yap-6.3/C/atomic.c

/*************************************************************************
*									 *
*	 YAP Prolog 							 *
*									 *
*	Yap Prolog was developed at NCCUP - Universidade do Porto	 *
*									 *
* Copyright L.Damas, V. Santos Costa and Universidade do Porto 1985--	 *
*									 *
**************************************************************************
*									 *
* File:		atoms.c							 *
* comments:	General-purpose C implemented system predicates		 *
*									 *
* Last rev:     $Date: 2008-07-24 16:02:00 $,$Author: vsc $	     	 *
*									 *
*************************************************************************/
#ifdef SCCS
static char     SccsId[] = "%W% %G%";
#endif

/** @addgroup Predicates_on_Atoms Predicates on Atoms and Strings
    @ingroup YAPChars
@{

The following predicates are used to manipulate atoms:

\toc
 
*/


#define HAS_CACHE_REGS 1
/*
 * This file includes the definition of a miscellania of standard operations
 * for yap refering to sequences of characters conversions.
 *
 */

#include "Yap.h"
#include "Yatom.h"
#include "YapHeap.h"
#include "eval.h"
#include "yapio.h"
#include "YapText.h"
#ifdef TABLING
#include "tab.macros.h"
#endif /* TABLING */
#include <stdio.h>
#if HAVE_STRING_H
#include <string.h>
#endif
#if HAVE_MALLOC_H
#include <malloc.h>
#endif
#include <wchar.h>

static Int name( USES_REGS1 );
static Int atom_chars( USES_REGS1 );
static Int atom_codes( USES_REGS1 );
static Int atom_length( USES_REGS1 );
static Int string_length( USES_REGS1 );
static Int atom_split( USES_REGS1 );
static Int number_chars( USES_REGS1 );
static Int number_codes( USES_REGS1 );
static Int current_atom( USES_REGS1 );
static Int cont_current_atom( USES_REGS1 );
static int AlreadyHidden(unsigned char *);
static Int hide( USES_REGS1 );
static Int hidden( USES_REGS1 );
static Int unhide( USES_REGS1 );



static int 
AlreadyHidden(unsigned char *name)
{
  AtomEntry      *chain;

  READ_LOCK(INVISIBLECHAIN.AERWLock);
  chain = RepAtom(INVISIBLECHAIN.Entry);
  READ_UNLOCK(INVISIBLECHAIN.AERWLock);
  while (!EndOfPAEntr(chain) && strcmp((char *)chain->StrOfAE, (char *)name) != 0)
    chain = RepAtom(chain->NextOfAE);
  if (EndOfPAEntr(chain))
    return (FALSE);
  return (TRUE);
}

/** @pred hide(+ _Atom_)
    Make atom  _Atom_ invisible.

    Notice that defining a new atom with the same characters will
    result in a different atom.xs

 **/
static Int 
hide( USES_REGS1 )
{				/* hide(+Atom)		 */
  Atom            atomToInclude;
  Term t1 = Deref(ARG1);

  if (IsVarTerm(t1)) {
    Yap_Error(INSTANTIATION_ERROR,t1,"hide/1");
    return(FALSE);
  }
  if (!IsAtomTerm(t1)) {
    Yap_Error(TYPE_ERROR_ATOM,t1,"hide/1");
    return(FALSE);
  }
  atomToInclude = AtomOfTerm(t1);
  if (AlreadyHidden(RepAtom(atomToInclude)->UStrOfAE)) {
    Yap_Error(SYSTEM_ERROR_INTERNAL,t1,"an atom of name %s was already hidden",
	  RepAtom(atomToInclude)->StrOfAE);
    return(FALSE);
  }
  Yap_ReleaseAtom(atomToInclude);
  WRITE_LOCK(INVISIBLECHAIN.AERWLock);
  WRITE_LOCK(RepAtom(atomToInclude)->ARWLock);
  RepAtom(atomToInclude)->NextOfAE = INVISIBLECHAIN.Entry;
  WRITE_UNLOCK(RepAtom(atomToInclude)->ARWLock);
  INVISIBLECHAIN.Entry = atomToInclude;
  WRITE_UNLOCK(INVISIBLECHAIN.AERWLock);
  return (TRUE);
}

/** @pred hidden( +Atom ) 
    Is the  atom _Ãtom_ visible to Prolog?

