yap-6.3/C/utilpreds.c

/*************************************************************************
 *									 *
 *	 YAP Prolog 							 *
 *									 *
 *	Yap Prolog was developed at NCCUP - Universidade do Porto	 *
 *									 *
 * Copyright L.Damas, V.S.Costa and Universidade do Porto 1985-1997	 *
 *									 *
 **************************************************************************
 *									 *
 * File:		utilpreds.c * Last rev:	4/03/88
 ** mods: * comments:	new utility predicates for YAP *
 *									 *
 *************************************************************************/
#ifdef SCCS
static char     SccsId[] = "@(#)utilpreds.c	1.3";
#endif
/**
 * @file utilpreds.c
 * 
 * @addtogroup Terms

 */

#include "absmi.h"
#include "YapHeap.h"
#include "yapio.h"
#include "attvar.h"
#ifdef HAVE_STRING_H
#include "string.h"
#endif

typedef struct non_single_struct_t {
  CELL *ptd0;
  CELL d0;
  CELL *pt0, *pt0_end;
} non_singletons_t;

#define def_trail_overflow()				\
  trail_overflow:{					\
    while (to_visit > to_visit0) {			\
      to_visit --;					\
      CELL *ptd0 = to_visit->ptd0;			\
      *ptd0 = to_visit->d0;				\
    }							\
    pop_text_stack(lvl);				\
    LOCAL_Error_TYPE = RESOURCE_ERROR_TRAIL;		\
    LOCAL_Error_Size = (TR-TR0)*sizeof(tr_fr_ptr *);	\
    clean_tr(TR0 PASS_REGS);				\
    HR = InitialH;					\
    return 0L;						\
  }

#define def_aux_overflow()						\
  while (to_visit_max-to_visit0 < 32) {							\
    size_t d1 = to_visit-to_visit0;					\
    size_t d2 = to_visit_max-to_visit0;             \
    size_t d3 = Yap_Min(d2+1024, d2 *2);					\
    to_visit0 = Realloc(to_visit0,d3*sizeof(struct non_single_struct_t)); \
    to_visit = to_visit0+d1;						\
    to_visit_max = to_visit0+(d3);					\
  }

#define def_global_overflow()			\
  global_overflow:{				\
    while (to_visit > to_visit0) {		\
      to_visit --;				\
      CELL *ptd0 = to_visit->ptd0;		\
      *ptd0 = to_visit->d0;			\
    }						\
    pop_text_stack(lvl);			\
    clean_tr(TR0 PASS_REGS);			\
    HR = InitialH;				\
    LOCAL_Error_TYPE = RESOURCE_ERROR_STACK;	\
    LOCAL_Error_Size = (ASP-HR)*sizeof(CELL);	\
    return false; }


static Int   p_copy_term( USES_REGS1 );


#ifdef DEBUG
static Int  p_force_trail_expansion( USES_REGS1 );
#endif /* DEBUG */

static inline void
clean_tr(tr_fr_ptr TR0 USES_REGS) {
  if (TR != TR0) {
    do {
      Term p = TrailTerm(--TR);
      RESET_VARIABLE(p);
    } while (TR != TR0);
  }
}

static inline void
clean_dirty_tr(tr_fr_ptr TR0 USES_REGS) {
  tr_fr_ptr pt0 = TR;
  while (pt0 != TR0) {
    Term p = TrailTerm(--pt0);
    if (IsApplTerm(p)) {
      CELL *pt = RepAppl(p);
#ifdef FROZEN_STACKS
      pt[0] = TrailVal(pt0);
#else
      pt[0] = TrailTerm(pt0 - 1);
      pt0 --;
#endif /* FROZEN_STACKS */
    } else {
      RESET_VARIABLE(p);
    }
  } 
  TR = TR0;
}

/// @brief recover original term while fixing direct refs.
///
/// @param USES_REGS 
///
static inline void
clean_complex_tr(tr_fr_ptr TR0 USES_REGS) {
  tr_fr_ptr pt0 = TR;
  while (pt0 != TR0) {
    Term p = TrailTerm(--pt0);
    if (IsApplTerm(p)) {
      /// pt: points to the address of the new term we may want to fix.
      CELL *pt = RepAppl(p);
      if (pt >= HB && pt < HR) { /// is it new?
	Term v = pt[0];
	if (IsApplTerm(v)) {
	  /// yes, more than a single ref
	  *pt = (CELL)RepAppl(v);
	}
#ifndef FROZEN_STACKS
	pt0 --;
#endif /* FROZEN_STACKS */
	continue;
      } 
#ifdef FROZEN_STACKS
      pt[0] = TrailVal(pt0);
#else
      pt[0] = TrailTerm(pt0 - 1);
      pt0 --;
#endif /* FROZEN_STACKS */
    } else {
      RESET_VARIABLE(p);
    }
  } 
  TR = TR0;
}

#define expand_stack(S0,SP,SF,TYPE)				\
  { size_t sz = SF-S0, used = SP-S0;				\
  sz += 1024;\
    S0  = Realloc(S0, sz*sizeof(TYPE) PASS_REGS);	\
    SP = S0+used; SF = S0+sz; }

#define MIN_ARENA_SIZE (1048L)


int Yap_copy_complex_term(register CELL *pt0, register CELL *pt0_end,
			  bool share, bool copy_att_vars, CELL *ptf,
			  CELL *HLow USES_REGS) {
  //  fprintf(stderr,"+++++++++\n");
  //CELL *x = pt0; while(x != pt0_end) Yap_DebugPlWriteln(*++ x);

  int lvl = push_text_stack();

  struct cp_frame *to_visit0,
    *to_visit = Malloc(1024*sizeof(struct cp_frame));
  struct cp_frame *to_visit_max;

  CELL *HB0 = HB;
  tr_fr_ptr TR0 = TR;
  int ground = true;

  HB = HLow;
  to_visit0 = to_visit;
  to_visit_max = to_visit+1024;
 loop:
  while (pt0 < pt0_end) {
    register CELL d0;
    register CELL *ptd0;
    
    ptd0 = ++pt0;
    d0 = *ptd0;
  deref:
    deref_head(d0, copy_term_unk);
  copy_term_nvar : {
      if (IsPairTerm(d0)) {
	CELL *headp = RepPair(d0);
	if (//(share && headp < HB) ||
	    (IsPairTerm(*headp) && RepPair(*headp) >= HB && RepPair(*headp) < HR)) {
	  /* If this is newer than the current term, just reuse */
	  *ptf++ = *headp;
	  continue;
	}
	if (to_visit >= to_visit_max-32) {
	  expand_stack(to_visit0, to_visit, to_visit_max, struct cp_frame);
	}
	*ptf = AbsPair(HR);
	ptf++;
	to_visit->start_cp = pt0;
	to_visit->end_cp = pt0_end;
	to_visit->to = ptf;
	to_visit->ground = ground;
	to_visit++;
	// move to new list
	d0 = *headp;
	if ((ADDR)TR > LOCAL_TrailTop - MIN_ARENA_SIZE)
          goto trail_overflow;
	TrailedMaBind(headp, AbsPair(HR));
	pt0 = headp;
	pt0_end = headp + 1;
	ptf = HR;
	ground = true;
	HR += 2;
	if (HR > ASP - MIN_ARENA_SIZE) {
	  goto overflow;
	}
	ptd0 = pt0;
	goto deref;
      } else if (IsApplTerm(d0)) {
	register Functor f;
	register CELL *headp;
	/* store the terms to visit */
	headp = RepAppl(d0);
	if (IsApplTerm(*headp)//(share && headp < HB) ||
	    ) {
	  /* If this is newer than the current term, just reuse */
	  *ptf++ = *headp;
	  continue;
	}
	f = (Functor)(*headp);

	if (IsExtensionFunctor(f)) {
	  switch ((CELL)f) {
	  case (CELL) FunctorDBRef:
	  case (CELL) FunctorAttVar:
	    *ptf++ = d0;
	    break;
	  case (CELL) FunctorLongInt:
	    if (HR > ASP - (MIN_ARENA_SIZE + 3)) {
	      goto overflow;
	    }
	    *ptf++ = AbsAppl(HR);
	    HR[0] = (CELL)f;
	    HR[1] = headp[1];
	    HR[2] = EndSpecials;
	    HR += 3;
	    if (HR > ASP - MIN_ARENA_SIZE) {
	      goto overflow;
	    }
	    break;
	  case (CELL) FunctorDouble:
	    if (HR >
		ASP - (MIN_ARENA_SIZE + (2 + SIZEOF_DOUBLE / sizeof(CELL)))) {
	      goto overflow;
	    }
	    *ptf++ = AbsAppl(HR);
	    HR[0] = (CELL)f;
	    HR[1] = headp[1];
#if SIZEOF_DOUBLE == 2 * SIZEOF_INT_P
	    HR[2] = headp[2];
	    HR[3] = EndSpecials;
	    HR += 4;
#else
	    HR[2] = EndSpecials;
	    HR += 3;
#endif
	    break;
	  case (CELL) FunctorString:
	    if (ASP - HR < MIN_ARENA_SIZE + 3 + headp[1]) {
	      goto overflow;
	    }
	    *ptf++ = AbsAppl(HR);
	    memmove(HR, headp, sizeof(CELL) * (3 + headp[1]));
	    HR += headp[1] + 3;
	    break;
	  default: {
	    /* big int */
	    size_t sz = (sizeof(MP_INT) + 3 * CellSize +
			 ((MP_INT *)(headp + 2))->_mp_alloc * sizeof(mp_limb_t)) /
	      CellSize,
	      i;

	    if (HR > ASP - (MIN_ARENA_SIZE + sz)) {
	      goto overflow;
	    }
	    *ptf++ = AbsAppl(HR);
	    HR[0] = (CELL)f;
	    for (i = 1; i < sz; i++) {
	      HR[i] = headp[i];

