library/matrix/Makefile library/matlab/Makefile library/regex/Makefile library/system/Makefile library/random/Makefile library/yap2swi/Makefile library/mpi/Makefile .depend library/Makefile LGPL/Makefile LGPL/chr/Makefile CLPBN/Makefile LGPL/clp/Makefile GPL/clpqr/Makefile library/lammpi/Makefile library/tries/Makefile library/rltree/Makefile LGPL/swi_console/Makefile  LGPL/JPL/Makefile LGPL/JPL/src/Makefile LGPL/JPL/java/Makefile  LGPL/JPL/jpl_paths.yap GPL/http/Makefile GPL/Makefile  cplint/Makefile LGPL/PLStream/Makefile)
 
 make depend
-
+(cd LGPL/PLStream; make depend; cd ../..)
diff --git a/include/SWI-Prolog.h b/include/SWI-Prolog.h
index 5edce0f2f..ba570d059 100644
--- a/include/SWI-Prolog.h
+++ b/include/SWI-Prolog.h
@@ -13,11 +13,6 @@
 #ifndef _FLI_H_INCLUDED
 #define _FLI_H_INCLUDED
 
-#ifndef __SWI_PROLOG__			/* use this to switch on Prolog dialect */
-#define __SWI_PROLOG__			/* normally defined by the plld compiler driver */
-#endif
-
-
 //=== includes ===============================================================
 #include "config.h"
 #include	<YapInterface.h>
@@ -36,6 +31,46 @@
 #endif
 #endif
 
+
+		 /*******************************
+		 *	       EXPORT		*
+		 *******************************/
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+See SWI-Prolog.h, containing the same code   for  an explanation on this
+stuff.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+#ifndef _PL_EXPORT_DONE
+#define _PL_EXPORT_DONE
+
+#if (defined(__WINDOWS__) || defined(__CYGWIN__)) && !defined(__LCC__)
+#define HAVE_DECLSPEC
+#endif
+
+#ifdef HAVE_DECLSPEC
+# ifdef PL_KERNEL
+#define PL_EXPORT(type)		__declspec(dllexport) type
+#define PL_EXPORT_DATA(type)	__declspec(dllexport) type
+#define install_t	 	void
+# else
+#  ifdef __BORLANDC__
+#define PL_EXPORT(type)	 	type _stdcall
+#define PL_EXPORT_DATA(type)	extern type
+#  else
+#define PL_EXPORT(type)	 	extern type
+#define PL_EXPORT_DATA(type)	__declspec(dllimport) type
+#  endif
+#define install_t	 	__declspec(dllexport) void
+# endif
+#else /*HAVE_DECLSPEC*/
+#define PL_EXPORT(type)	 	extern type
+#define PL_EXPORT_DATA(type)	extern type
+#define install_t	 	void
+#endif /*HAVE_DECLSPEC*/
+#endif /*_PL_EXPORT_DONE*/
+
+typedef	int    bool;
 typedef	unsigned long    term_t;
 typedef	void *module_t;
 typedef	void *record_t;
@@ -83,6 +118,7 @@ typedef void *PL_engine_t;
 #define PL_FA_NONDETERMINISTIC	(0x04)	/* foreign is non-deterministic */
 #define PL_FA_VARARGS		(0x08)	/* call using t0, ac, ctx */
 #define PL_FA_CREF		(0x10)	/* Internal: has clause-reference */
+#define PL_FA_ISO		(0x20)	/* Internal: ISO core predicate */
 
 /* begin from pl-itf.h */
 #define PL_VARIABLE      (1)            /* nothing */
@@ -163,6 +199,13 @@ consistent  with  the  definitions  in  pl-itf.h, which is included with
 users foreign language code.
 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 
+#define NOTRACE PL_FA_NOTRACE
+#define META    PL_FA_TRANSPARENT
+#define NDET	PL_FA_NONDETERMINISTIC
+#define VA	PL_FA_VARARGS
+#define CREF	PL_FA_CREF
+#define ISO	PL_FA_ISO
+
 typedef enum
 { FRG_FIRST_CALL = 0,		/* Initial call */
   FRG_CUTTED     = 1,		/* Context was cutted */
@@ -223,6 +266,8 @@ typedef struct foreign_context *control_t;
 #define ForeignContextPtr(h)	((void *)(h)->context)
 #define ForeignEngine(h)	((h)->engine)
 