 **/
static Int 
hidden( USES_REGS1 )
{				/* '$hidden'(+F)		 */
  Atom            at;
  AtomEntry      *chain;
  Term t1 = Deref(ARG1);

  if (IsVarTerm(t1))
    return (FALSE);
  if (IsAtomTerm(t1))
    at = AtomOfTerm(t1);
  else if (IsApplTerm(t1))
    at = NameOfFunctor(FunctorOfTerm(t1));
  else
    return (FALSE);
  READ_LOCK(INVISIBLECHAIN.AERWLock);
  chain = RepAtom(INVISIBLECHAIN.Entry);
  while (!EndOfPAEntr(chain) && AbsAtom(chain) != at)
    chain = RepAtom(chain->NextOfAE);
  READ_UNLOCK(INVISIBLECHAIN.AERWLock);
  if (EndOfPAEntr(chain))
    return (FALSE);
  return (TRUE);
}


/** @pred unhide(+ _Atom_) 
    Make hidden atom  _Atom_ visible
    
    Note that the operation fails if another atom with name _Atom_ was defined since.

 **/
static Int 
unhide( USES_REGS1 )
{				/* unhide(+Atom)		 */
  AtomEntry      *atom, *old, *chain;
  Term t1 = Deref(ARG1);

  if (IsVarTerm(t1)) {
    Yap_Error(INSTANTIATION_ERROR,t1,"unhide/1");
    return(FALSE);
  }
  if (!IsAtomTerm(t1)) {
    Yap_Error(TYPE_ERROR_ATOM,t1,"unhide/1");
    return(FALSE);
  }
  atom = RepAtom(AtomOfTerm(t1));
  WRITE_LOCK(atom->ARWLock);
  if (atom->PropsOfAE != NIL) {
    Yap_Error(SYSTEM_ERROR_INTERNAL,t1,"cannot unhide an atom in use");
    return(FALSE);
  }
  WRITE_LOCK(INVISIBLECHAIN.AERWLock);
  chain = RepAtom(INVISIBLECHAIN.Entry);
  old = NIL;
  while (!EndOfPAEntr(chain) && strcmp((char *)chain->StrOfAE, (char *)atom->StrOfAE) != 0) {
    old = chain;
    chain = RepAtom(chain->NextOfAE);
  }
  if (EndOfPAEntr(chain))
    return (FALSE);
  atom->PropsOfAE = chain->PropsOfAE;
  if (old == NIL)
    INVISIBLECHAIN.Entry = chain->NextOfAE;
  else
    old->NextOfAE = chain->NextOfAE;
  WRITE_UNLOCK(INVISIBLECHAIN.AERWLock);
  WRITE_UNLOCK(atom->ARWLock);
  return (TRUE);
}

static Int 
char_code( USES_REGS1 )
{
  Int t0 = Deref(ARG1);
  if (IsVarTerm(t0)) {
    Term t1 = Deref(ARG2);
    if (IsVarTerm(t1)) {
      Yap_Error(INSTANTIATION_ERROR,t0,"char_code/2");
      return(FALSE);
    } else if (!IsIntegerTerm(t1)) {
      if (!IsBigIntTerm(t1)) {
	Yap_Error(REPRESENTATION_ERROR_INT,t1,"char_code/2");
	return(FALSE);
      }
      Yap_Error(TYPE_ERROR_INTEGER,t1,"char_code/2");
      return(FALSE);
    } else {
      Int code = IntegerOfTerm(t1);
      Term tout;

      if (code < 0) {
	Yap_Error(REPRESENTATION_ERROR_CHARACTER_CODE,t1,"char_code/2");
	return(FALSE);
      }
      if (code > MAX_ISO_LATIN1) {
	wchar_t wcodes[2];

	if (code > CHARCODE_MAX) {
	  Yap_Error(REPRESENTATION_ERROR_INT,t1,"char_code/2");
	  return(FALSE);
	}
	wcodes[0] = code;
	wcodes[1] = '\0';
	tout = MkAtomTerm(Yap_LookupWideAtom(wcodes));
      } else {
	char codes[2];