	    }
	    HR += sz;
	  }
	  }
	  continue;
        }
       	*ptf = AbsAppl(HR);
	ptf++;
	/* store the terms to visit */
	to_visit->start_cp = pt0;
	to_visit->end_cp = pt0_end;
	to_visit->to = ptf;
	to_visit->ground = ground;
	if (++to_visit >= to_visit_max-32) {
	  expand_stack(to_visit0, to_visit, to_visit_max, struct cp_frame);
	}
	if ((ADDR)TR > LOCAL_TrailTop - MIN_ARENA_SIZE)
          goto trail_overflow;
	TrailedMaBind(headp,AbsAppl(HR));
	ptf = HR;
	*ptf++ = (CELL)f;
	ground = true;
	arity_t a = ArityOfFunctor(f); 
	HR = ptf+a;
	if (HR > ASP - MIN_ARENA_SIZE) {
	  goto overflow;
	}
	pt0 = headp;
	pt0_end = headp+a;
	ground = (f != FunctorMutable);
      } else {
	/* just copy atoms or integers */
	*ptf++ = d0;
      }
      continue;
    }

    derefa_body(d0, ptd0, copy_term_unk, copy_term_nvar);
    ground = false;
    /* don't need to copy variables if we want to share the global term */
    if (//(share && ptd0 < HB && ptd0 > H0) ||
	(ptd0 >= HLow && ptd0 < HR)) {
      /* we have already found this cell */
      *ptf++ = (CELL)ptd0;
    } else {
      if (copy_att_vars && GlobalIsAttachedTerm((CELL)ptd0)) {
        /* if unbound, call the standard copy term routine */
        struct cp_frame *bp;
        CELL new;

        bp = to_visit;
        if (!GLOBAL_attas[ExtFromCell(ptd0)].copy_term_op(ptd0, &bp,
                                                          ptf PASS_REGS)) {
          goto overflow;
        }
        to_visit = bp;
        new = *ptf;
	if ((ADDR)TR > LOCAL_TrailTop - MIN_ARENA_SIZE)
          goto trail_overflow;
        TrailedMaBind(ptd0, new);
        ptf++;
      } else {
        /* first time we met this term */
        RESET_VARIABLE(ptf);
	if ((ADDR)TR > LOCAL_TrailTop - MIN_ARENA_SIZE)
          goto trail_overflow;
        TrailedMaBind(ptd0, (CELL)ptf);
        ptf++;
      }
    }
  }

  /* Do we still have compound terms to visit */
  if (to_visit > to_visit0) {
    to_visit--;
    pt0 = to_visit->start_cp;
    pt0_end = to_visit->end_cp;
    ptf = to_visit->to;
    ground = (ground && to_visit->ground);
    goto loop;
  }

  /* restore our nice, friendly, term to its original state */
  clean_dirty_tr(TR0 PASS_REGS);
  /* follow chain of multi-assigned variables */
  pop_text_stack(lvl);
  return 0;
        

 overflow:
  /* oops, we're in trouble */
  HR = HLow;
  /* we've done it */
  /* restore our nice, friendly, term to its original state */
  HB = HB0;
  while (to_visit > to_visit0) {
    to_visit--;
    pt0 = to_visit->start_cp;
    pt0_end = to_visit->end_cp;
    ptf = to_visit->to;
  }
  reset_trail(TR0);
  pop_text_stack(lvl);
  return -1;

 trail_overflow:
  /* oops, we're in trouble */
  HR = HLow;
  /* we've done it */
  /* restore our nice, friendly, term to its original state */
  HB = HB0;
  while (to_visit > to_visit0) {
    to_visit--;
    pt0 = to_visit->start_cp;
    pt0_end = to_visit->end_cp;
    ptf = to_visit->to;
  }
  reset_trail(TR0);
  pop_text_stack(lvl);
  return -4;
}


static Term
handle_cp_overflow(int res, tr_fr_ptr TR0, UInt arity, Term t)
{
  CACHE_REGS
    XREGS[arity+1] = t;
  switch(res) {
  case -1:
    if (!Yap_gcl((ASP-HR)*sizeof(CELL), arity+1, ENV, gc_P(P,CP))) {
      Yap_Error(RESOURCE_ERROR_STACK, TermNil, LOCAL_ErrorMessage);
      return 0L;
    }
    return Deref(XREGS[arity+1]);
  case -2:
    return Deref(XREGS[arity+1]);
  case -3:
    {
      UInt size = LOCAL_Error_Size;
      LOCAL_Error_Size = 0L;
      if (size > 4*1024*1024)
	size = 4*1024*1024;
      if (!Yap_ExpandPreAllocCodeSpace(size, NULL, TRUE)) {
	Yap_Error(RESOURCE_ERROR_AUXILIARY_STACK, TermNil, LOCAL_ErrorMessage);
	return 0L;
      }
    }
    return Deref(XREGS[arity+1]);
  case -4:
    if (!Yap_growtrail((TR-TR0)*sizeof(tr_fr_ptr *), FALSE)) {
      Yap_Error(RESOURCE_ERROR_TRAIL, TermNil, LOCAL_ErrorMessage);
      return 0L;
    }
    return Deref(XREGS[arity+1]);
  default:
    return 0L;
  }
}


static Term
CopyTerm(Term inp, UInt arity, int share, int newattvs USES_REGS) {
  Term t = Deref(inp);
  tr_fr_ptr TR0 = TR;
    CELL *Hi;

  if (IsPrimitiveTerm(t)) {
    return t;
  }
  while( true ) {
     int res;
    Hi = HR;
    HR ++;
    
      if ((res = Yap_copy_complex_term((&t)-1, &t, share, newattvs, Hi, HR PASS_REGS)) < 0) {
	HR = Hi;
	if ((t = handle_cp_overflow(res, TR0, arity, t))== 0L)
	  return FALSE;
      } else if (res && share) {
	HR = Hi;
	return t;
      }
  return Hi[0];
    }
  return 0;
}

Term
Yap_CopyTerm(Term inp) {
  CACHE_REGS
    return CopyTerm(inp, 0, false, TRUE PASS_REGS);
}

Term
Yap_CopyTermNoShare(Term inp) {
  CACHE_REGS
    return CopyTerm(inp, 0, FALSE, FALSE PASS_REGS);
}

static Int
p_copy_term( USES_REGS1 )		/* copy term t to a new instance  */
{
  Term t = CopyTerm(ARG1, 2, false, TRUE PASS_REGS);
  if (t == 0L)
    return FALSE;
  /* be careful, there may be a stack shift here */
  return Yap_unify(ARG2,t);
}

static Int
p_duplicate_term( USES_REGS1 )		/* copy term t to a new instance  */
{
  Term t = CopyTerm(ARG1, 2, FALSE, TRUE PASS_REGS);
  if (t == 0L)
    return FALSE;
  /* be careful, there may be a stack shift here */
  return Yap_unify(ARG2,t);
}

static Int
p_copy_term_no_delays( USES_REGS1 )		/* copy term t to a new instance  */
{
  Term t = CopyTerm(ARG1, 2, TRUE, FALSE PASS_REGS);
  if (t == 0L) {
    return FALSE;
  }
  /* be careful, there may be a stack shift here */
  return(Yap_unify(ARG2,t));
}



typedef struct bp_frame {
  CELL *start_cp;
  CELL *end_cp;
  CELL *to;
  CELL *oldp;
  CELL oldv;
} bp_frame_t;



typedef struct copy_frame {
  CELL *start_cp;
  CELL *end_cp;
  CELL *to;
} copy_frame_t;



/*
  FAST EXPORT ROUTINE. Export a Prolog term to something like:

  CELL 0: offset for start of term
  CELL 1: size of actual term (to be copied to stack)
  CELL 2: the original term (just for reference)

  Atoms and functors:
  - atoms are either:
  0 and a char *string
  -1 and a wchar_t *string
  - functors are a CELL with arity and a string.

  Compiled Term.

*/

static inline
CELL *CellDifH(CELL *hptr, CELL *hlow)
{
  return (CELL *)((char *)hptr-(char *)hlow);
}

#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)
{
  char *ptr, *p0;
  size_t sz;

  ptr = *hpp;
  ptr = (char *)AdjustSize((CELL*)ptr, buf);

  p0 = ptr;
  *ptr++ = 0;
  sz = strlen(RepAtom(at)->StrOfAE);
  if (sz + 1  >= len)
    return (Atom)NULL;
  strcpy(ptr, RepAtom(at)->StrOfAE);
  *hpp = ptr+(sz+1);
  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 = AdjustSize((CELL *)*hpp, buf);
  UInt arity = ArityOfFunctor(f);
  if (2*sizeof(CELL) >= len)
    return NULL;
  hptr[0] = arity;
  *hpp = (char *)(hptr+1);
  if (!export_atom(NameOfFunctor(f), hpp, buf, len))
    return NULL;
  /* 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);
}

#define export_derefa_body(D,A,LabelUnk,LabelNonVar)			\
  do {									\
    if ((CELL *)(D) < CellDifH(HR,HLow)) { (A) = (CELL *)(D); break; }	\
    (A) = (CELL *)(D);							\
    (D) = *(CELL *)(D);							\
    if(!IsVarTerm(D)) goto LabelNonVar;					\
  LabelUnk:      ;							\
  } while (Unsigned(A) != (D))


static int
export_term_to_buffer(Term inpt, char *buf, char *bptr, CELL *t0 , CELL *tf, size_t len)
{
  char *td = bptr;
  CELL *bf = (CELL *)buf;
  if (buf + len < (char *)((CELL *)td + (tf-t0))) {
    return FALSE;
  }
  memmove((void *)td, (void *)t0, (tf-t0)* sizeof(CELL));
  bf[0] = (td-buf);
  bf[1] = (tf-t0);
  bf[2] = inpt;
  return bf[0]+sizeof(CELL)*bf[1];
}


static size_t
export_complex_term(Term tf, CELL *pt0, CELL *pt0_end, char * buf, size_t len0, int newattvs, CELL *ptf, CELL *HLow USES_REGS)
{
  struct cp_frame *to_visit0, *to_visit = (struct cp_frame *)Yap_PreAllocCodeSpace();
  CELL *HB0 = HB;
  tr_fr_ptr TR0 = TR;
  int ground = TRUE;
  char *bptr = buf+ 3*sizeof(CELL);
  size_t len = len0;

  HB = HLow;
  to_visit0 = to_visit;
 loop:
  while (pt0 < pt0_end) {
    register CELL d0;
    register CELL *ptd0;
    ++ pt0;
    ptd0 = pt0;
    d0 = *ptd0;
    deref_head(d0, export_term_unk);
  export_term_nvar:
    {
      if (IsPairTerm(d0)) {
	CELL *ap2 = RepPair(d0);
	if (ap2 < CellDifH(HR,HLow)) {
	  /* If this is newer than the current term, just reuse */
	  *ptf++ = d0;
	  continue;
	}
	*ptf = AbsPair(CellDifH(HR,HLow));
	ptf++;
#ifdef RATIONAL_TREES
	if (to_visit+1 >= (struct cp_frame *)AuxSp) {
	  goto heap_overflow;
	}
	to_visit->start_cp = pt0;
	to_visit->end_cp = pt0_end;
	to_visit->to = ptf;
	to_visit->oldv = *pt0;
	to_visit->ground = ground;
	/* fool the system into thinking we had a variable there */
	*pt0 = AbsPair(CellDifH(HR,HLow));
	to_visit ++;
#else
	if (pt0 < pt0_end) {
	  if (to_visit+1 >= (struct cp_frame *)AuxSp) {
	    goto heap_overflow;
	  }
	  to_visit->start_cp = pt0;
	  to_visit->end_cp = pt0_end;
	  to_visit->to = ptf;
	  to_visit->ground = ground;
	  to_visit ++;
	}
#endif
	pt0 = ap2 - 1;
	pt0_end = ap2 + 1;
	ptf = HR;
	HR += 2;
	if (HR > ASP - 2048) {
	  goto overflow;
	}
      } else if (IsApplTerm(d0)) {
	register Functor f;
	register CELL *ap2;
	/* store the terms to visit */
	ap2 = RepAppl(d0);
	if (ap2 < CellDifH(HR,HLow)) {
	  /* If this is newer than the current term, just reuse */
	  *ptf++ = d0;
	  continue;
	}
	f = (Functor)(*ap2);

