diff --git a/C/heapgc.c b/C/heapgc.c
index 83e2d875e..0e63cfd58 100644
--- a/C/heapgc.c
+++ b/C/heapgc.c
@@ -4130,9 +4130,11 @@ call_gc(UInt gc_lim, Int predarity, CELL *current_env, yamop *nextop USES_REGS)
   if (ASP - H < gc_margin/sizeof(CELL) ||
       effectiveness < 20) {
     LeaveGCMode( PASS_REGS1 );
+#ifndef YAPOR
     if (gc_margin < 2*CalculateStackGap())
       gc_margin = 2*CalculateStackGap();
     return Yap_growstack(gc_margin);
+#endif
   }
   /*
    * debug for(save_total=1; save_total<=N; ++save_total)
diff --git a/C/utilpreds.c b/C/utilpreds.c
index b71318f16..8cbce9246 100644
--- a/C/utilpreds.c
+++ b/C/utilpreds.c
@@ -1166,8 +1166,16 @@ CELL *CellDifH(CELL *hptr, CELL *hlow)
   return (CELL *)((char *)hptr-(char *)hlow);
 }
 
-#define AdjustSizeAtom(X)	((char *)(((CELL)(X)+(8-1)) & ~(8-1)))
+#define AdjustSizeAtom(X)	(((CELL)(X)+(8-1)) & ~(8-1))
 
+static inline
+CELL *AdjustSize(CELL *x, char *buf)
+{
+  UInt offset = (char *)x-buf;
+  return (CELL*)(buf+AdjustSizeAtom(offset));
+}
+
+/* export an atom from the symbol table to a buffer */
 static inline 
 Atom export_atom(Atom at, char **hpp, char *buf, size_t len)
 {				 
@@ -1175,7 +1183,7 @@ Atom export_atom(Atom at, char **hpp, char *buf, size_t len)
   size_t sz;
 
   ptr = *hpp;
-  ptr = AdjustSizeAtom(ptr);
+  ptr = (char *)AdjustSize((CELL*)ptr, buf);
   
   p0 = ptr;
   if (IsWideAtom(at)) {
@@ -1189,7 +1197,7 @@ Atom export_atom(Atom at, char **hpp, char *buf, size_t len)
   } else {
     *ptr++ = 0;
     sz = strlen(RepAtom(at)->StrOfAE);
-    if (sz +1 >= len)
+    if (sz + 1 + sizeof(wchar_t) >= len)
       return (Atom)NULL;
     strcpy(ptr, RepAtom(at)->StrOfAE);
     *hpp = ptr+(sz+1);
@@ -1198,10 +1206,11 @@ Atom export_atom(Atom at, char **hpp, char *buf, size_t len)
   return (Atom)(p0-buf);
 }
 
+/* place a buffer: first arity then the atom */
 static inline 
 Functor export_functor(Functor f, char **hpp, char *buf, size_t len)
 {
-  CELL *hptr = (UInt *)AdjustSizeAtom(*hpp);
+  CELL *hptr = AdjustSize((CELL *)*hpp, buf);
   UInt arity = ArityOfFunctor(f);
   if (2*sizeof(CELL) >= len)
     return NULL;
@@ -1209,7 +1218,9 @@ Functor export_functor(Functor f, char **hpp, char *buf, size_t len)
   *hpp = (char *)(hptr+1);
   if (!export_atom(NameOfFunctor(f), hpp, buf, len))
     return NULL;
-  /* increment so that it cannot be mistaken with a standard functor */
+  /* increment so that it cannot be mistaken with a functor on the stack,
+     (increment is used as a tag ........01
+  */
   return (Functor)(((char *)hptr-buf)+1);
 }
 