	codes[0] = code;
	codes[1] = '\0';
	tout = MkAtomTerm(Yap_LookupAtom(codes));
      }
      return Yap_unify(ARG1,tout);
    }
  } else if (!IsAtomTerm(t0)) {
    Yap_Error(TYPE_ERROR_CHARACTER,t0,"char_code/2");
    return(FALSE);
  } else {
    Atom at = AtomOfTerm(t0);
    Term tf;

    if (IsWideAtom(at)) {
      wchar_t *c = RepAtom(at)->WStrOfAE;
      
      if (c[1] != '\0') {
	Yap_Error(TYPE_ERROR_CHARACTER,t0,"char_code/2");
	return FALSE;
      }
      tf = MkIntegerTerm(c[0]);
    } else {
      unsigned char *c = RepAtom(at)->UStrOfAE;
      
      if (c[1] != '\0') {
	Yap_Error(TYPE_ERROR_CHARACTER,t0,"char_code/2");
	return FALSE;
      }
      tf = MkIntTerm((unsigned char)(c[0]));
    }
    return Yap_unify(ARG2,tf);
  }
}

static Int 
name( USES_REGS1 )
{				/* name(?Atomic,?String)		 */
  Term            t = Deref(ARG2), NewT, AtomNameT = Deref(ARG1);
  LOCAL_MAX_SIZE = 1024;

 restart_aux:
  if (Yap_IsGroundTerm(AtomNameT)) {
    if (!IsVarTerm(t) && !IsPairTerm(t) && t != TermNil) {
      Yap_Error(TYPE_ERROR_LIST,ARG2,
		"name/2");
      return FALSE;
    }
    // verify if an atom, int, float or bi§gnnum
    NewT = Yap_AtomicToListOfCodes( AtomNameT PASS_REGS );
    if (NewT)
      return Yap_unify(NewT, ARG2);
    // else
  } else if (IsVarTerm(t)){
    Yap_Error(INSTANTIATION_ERROR,t,
              "name/2");
    return FALSE;
  } else {
    Term at = Yap_ListToAtomic( t PASS_REGS );
    if (at) return Yap_unify(at, ARG1);
  }
  if (LOCAL_Error_TYPE && Yap_HandleError( "atom/2" )) {
    AtomNameT = Deref(ARG1);
    t = Deref(ARG2);
    goto restart_aux;
  }
  return FALSE;
}

static Int 
string_to_atomic( USES_REGS1 )
{				/* string_to_atom(?String,?Atom)		 */
  Term            t2 = Deref(ARG2), t1 = Deref(ARG1);
  LOCAL_MAX_SIZE = 1024;

 restart_aux:
  if (Yap_IsGroundTerm(t1)) {
    Term t;
    // verify if an atom, int, float or bignnum
    t = Yap_StringToAtomic( t1 PASS_REGS );
    if (t != 0L)
      return Yap_unify(t, t2);
    // else
  } else {
    Term t0 = Yap_AtomicToString( t2 PASS_REGS );
    if (t0) return Yap_unify(t0, t1);
  }
  if (LOCAL_Error_TYPE && Yap_HandleError( "string_to_atomic/2" )) {
    t1 = Deref(ARG1);
    t2 = Deref(ARG2);
    goto restart_aux;
  }
  return FALSE;
}

static Int 
string_to_atom( USES_REGS1 )
{				/* string_to_atom(?String,?Atom)		 */
  Term            t2 = Deref(ARG2), t1 = Deref(ARG1);
  LOCAL_MAX_SIZE = 1024;

 restart_aux:
  if (Yap_IsGroundTerm(t1)) {
    Atom at;
    // verify if an atom, int, float or bignnum
    at = Yap_StringSWIToAtom( t1 PASS_REGS );
    if (at)
      return Yap_unify(MkAtomTerm(at), t2);
    // else
  } else {
    Term t0 = Yap_AtomSWIToString( t2 PASS_REGS );
    if (t0) return Yap_unify(t0, t1);
  }
  if (LOCAL_Error_TYPE && Yap_HandleError( "string_to_atom/2" )) {
    t1 = Deref(ARG1);
    t2 = Deref(ARG2);
    goto restart_aux;
  }
  return FALSE;
}

static Int 
string_to_list( USES_REGS1 )
{				
  Term            list = Deref(ARG2), string = Deref(ARG1);
  LOCAL_MAX_SIZE = 1024;