	*ptf++ = AbsAppl(CellDifH(HR,HLow));
	if (IsExtensionFunctor(f)) {
	  UInt sz;

	  /* make sure to export floats */
	  if (f== FunctorDouble) {
	    sz = sizeof(Float)/sizeof(CELL)+2;
	  } else if (f== FunctorLongInt) {
	    sz = 3;
	  } else if (f== FunctorString) {
	    sz = 3+ap2[1];
	  } else {
	    CELL *pt = ap2+1;
	    sz = 2+sizeof(MP_INT)+(((MP_INT *)(pt+1))->_mp_alloc*sizeof(mp_limb_t));
	  }
	  if (HR+sz > ASP - 2048) {
	    goto overflow;
	  }
	  memmove((void *)HR, (void *)ap2, sz*sizeof(CELL));
	  HR += sz;
	  continue;
	}
	/* store the terms to visit */
#ifdef RATIONAL_TREES
	if (to_visit+1 >= (struct cp_frame *)AuxSp) {
	  goto heap_overflow;
	}
	to_visit->start_cp = pt0;
	to_visit->end_cp = pt0_end;
	to_visit->to = ptf;
	to_visit->oldv = *pt0;
	to_visit->ground = ground;
	/* fool the system into thinking we had a variable there */
	*pt0 = AbsAppl(HR);
	to_visit ++;
#else
	if (pt0 < pt0_end) {
	  if (to_visit+1 >= (struct cp_frame *)AuxSp) {
	    goto heap_overflow;
	  }
	  to_visit->start_cp = pt0;
	  to_visit->end_cp = pt0_end;
	  to_visit->to = ptf;
	  to_visit->ground = ground;
	  to_visit ++;
	}
#endif
	ground = (f != FunctorMutable);
	d0 = ArityOfFunctor(f);
	pt0 = ap2;
	pt0_end = ap2 + d0;
	/* store the functor for the new term */
	ptf = HR+1;
	HR += 1+d0;
	if (HR > ASP - 2048) {
	  goto overflow;
	}
	ptf[-1] = (CELL)export_functor(f, &bptr, buf, len);
	len = len0 - (bptr-buf);
	if (HR > ASP - 2048) {
	  goto overflow;
	}
      } else {
	if (IsAtomTerm(d0)) {
	  *ptf = MkAtomTerm(export_atom(AtomOfTerm(d0), &bptr, buf, len));
	  ptf++;
	  len = len0 - (bptr-buf);
	} else {
	  *ptf++ = d0;
	}
      }
      continue;
    }

    export_derefa_body(d0, ptd0, export_term_unk, export_term_nvar);
    ground = FALSE;
    if (ptd0 < CellDifH(HR,HLow)) {
      /* we have already found this cell */
      *ptf++ = (CELL) ptd0;
    } else {
#if COROUTINING
      if (newattvs && IsAttachedTerm((CELL)ptd0) && FALSE) {
	/* if unbound, call the standard export term routine */
	struct cp_frame *bp;

	CELL new;

	bp = to_visit;
	if (!GLOBAL_attas[ExtFromCell(ptd0)].copy_term_op(ptd0, &bp, ptf PASS_REGS)) {
	  goto overflow;
	}
	to_visit = bp;
	new = *ptf;
	Bind_NonAtt(ptd0, new);
	ptf++;
      } else {
#endif
	/* first time we met this term */
	*ptf = (CELL)CellDifH(ptf,HLow);
	if (TR > (tr_fr_ptr)LOCAL_TrailTop - 256) {
	  /* Trail overflow */
	  if (!Yap_growtrail((TR-TR0)*sizeof(tr_fr_ptr *), TRUE)) {
	    goto trail_overflow;
	  }
	}
	Bind_NonAtt(ptd0, (CELL)ptf);
	ptf++;
#ifdef COROUTINING
      }
#endif
    }
  }
  /* Do we still have compound terms to visit */
  if (to_visit > to_visit0) {
    to_visit --;
    pt0 = to_visit->start_cp;
    pt0_end = to_visit->end_cp;
    ptf = to_visit->to;
#ifdef RATIONAL_TREES
    *pt0 = to_visit->oldv;
#endif
    ground = (ground && to_visit->ground);
    goto loop;
  }

  /* restore our nice, friendly, term to its original state */
  clean_dirty_tr(TR0 PASS_REGS);
  HB = HB0;
  return export_term_to_buffer(tf, buf, bptr, HLow, HR, len0);

 overflow:
  /* oops, we're in trouble */
  HR = HLow;
  /* we've done it */
  /* restore our nice, friendly, term to its original state */
  HB = HB0;
#ifdef RATIONAL_TREES
  while (to_visit > to_visit0) {
    to_visit --;
    pt0 = to_visit->start_cp;
    pt0_end = to_visit->end_cp;
    ptf = to_visit->to;
    *pt0 = to_visit->oldv;
  }
#endif
  reset_trail(TR0);
  /* follow chain of multi-assigned variables */
  return -1;

 trail_overflow:
  /* oops, we're in trouble */
  HR = HLow;
  /* we've done it */
  /* restore our nice, friendly, term to its original state */
  HB = HB0;
#ifdef RATIONAL_TREES
  while (to_visit > to_visit0) {
    to_visit --;
    pt0 = to_visit->start_cp;
    pt0_end = to_visit->end_cp;
    ptf = to_visit->to;
    *pt0 = to_visit->oldv;
  }
#endif
  {
    tr_fr_ptr oTR =  TR;
    reset_trail(TR0);
    if (!Yap_growtrail((oTR-TR0)*sizeof(tr_fr_ptr *), TRUE)) {
      return -4;
    }
    return -2;
  }

 heap_overflow:
  /* oops, we're in trouble */
  HR = HLow;
  /* we've done it */
  /* restore our nice, friendly, term to its original state */
  HB = HB0;
#ifdef RATIONAL_TREES
  while (to_visit > to_visit0) {
    to_visit --;
    pt0 = to_visit->start_cp;
    pt0_end = to_visit->end_cp;
    ptf = to_visit->to;
    *pt0 = to_visit->oldv;
  }
#endif
  reset_trail(TR0);
  LOCAL_Error_Size = (ADDR)AuxSp-(ADDR)to_visit0;
  return -3;
}

static size_t
ExportTerm(Term inp, char * buf, size_t len, UInt arity, int newattvs USES_REGS) {
  Term t = Deref(inp);
  tr_fr_ptr TR0 = TR;
  size_t res = 0;
  CELL *Hi = HR;

  do {
    if (IsVarTerm(t) || IsIntTerm(t)) {
      return export_term_to_buffer(t, buf, buf+ 3*sizeof(CELL), &inp, &inp, len);
    }
    if (IsAtomTerm(t)) {
      Atom at = AtomOfTerm(t);
      char *b = buf+3*sizeof(CELL);
      export_atom(at, &b, b, len-3*sizeof(CELL));
      return export_term_to_buffer(t, buf, b, &inp, &inp, len);
    }
    if ((Int)res < 0) {
      HR = Hi;
      TR = TR0;
      if ((t = handle_cp_overflow(res, TR0, arity, t))== 0L)
	return res;
    }
    Hi = HR;
    TR0 = TR;
    res = export_complex_term(inp, &t-1, &t, buf, len, newattvs, Hi, Hi PASS_REGS);
  } while ((Int)res < 0);
  return res;
}

size_t
Yap_ExportTerm(Term inp, char * buf, size_t len, UInt arity) {
  CACHE_REGS
    return ExportTerm(inp, buf, len, arity, TRUE PASS_REGS);
}


static CELL *
ShiftPtr(CELL t, char *base)
{
  return (CELL *)(base+t);
}

static Atom
addAtom(Atom t, char *buf)
{
  char *s = buf+(UInt)t;

  if (!*s) {
    return Yap_LookupAtom(s+1);
  }
  return NULL;
}

static UInt
FetchFunctor(CELL *pt, char *buf)
{
  CELL *ptr = (CELL *)(buf+(*pt-1));
  // do arity first
  UInt arity = *ptr++;
  Atom name, at;
  // and then an atom
  ptr = AdjustSize(ptr, buf);
  name = (Atom)((char *)ptr-buf);
  at = addAtom(name, buf);
  *pt = (CELL)Yap_MkFunctor(at, arity);
  return arity;
}


static CELL *import_compound(CELL *hp, char *abase, char *buf, CELL *amax);
static CELL *import_pair(CELL *hp, char *abase, char *buf, CELL *amax);

static CELL *
import_arg(CELL *hp, char *abase, char *buf, CELL *amax)
{
  Term t = *hp;
  if (IsVarTerm(t)) {
    hp[0] = (CELL)ShiftPtr(t, abase);
  } else if (IsAtomTerm(t)) {
    hp[0] = MkAtomTerm(addAtom(AtomOfTerm(t), buf));
  } else if (IsPairTerm(t)) {
    CELL *newp = ShiftPtr((CELL)RepPair(t), abase);
    hp[0] = AbsPair(newp);
    if (newp > amax) {
      amax = import_pair(newp, abase, buf, newp);
    }
  } else if (IsApplTerm(t)) {
    CELL *newp = ShiftPtr((CELL)RepAppl(t), abase);
    hp[0] = AbsAppl(newp);
    if (newp > amax) {
      amax = import_compound(newp, abase, buf, newp);
    }
  }
  return amax;
}

static CELL *
import_compound(CELL *hp, char *abase, char *buf, CELL *amax)
{
  Functor f = (Functor)*hp;
  UInt ar, i;

  if (!((CELL)f & 1) && IsExtensionFunctor(f))
    return amax;
  ar = FetchFunctor(hp, buf);
  for (i=1; i<=ar; i++) {
    amax = import_arg(hp+i, abase, buf, amax);
  }
  return amax;
}

static CELL *
import_pair(CELL *hp, char *abase, char *buf, CELL *amax)
{
  amax = import_arg(hp, abase, buf, amax);
  amax = import_arg(hp+1, abase, buf, amax);
  return amax;
}