+#define FRG(n, a, f, flags) { n, a, f, flags }
+
 /* end from pl-itf.h */
 
 		 /*******************************
@@ -240,9 +285,6 @@ typedef struct foreign_context *control_t;
 #define PL_Q_DETERMINISTIC	0x20	/* call was deterministic */
 #endif
 
-/* copied from old SICStus/SWI interface */
-typedef void install_t;
-
 #define PL_fail		return FALSE	/* fail */
 #define PL_succeed	return TRUE	/* success */
 
diff --git a/include/SWI-Stream.h b/include/SWI-Stream.h
index dc5dae2c6..9f163ba46 100644
--- a/include/SWI-Stream.h
+++ b/include/SWI-Stream.h
@@ -2,17 +2,34 @@
 #ifndef _PL_STREAM_H
 #define _PL_STREAM_H
 
-#ifndef X_API
-#if defined(_MSC_VER) && defined(YAP_EXPORTS)
-#define X_API __declspec(dllexport)
-#else
-#define X_API
-#endif
+#ifndef _PL_EXPORT_DONE
+#define _PL_EXPORT_DONE
+
+#if (defined(__WINDOWS__) || defined(__CYGWIN__)) && !defined(__LCC__)
+#define HAVE_DECLSPEC
 #endif
 
-#ifndef PL_EXPORT
-#define PL_EXPORT(type)		extern X_API type
-#endif
+#ifdef HAVE_DECLSPEC
+# ifdef PL_KERNEL
+#define PL_EXPORT(type)		__declspec(dllexport) type
+#define PL_EXPORT_DATA(type)	__declspec(dllexport) type
+#define install_t	 	void
+# else
+#  ifdef __BORLANDC__
+#define PL_EXPORT(type)	 	type _stdcall
+#define PL_EXPORT_DATA(type)	extern type
+#  else
+#define PL_EXPORT(type)	 	extern type
+#define PL_EXPORT_DATA(type)	__declspec(dllimport) type
+#  endif
+#define install_t	 	__declspec(dllexport) void
+# endif
+#else /*HAVE_DECLSPEC*/
+#define PL_EXPORT(type)	 	extern type
+#define PL_EXPORT_DATA(type)	extern type
+#define install_t	 	void
+#endif /*HAVE_DECLSPEC*/
+#endif /*_PL_EXPORT_DONE*/
 
 /* This appears to make the wide-character support compile and work
    on HPUX 11.23.  There really should be a cleaner way ...
diff --git a/library/yap2swi/yap2swi.c b/library/yap2swi/yap2swi.c
index deb86cd56..6cddc108b 100644
--- a/library/yap2swi/yap2swi.c
+++ b/library/yap2swi/yap2swi.c
@@ -52,6 +52,18 @@ SWIAtomToAtom(atom_t at)
   return (Atom)at;
 }
 
+static inline functor_t
+FunctorToSWIFunctor(Functor at)
+{
+  return (functor_t)at;
+}
+
+static inline Functor
+SWIFunctorToFunctor(functor_t at)
+{
+  return (Functor)at;
+}
+
 static void
 PredicateInfo(void *p, Atom* a, unsigned long int* arity, Term* m)
 {
@@ -86,6 +98,23 @@ UserCPredicateWithArgs(char *a, CPredicate def, unsigned long int arity, Term mo
   CurrentModule = cm;
 } 
 
+static void
+UserCPredicateVarargs(char *a, CPredicate def, unsigned long int arity, Term mod)
+{
+  PredEntry *pe;
+  Term cm = CurrentModule;
+  CurrentModule = mod;
+  Yap_InitCPred(a, arity, def, UserCPredFlag);
+  if (arity == 0) {
+    pe = RepPredProp(PredPropByAtom(Yap_LookupAtom(a),mod));
+  } else {
+    Functor f = Yap_MkFunctor(Yap_LookupAtom(a), arity);
+    pe = RepPredProp(PredPropByFunc(f,mod));
+  }
+  pe->PredFlags |= SWIEnvPredFlag;
+  CurrentModule = cm;
+} 
+
 char buffers[TMP_BUF_SIZE+BUF_SIZE*BUF_RINGS];
 static int buf_index = 0;
 