 restart_aux:
  if (Yap_IsGroundTerm(list)) {
    Term t1 = Yap_ListToString( list PASS_REGS);
    if (t1)
      return Yap_unify( ARG1, t1 );
  } else {
    Term tf = Yap_StringToListOfCodes(string PASS_REGS);
    return Yap_unify( ARG2, tf );
  }
  if (LOCAL_Error_TYPE && Yap_HandleError( "string_to_list/2" )) {
    string = Deref(ARG1);
    list = Deref(ARG2);
    goto restart_aux;
  }
  return FALSE;
}

static Int 
atom_string( USES_REGS1 )
{
  Term            t1 = Deref(ARG1), t2 = Deref(ARG2);
  LOCAL_MAX_SIZE = 1024;

 restart_aux:
  if (Yap_IsGroundTerm(t2)) {
    Atom at;
    // verify if an atom, int, float or bignnum
    at = Yap_StringSWIToAtom( t2 PASS_REGS );
    if (at)
      return Yap_unify(MkAtomTerm(at), t1);
    // else
  } else {
    Term t0 = Yap_AtomSWIToString( t1 PASS_REGS );
    if (t0) return Yap_unify(t0, t2);
  }
  if (LOCAL_Error_TYPE && Yap_HandleError( "atom_string/2" )) {
    t1 = Deref(ARG1);
    t2 = Deref(ARG2);
    goto restart_aux;
  }
  return FALSE;
}

static Int 
atom_chars( USES_REGS1 )
{
  Term t1;
  LOCAL_MAX_SIZE = 1024;

 restart_aux:
  t1  = Deref(ARG1);
  if (Yap_IsGroundTerm(t1)) {
    Term tf = Yap_AtomSWIToListOfAtoms(t1 PASS_REGS);
    if (tf)
      return Yap_unify( ARG2, tf );
  } else {
    /* ARG1 unbound */
    Term   t = Deref(ARG2);
    Atom af = Yap_ListOfAtomsToAtom(t PASS_REGS);
    if (af)
      return Yap_unify( ARG1, MkAtomTerm(af) );
  /* error handling */
  }
  if (LOCAL_Error_TYPE && Yap_HandleError( "atom_chars/2" )) {
    goto restart_aux;
  }
  return false;
}

static Int 
atom_codes( USES_REGS1 )
{
  Term t1;
 restart_aux:
  t1  = Deref(ARG1);
  if (Yap_IsGroundTerm(t1)) {
    Term tf = Yap_AtomicToListOfCodes(t1 PASS_REGS);
    if (tf)
      return Yap_unify( ARG2, tf );
  } else {
    /* ARG1 unbound */
    Term   t = Deref(ARG2);
    Atom af = Yap_ListToAtom(t PASS_REGS);
    if (af)
      return Yap_unify( ARG1, MkAtomTerm(af) );
  }
  /* error handling */
  if (LOCAL_Error_TYPE && Yap_HandleError( "atom_codes/2" )) {
    t1 = Deref(ARG1);
    goto restart_aux;
  }
  return FALSE;
}

static Int 
string_codes( USES_REGS1 )
{
  Term t1;
 restart_aux:
  t1  = Deref(ARG1);
  if (Yap_IsGroundTerm(t1)) {
    Term tf = Yap_StringSWIToListOfCodes(t1 PASS_REGS);
    if (tf)
      return Yap_unify( ARG2, tf );
  } else {
    /* ARG1 unbound */
    Term   t = Deref(ARG2);
    Term tf = Yap_ListSWIToString(t PASS_REGS);
    if (tf)
      return Yap_unify( ARG1, tf );
  }
  /* error handling */
  if (LOCAL_Error_TYPE && Yap_HandleError( "atom_codes/2" )) {
    t1 = Deref(ARG1);
    goto restart_aux;
  }
  return FALSE;
}

static Int 
string_chars( USES_REGS1 )
{
  Term t1;
 restart_aux:
  t1  = Deref(ARG1);
  if (Yap_IsGroundTerm(t1)) {
    Term tf = Yap_StringSWIToListOfAtoms(t1 PASS_REGS);
    if (tf)
      return Yap_unify( ARG2, tf );
  } else {
    /* ARG1 unbound */
    Term   t = Deref(ARG2);
    Term tf = Yap_ListSWIToString(t PASS_REGS);
    if (tf)
      return Yap_unify( ARG1, tf );
  }
  /* error handling */
  if (LOCAL_Error_TYPE && Yap_HandleError( "string_chars/2" )) {
    t1 = Deref(ARG1);
    goto restart_aux;
  }
  return FALSE;
}

/** @pred  number_chars(? _I_,? _L_) is iso 

The predicate holds when at least one of the arguments is ground
(otherwise, an error message will be displayed). The argument  _I_ must
be unifiable with a number, and the argument  _L_ with the list of the
characters of the external representation of  _I_.
 