@@ -1228,9 +1239,10 @@ export_term_to_buffer(Term inpt, char *buf, char *bptr, CELL *t0 , CELL *tf, siz
 {
   char *td = bptr;
   CELL *bf = (CELL *)buf;
-  if (buf + len < (char *)((CELL *)td + (tf-t0)))
+  if (buf + len < (char *)((CELL *)td + (tf-t0))) {
     return FALSE;
-  memcpy((void *)td, (void *)t0, (tf-t0)* sizeof(CELL));
+  }
+  memcpy((void *)td, (void *)t0, (tf-t0)* sizeof(CELL)); 
   bf[0] = (td-buf);
   bf[1] = (tf-t0);
   bf[2] = inpt;
@@ -1541,6 +1553,7 @@ static Atom
 AddAtom(Atom t, char *buf)
 {
   char *s = buf+(UInt)t;
+
   if (!*s) {
     return Yap_LookupAtom(s+1);
   } else {
@@ -1557,7 +1570,7 @@ FetchFunctor(CELL *pt, char *buf)
   UInt arity = *ptr++;
   Atom name, at;
   // and then an atom
-  ptr = (CELL *)AdjustSizeAtom((char*)ptr);
+  ptr = AdjustSize(ptr, buf);
   name = (Atom)((char *)ptr-buf);
   at = AddAtom(name, buf);
   *pt = (CELL)Yap_MkFunctor(at, arity);
@@ -1627,7 +1640,7 @@ Yap_ImportTerm(char * buf) {
     return MkVarTerm();
   if (IsAtomOrIntTerm(tinp)) {
     if (IsAtomTerm(tinp)) {
-      char *pt = AdjustSizeAtom((char *)(bc+3));
+      char *pt = (char *)AdjustSize(bc+3, buf);
       return MkAtomTerm(Yap_LookupAtom(pt));
     } else
       return tinp;
@@ -4189,6 +4202,298 @@ p_subsumes( USES_REGS1 ) /* subsumes terms t1 and t2	 */
   }
 }
 