@@ -381,7 +410,7 @@ X_API int PL_get_functor(term_t ts, functor_t *f)
   if ( IsAtomTerm(t)) {
     *f = t;
   } else {
-    *f = (functor_t)YAP_FunctorOfTerm(t);
+    *f = FunctorToSWIFunctor(FunctorOfTerm(t));
   }
   return 1;
 }
@@ -669,9 +698,9 @@ X_API functor_t PL_new_functor(atom_t name, int arity)
   functor_t f;
   Atom at = SWIAtomToAtom(name);
   if (arity == 0) {
-    f = (functor_t)MkAtomTerm(at);
+    f = FunctorToSWIFunctor((Functor)MkAtomTerm(at));
   } else {
-    f = (functor_t)Yap_MkFunctor(at,arity);
+    f = FunctorToSWIFunctor(Yap_MkFunctor(at,arity));
   }
   return f;
 }
@@ -679,9 +708,9 @@ X_API functor_t PL_new_functor(atom_t name, int arity)
 X_API atom_t PL_functor_name(functor_t f)
 {
   if (IsAtomTerm(f)) {
-    return AtomToSWIAtom(AtomOfTerm(f));
+    return AtomToSWIAtom(AtomOfTerm((Term)SWIFunctorToFunctor(f)));
   } else {
-    return AtomToSWIAtom(NameOfFunctor((Functor)f));
+    return AtomToSWIAtom(NameOfFunctor(SWIFunctorToFunctor(f)));
   }
 }
 
@@ -690,7 +719,7 @@ X_API int PL_functor_arity(functor_t f)
   if (IsAtomTerm(f)) {
     return 0;
   } else {
-    return YAP_ArityOfFunctor((YAP_Functor)f);
+    return ArityOfFunctor(SWIFunctorToFunctor(f));
   }
 }
 
@@ -703,12 +732,13 @@ X_API void PL_cons_functor(term_t d, functor_t f,...)
   va_list ap;
   int arity, i;
   YAP_Term *tmp = (YAP_CELL *)buffers;
+  Functor ff = SWIFunctorToFunctor(f);
 
-  if (IsAtomTerm((YAP_Term)f)) {
+  if (IsAtomTerm((Term)ff)) {
     Yap_PutInSlot(d, (YAP_Term)f);
     return;
   }
-  arity = YAP_ArityOfFunctor((YAP_Functor)f);
+  arity = ArityOfFunctor(ff);
   if (arity > TMP_BUF_SIZE/sizeof(YAP_CELL)) {
     fprintf(stderr,"PL_cons_functor: arity too large (%d)\n", arity); 
     return;
@@ -718,25 +748,26 @@ X_API void PL_cons_functor(term_t d, functor_t f,...)
     tmp[i] =  Yap_GetFromSlot(va_arg(ap, term_t));
   }
   va_end (ap);
-  if (arity == 2 && (Functor)f == Yap_MkFunctor(AtomDot,2))
+  if (arity == 2 && ff == FunctorDot)
     Yap_PutInSlot(d,YAP_MkPairTerm(tmp[0],tmp[1]));
   else
-    Yap_PutInSlot(d,YAP_MkApplTerm((YAP_Functor)f,arity,tmp));
+    Yap_PutInSlot(d,YAP_MkApplTerm((YAP_Functor)ff,arity,tmp));
 }
 
 X_API void PL_cons_functor_v(term_t d, functor_t f,term_t a0)
 {
   int arity;
+  Functor ff = SWIFunctorToFunctor(f);
 
-  if (IsAtomTerm(f)) {
-    Yap_PutInSlot(d,(YAP_Term)f);
+  if (IsAtomTerm((Term)ff)) {
+    Yap_PutInSlot(d,(Term)ff);
     return;
   }
-  arity = YAP_ArityOfFunctor((YAP_Functor)f);
-  if (arity == 2 && (Functor)f == Yap_MkFunctor(AtomDot,2))
+  arity = ArityOfFunctor(ff);
+  if (arity == 2 && ff == FunctorDot)
     Yap_PutInSlot(d,YAP_MkPairTerm(Yap_GetFromSlot(a0),Yap_GetFromSlot(a0+1)));    
   else
-    Yap_PutInSlot(d,YAP_MkApplTerm((YAP_Functor)f,arity,YAP_AddressFromSlot(a0)));
+    Yap_PutInSlot(d,YAP_MkApplTerm((YAP_Functor)ff,arity,YAP_AddressFromSlot(a0)));
 }
 