*/
static Int 
number_chars( USES_REGS1 )
{
  Term t1;
 restart_aux:
  t1  = Deref(ARG1);
  if (Yap_IsGroundTerm(t1)) {
    Term tf;
    tf = Yap_NumberToListOfAtoms(t1 PASS_REGS);
    if (tf) {
      LOCAL_Error_TYPE = YAP_NO_ERROR;
      return Yap_unify( ARG2, tf );
    }
  } else {
    /* ARG1 unbound */
    Term   t = Deref(ARG2);
    Term tf = Yap_ListToNumber(t PASS_REGS);
    if (tf) {
      LOCAL_Error_TYPE = YAP_NO_ERROR;
      return Yap_unify( ARG1, tf );
    }
  }
  /* error handling */
  if (LOCAL_Error_TYPE && Yap_HandleError( "number_chars/2" )) {
    goto restart_aux;
  }
  return FALSE;
}

static Int 
number_atom( USES_REGS1 )
{
  Term t1;
 restart_aux:
  t1  = Deref(ARG1);
  if (Yap_IsGroundTerm(t1)) {
    Atom af;
    af = Yap_NumberToAtom(t1 PASS_REGS);
    if (af)
      return Yap_unify( ARG2, MkAtomTerm(af) );
  } else {
    /* ARG1 unbound */
    Term   t = Deref(ARG2);
    Term tf = Yap_AtomToNumber(t PASS_REGS);
    if (tf)
      return Yap_unify( ARG1, tf );
  }
  /* error handling */
  if (LOCAL_Error_TYPE && Yap_HandleError( "number_atom/2")) {
    goto restart_aux;
  }
  return FALSE;
}

static Int 
number_string( USES_REGS1 )
{
  Term t1;
 restart_aux:
  t1  = Deref(ARG1);
  if (Yap_IsGroundTerm(t1)) {
    Term tf;
    tf = Yap_NumberToString(t1 PASS_REGS);
    if (tf)
      return Yap_unify( ARG2, tf );
  } else {
    /* ARG1 unbound */
    Term   t = Deref(ARG2);
    Term tf = Yap_StringToNumber(t PASS_REGS);
    if (tf)
      return Yap_unify( ARG1, tf );
  }
  /* error handling */
  if (LOCAL_Error_TYPE && Yap_HandleError( "number_string/2")) {
    goto restart_aux;
  }
  return FALSE;
}

static Int 
number_codes( USES_REGS1 )
{
  Term t1;
 restart_aux:
  t1  = Deref(ARG1);
  if (Yap_IsGroundTerm(t1)) {
    Term tf;
    tf = Yap_NumberToListOfCodes(t1 PASS_REGS);
    if (tf)
      return Yap_unify( ARG2, tf );
  } else {
    /* ARG1 unbound */
    Term   t = Deref(ARG2);
    Term tf = Yap_ListToNumber(t PASS_REGS);
    if (tf)
      return Yap_unify( ARG1, tf );
  }
  /* error handling */
  if (LOCAL_Error_TYPE && Yap_HandleError( "number_codes/2" )) {
    goto restart_aux;
  }
  return FALSE;
}