Term
Yap_ImportTerm(char * buf) {
  CACHE_REGS
    CELL *bc = (CELL *)buf;
  size_t sz = bc[1];
  Term tinp, tret;
  tinp = bc[2];
  if (IsVarTerm(tinp))
    return MkVarTerm();
  else if (IsIntTerm(tinp))
    return tinp;
  else if (IsAtomTerm(tinp)) {
    tret = MkAtomTerm(addAtom(NULL,(char *)(bc+3)));
    return tret;
  }
  // call the gc/stack shifter mechanism
  // if not enough stack available
  while (HR + sz > ASP - 4096) {
    if (!Yap_gcl( (sz+4096)*sizeof(CELL), PP->ArityOfPE, ENV, gc_P(P,CP))) {
      Yap_Error(RESOURCE_ERROR_STACK, TermNil, LOCAL_ErrorMessage);
      return 0L;
    }
  }
  memmove(HR, buf+bc[0], sizeof(CELL)*sz);
  if (IsApplTerm(tinp)) {
    tret = AbsAppl(HR);
    import_compound(HR, (char *)HR, buf, HR);
  } else {
    tret = AbsPair(HR);
    import_pair(HR, (char *)HR, buf, HR);
  }
  HR += sz;
  return tret;
}

size_t
Yap_SizeOfExportedTerm(char * buf) {
  CELL *bc = (CELL *)buf;

  return bc[0]+bc[1]*sizeof(CELL);
}

static Int
p_export_term( USES_REGS1 )
{
  size_t sz = 4096, osz;
  char *export_buf;
  do {
    export_buf  = malloc(sz);
    if (!export_buf)
      return FALSE;
    if (!(osz = Yap_ExportTerm(ARG1, export_buf, sz, 1))) {
      sz += 4096;
      free(export_buf);
    }
  } while (!osz);
  return Yap_unify(ARG3,MkIntegerTerm(osz)) &&
    Yap_unify(ARG2, MkIntegerTerm((Int)export_buf));
}

static Int
p_import_term( USES_REGS1 )
{
  char *export_buf = (char *)IntegerOfTerm(Deref(ARG1));
  if (!export_buf)
    return FALSE;
  Int out = Yap_unify(ARG2,Yap_ImportTerm(export_buf));
  return out;
}

static Int
p_kill_exported_term( USES_REGS1 )
{
  char *export_buf = (char *)IntegerOfTerm(Deref(ARG1));
  if (!export_buf)
    return FALSE;
  free(export_buf);
  return TRUE;
}



static int
SizeOfExtension(Term t)
{
  Functor f = FunctorOfTerm(t);
  if (f== FunctorDouble) {
    return 2 + sizeof(Float)/sizeof(CELL);
  }
  if (f== FunctorString) {
    return 3 + RepAppl(t)[1];
  }
  if (f== FunctorLongInt) {
    return 2 + sizeof(Float)/sizeof(CELL);
  }
  if (f== FunctorDBRef) {
    return 0;
  }
  if (f== FunctorBigInt) {
    CELL *pt = RepAppl(t)+2;
    return 3+sizeof(MP_INT)+(((MP_INT *)(pt))->_mp_alloc*sizeof(mp_limb_t));
  }
  return 0;
}


static Int sz_ground_complex_term(register CELL *pt0, register CELL *pt0_end, int ground USES_REGS)
{

  register CELL **to_visit0, **to_visit = (CELL **)Yap_PreAllocCodeSpace();
  Int sz = 0;

  to_visit0 = to_visit;
 loop:
  while (pt0 < pt0_end) {
    register CELL d0;
    register CELL *ptd0;

    ++pt0;
    ptd0 = pt0;
    d0 = *ptd0;
    deref_head(d0, vars_in_term_unk);
  vars_in_term_nvar:
    {
      if (IsPairTerm(d0)) {
	sz += 2;
	if (to_visit + 1024 >= (CELL **)AuxSp) {
	  goto aux_overflow;
	}
#ifdef RATIONAL_TREES
	to_visit[0] = pt0;
	to_visit[1] = pt0_end;
	to_visit[2] = (CELL *)*pt0;
	to_visit += 3;
	*pt0 = TermNil;
#else
	if (pt0 < pt0_end) {
	  to_visit[0] = pt0;
	  to_visit[1] = pt0_end;
	  to_visit += 2;
	}
#endif
	pt0 = RepPair(d0) - 1;
	pt0_end = RepPair(d0) + 1;
      } else if (IsApplTerm(d0)) {
	register Functor f;
	register CELL *ap2;
	/* store the terms to visit */
	ap2 = RepAppl(d0);
	f = (Functor)(*ap2);

	if (IsExtensionFunctor(f)) {
	  sz += SizeOfExtension(d0);
	  continue;
	}
	if (to_visit + 1024 >= (CELL **)AuxSp) {
	  goto aux_overflow;
	}
#ifdef RATIONAL_TREES
	to_visit[0] = pt0;
	to_visit[1] = pt0_end;
	to_visit[2] = (CELL *)*pt0;
	to_visit += 3;
	*pt0 = TermNil;
#else
	/* store the terms to visit */
	if (pt0 < pt0_end) {
	  to_visit[0] = pt0;
	  to_visit[1] = pt0_end;
	  to_visit += 2;
	}
#endif
	d0 = ArityOfFunctor(f);
	sz += (1+d0);
	pt0 = ap2;
	pt0_end = ap2 + d0;
      }
      continue;
    }


    derefa_body(d0, ptd0, vars_in_term_unk, vars_in_term_nvar);
    if (!ground)
      continue;
#ifdef RATIONAL_TREES
    while (to_visit > to_visit0) {
      to_visit -= 3;
      pt0 = to_visit[0];
      pt0_end = to_visit[1];
      *pt0 = (CELL)to_visit[2];
    }
#endif
    return 0;
  }
  /* Do we still have compound terms to visit */
  if (to_visit > to_visit0) {
#ifdef RATIONAL_TREES
    to_visit -= 3;
    pt0 = to_visit[0];
    pt0_end = to_visit[1];
    *pt0 = (CELL)to_visit[2];
#else
    to_visit -= 2;
    pt0 = to_visit[0];
    pt0_end = to_visit[1];
#endif
    goto loop;
  }
  return sz;

 aux_overflow:
  /* unwind stack */
#ifdef RATIONAL_TREES
  while (to_visit > to_visit0) {
    to_visit -= 3;
    pt0 = to_visit[0];
    *pt0 = (CELL)to_visit[2];
  }
#endif
  return -1;
}

int
Yap_SizeGroundTerm(Term t, int ground)
{
  CACHE_REGS
    if (IsVarTerm(t)) {
      if (!ground)
	return 1;
      return 0;
    }  else if (IsPrimitiveTerm(t)) {
      return 1;
    } else if (IsPairTerm(t)) {
      int sz = sz_ground_complex_term(RepPair(t)-1, RepPair(t)+1, ground PASS_REGS);
      if (sz <= 0)
	return sz;
      return sz+2;
    } else {
      int sz = 0;
      Functor fun = FunctorOfTerm(t);

      if (IsExtensionFunctor(fun))
	return 1+ SizeOfExtension(t);

      sz = sz_ground_complex_term(RepAppl(t),
				  RepAppl(t)+
				  ArityOfFunctor(fun),
				  ground PASS_REGS);
      if (sz <= 0)
	return sz;
      return 1+ArityOfFunctor(fun)+sz;
    }
}


/* The code for TermHash was originally contributed by Gertjen Van Noor */

/* This code with max_depth == -1 will loop for infinite trees */


//-----------------------------------------------------------------------------
// MurmurHash2, by Austin Appleby

// Note - This code makes a few assumptions about how your machine behaves -

// 1. We can read a 4-byte value from any address without crashing
// 2. sizeof(int) == 4

// And it has a few limitations -

// 1. It will not work incrementally.
// 2. It will not produce the same results on litle-endian and big-endian
//    machines.

static unsigned int
MurmurHashNeutral2 ( const void * key, int len, unsigned int seed )
{
  const unsigned int m = 0x5bd1e995;
  const int r = 24;

  unsigned int h = seed ^ len;

  const unsigned char * data = (const unsigned char *)key;

  while(len >= 4)
    {
      unsigned int k;

      k  = data[0];
      k |= data[1] << 8;
      k |= data[2] << 16;
      k |= data[3] << 24;

      k *= m;
      k ^= k >> r;
      k *= m;

      h *= m;
      h ^= k;

      data += 4;
      len -= 4;
    }

  switch(len)
    {
    case 3: h ^= data[2] << 16;
    case 2: h ^= data[1] << 8;
    case 1: h ^= data[0];
      h *= m;
    };

  h ^= h >> 13;
  h *= m;
  h ^= h >> 15;

  return h;
}

static CELL *
addAtomToHash(CELL *st, Atom at)
{
  unsigned int len;

  char *c = RepAtom(at)->StrOfAE;
  int ulen = strlen(c);
  /* fix hashing over empty atom */
  if (!ulen) {
    return st;
  }
  if (ulen % CellSize == 0) {
    len = ulen/CellSize;
  } else {
    len = ulen/CellSize;
    len++;
  }
  st[len-1] = 0L;
  strncpy((char *)st, c, ulen);
  return st+len;
}

typedef struct visited {
  CELL *start;
  CELL  *end;
  CELL old;
  UInt vdepth;
} visited_t;

static CELL *
hash_complex_term(register CELL *pt0,
		  register CELL *pt0_end,
		  Int depth,
		  CELL *st,
		  int variant USES_REGS)
{
  register visited_t *to_visit0, *to_visit = (visited_t *)Yap_PreAllocCodeSpace();

  to_visit0 = to_visit;
 loop:
  while (pt0 < pt0_end) {
    register CELL d0;
    register CELL *ptd0;
    ++ pt0;
    ptd0 = pt0;
    d0 = *ptd0;
    deref_head(d0, hash_complex_unk);
  hash_complex_nvar:
    {
      if (st + 1024 >= ASP) {
	goto global_overflow;
      }
      if (IsAtomOrIntTerm(d0)) {
	if (d0 != TermFoundVar) {
	  if (IsAtomTerm(d0)) {
	    st = addAtomToHash(st, AtomOfTerm(d0));
	  } else {
	    *st++ = IntOfTerm(d0);
	  }
	}
	continue;
      } else if (IsPairTerm(d0)) {
	st = addAtomToHash(st, AtomDot);
	if (depth == 1)
	  continue;
	if (to_visit + 256 >= (visited_t *)AuxSp) {
	  goto aux_overflow;
	}
	to_visit->start = pt0;
	to_visit->end = pt0_end;
	to_visit->old = *pt0;
	to_visit->vdepth = depth;
	to_visit++;
	depth--;
	*pt0 = TermFoundVar;
	pt0 = RepPair(d0) - 1;
	pt0_end = RepPair(d0) + 1;
	continue;
      } else if (IsApplTerm(d0)) {
	register Functor f;
	register CELL *ap2;
	/* store the terms to visit */
	ap2 = RepAppl(d0);
	f = (Functor)(*ap2);

	if (IsExtensionFunctor(f)) {
	  CELL fc = (CELL)f;