 X_API void PL_cons_list(term_t d, term_t h, term_t t)
@@ -762,14 +793,16 @@ X_API void PL_put_float(term_t t, double fl)
 X_API void PL_put_functor(term_t t, functor_t f)
 {
   long int  arity;
-  if (IsAtomTerm(f)) {
-    Yap_PutInSlot(t,f);
+  Functor ff = SWIFunctorToFunctor(f);
+
+  if (IsAtomTerm((Term)ff)) {
+    Yap_PutInSlot(t,(Term)ff);
   } else {
-    arity = YAP_ArityOfFunctor((YAP_Functor)f);
-    if (arity == 2 && (Functor)f == Yap_MkFunctor(AtomDot,2))
+    arity = ArityOfFunctor(ff);
+    if (arity == 2 && ff == FunctorDot)
       Yap_PutInSlot(t,YAP_MkNewPairTerm());    
     else
-      Yap_PutInSlot(t,YAP_MkNewApplTerm((YAP_Functor)f,arity));
+      Yap_PutInSlot(t,YAP_MkNewApplTerm((YAP_Functor)ff,arity));
   }
 }
 
@@ -910,11 +943,14 @@ X_API int PL_unify_integer(term_t t, long n)
 X_API int PL_unify_functor(term_t t, functor_t f)
 {	
   YAP_Term tt = Yap_GetFromSlot(t);
+  Functor ff = SWIFunctorToFunctor(f);
   if (YAP_IsVarTerm(tt))
-    return YAP_Unify(tt, YAP_MkNewApplTerm((YAP_Functor)f,YAP_ArityOfFunctor((YAP_Functor)f)));
+    return YAP_Unify(tt, YAP_MkNewApplTerm((YAP_Functor)ff,YAP_ArityOfFunctor((YAP_Functor)f)));
+  if (YAP_IsPairTerm(tt))
+    return ff == FunctorDot;
   if (!YAP_IsApplTerm(tt))
     return FALSE;
-  return f == (functor_t)YAP_FunctorOfTerm(tt);
+  return ff == FunctorOfTerm(tt);
 }
 
 /* SWI: int PL_unify_integer(term_t ?t, long n)
@@ -1144,18 +1180,19 @@ get_term(arg_types **buf)
       functor_t f = ptr->arg.f;
       long int  arity, i;
       term_t loc;
+      Functor ff = SWIFunctorToFunctor(f);
 
-      if (IsAtomTerm((YAP_Term)f)) {
-	t = (YAP_Term)f;
+      if (IsAtomTerm((Term)ff)) {
+	t = (Term)ff;
 	break;
       }
-      arity = YAP_ArityOfFunctor((YAP_Functor)f);
+      arity = YAP_ArityOfFunctor((YAP_Functor)ff);
       loc = Yap_NewSlots(arity);
       ptr++;
       for (i= 0; i < arity; i++) {
 	Yap_PutInSlot(loc+i,get_term(&ptr));
       }
-      t = YAP_MkApplTerm((YAP_Functor)f,arity,YAP_AddressFromSlot(loc));
+      t = YAP_MkApplTerm((YAP_Functor)ff,arity,YAP_AddressFromSlot(loc));
     }
     break;
   case PL_LIST:
@@ -1230,9 +1267,10 @@ X_API int PL_unify_term(term_t l,...)
     case PL_FUNCTOR:
       {
 	functor_t f = va_arg(ap, functor_t);
+	Functor ff = SWIFunctorToFunctor(f);
 	ptr->arg.f = f;
-	if (!IsAtomTerm((YAP_Term)f)) {
-	  nels += YAP_ArityOfFunctor((YAP_Functor)f);
+	if (!IsAtomTerm((YAP_Term)ff)) {
+	  nels += YAP_ArityOfFunctor((YAP_Functor)ff);
 	}
       }
       break;
@@ -1309,10 +1347,11 @@ X_API int PL_is_compound(term_t ts)
 X_API int PL_is_functor(term_t ts, functor_t f)
 {
   YAP_Term t = Yap_GetFromSlot(ts);
+  Functor ff = SWIFunctorToFunctor(f);
   if (YAP_IsApplTerm(t)) {
-    return YAP_FunctorOfTerm(t) == (YAP_Functor)f;
+    return FunctorOfTerm(t) == (Functor)ff;
   } else if (YAP_IsPairTerm(t)) {
-    return FunctorOfTerm(t) == Yap_MkFunctor(AtomDot,2);
+    return FunctorOfTerm(t) == FunctorDot;
   } else
     return 0;
 }
@@ -1541,11 +1580,11 @@ X_API atom_t PL_module_name(module_t m)
 