+
+static int term_subsumer_complex(register CELL *pt0, register CELL *pt0_end, register
+				 CELL *pt1, CELL *npt USES_REGS)
+{
+  register CELL **to_visit = (CELL **)ASP;
+  tr_fr_ptr OLDTR = TR;
+  int out;
+  CELL *bindings = NULL, *tbindings = NULL;
+  HB = H;
+
+ loop:
+  while (pt0 < pt0_end) {
+    register CELL d0, d1;
+
+    ++ pt0;
+    ++ pt1;
+    d0 = Derefa(pt0);
+    d1 = Derefa(pt1);
+    if (d0 == d1) {
+      *npt++ = d0;
+      continue;
+    } else if (IsVarTerm(d0)) {
+      CELL *match, *omatch = NULL;
+
+      match = VarOfTerm(d0); 
+      if (match >= HB) {
+	while (match >= HB) {
+	  /* chained to a sequence */
+	  if (Yap_eq(d1, match[1]) ) {
+	    *npt++ = match[2];
+	    break;
+	  }
+	  omatch = match;
+	  match = (CELL *)match[3];
+	}
+	/* found a match */
+	if (match >= HB)
+	  continue;
+	/* could not find a match, add to end of chain */
+ 	RESET_VARIABLE(H); /* key */
+ 	H[1] = d1; /* comparison value */
+	H[2] = (CELL)npt; /* new value */
+	H[3] = (CELL)match; /* end of chain points back to first cell */
+	omatch[3] = (CELL)H;
+	H+=4;
+	RESET_VARIABLE(npt);
+	npt++;
+	continue;
+      }
+      if (TR > (tr_fr_ptr)LOCAL_TrailTop - 256) {
+	goto trail_overflow;
+      }
+      RESET_VARIABLE(H);
+      H[1] = d1;
+      H[2] = (CELL)npt;
+      H[3] = d0;
+      Bind(VarOfTerm(d0), (CELL)H);
+      H+=4;
+      RESET_VARIABLE(npt);
+      npt++;
+      continue;
+    } else if (IsPairTerm(d0) && IsPairTerm(d1)) {
+      CELL *match = bindings;
+
+      while (match) {
+	if (match[0] == d0 && match[1] == d1) {
+	  *npt++ = match[2];
+	  break;
+	}
+	match = (CELL *)match[3];
+      }
+      if (match) {
+	continue;
+      }
+      if (bindings) {
+	*tbindings = (CELL)H;
+      } else {
+	bindings = H;
+      }
+      H[0] = d0;
+      H[1] = d1;
+      H[2] = AbsPair(H+4);
+      H[3] = (CELL)NULL;
+      tbindings = H+3;
+      H+=4;
+      *npt++ = AbsPair(H);
+#ifdef RATIONAL_TREES
+      /* now link the two structures so that no one else will */
+      /* come here */
+      to_visit -= 5;
+      to_visit[0] = pt0;
+      to_visit[1] = pt0_end;
+      to_visit[2] = pt1;
+      to_visit[3] = tbindings;
+      to_visit[4] = npt;
+#else
+      /* store the terms to visit */
+      if (pt0 < pt0_end) {
+	to_visit -= 4;
+	to_visit[0] = pt0;
+	to_visit[1] = pt0_end;
+	to_visit[2] = pt1;
+	to_visit[3] = npt;
+      }
+#endif
+      pt0 = RepPair(d0) - 1;
+      pt0_end = RepPair(d0) + 1;
+      pt1 = RepPair(d1) - 1;
+      npt = H;
+      H += 2;
+      if (H > (CELL *)to_visit -1024)
+	goto stack_overflow;
+      continue;
+    } else if (IsApplTerm(d0) && IsApplTerm(d1)) {
+      CELL *ap2 = RepAppl(d0);
+      CELL *ap3 = RepAppl(d1);
+      Functor f = (Functor)(*ap2);
+      Functor f2 = (Functor)(*ap3);
+      if (f == f2) {
+	CELL *match = bindings;
+
+	if (IsExtensionFunctor(f)) {
+	  if (unify_extension(f, d0, ap2, d1)) {
+	    *npt++ = d0;
+	    continue;
+	  }
+	}
+	while (match) {
+	  if (match[0] == d0 && match[1] == d1) {
+	    *npt++ = match[2];
+	    break;
+	  }
+	  match = (CELL *)match[3];
+	}
+	if (match) {
+	  continue;
+	}
+	if (bindings) {
+	  *tbindings = (CELL)H;
+	} else {
+	  bindings = H;
+	}
+	H[0] = d0;
+	H[1] = d1;
+	H[2] = AbsAppl(H+4);
+	H[3] = (CELL)NULL;
+	tbindings = H+3;
+	H+=4;
+	*npt++ = AbsAppl(H);
+#ifdef RATIONAL_TREES
+	/* now link the two structures so that no one else will */
+	/* come here */
+	to_visit -= 5;
+	to_visit[0] = pt0;
+	to_visit[1] = pt0_end;
+	to_visit[2] = pt1;
+	to_visit[3] = tbindings;
+	to_visit[4] = npt;
+#else
+	/* store the terms to visit */
+	if (pt0 < pt0_end) {