static Int 
cont_atom_concat3( USES_REGS1 )
{
  Term t3;
  Atom ats[2];
  Int i, max;
 restart_aux:
  t3 = Deref(ARG3);
  i = IntOfTerm(EXTRA_CBACK_ARG(3,1));
  max = IntOfTerm(EXTRA_CBACK_ARG(3,2));
  EXTRA_CBACK_ARG(3,1) = MkIntTerm(i+1);
  if ( ! Yap_SpliceAtom( t3, ats, i, max PASS_REGS ) ) {
    cut_fail();
  } else {
    if (i < max) return Yap_unify( ARG1, MkAtomTerm(ats[0])) &&
		   Yap_unify( ARG2, MkAtomTerm(ats[1])) ;
    if (Yap_unify( ARG1, MkAtomTerm(ats[0])) &&
	Yap_unify( ARG2, MkAtomTerm(ats[1]))) cut_succeed();
    cut_fail();
  }
  /* Error handling */
  if (LOCAL_Error_TYPE) {
    if (Yap_HandleError( "atom_concat/3" )) {
      goto restart_aux;
    } else {
      return FALSE;
    }
  }
  cut_fail();
}


static Int 
atom_concat3( USES_REGS1 )
{
  Term t1;
  Term t2, t3, ot;
  Atom at;
 restart_aux:
  t1 = Deref(ARG1);
  t2 = Deref(ARG2);
  t3 = Deref(ARG3);
  if (Yap_IsGroundTerm(t1) && Yap_IsGroundTerm(t2)) {
    at = Yap_ConcatAtoms( t1, t2 PASS_REGS );
    ot = ARG3;
  } else if (Yap_IsGroundTerm(t1) && Yap_IsGroundTerm(t3) ) {
    at = Yap_SubtractHeadAtom( Deref(ARG3), t1 PASS_REGS );
    ot = ARG2;
  } else if (Yap_IsGroundTerm(t2) && Yap_IsGroundTerm(t3)) {
    at = Yap_SubtractTailAtom( Deref(ARG3), t2 PASS_REGS );
    ot = ARG1;
  } else if (Yap_IsGroundTerm(t3)) {
    EXTRA_CBACK_ARG(3,1) = MkIntTerm(0);
    EXTRA_CBACK_ARG(3,2) = MkIntTerm(Yap_AtomToLength(t3 PASS_REGS));
    return cont_atom_concat3( PASS_REGS1 );
  } else {
    LOCAL_Error_TYPE = INSTANTIATION_ERROR;
    LOCAL_Error_Term = t1;
    Yap_Error( INSTANTIATION_ERROR, IsVarTerm(t1) ? t1 : t2, "got atom_concat(X,atom,Z) or atom_concat(,atom,Y,Z)" );
    return false;
  }
  if (at) {
    if (Yap_unify(ot, MkAtomTerm(at))) cut_succeed();
    else cut_fail();
  }
  /* Error handling */
  if (LOCAL_Error_TYPE) {
    if (Yap_HandleError( "atom_concat/3" )) {
      goto restart_aux;
    } else {
      return FALSE;
    }
  }
  cut_fail();
}

#define CastToAtom(x) CastToAtom__(x PASS_REGS)

static Term
CastToAtom__(Term t USES_REGS)
{
  if (IsAtomTerm(t))
    return t;
  return MkAtomTerm(Yap_AtomicToAtom( t PASS_REGS));
}

#define CastToNumeric(x) CastToNumeric__(x PASS_REGS)

static Term
CastToNumeric__(Atom at USES_REGS)
{
    Term t;
  if ((t = Yap_AtomToNumber( MkAtomTerm( at ) PASS_REGS) ) )
    return t;
  return MkAtomTerm(at);
}


static Int 
cont_atomic_concat3( USES_REGS1 )
{
  Term t3;
  Atom ats[2];
  size_t i, max;
 restart_aux:
  t3 = Deref(ARG3);
  i = IntOfTerm(EXTRA_CBACK_ARG(3,1));
  max = IntOfTerm(EXTRA_CBACK_ARG(3,2));
  EXTRA_CBACK_ARG(3,1) = MkIntTerm(i+1);
  if ( ! Yap_SpliceAtom( t3, ats, i, max PASS_REGS ) ) {
    cut_fail();
  } else {
      Term t1 = CastToNumeric(ats[0]);
      Term t2 = CastToNumeric(ats[1]);
    if (i < max) return Yap_unify( ARG1, t1) &&
		   Yap_unify( ARG2, t2) ;
    if (Yap_unify( ARG1, t1) &&
	Yap_unify( ARG2, t2)) cut_succeed();
    cut_fail();
  }
  /* Error handling */
  if (LOCAL_Error_TYPE) {
    if (Yap_HandleError( "string_concat/3" )) {
      goto restart_aux;
    } else {
      return FALSE;
    }
  }
  cut_fail();
}