	  switch(fc) {

	  case (CELL)FunctorDBRef:
	    *st++ = fc;
	    break;
	  case (CELL)FunctorLongInt:
	    *st++ = LongIntOfTerm(d0);
	    break;
	  case (CELL)FunctorString:
	    memmove(st, RepAppl(d0), (3+RepAppl(d0)[1])*sizeof(CELL));
	    st += 3+RepAppl(d0)[1];
	    break;
#ifdef USE_GMP
	  case (CELL)FunctorBigInt:
	    {
	      CELL *pt = RepAppl(d0);
	      Int sz =
		sizeof(MP_INT)+1+
		(((MP_INT *)(pt+2))->_mp_alloc*sizeof(mp_limb_t));

	      if (st + (1024 + sz/CellSize) >= ASP) {
		goto global_overflow;
	      }
	      /* then the actual number */
	      memmove((void *)(st+1), (void *)(pt+1), sz);
	      st = st+sz/CellSize;
	    }
	    break;
#endif
	  case (CELL)FunctorDouble:
	    {
	      CELL *pt = RepAppl(d0);
	      *st++ = pt[1];
#if  SIZEOF_DOUBLE == 2*SIZEOF_INT_P
	      *st++ = pt[2];
#endif
	      break;
	    }
	  }
	  continue;
	}
	st = addAtomToHash(st, NameOfFunctor(f));
	if (depth == 1)
	  continue;
	if (to_visit + 1024 >= (visited_t *)AuxSp) {
	  goto aux_overflow;
	}
	to_visit->start = pt0;
	to_visit->end = pt0_end;
	to_visit->old = *pt0;
	to_visit->vdepth = depth;
	to_visit++;
	depth--;
	*pt0 = TermFoundVar;
	d0 = ArityOfFunctor(f);
	pt0 = ap2;
	pt0_end = ap2 + d0;
      }
      continue;
    }


    deref_body(d0, ptd0, hash_complex_unk, hash_complex_nvar);
    if (!variant)
      return NULL;
    else
      continue;
  }
  /* Do we still have compound terms to visit */
  if (to_visit > to_visit0) {
    to_visit--;
    pt0 = to_visit->start;
    pt0_end = to_visit->end;
    *pt0 = to_visit->old;
    depth = to_visit->vdepth;
    goto loop;
  }
  return st;

 aux_overflow:
  /* unwind stack */
  while (to_visit > to_visit0) {
    to_visit --;
    pt0 = to_visit->start;
    *pt0 = to_visit->old;
  }
  return (CELL *)-1;

 global_overflow:
  /* unwind stack */
  while (to_visit > to_visit0) {
    to_visit --;
    pt0 = to_visit->start;
    *pt0 = to_visit->old;
  }
  return (CELL *) -2;
}

Int
Yap_TermHash(Term t, Int size, Int depth, int variant)
{
  CACHE_REGS
    unsigned int i1;
  Term t1 = Deref(t);

  while (TRUE) {
    CELL *ar = hash_complex_term(&t1-1, &t1, depth, HR, FALSE PASS_REGS);
    if (ar == (CELL *)-1) {
      if (!Yap_ExpandPreAllocCodeSpace(0, NULL, TRUE)) {
	Yap_Error(RESOURCE_ERROR_AUXILIARY_STACK, ARG1, "overflow in term_hash");
	return FALSE;
      }
      t1 = Deref(ARG1);
    } else if(ar == (CELL *)-2) {
      if (!Yap_gcl((ASP-HR)*sizeof(CELL), 0, ENV, gc_P(P,CP))) {
	Yap_Error(RESOURCE_ERROR_STACK, TermNil, "in term_hash");
	return FALSE;
      }
      t1 = Deref(ARG1);
    } else if (ar == NULL) {
      return FALSE;
    } else {
      i1 = MurmurHashNeutral2((const void *)HR, CellSize*(ar-HR),0x1a3be34a);
      break;
    }
  }
  /* got the seed and hash from SWI-Prolog */
  return i1 % size;
}

static Int
p_term_hash( USES_REGS1 )
{
  unsigned int i1;
  Term t1 = Deref(ARG1);
  Term t2 = Deref(ARG2);
  Term t3 = Deref(ARG3);
  Term result;
  Int size, depth;

  if (IsVarTerm(t2)) {
    Yap_Error(INSTANTIATION_ERROR,t2,"term_hash/4");
    return(FALSE);
  }
  if (!IsIntegerTerm(t2)) {
    Yap_Error(TYPE_ERROR_INTEGER,t2,"term_hash/4");
    return(FALSE);
  }
  depth = IntegerOfTerm(t2);
  if (depth == 0) {
    if (IsVarTerm(t1)) return(TRUE);
    return(Yap_unify(ARG4,MkIntTerm(0)));
  }
  if (IsVarTerm(t3)) {
    Yap_Error(INSTANTIATION_ERROR,t3,"term_hash/4");
    return(FALSE);
  }
  if (!IsIntegerTerm(t3)) {
    Yap_Error(TYPE_ERROR_INTEGER,t3,"term_hash/4");
    return(FALSE);
  }
  size = IntegerOfTerm(t3);
  while (TRUE) {
    CELL *ar = hash_complex_term(&t1-1, &t1, depth, HR, FALSE PASS_REGS);
    if (ar == (CELL *)-1) {
      if (!Yap_ExpandPreAllocCodeSpace(0, NULL, TRUE)) {
	Yap_Error(RESOURCE_ERROR_AUXILIARY_STACK, ARG1, "overflow in term_hash");
	return FALSE;
      }
      t1 = Deref(ARG1);
    } else if(ar == (CELL *)-2) {
      if (!Yap_gcl((ASP-HR)*sizeof(CELL), 4, ENV, gc_P(P,CP))) {
	Yap_Error(RESOURCE_ERROR_STACK, TermNil, "in term_hash");
	return FALSE;
      }
      t1 = Deref(ARG1);
    } else if (ar == NULL) {
      return FALSE;
    } else {
      i1 = MurmurHashNeutral2((const void *)HR, CellSize*(ar-HR),0x1a3be34a);
      break;
    }
  }
  /* got the seed and hash from SWI-Prolog */
  result = MkIntegerTerm(i1 % size);
  return Yap_unify(ARG4,result);
}

static Int
p_instantiated_term_hash( USES_REGS1 )
{
  unsigned int i1;
  Term t1 = Deref(ARG1);
  Term t2 = Deref(ARG2);
  Term t3 = Deref(ARG3);
  Term result;
  Int size, depth;

  if (IsVarTerm(t2)) {
    Yap_Error(INSTANTIATION_ERROR,t2,"term_hash/4");
    return(FALSE);
  }
  if (!IsIntegerTerm(t2)) {
    Yap_Error(TYPE_ERROR_INTEGER,t2,"term_hash/4");
    return(FALSE);
  }
  depth = IntegerOfTerm(t2);
  if (depth == 0) {
    if (IsVarTerm(t1)) return(TRUE);
    return(Yap_unify(ARG4,MkIntTerm(0)));
  }
  if (IsVarTerm(t3)) {
    Yap_Error(INSTANTIATION_ERROR,t3,"term_hash/4");
    return(FALSE);
  }
  if (!IsIntegerTerm(t3)) {
    Yap_Error(TYPE_ERROR_INTEGER,t3,"term_hash/4");
    return(FALSE);
  }
  size = IntegerOfTerm(t3);
  while (TRUE) {
    CELL *ar = hash_complex_term(&t1-1, &t1, depth, HR, TRUE PASS_REGS);
    if (ar == (CELL *)-1) {
      if (!Yap_ExpandPreAllocCodeSpace(0, NULL, TRUE)) {
	Yap_Error(RESOURCE_ERROR_AUXILIARY_STACK, ARG1, "overflow in term_hash");
	return FALSE;
      }
      t1 = Deref(ARG1);
    } else if(ar == (CELL *)-2) {
      if (!Yap_gcl((ASP-HR)*sizeof(CELL), 4, ENV, gc_P(P,CP))) {
	Yap_Error(RESOURCE_ERROR_STACK, TermNil, "in term_hash");
	return FALSE;
      }
      t1 = Deref(ARG1);
    } else if (ar == NULL) {
      return FALSE;
    } else {
      i1 = MurmurHashNeutral2((const void *)HR, CellSize*(ar-HR),0x1a3be34a);
      break;
    }
  }
  /* got the seed and hash from SWI-Prolog */
  result = MkIntegerTerm(i1 % size);
  return Yap_unify(ARG4,result);
}

static int variant_complex(register CELL *pt0, register CELL *pt0_end, register
			   CELL *pt1 USES_REGS)
{
  tr_fr_ptr OLDTR = TR;
  register CELL **to_visit = (CELL **)ASP;
  /* make sure that unification always forces trailing */
  HBREG = HR;


 loop:
  while (pt0 < pt0_end) {
    register CELL d0, d1;
    ++ pt0;
    ++ pt1;
    d0 = Derefa(pt0);
    d1 = Derefa(pt1);
    if (IsVarTerm(d0)) {
      if (IsVarTerm(d1)) {
	CELL *pt0 = VarOfTerm(d0);
	CELL *pt1 = VarOfTerm(d1);
	if (pt0 >= HBREG || pt1 >= HBREG) {
	  /* one of the variables has been found before */
	  if (VarOfTerm(d0)+1 == VarOfTerm(d1)) continue;
	  goto fail;
	} else {
	  /* two new occurrences of the same variable */
	  Term n0 = MkVarTerm(), n1 = MkVarTerm();
	  Bind_Global(VarOfTerm(d0), n0);
	  Bind_Global(VarOfTerm(d1), n1);
	}
	continue;
      } else {
	goto fail;
      }
    } else if (IsVarTerm(d1)) {
      goto fail;
    } else {
      if (d0 == d1) continue;
      else if (IsAtomOrIntTerm(d0)) {
	goto fail;
      } else if (IsPairTerm(d0)) {
	if (!IsPairTerm(d1)) {
	  goto fail;
	}
#ifdef RATIONAL_TREES
	/* now link the two structures so that no one else will */
	/* come here */
	to_visit -= 4;
	if ((CELL *)to_visit < HR+1024)
	  goto out_of_stack;
	to_visit[0] = pt0;
	to_visit[1] = pt0_end;
	to_visit[2] = pt1;
	to_visit[3] = (CELL *)*pt0;
	*pt0 = d1;
#else
	/* store the terms to visit */
	if (pt0 < pt0_end) {
	  to_visit -= 3;
	  if ((CELL *)to_visit < HR+1024)
	    goto out_of_stack;
	  to_visit[0] = pt0;
	  to_visit[1] = pt0_end;
	  to_visit[2] = pt1;
	}
#endif
	pt0 = RepPair(d0) - 1;
	pt0_end = RepPair(d0) + 1;
	pt1 = RepPair(d1) - 1;
	continue;
      } else if (IsApplTerm(d0)) {
	register Functor f;
	register CELL *ap2, *ap3;
	if (!IsApplTerm(d1)) {
	  goto fail;
	} else {
	  /* store the terms to visit */
	  Functor f2;
	  ap2 = RepAppl(d0);
	  ap3 = RepAppl(d1);
	  f = (Functor)(*ap2);
	  f2 = (Functor)(*ap3);
	  if (f != f2)
	    goto fail;
	  if (IsExtensionFunctor(f)) {
	    if (!unify_extension(f, d0, ap2, d1))
	      goto fail;
	    continue;
	  }
#ifdef RATIONAL_TREES
	  /* now link the two structures so that no one else will */
	  /* come here */
	  to_visit -= 4;
	  if ((CELL *)to_visit < HR+1024)
	    goto out_of_stack;
	  to_visit[0] = pt0;
	  to_visit[1] = pt0_end;
	  to_visit[2] = pt1;
	  to_visit[3] = (CELL *)*pt0;
	  *pt0 = d1;
#else
	  /* store the terms to visit */
	  if (pt0 < pt0_end) {
	    to_visit -= 3;
	    if ((CELL *)to_visit < HR+1024)
	      goto out_of_stack;
	    to_visit[0] = pt0;
	    to_visit[1] = pt0_end;
	    to_visit[2] = pt1;
	  }
#endif
	  d0 = ArityOfFunctor(f);
	  pt0 = ap2;
	  pt0_end = ap2 + d0;
	  pt1 = ap3;
	  continue;
	}
      }
    }
  }
  /* 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];
    *pt0 = (CELL)to_visit[3];
    to_visit += 4;
#else
    pt0 = to_visit[0];
    pt0_end = to_visit[1];
    pt1 = to_visit[2];
    to_visit += 3;
#endif
    goto loop;
  }