+	  to_visit -= 4;
+	  to_visit[0] = pt0;
+	  to_visit[1] = pt0_end;
+	  to_visit[2] = pt1;
+	  to_visit[3] = npt;
+	}
+#endif
+	d0 = ArityOfFunctor(f);
+	pt0 = ap2;
+	pt0_end = ap2 + d0;
+	pt1 = ap3;
+	npt = H;
+	*npt++ = (CELL)f;
+	H += d0;
+	if (H > (CELL *)to_visit -1024)
+	  goto stack_overflow;
+	continue;
+      }
+    }
+    RESET_VARIABLE(npt);
+    npt++;
+  }
+  /* Do we still have compound terms to visit */
+  if (to_visit < (CELL **)ASP) {
+#ifdef RATIONAL_TREES
+    pt0 = to_visit[0];
+    pt0_end = to_visit[1];
+    pt1 = to_visit[2];
+    tbindings = to_visit[3];
+    npt = to_visit[ 4];
+    if (!tbindings) {
+      bindings = NULL;
+    }
+    to_visit += 5;
+#else
+    pt0 = to_visit[0];
+    pt0_end = to_visit[1];
+    pt1 = to_visit[2];
+    npt = to_visit[3];
+    to_visit += 4;
+#endif
+    goto loop;
+  }
+  out = 1;
+
+ complete:
+  /* get rid of intermediate variables  */
+  while (TR != OLDTR) {
+    CELL *pt1 = (CELL *) TrailTerm(--TR);
+    RESET_VARIABLE(pt1);
+  }
+  HBREG = B->cp_h;
+  return out;
+
+ stack_overflow:
+  out = -1;
+  goto complete;
+
+ trail_overflow:
+  out = -2;
+  goto complete;
+
+}
+
+static Int 
+p_term_subsumer( USES_REGS1 ) /* term_subsumer terms t1 and t2	 */
+{
+  int out = 0; 
+
+  while (out != 1) {
+    Term t1 = Deref(ARG1);
+    Term t2 = Deref(ARG2);
+    CELL *oldH = H;
+
+    if (t1 == t2)
+      return Yap_unify(ARG3,t1);
+    if (IsPairTerm(t1) && IsPairTerm(t2)) {
+      Term tf = AbsAppl(H);
+      H += 2;
+      HB = H;
+      if ((out = term_subsumer_complex(RepPair(t1)-1,
+				       RepPair(t1)+1,
+				       RepPair(t2)-1, H-2 PASS_REGS)) > 0) {
+	HB = B->cp_h;
+	return Yap_unify(ARG3,tf);
+      }
+  } else if (IsApplTerm(t1) && IsApplTerm(t2)) {
+      Functor f1;
+
+      if ((f1 = FunctorOfTerm(t1)) == FunctorOfTerm(t2)) {
+	if (IsExtensionFunctor(f1)) {
+	  if (unify_extension(f1, t1, RepAppl(t1), t2)) {
+	    return Yap_unify(ARG3,t1);
+	  }
+	} else {
+	  Term tf = AbsAppl(H);
+	  UInt ar = ArityOfFunctor(f1);
+	  H[0] = (CELL)f1;
+	  H += 1+ar;
+	  HB = H;
+	  if ((out = term_subsumer_complex(RepAppl(t1),
+					   RepAppl(t1)+ArityOfFunctor(f1),
+					   RepAppl(t2), H-ar PASS_REGS)) > 0) {
+	    HB = B->cp_h;
+	    return Yap_unify(ARG3,tf);
+	  }
+	}
+      }
+    }
+    HB = B->cp_h;
+    if (out == 0) {
+      return Yap_unify(ARG3, MkVarTerm());
+    } else {
+      H = oldH;
+      if (out == -1) {
+	if (!Yap_gcl((ASP-H)*sizeof(CELL), 0, ENV, gc_P(P,CP))) {
+	  Yap_Error(OUT_OF_STACK_ERROR, TermNil, "in term_subsumer");
+	  return FALSE;
+	}
+      } else {
+	/* Trail overflow */
+	if (!Yap_growtrail(0, FALSE)) {
+	  Yap_Error(OUT_OF_TRAIL_ERROR, TermNil, "in term_subsumer");
+	  return FALSE;
+	} 
+      }
+    }
+  }
+  return FALSE;
+}
+
 #ifdef DEBUG
 static Int
 p_force_trail_expansion( USES_REGS1 )
@@ -4875,6 +5180,7 @@ void Yap_InitUtilCPreds(void)
   Yap_InitCPred("instantiated_term_hash", 4, p_instantiated_term_hash, 0);
   Yap_InitCPred("variant", 2, p_variant, 0);
   Yap_InitCPred("subsumes", 2, p_subsumes, 0);
+  Yap_InitCPred("term_subsumer", 3, p_term_subsumer, 0);
   Yap_InitCPred("variables_within_term", 3, p_variables_within_term, 0);
   Yap_InitCPred("new_variables_in_term", 3, p_new_variables_in_term, 0);
   Yap_InitCPred("export_term", 3, p_export_term, 0);
diff --git a/H/TermExt.h b/H/TermExt.h
index a30eae80d..ec8c08dd4 100644
--- a/H/TermExt.h
+++ b/H/TermExt.h
@@ -103,7 +103,7 @@ inline EXTERN blob_type BlobOfFunctor (Functor f);
 inline EXTERN blob_type
 BlobOfFunctor (Functor f)
 {
-  return (blob_type) (f);
+  return (blob_type) ((CELL)f);
 }
 