static Int
atomic_concat3( USES_REGS1 )
{
  Term t1;
  Term t2, t3, ot;
  Atom at;
 restart_aux:
  t1 = Deref(ARG1);
  t2 = Deref(ARG2);
  t3 = Deref(ARG3);
  if (Yap_IsGroundTerm(t1) && Yap_IsGroundTerm(t2)) {
    at = Yap_ConcatAtoms( CastToAtom(t1), CastToAtom(t2) PASS_REGS );
    ot = ARG3;
  } else if (Yap_IsGroundTerm(t1) && Yap_IsGroundTerm(t3) ) {
    at = Yap_SubtractHeadAtom( t3, CastToAtom(t1) PASS_REGS );
    ot = ARG2;
  } else if (Yap_IsGroundTerm(t2) && Yap_IsGroundTerm(t3)) {
    at = Yap_SubtractTailAtom( t3, CastToAtom(t2) PASS_REGS );
    ot = ARG1;
  } else if (Yap_IsGroundTerm(t3)) {
      EXTRA_CBACK_ARG(3,1) = MkIntTerm(0);
      EXTRA_CBACK_ARG(3,2) = MkIntTerm(Yap_AtomicToLength(t3 PASS_REGS));
      return cont_atomic_concat3( PASS_REGS1 );
  } else {
    LOCAL_Error_TYPE = INSTANTIATION_ERROR;
    LOCAL_Error_Term = t1;
  }
  if (at) {
    if (Yap_unify(ot, CastToNumeric(at))) cut_succeed();
    else cut_fail();
  }
  /* Error handling */
  if (LOCAL_Error_TYPE) {
    if (Yap_HandleError( "atomic_concat/3" )) {
      goto restart_aux;
    } else {
      return FALSE;
    }
  }
  cut_fail();
}


static Int 
cont_string_concat3( USES_REGS1 )
{
  Term t3;
  Term ts[2];
  size_t i, max;
 restart_aux:
  t3 = Deref(ARG3);
  i = IntOfTerm(EXTRA_CBACK_ARG(3,1));
  max = IntOfTerm(EXTRA_CBACK_ARG(3,2));
  EXTRA_CBACK_ARG(3,1) = MkIntTerm(i+1);
  if ( ! Yap_SpliceString( t3, ts, i, max PASS_REGS ) ) {
    cut_fail();
  } else {
    if (i < max) return Yap_unify( ARG1, ts[0]) &&
                   Yap_unify( ARG2, ts[1]) ;
    if (Yap_unify( ARG1, ts[0]) &&
        Yap_unify( ARG2, ts[1])) cut_succeed();
    cut_fail();
  }
  /* Error handling */
  if (LOCAL_Error_TYPE) {
    if (Yap_HandleError( "string_concat/3" )) {
      goto restart_aux;
    } else {
      return FALSE;
    }
  }
  cut_fail();
}


static Int
string_concat3( USES_REGS1 )
{
  Term t1;
  Term t2, t3, ot;
  Term tf;
 restart_aux:
  t1 = Deref(ARG1);
  t2 = Deref(ARG2);
  t3 = Deref(ARG3);
  if (Yap_IsGroundTerm(t1) && Yap_IsGroundTerm(t2)) {
    tf = Yap_ConcatStrings( t1, t2 PASS_REGS );
    ot = ARG3;
  } else if (Yap_IsGroundTerm(t1) && Yap_IsGroundTerm(t3) ) {
    tf = Yap_SubtractHeadString(t3, t1 PASS_REGS );
    ot = ARG2;
  } else if (Yap_IsGroundTerm(t2) && Yap_IsGroundTerm(t3)) {
    tf = Yap_SubtractTailString( t3, t2 PASS_REGS );
    ot = ARG1;
  } else if (Yap_IsGroundTerm(t3)) {
      EXTRA_CBACK_ARG(3,1) = MkIntTerm(0);
      EXTRA_CBACK_ARG(3,2) = MkIntTerm(Yap_StringToLength(t3 PASS_REGS));
      return cont_string_concat3( PASS_REGS1 );
  } else {
    LOCAL_Error_TYPE = INSTANTIATION_ERROR;
    LOCAL_Error_Term = t1;
  }
  if (tf) {
    if (Yap_unify(ot, tf)) { cut_succeed(); }
    else { cut_fail(); }
  }
  /* Error handling */
  if (LOCAL_Error_TYPE) {
    if (Yap_HandleError( "string_concat/3" )) {
      goto restart_aux;
    } else {
      return FALSE;
    }
  }
  cut_fail();
}