  HR = HBREG;
  /* untrail all bindings made by variant */
  while (TR != (tr_fr_ptr)OLDTR) {
    CELL *pt1 = (CELL *) TrailTerm(--TR);
    RESET_VARIABLE(pt1);
  }
  HBREG = B->cp_h;
  return TRUE;

 out_of_stack:
  HR = HBREG;
  /* untrail all bindings made by variant */
#ifdef RATIONAL_TREES
  while (to_visit < (CELL **)ASP) {
    pt0 = to_visit[0];
    pt0_end = to_visit[1];
    pt1 = to_visit[2];
    *pt0 = (CELL)to_visit[3];
    to_visit += 4;
  }
#endif
  while (TR != (tr_fr_ptr)OLDTR) {
    CELL *pt1 = (CELL *) TrailTerm(--TR);
    RESET_VARIABLE(pt1);
  }
  HBREG = B->cp_h;
  return -1;


 fail:
  /* failure */
  HR = HBREG;
#ifdef RATIONAL_TREES
  while (to_visit < (CELL **)ASP) {
    pt0 = to_visit[0];
    pt0_end = to_visit[1];
    pt1 = to_visit[2];
    *pt0 = (CELL)to_visit[3];
    to_visit += 4;
  }
#endif
  /* untrail all bindings made by variant */
  while (TR != (tr_fr_ptr)OLDTR) {
    CELL *pt1 = (CELL *) TrailTerm(--TR);
    RESET_VARIABLE(pt1);
  }
  HBREG = B->cp_h;
  return FALSE;
}

static bool
is_variant(Term t1, Term t2, int parity USES_REGS)
{
  int out;

  if (t1 == t2)
    return true;
  if (IsVarTerm(t1)) {
    if (IsVarTerm(t2))
      return true;
    return false;
  } else if (IsVarTerm(t2))
    return false;
  if (IsAtomOrIntTerm(t1)) {
    return(t1 == t2);
  }
  if (IsPairTerm(t1)) {
    if (IsPairTerm(t2)) {
      out = variant_complex(RepPair(t1)-1,
			    RepPair(t1)+1,
			    RepPair(t2)-1 PASS_REGS);
      if (out < 0) goto error;
      return out != 0;
    }
    else return false;
  }
  if (!IsApplTerm(t2)) {
    return false;
  } else {
    Functor f1 = FunctorOfTerm(t1);

    if (f1 != FunctorOfTerm(t2)) return(FALSE);
    if (IsExtensionFunctor(f1)) {
      return(unify_extension(f1, t1, RepAppl(t1), t2));
    }
    out = variant_complex(RepAppl(t1),
			  RepAppl(t1)+ArityOfFunctor(f1),
			  RepAppl(t2) PASS_REGS);
    if (out < 0) goto error;
    return out != 0;
  }
 error:
  if (out == -1) {
    if (!Yap_gcl((ASP-HR)*sizeof(CELL), parity, ENV, gc_P(P,CP))) {
      Yap_Error(RESOURCE_ERROR_STACK, TermNil, "in variant");
      return FALSE;
    }
    return is_variant(t1, t2, parity PASS_REGS);
  }
  return false;
}

bool
Yap_Variant(Term t1, Term t2)
{
  CACHE_REGS
    return is_variant(t1, t2, 0 PASS_REGS);
}

static Int
p_variant( USES_REGS1 ) /* variant terms t1 and t2	 */
{
  return is_variant(Deref(ARG1), Deref(ARG2), 2 PASS_REGS);
}


static int subsumes_complex(register CELL *pt0, register CELL *pt0_end, register
			    CELL *pt1 USES_REGS)
{
  register CELL **to_visit = (CELL **)ASP;
  tr_fr_ptr OLDTR = TR, new_tr;
  UInt write_mode = TRUE;


  HBREG = HR;
 loop:
  while (pt0 < pt0_end) {
    register CELL d0, d1;
    Int our_write_mode = write_mode;

    ++ pt0;
    ++ pt1;
    /* this is a version of Derefa that checks whether we are trying to
       do something evil */
    {
      CELL *npt0 = pt0;

    restart_d0:
      if (npt0 >= HBREG) {
	our_write_mode = FALSE;
      }
      d0 = *npt0;
      if (IsVarTerm(d0) &&
	  d0 != (CELL)npt0
	  ) {
	npt0 = (CELL *)d0;
	goto restart_d0;
      }
    }
    {
      CELL *npt1 = pt1;

    restart_d1:
      d1 = *npt1;
      if (IsVarTerm(d1)
	  && d1 != (CELL)npt1
	  ) {
	/* never dereference through a variable from the left-side */
	if (npt1 >= HBREG) {
	  goto fail;
	} else {
	  npt1 = (CELL *)d1;
	  goto restart_d1;
	}
      }
    }
    if (IsVarTerm(d0)) {
      if (our_write_mode) {
	/* generate a new binding */
	CELL *pt0 = VarOfTerm(d0);
	Term new = MkVarTerm();

	Bind_Global(pt0, new);
	if (d0 != d1) { /* avoid loops */
	  Bind_Global(VarOfTerm(new), d1);
	  if (Yap_rational_tree_loop(VarOfTerm(new)-1,VarOfTerm(new),(CELL **)AuxSp,(CELL **)AuxBase))
	    goto fail;
	}
      } else {
	if (d0 == d1) continue;
	goto fail;
      }
      continue;
    } else if (IsVarTerm(d1)) {
      goto fail;
    } else {
      if (d0 == d1) continue;
      else if (IsAtomOrIntTerm(d0)) {
	goto fail;
      } else if (IsPairTerm(d0)) {
	if (!IsPairTerm(d1)) {
	  goto fail;
	}
#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] = (CELL *)*pt0;
	to_visit[4] = (CELL *)write_mode;
	*pt0 = d1;
#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] = (CELL *)write_mode;
	}
#endif
	write_mode = our_write_mode;
	pt0 = RepPair(d0) - 1;
	pt0_end = RepPair(d0) + 1;
	pt1 = RepPair(d1) - 1;
	continue;
      } else if (IsApplTerm(d0)) {
	register Functor f;
	register CELL *ap2, *ap3;
	if (!IsApplTerm(d1)) {
	  goto fail;
	} else {
	  /* store the terms to visit */
	  Functor f2;
	  ap2 = RepAppl(d0);
	  ap3 = RepAppl(d1);
	  f = (Functor)(*ap2);
	  f2 = (Functor)(*ap3);
	  if (f != f2)
	    goto fail;
	  if (IsExtensionFunctor(f)) {
	    if (!unify_extension(f, d0, ap2, d1))
	      goto fail;
	    continue;
	  }
#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] = (CELL *)*pt0;
	  to_visit[4] = (CELL *)write_mode;
	  *pt0 = d1;
#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] = (CELL *)write_mode;
	  }
#endif
	  write_mode = our_write_mode;
	  d0 = ArityOfFunctor(f);
	  pt0 = ap2;
	  pt0_end = ap2 + d0;
	  pt1 = ap3;
	  continue;
	}
      }
    }
  }
  /* 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];
    *pt0 = (CELL)to_visit[3];
    write_mode = (Int)to_visit[ 4];
    to_visit += 5;
#else
    pt0 = to_visit[0];
    pt0_end = to_visit[1];
    pt1 = to_visit[2];
    write_mode = (UInt)to_visit[3];
    to_visit += 4;
#endif
    goto loop;
  }

  HR = HBREG;
  /* get rid of intermediate variables  */
  new_tr = TR;
  while (TR != OLDTR) {
    /* cell we bound */
    CELL *pt1 = (CELL *) TrailTerm(--TR);
    /* cell we created */
    CELL *npt1 = (CELL *)*pt1;
    /* shorten the chain */
    if (IsVarTerm(*pt1) && IsUnboundVar(pt1)) {
      RESET_VARIABLE(pt1);
    } else {
      *pt1 = *npt1;
    }
  }
  TR = new_tr;
  HBREG = B->cp_h;
  return TRUE;

 fail:
  HR = HBREG;
#ifdef RATIONAL_TREES
  while (to_visit < (CELL **)ASP) {
    pt0 = to_visit[0];
    pt0_end = to_visit[1];
    pt1 = to_visit[2];
    *pt0 = (CELL)to_visit[3];
    to_visit += 5;
  }
#endif
  /* untrail all bindings made by variant */
  while (TR != (tr_fr_ptr)OLDTR) {
    CELL *pt1 = (CELL *) TrailTerm(--TR);
    RESET_VARIABLE(pt1);
  }
  HBREG = B->cp_h;
  return FALSE;
}

static Int
p_subsumes( USES_REGS1 ) /* subsumes terms t1 and t2	 */
{
  Term t1 = Deref(ARG1);
  Term t2 = Deref(ARG2);

  if (t1 == t2)
    return (TRUE);
  if (IsVarTerm(t1)) {
    YapBind(VarOfTerm(t1), t2);
    if (Yap_rational_tree_loop(VarOfTerm(t1)-1,VarOfTerm(t1),(CELL **)AuxSp,(CELL **)AuxBase))
      return FALSE;
    return TRUE;
  } else if (IsVarTerm(t2))
    return(FALSE);
  if (IsAtomOrIntTerm(t1)) {
    return(t1 == t2);
  }
  if (IsPairTerm(t1)) {
    if (IsPairTerm(t2)) {
      return(subsumes_complex(RepPair(t1)-1,
			      RepPair(t1)+1,
			      RepPair(t2)-1 PASS_REGS));
    }
    else return (FALSE);
  } else {
    Functor f1;

    if (!IsApplTerm(t2)) return(FALSE);
    f1 = FunctorOfTerm(t1);
    if (f1 != FunctorOfTerm(t2))
      return(FALSE);
    if (IsExtensionFunctor(f1)) {
      return(unify_extension(f1, t1, RepAppl(t1), t2));
    }
    return(subsumes_complex(RepAppl(t1),
			    RepAppl(t1)+ArityOfFunctor(f1),
			    RepAppl(t2) PASS_REGS));
  }
}