 typedef struct cp_frame {
@@ -148,8 +148,8 @@ exts;
 
 #endif
 
-#ifdef YAP_H
 
+#ifdef YAP_H
 /* make sure that these data structures are the first thing to be allocated
    in the heap when we start the system */
 #ifdef THREADS
@@ -175,7 +175,9 @@ typedef struct special_functors_struct
 special_functors;
 #endif
 
-inline EXTERN Float STD_PROTO (CpFloatUnaligned, (CELL *));
+#endif /* YAP_H */
+
+inline extern Float CpFloatUnaligned(CELL *ptr);
 
 #if SIZEOF_DOUBLE == SIZEOF_LONG_INT
 
@@ -214,7 +216,7 @@ CpFloatUnaligned(CELL *ptr)
 
 #if SIZEOF_DOUBLE == 2*SIZEOF_LONG_INT
 
-inline EXTERN void STD_PROTO (AlignGlobalForDouble, ( USES_REGS1 ));
+inline extern void AlignGlobalForDouble( USES_REGS1 );
 
 #define DOUBLE_ALIGNED(ADDR) ((CELL)(ADDR) & 0x4)
 
@@ -272,13 +274,16 @@ FloatOfTerm (Term t)
 #endif
 #endif
 
-Term STD_PROTO (Yap_MkBlobStringTerm, (const char *, size_t len));
-Term STD_PROTO (Yap_MkBlobWideStringTerm, (const wchar_t *, size_t len));
-char *STD_PROTO (Yap_BlobStringOfTerm, (Term));
-wchar_t *STD_PROTO (Yap_BlobWideStringOfTerm, (Term));
-char *STD_PROTO (Yap_BlobStringOfTermAndLength, (Term, size_t *));
+#ifndef YAP_H
+#include <stddef.h>
+#endif
+
+Term Yap_MkBlobStringTerm(const char *, size_t len);
+Term Yap_MkBlobWideStringTerm(const wchar_t *, size_t len);
+char *Yap_BlobStringOfTerm(Term);
+wchar_t *Yap_BlobWideStringOfTerm(Term);
+char *Yap_BlobStringOfTermAndLength(Term, size_t *);
 
-#endif /* YAP_NOT_INSTALLED */
 
 
 inline EXTERN int IsFloatTerm (Term);
@@ -294,7 +299,6 @@ IsFloatTerm (Term t)
 
 /* extern Functor FunctorLongInt; */
 
-#ifdef YAP_H
 inline EXTERN Term MkLongIntTerm (Int);
 
 inline EXTERN Term
@@ -308,7 +312,6 @@ MkLongIntTerm (Int i)
   return AbsAppl(H - 3);
 }
 
-#endif
 
 inline EXTERN Int LongIntOfTerm (Term t);
 
diff --git a/H/Yap.h b/H/Yap.h
index 5ccf5903b..768906d2d 100755
--- a/H/Yap.h
+++ b/H/Yap.h
@@ -818,6 +818,12 @@ extern struct worker_local Yap_local;
 #include "dlocals.h"
 
 
+/*************************************************************************************************
+                                       unification support
+*************************************************************************************************/
+
+#include "YapCompoundTerm.h"
+
 /*************************************************************************************************
                                        unification routines
 *************************************************************************************************/
@@ -831,69 +837,6 @@ extern struct worker_local Yap_local;
 
 
 
-/*************************************************************************************************
-                           High level macros to access arguments
-*************************************************************************************************/
-
-inline EXTERN Term ArgOfTerm (int i, Term t);
-
-inline EXTERN Term
-ArgOfTerm (int i, Term t)
-{
-  return (Term) (Derefa (RepAppl (t) + (i)));
-}
-
-
-
-inline EXTERN Term HeadOfTerm (Term);
-
-inline EXTERN Term
-HeadOfTerm (Term t)
-{
-  return (Term) (Derefa (RepPair (t)));
-}
-
-
-
-inline EXTERN Term TailOfTerm (Term);
-
-inline EXTERN Term
-TailOfTerm (Term t)
-{
-  return (Term) (Derefa (RepPair (t) + 1));
-}
-
-
-
-
-inline EXTERN Term ArgOfTermCell (int i, Term t);
-
-inline EXTERN Term
-ArgOfTermCell (int i, Term t)
-{
-  return (Term) ((CELL) (RepAppl (t) + (i)));
-}
-
-
-
-inline EXTERN Term HeadOfTermCell (Term);
-
-inline EXTERN Term
-HeadOfTermCell (Term t)
-{
-  return (Term) ((CELL) (RepPair (t)));
-}
-
-
-
-inline EXTERN Term TailOfTermCell (Term);
-
-inline EXTERN Term
-TailOfTermCell (Term t)
-{
-  return (Term) ((CELL) (RepPair (t) + 1));
-}
-
 