 X_API predicate_t PL_pred(functor_t f, module_t m)
 {
-  if (IsAtomTerm(f)) {
-    return YAP_Predicate(YAP_AtomOfTerm(f),0,(YAP_Module)m);
+  Functor ff = SWIFunctorToFunctor(f);
+  if (IsAtomTerm((Term)f)) {
+    return YAP_Predicate(YAP_AtomOfTerm((Term)f),0,(YAP_Module)m);
   } else {
-    YAP_Functor tf = (YAP_Functor)f;
-    return YAP_Predicate(YAP_NameOfFunctor(tf),YAP_ArityOfFunctor(tf),(YAP_Module)m);
+    return YAP_Predicate((YAP_Atom)NameOfFunctor(ff),ArityOfFunctor(ff),(YAP_Module)m);
   }
 }
 
@@ -1670,7 +1709,9 @@ X_API void PL_register_extensions(PL_extension *ptr)
       YAP_Error(0,YAP_MkIntTerm(ptr->flags),"non-implemented flag %x when creating predicates", ptr->flags);
       return;      
     }      
-    if (ptr->flags & PL_FA_TRANSPARENT)
+    if (ptr->flags & PL_FA_VARARGS)
+      UserCPredicateVarargs(ptr->predicate_name,(YAP_Bool (*)(void))ptr->function,ptr->arity,MkAtomTerm(Yap_LookupAtom("prolog")));
+    else if (ptr->flags & PL_FA_TRANSPARENT)
       UserCPredicateWithArgs(ptr->predicate_name,(YAP_Bool (*)(void))ptr->function,ptr->arity,MkAtomTerm(Yap_LookupAtom("prolog")));
     else
       UserCPredicateWithArgs(ptr->predicate_name,(YAP_Bool (*)(void))ptr->function,ptr->arity,YAP_CurrentModule());
@@ -1684,12 +1725,14 @@ X_API void PL_register_foreign_in_module(const char *module, const char *name, i
       YAP_Error(0,YAP_MkIntTerm(flags),"non-implemented flag %x when creating predicates", flags);
       return;      
     }      
-  if (flags & PL_FA_TRANSPARENT)
-    UserCPredicateWithArgs((char *)name,(YAP_Bool (*)(void))function,arity,MkAtomTerm(Yap_LookupAtom("prolog")));
-  else if (module == NULL)
-    UserCPredicateWithArgs((char *)name,(YAP_Bool (*)(void))function,arity,YAP_CurrentModule());
-  else
-    UserCPredicateWithArgs((char *)name,(YAP_Bool (*)(void))function,arity,MkAtomTerm(Yap_LookupAtom((char *)module)));
+    if (flags & PL_FA_VARARGS)
+      UserCPredicateVarargs((char *)name,(YAP_Bool (*)(void))function,arity,MkAtomTerm(Yap_LookupAtom("prolog")));
+    else if (flags & PL_FA_TRANSPARENT)
+      UserCPredicateWithArgs((char *)name,(YAP_Bool (*)(void))function,arity,MkAtomTerm(Yap_LookupAtom("prolog")));
+    else if (module == NULL)
+      UserCPredicateWithArgs((char *)name,(YAP_Bool (*)(void))function,arity,YAP_CurrentModule());
+    else
+      UserCPredicateWithArgs((char *)name,(YAP_Bool (*)(void))function,arity,MkAtomTerm(Yap_LookupAtom((char *)module)));
 }
 
 X_API void PL_load_extensions(PL_extension *ptr)