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 = HR;

 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(HR); /* key */
 	HR[1] = d1; /* comparison value */
	HR[2] = (CELL)npt; /* new value */
	HR[3] = (CELL)match; /* end of chain points back to first cell */
	omatch[3] = (CELL)HR;
	HR+=4;
	RESET_VARIABLE(npt);
	npt++;
	continue;
      }
      if (TR > (tr_fr_ptr)LOCAL_TrailTop - 256) {
	goto trail_overflow;
      }
      RESET_VARIABLE(HR);
      HR[1] = d1;
      HR[2] = (CELL)npt;
      HR[3] = d0;
      YapBind(VarOfTerm(d0), (CELL)HR);
      HR+=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)HR;
      } else {
	bindings = HR;
      }
      HR[0] = d0;
      HR[1] = d1;
      HR[2] = AbsPair(HR+4);
      HR[3] = (CELL)NULL;
      tbindings = HR+3;
      HR+=4;
      *npt++ = AbsPair(HR);
#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 = HR;
      HR += 2;
      if (HR > (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)HR;
	} else {
	  bindings = HR;
	}
	HR[0] = d0;
	HR[1] = d1;
	HR[2] = AbsAppl(HR+4);
	HR[3] = (CELL)NULL;
	tbindings = HR+3;
	HR+=4;
	*npt++ = AbsAppl(HR);
#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 = HR;
	*npt++ = (CELL)f;
	HR += d0;
	if (HR > (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 = HR;

    if (t1 == t2)
      return Yap_unify(ARG3,t1);
    if (IsPairTerm(t1) && IsPairTerm(t2)) {
      Term tf = AbsAppl(HR);
      HR += 2;
      HB = HR;
      if ((out = term_subsumer_complex(RepPair(t1)-1,
				       RepPair(t1)+1,
				       RepPair(t2)-1, HR-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(HR);
	  UInt ar = ArityOfFunctor(f1);
	  HR[0] = (CELL)f1;
	  HR += 1+ar;
	  HB = HR;
	  if ((out = term_subsumer_complex(RepAppl(t1),
					   RepAppl(t1)+ArityOfFunctor(f1),
					   RepAppl(t2), HR-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 {
      HR = oldH;
      if (out == -1) {
	if (!Yap_gcl((ASP-HR)*sizeof(CELL), 0, ENV, gc_P(P,CP))) {
	  Yap_Error(RESOURCE_ERROR_STACK, TermNil, "in term_subsumer");
	  return FALSE;
	}
      } else {
	/* Trail overflow */
	if (!Yap_growtrail(0, FALSE)) {
	  Yap_Error(RESOURCE_ERROR_TRAIL, TermNil, "in term_subsumer");
	  return FALSE;
	}
      }
    }
  }
  return FALSE;
}

#ifdef DEBUG
static Int
p_force_trail_expansion( USES_REGS1 )
{
  Int i = IntOfTerm(Deref(ARG1))*1024, j = 0;
  tr_fr_ptr OTR = TR;

  for (j = 0; j < i; j++) {
    TrailTerm(TR) = 0;
    TR++;
  }
  TR = OTR;

  return(TRUE);
}

static Int
camacho_dum( USES_REGS1 )
{
  Term t1, t2;
  int  max = 3;

  /* build output list */

  t1 = TermNil;
  t2 = MkPairTerm(MkIntegerTerm(max), t1);

  return(Yap_unify(t2, ARG1));
}



#endif /* DEBUG */

bool
Yap_IsListTerm(Term t)
{
  Term *tailp;
  Yap_SkipList(&t, &tailp);
  return *tailp == TermNil;
}

static Int
p_is_list( USES_REGS1 )
{
  return Yap_IsListTerm(Deref(ARG1));
}

bool
Yap_IsListOrPartialListTerm(Term t)
{
  Term *tailp, tail;
  Yap_SkipList(&t, &tailp);
  tail = *tailp;
  return tail == TermNil || IsVarTerm(tail);
}

static Int
p_is_list_or_partial_list( USES_REGS1 )
{
  return Yap_IsListOrPartialListTerm(Deref(ARG1));
}

#if 0
static Term
numbervar_singleton(USES_REGS1)
{
  Term ts[1];
  ts[0] = MkIntegerTerm(-1);
  return Yap_MkApplTerm(FunctorDollarVar, 1, ts);
}

static void
renumbervar(Term t, Int id USES_REGS)
{
  Term *ts = RepAppl(t);
  ts[1] = MkIntegerTerm(id);
}
#endif

static int
unnumber_complex_term(CELL *pt0, CELL *pt0_end, CELL *ptf, CELL *HLow, int share USES_REGS)
{

  struct cp_frame *to_visit0, *to_visit = (struct cp_frame *)Yap_PreAllocCodeSpace();
  CELL *HB0 = HB;
  tr_fr_ptr TR0 = TR;
  int ground = share;
  Int max = -1;

  int lvl = push_text_stack();
  HB = HLow;
  to_visit0 = to_visit;
 loop:
  while (pt0 < pt0_end) {
    register CELL d0;
    register CELL *ptd0;
    ++ pt0;
    ptd0 = pt0;
    d0 = *ptd0;
    deref_head(d0, unnumber_term_unk);
  unnumber_term_nvar:
    {
      if (IsPairTerm(d0)) {
	CELL *ap2 = RepPair(d0);
	if (ap2 >= HB && ap2 < HR) {
	  /* If this is newer than the current term, just reuse */
	  *ptf++ = d0;
	  continue;
	}
	*ptf = AbsPair(HR);
	ptf++;
	if (to_visit+1 >= (struct cp_frame *)AuxSp) {
	  goto heap_overflow;
	}
	to_visit->start_cp = pt0;
	to_visit->end_cp = pt0_end;
	to_visit->to = ptf;
	to_visit->oldv = *pt0;
	to_visit->ground = ground;
	/* fool the system into thinking we had a variable there */
	*pt0 = AbsPair(HR);
	to_visit ++;
	ground = share;
	pt0 = ap2 - 1;
	pt0_end = ap2 + 1;
	ptf = HR;
	HR += 2;
	if (HR > ASP - 2048) {
	  goto overflow;
	}
      } else if (IsApplTerm(d0)) {
	register Functor f;
	register CELL *ap2;
	/* store the terms to visit */
	ap2 = RepAppl(d0);
	if (ap2 >= HB && ap2 <= HR) {
	  /* If this is newer than the current term, just reuse */
	  *ptf++ = d0;
	  continue;
	}
	f = (Functor)(*ap2);

	if (IsExtensionFunctor(f)) {
	  *ptf++ = d0;  /* you can just unnumber other extensions. */
	  continue;
	}
	if (f == FunctorDollarVar) {
	  Int id = IntegerOfTerm(ap2[1]);
	  ground = FALSE;
	  if (id < -1) {
	    pop_text_stack(lvl);
	    Yap_Error(RESOURCE_ERROR_STACK, TermNil, "unnumber vars cannot cope with VAR(-%d)", id);
	    return 0L;
	  }
	  if (id <= max) {
	    if (ASP-(max+1) <= HR) {
	      goto overflow;
	    }
	    /* we found this before? */
	    if (ASP[-id-1])
	      *ptf++ = ASP[-id-1];
	    else {
	      RESET_VARIABLE(ptf);
	      ASP[-id-1] = (CELL)ptf;
	      ptf++;
	    }
	    continue;
	  }
	  /* alloc more space */
	  if (ASP-(id+1) <= HR) {
	    goto overflow;
	  }
	  while (id > max) {
	    ASP[-(id+1)] = 0L;
	    max++;
	  }
	  /* new variable */
	  RESET_VARIABLE(ptf);
	  ASP[-(id+1)] = (CELL)ptf;
	  ptf++;
	  continue;
	}
	*ptf = AbsAppl(HR);
	ptf++;
	/* store the terms to visit */
	if (to_visit+1 >= (struct cp_frame *)AuxSp) {
	  goto heap_overflow;
	}
	to_visit->start_cp = pt0;
	to_visit->end_cp = pt0_end;
	to_visit->to = ptf;
	to_visit->oldv = *pt0;
	to_visit->ground = ground;
	/* fool the system into thinking we had a variable there */
	*pt0 = AbsAppl(HR);
	to_visit ++;
	ground = (f != FunctorMutable) && share;
	d0 = ArityOfFunctor(f);
	pt0 = ap2;
	pt0_end = ap2 + d0;
	/* store the functor for the new term */
	HR[0] = (CELL)f;
	ptf = HR+1;
	HR += 1+d0;
	if (HR > ASP - 2048) {
	  goto overflow;
	}
      } else {
	/* just unnumber atoms or integers */
	*ptf++ = d0;
      }
      continue;
    }

    derefa_body(d0, ptd0, unnumber_term_unk, unnumber_term_nvar);
    /* this should never happen ? */
    ground = FALSE;
    *ptf++ = (CELL) ptd0;
  }
  /* Do we still have compound terms to visit */
  if (to_visit > to_visit0) {
    to_visit --;
    if (ground) {
      CELL old = to_visit->oldv;
      CELL *newp = to_visit->to-1;
      CELL new = *newp;

      *newp = old;
      if (IsApplTerm(new))
	HR = RepAppl(new);
      else
	HR = RepPair(new);
    }
    pt0 = to_visit->start_cp;
    pt0_end = to_visit->end_cp;
    ptf = to_visit->to;
#ifdef RATIONAL_TREES
    *pt0 = to_visit->oldv;
#endif
    ground = (ground && to_visit->ground);
    goto loop;
  }