 /*************************************************************************************************
                                            slots
diff --git a/H/YapCompoundTerm.h b/H/YapCompoundTerm.h
new file mode 100644
index 000000000..e8b1d3be1
--- /dev/null
+++ b/H/YapCompoundTerm.h
@@ -0,0 +1,115 @@
+/*************************************************************************
+*									 *
+*	 YAP Prolog 	%W% %G% 					 *
+*	Yap Prolog was developed at NCCUP - Universidade do Porto	 *
+*									 *
+* Copyright L.Damas, V.S.Costa and Universidade do Porto 1985-2012	 *
+*									 *
+**************************************************************************
+*									 *
+* File:		YapCompounTerm.h					 *
+* mods:									 *
+* comments:	main header file for YAP				 *
+* version:      $Id: Yap.h,v 1.38 2008-06-18 10:02:27 vsc Exp $	 *
+*************************************************************************/
+
+/*************************************************************************************************
+                           High level macros to access arguments
+*************************************************************************************************/
+
+#ifndef YAPCOMPOUNDTERM_H
+
+#define YAPCOMPOUNDTERM_H 1
+
+EXTERN Int Yap_unify(Term a,Term b);
+
+EXTERN inline Term Deref(Term a);
+
+EXTERN inline Term Deref(Term a)
+{
+   while(IsVarTerm(a)) {
+	Term *b = (Term *) a;
+	a = *b;
+	if(a==((Term) b)) return a;
+   }
+   return(a);
+}
+
+EXTERN inline Term Derefa(CELL *b);
+
+EXTERN inline Term
+Derefa(CELL *b)
+{
+  Term a = *b;
+ restart:
+  if (!IsVarTerm(a)) {
+    return(a);
+  } else if (a == (CELL)b) {
+    return(a);
+  } else {
+    b = (CELL *)a;
+    a = *b;
+    goto restart;
+  }
+}
+
+inline EXTERN Term ArgOfTerm (int i, Term t);
+
+inline EXTERN Term
+ArgOfTerm (int i, Term t)
+{
+  return (Term) (Derefa (RepAppl (t) + (i)));
+}
+
+
+
+inline EXTERN Term HeadOfTerm (Term);
+
+inline EXTERN Term
+HeadOfTerm (Term t)
+{
+  return (Term) (Derefa (RepPair (t)));
+}
+
+
+
+inline EXTERN Term TailOfTerm (Term);
+
+inline EXTERN Term
+TailOfTerm (Term t)
+{
+  return (Term) (Derefa (RepPair (t) + 1));
+}
+
+
+
+
+inline EXTERN Term ArgOfTermCell (int i, Term t);
+
+inline EXTERN Term
+ArgOfTermCell (int i, Term t)
+{
+  return (Term) ((CELL) (RepAppl (t) + (i)));
+}
+
+
+
+inline EXTERN Term HeadOfTermCell (Term);
+
+inline EXTERN Term
+HeadOfTermCell (Term t)
+{
+  return (Term) ((CELL) (RepPair (t)));
+}
+
+
+
+inline EXTERN Term TailOfTermCell (Term);
+
+inline EXTERN Term
+TailOfTermCell (Term t)
+{
+  return (Term) ((CELL) (RepPair (t) + 1));
+}
+
+#endif /* YAPCOMPOUNDTERM_H */
diff --git a/H/YapTags.h b/H/YapTags.h
index 3de5c6c25..f43d1e4e4 100644
--- a/H/YapTags.h
+++ b/H/YapTags.h
@@ -184,8 +184,6 @@ IsUnboundVar (Term * t)
 
 #else
 
-#ifdef YAP_H
-
 inline EXTERN Term MkVarTerm__ ( USES_REGS1 );
 
 inline EXTERN Term
@@ -194,8 +192,6 @@ MkVarTerm__ ( USES_REGS1 )
   return (Term) ((*H = (CELL) H, H++));
 }
 
-#endif
-
 
 inline EXTERN int IsUnboundVar (Term *);
 
@@ -316,8 +312,7 @@ IsIntTerm (Term t)
 }
 
 
-#ifdef YAP_H
-EXTERN inline Term STD_PROTO (MkPairTerm__, (Term, Term CACHE_TYPE) );
+EXTERN inline Term MkPairTerm__(Term head, Term  tail USES_REGS );
 