  /* restore our nice, friendly, term to its original state */
  clean_dirty_tr(TR0 PASS_REGS);
  HB = HB0;
  pop_text_stack(lvl);
  return ground;

 overflow:
  /* oops, we're in trouble */
  HR = HLow;
  /* we've done it */
  /* restore our nice, friendly, term to its original state */
  HB = HB0;
  while (to_visit > to_visit0) {
    to_visit --;
    pt0 = to_visit->start_cp;
    pt0_end = to_visit->end_cp;
    ptf = to_visit->to;
    *pt0 = to_visit->oldv;
  }
  reset_trail(TR0);
  /* follow chain of multi-assigned variables */
  pop_text_stack(lvl);
  return -1;

 heap_overflow:
  /* oops, we're in trouble */
  HR = HLow;
  /* we've done it */
  /* restore our nice, friendly, term to its original state */
  HB = HB0;
  while (to_visit > to_visit0) {
    to_visit --;
    pt0 = to_visit->start_cp;
    pt0_end = to_visit->end_cp;
    ptf = to_visit->to;
    *pt0 = to_visit->oldv;
  }
  reset_trail(TR0);
  LOCAL_Error_Size = (ADDR)AuxSp-(ADDR)to_visit0;
  pop_text_stack(lvl);
  return -3;
}


static Term
UnnumberTerm(Term inp, UInt arity, int share USES_REGS) {
  Term t = Deref(inp);
  tr_fr_ptr TR0 = TR;

  if (IsVarTerm(t)) {
    return inp;
  } else if (IsPrimitiveTerm(t)) {
    return t;
  } else if (IsPairTerm(t)) {
    Term tf;
    CELL *ap;
    CELL *Hi;

  restart_list:
    ap = RepPair(t);
    Hi = HR;
    tf = AbsPair(HR);
    HR += 2;
    {
      int res;
      if ((res = unnumber_complex_term(ap-1, ap+1, Hi, Hi, share PASS_REGS)) < 0) {
	HR = Hi;
	if ((t = handle_cp_overflow(res, TR0, arity, t))== 0L)
	  return FALSE;
	goto restart_list;
      } else if (res) {
	HR = Hi;
	return t;
      }
    }
    return tf;
  } else {
    Functor f = FunctorOfTerm(t);
    Term tf;
    CELL *HB0;
    CELL *ap;

  restart_appl:
    f = FunctorOfTerm(t);
    HB0 = HR;
    ap = RepAppl(t);
    tf = AbsAppl(HR);
    HR[0] = (CELL)f;
    HR += 1+ArityOfFunctor(f);
    if (HR > ASP-128) {
      HR = HB0;
      if ((t = handle_cp_overflow(-1, TR0, arity, t))== 0L)
	return FALSE;
      goto restart_appl;
    } else {
      int res;

      if ((res = unnumber_complex_term(ap, ap+ArityOfFunctor(f), HB0+1, HB0, share PASS_REGS)) < 0) {
	HR = HB0;
	if ((t = handle_cp_overflow(res, TR0, arity, t))== 0L)
	  return FALSE;
	goto restart_appl;
      } else if (res && FunctorOfTerm(t) != FunctorMutable) {
	HR = HB0;
	return t;
      }
    }
    return tf;
  }
}

Term
Yap_UnNumberTerm(Term inp, int share) {
  CACHE_REGS
    return UnnumberTerm(inp, 0, share PASS_REGS);
}

static Int
p_unnumbervars( USES_REGS1 ) {
  /* this should be a standard Prolog term, so we allow sharing? */
  return Yap_unify(UnnumberTerm(ARG1, 2, FALSE PASS_REGS), ARG2);
}

Int
Yap_SkipList(Term *l, Term **tailp)
{
  Int length = 0;
  Term *s; /* slow */
  Term v; /* temporary */

  do_derefa(v,l,derefa_unk,derefa_nonvar);
  s = l;

  if ( IsPairTerm(*l) )
    { intptr_t power = 1, lam = 0;
      do
	{ if ( power == lam )
	    { s = l;
	      power *= 2;
	      lam = 0;
	    }
	  lam++;
	  length++;
	  l = RepPair(*l)+1;
	  do_derefa(v,l,derefa2_unk,derefa2_nonvar);
	} while ( *l != *s && IsPairTerm(*l) );
    }
  *tailp = l;

  return length;
}


static Int
p_skip_list( USES_REGS1 ) {
  Term *tail;
  Int len = Yap_SkipList(XREGS+2, &tail);

  return Yap_unify(MkIntegerTerm(len), ARG1) &&
    Yap_unify(*tail, ARG3);
}

static Int
p_skip_list4( USES_REGS1 ) {
  Term *tail;
  Int len, len1 = -1;
  Term t2 = Deref(ARG2), t;

  if (!IsVarTerm(t2)) {
    if (!IsIntegerTerm(t2)) {
      Yap_Error(TYPE_ERROR_INTEGER, t2, "length/2");
      return FALSE;
    }
    if ((len1 = IntegerOfTerm(t2)) < 0) {
      Yap_Error(DOMAIN_ERROR_NOT_LESS_THAN_ZERO, t2, "length/2");
      return FALSE;
    }
  }
  /* we need len here */
  len = Yap_SkipList(XREGS+1, &tail);
  t = *tail;
  /* don't set M0 if full list, just check M */
  if (t == TermNil) {
    if (len1 >= 0) { /* ARG2 was bound */
      return
	len1 == len &&
	Yap_unify(t, ARG4);
    } else {
      return Yap_unify_constant(ARG4, TermNil) &&
	Yap_unify_constant(ARG2, MkIntegerTerm(len));
    }
  }
  return Yap_unify(MkIntegerTerm(len), ARG3) &&
    Yap_unify(t, ARG4);
}

static Int
p_free_arguments( USES_REGS1 )
{
  Term t = Deref(ARG1);
  if (IsVarTerm(t))
    return FALSE;
  if (IsAtomTerm(t) || IsIntTerm(t))
    return TRUE;
  if (IsPairTerm(t)) {
    Term th = HeadOfTerm(t);
    Term tl = TailOfTerm(t);
    return IsVarTerm(th) && IsVarTerm(tl) && th != tl;
  } else {
    Functor f = FunctorOfTerm(t);
    UInt i, ar;
    Int ret = TRUE;

    if (IsExtensionFunctor(f))
      return TRUE;
    ar = ArityOfFunctor(f);
    for (i = 1 ; i <= ar; i++) {
      Term ta = ArgOfTerm(i, t);
      Int j;

      ret = IsVarTerm(ta);
      if (!ret) break;
      /* stupid quadractic algorithm, but needs no testing for overflows */
      for (j = 1 ; j < i; j++) {
	ret = ArgOfTerm(j, t) != ta;
	if (!ret) break;
      }
      if (!ret) break;
    }
    return ret;
  }
}

static Int
p_freshen_variables( USES_REGS1 )
{
  Term t = Deref(ARG1);
  Functor f = FunctorOfTerm(t);
  UInt arity = ArityOfFunctor(f), i;
  Term tn = Yap_MkNewApplTerm(f, arity);
  CELL *src = RepAppl(t)+1;
  CELL *targ = RepAppl(tn)+1;
  for (i=0; i< arity; i++) {
    RESET_VARIABLE(targ);
    *VarOfTerm(*src) = (CELL)targ;
    targ++;
    src++;
  }
  return TRUE;
}

static Int
p_reset_variables( USES_REGS1 )
{
  Term t = Deref(ARG1);
  Functor f = FunctorOfTerm(t);
  UInt arity = ArityOfFunctor(f), i;
  CELL *src = RepAppl(t)+1;

  for (i=0; i< arity; i++) {
    RESET_VARIABLE(VarOfTerm(*src));
    src++;
  }
  return TRUE;
}

void Yap_InitUtilCPreds(void)
{
  CACHE_REGS
    Term cm = CurrentModule;
  Yap_InitCPred("copy_term", 2, p_copy_term, 0);
  /** @pred  copy_term(? _TI_,- _TF_) is iso


      Term  _TF_ is a variant of the original term  _TI_, such that for
      each variable  _V_ in the term  _TI_ there is a new variable  _V'_
      in term  _TF_. Notice that:

      + suspended goals and attributes for attributed variables in _TI_ are also duplicated;
      + ground terms are shared between the new and the old term.

      If you do not want any sharing to occur please use
      duplicate_term/2.


  */
  Yap_InitCPred("duplicate_term", 2, p_duplicate_term, 0);
  /** @pred  duplicate_term(? _TI_,- _TF_)


      Term  _TF_ is a variant of the original term  _TI_, such that
      for each variable  _V_ in the term  _TI_ there is a new variable
      _V'_ in term  _TF_, and the two terms do not share any
      structure. All suspended goals and attributes for attributed variables
      in  _TI_ are also duplicated.

      Also refer to copy_term/2.


  */
  Yap_InitCPred("copy_term_nat", 2, p_copy_term_no_delays, 0);
  /** @pred copy_term_nat(? _TI_,- _TF_)


      As copy_term/2.  Attributes however, are <em>not</em> copied but replaced
      by fresh variables.




  */
  Yap_InitCPred("is_list", 1, p_is_list, SafePredFlag|TestPredFlag);
  Yap_InitCPred("$is_list_or_partial_list", 1, p_is_list_or_partial_list, SafePredFlag|TestPredFlag);
  /** @pred  term_factorized(? _TI_,- _TF_, ?SubTerms)


      Similar to rational_term_to_tree/4, but _SubTerms_ is a proper list.


  */
  Yap_InitCPred("=@=", 2, p_variant, 0);
  Yap_InitCPred("unnumbervars", 2, p_unnumbervars, 0);
  /** @pred  unnumbervars( _T_,+ _NT_)


      Replace every `$VAR( _I_)` by a free variable.


  */
  /* use this carefully */
  Yap_InitCPred("$skip_list", 3, p_skip_list, SafePredFlag|TestPredFlag);
  Yap_InitCPred("$skip_list", 4, p_skip_list4, SafePredFlag|TestPredFlag);
  Yap_InitCPred("$free_arguments", 1, p_free_arguments, TestPredFlag);
  CurrentModule = TERMS_MODULE;
  Yap_InitCPred("term_hash", 4, p_term_hash, 0);
  Yap_InitCPred("instantiated_term_hash", 4, p_instantiated_term_hash, 0);
  Yap_InitCPred("variant", 2, p_variant, 0);
  Yap_InitCPred("subsumes", 2, p_subsumes, 0);
  Yap_InitCPred("term_subsumer", 3, p_term_subsumer, 0);
  Yap_InitCPred("export_term", 3, p_export_term, 0);
  Yap_InitCPred("kill_exported_term", 1, p_kill_exported_term, SafePredFlag);
  Yap_InitCPred("import_term", 2, p_import_term, 0);
  Yap_InitCPred("freshen_variables", 1, p_freshen_variables, 0);
  Yap_InitCPred("reset_variables", 1, p_reset_variables, 0);
  CurrentModule = cm;
#ifdef DEBUG
  Yap_InitCPred("$force_trail_expansion", 1, p_force_trail_expansion, SafePredFlag);
  Yap_InitCPred("dum", 1, camacho_dum, SafePredFlag);
#endif
}