 EXTERN inline Term
 MkPairTerm__ (Term head, Term tail USES_REGS)
@@ -330,7 +325,6 @@ MkPairTerm__ (Term head, Term tail USES_REGS)
   return (AbsPair (p));
 }
 
-#endif
 
 
 /* Needed to handle numbers:
@@ -395,4 +389,6 @@ IntegerOfTerm (Term t)
   return (Int) (IsIntTerm (t) ? IntOfTerm (t) : LongIntOfTerm (t));
 }
 
+#ifndef YAP_H
 
+#endif
diff --git a/H/YapTerm.h b/H/YapTerm.h
index 40f9a04f0..d9e7f1fb5 100644
--- a/H/YapTerm.h
+++ b/H/YapTerm.h
@@ -18,6 +18,7 @@
 
 typedef void *Functor;
 typedef void *Atom;
+
 #endif
 
 #ifndef EXTERN
@@ -134,3 +135,4 @@ typedef unsigned long int YAP_ULONG_LONG;
 
 #define	Unsigned(V)	((CELL) (V))
 #define	Signed(V)	((Int) (V))
+
diff --git a/H/amiops.h b/H/amiops.h
index f6a8e62de..0b14c43e5 100644
--- a/H/amiops.h
+++ b/H/amiops.h
@@ -87,35 +87,6 @@ Dereferencing macros
 
 #endif /* UNIQUE_TAG_FOR_PAIRS */
 
-EXTERN Term STD_PROTO(Deref,(Term));
-EXTERN Term STD_PROTO(Derefa,(CELL *));
-
-EXTERN inline Term Deref(Term a)
-{
-   while(IsVarTerm(a)) {
-	Term *b = (Term *) a;
-	a = *b;
-	if(a==((Term) b)) return a;
-   }
-   return(a);
-}
-
-EXTERN inline Term
-Derefa(CELL *b)
-{
-  Term a = *b;
- restart:
-  if (!IsVarTerm(a)) {
-    return(a);
-  } else if (a == (CELL)b) {
-    return(a);
-  } else {
-    b = (CELL *)a;
-    a = *b;
-    goto restart;
-  }
-}
-
 /************************************************************
 
 TRAIL VARIABLE
@@ -309,8 +280,6 @@ Unification Routines
 
 *************************************************************/
 
-EXTERN Int STD_PROTO(Yap_unify,(Term,Term));
-
 inline EXTERN void STD_PROTO(reset_trail,(tr_fr_ptr));
 
 inline EXTERN void
diff --git a/Makefile.in b/Makefile.in
index a15e19674..0866f07a6 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -122,8 +122,9 @@ INTERFACE_HEADERS = \
 	$(srcdir)/H/Tags_32LowTag.h \
 	$(srcdir)/H/Tags_64bits.h \
 	$(srcdir)/H/Tags_24bits.h \
-	$(srcdir)/H/YapTerm.h \
+	$(srcdir)/H/YapCompoundTerm.h \
 	$(srcdir)/include/YapRegs.h \
+	$(srcdir)/H/YapTerm.h \
 	$(srcdir)/library/dialect/bprolog/fli/bprolog.h \
 	$(srcdir)/os/SWI-Stream.h
 
@@ -409,7 +410,9 @@ all: parms.h startup.yss @ENABLE_WINCONSOLE@ pl-yap@EXEC_SUFFIX@
 
 Makefile: $(srcdir)/Makefile.in
 
-$(srcdir)/H/Yap.h: config.h YapTermConfig.h $(srcdir)/H/YapTags.h
+$(srcdir)/H/Yap.h: config.h YapTermConfig.h \
+		$(srcdir)/H/YapTags.h \
+		$(srcdir)/H/YapCompoundTerm.h
 
 config.h:	parms.h
 
diff --git a/config.h.in b/config.h.in
index 388312e6c..0cce26ee2 100644
--- a/config.h.in
+++ b/config.h.in
@@ -1,4 +1,8 @@
 
+#ifndef YAP_CONFIG_H
+
+#define YAP_CONFIG_H
+
 #include "parms.h"
 
 /* are dynamic arrays supported? */
@@ -347,5 +351,4 @@
 
 #undef MAX_THREADS
 
-
-
+#endif /* YAP_CONFIG_H */
\ No newline at end of file
diff --git a/configure b/configure
index f9bdcca15..82307a5a2 100755
--- a/configure
+++ b/configure
@@ -4998,6 +4998,45 @@ else
   INSTALL_MATLAB=""
 fi
 
+ac_ext=cpp
+ac_cpp='$CXXCPP $CPPFLAGS'
+ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
+
+my_save_cxxflags="$CXXFLAGS"
+CXXFLAGS=-std=c++0x
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether CXX supports -std-c++0x" >&5
+$as_echo_n "checking whether CXX supports -std-c++0x... " >&6; }
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_compile "$LINENO"; then :
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+    yap_cv_clpbn_bp=yes
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+CXXFLAGS="$my_save_cflags"
+ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+
 if test "$yap_cv_clpbn_bp" = no
 then
   ENABLE_CLPBN_BP="@# "
diff --git a/configure.in b/configure.in
index 81732e741..7c2f89f18 100755
--- a/configure.in
+++ b/configure.in
@@ -501,6 +501,18 @@ else
   INSTALL_MATLAB=""
 fi
 
+AC_LANG_PUSH([C++])
+my_save_cxxflags="$CXXFLAGS"
+CXXFLAGS=-std=c++0x
+AC_MSG_CHECKING([whether CXX supports -std-c++0x])
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM([])],
+    [AC_MSG_RESULT([yes])]
+    [yap_cv_clpbn_bp=yes],
+    [AC_MSG_RESULT([no])]
+)
+CXXFLAGS="$my_save_cflags"
+AC_LANG_POP()
+
 if test "$yap_cv_clpbn_bp" = no 
 then
   ENABLE_CLPBN_BP="@# "
diff --git a/docs/yap.tex b/docs/yap.tex
index a97070270..ada1ed178 100644
--- a/docs/yap.tex
+++ b/docs/yap.tex
@@ -3430,6 +3430,15 @@ Same as @code{variant/2}, succeeds if @var{Term1} and @var{Term2} are variant te
 Succeed if @var{Submuser} subsumes @var{Subsuned} but does not bind any
 variable in @var{Subsumer}.
 
+@item term_subsumer(?@var{T1}, ?@var{T2}, ?@var{Subsumer})
+@findex  term_subsumer/2
+@syindex term_subsumer/2
+@cnindex term_subsumer/2
+
+Succeed if @var{Subsumer} unifies with the least general
+generalization over @var{T1} and
+@var{T2}.
+
 @item acyclic_term(?@var{Term})
 @findex cyclic_term/1
 @syindex cyclic_term/1
diff --git a/library/terms.yap b/library/terms.yap
index 0fc3ef41b..5f2237056 100644
--- a/library/terms.yap
+++ b/library/terms.yap
@@ -18,6 +18,7 @@
 :- module(terms, [
 		  term_hash/2,
 		  term_hash/4,
+		  term_subsumer/3,
 		  instantiated_term_hash/4,
 		  variant/2,
 		  unifiable/3,
diff --git a/packages/prism/src/c/core/bpx.h b/packages/prism/src/c/core/bpx.h
index f15f36704..5b128ea10 100644
--- a/packages/prism/src/c/core/bpx.h
+++ b/packages/prism/src/c/core/bpx.h
@@ -9,8 +9,8 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <YapTerm.h>
-#include <YapTags.h>
 #include <YapRegs.h>
+#include <YapTags.h>
 
 typedef void *SYM_REC_PTR;
 
diff --git a/pl/flags.yap b/pl/flags.yap
index f2dc8c251..da0ed4b14 100644
--- a/pl/flags.yap
+++ b/pl/flags.yap
@@ -617,7 +617,7 @@ yap_flag(system_options,X) :-
 '$system_options'(readline) :-
 	'$swi_current_prolog_flag'(readline, true).
 '$system_options'(tabling) :-
-	\+ '$undefined'('$c_table'(_,_), prolog).
+	\+ '$undefined'('$c_table'(_,_,_), prolog).
 '$system_options'(threads) :-
 	\+ '$no_threads'.
 '$system_options'(wam_profiler) :-