static Int 
cont_string_code3( USES_REGS1 )
{
  Term t2;
  Int i, j;
  utf8proc_int32_t chr;
  const unsigned char *s;
  const unsigned char *s0;
 restart_aux:
  t2 = Deref(ARG2);
  s0 = UStringOfTerm( t2 );
  i = IntOfTerm(EXTRA_CBACK_ARG(3,1)); // offset in coded string, increases by 1..6
  j = IntOfTerm(EXTRA_CBACK_ARG(3,2)); // offset in UNICODE string, always increases by 1
  s = (s0+i) + get_utf8( (unsigned char *)s0+i, &chr );
  if (s[0]) {
    EXTRA_CBACK_ARG(3,1) = MkIntTerm(s-s0);
    EXTRA_CBACK_ARG(3,2) = MkIntTerm(j+1);
    return Yap_unify(MkIntegerTerm( chr ), ARG3) && Yap_unify(MkIntegerTerm( j+1 ), ARG1);
  }
  if (Yap_unify(MkIntegerTerm( chr ), ARG3) && Yap_unify(MkIntegerTerm( j ), ARG1))
    cut_succeed();
  else
    cut_fail();
  /* Error handling */
  if (LOCAL_Error_TYPE) {
    if (Yap_HandleError( "string_code/3" )) {
      goto restart_aux;
    } else {
      return FALSE;
    }
  }
  cut_fail();
}


static Int 
string_code3( USES_REGS1 )
{
  Term t1;
  Term t2;
  const unsigned char *s;
 restart_aux:
  t1 = Deref(ARG1);
  t2 = Deref(ARG2);
  if (IsVarTerm(t2)) {
    LOCAL_Error_TYPE = INSTANTIATION_ERROR;
    LOCAL_Error_Term = t2;
  } else if (!IsStringTerm(t2)) {
    LOCAL_Error_TYPE = TYPE_ERROR_STRING;
    LOCAL_Error_Term = t2;
  } else {
    s = UStringOfTerm( t2 );
    t1 = Deref(ARG1);
    if (IsVarTerm(t1)) {
      EXTRA_CBACK_ARG(3,1) = MkIntTerm(0);
      EXTRA_CBACK_ARG(3,2) = MkIntTerm(0);
      return cont_string_code3( PASS_REGS1 );
    } else if (!IsIntegerTerm( t1 )) {
      LOCAL_Error_TYPE = TYPE_ERROR_INTEGER;
      LOCAL_Error_Term = t1;
    } else {
      const unsigned char *ns = s;
      utf8proc_int32_t chr;
      Int indx = IntegerOfTerm( t1 );
      if (indx <= 0) {
	if (indx < 0) {
	  LOCAL_Error_TYPE = DOMAIN_ERROR_NOT_LESS_THAN_ZERO;
	  LOCAL_Error_Term = t1;
	}
	cut_fail();
      }
      ns = skip_utf8((unsigned char *)s, indx);
      if (ns == NULL) {
	cut_fail(); // silently fail?
      }
      get_utf8( (unsigned char *)ns, &chr);
      if ( chr == '\0') cut_fail();
      if (Yap_unify(ARG3, MkIntegerTerm(chr))) cut_succeed();
      cut_fail();
    }
  }
  /* Error handling */
  if (LOCAL_Error_TYPE) {
    if (Yap_HandleError( "string_code/3" )) {
      goto restart_aux;
    } else {
      return FALSE;
    }
  }
  cut_fail();
}


static Int 
get_string_code3( USES_REGS1 )
{
  Term t1;
  Term t2;
  const unsigned char *s;
 restart_aux:
  t1 = Deref(ARG1);
  t2 = Deref(ARG2);
  if (IsVarTerm(t2)) {
    LOCAL_Error_TYPE = INSTANTIATION_ERROR;
    LOCAL_Error_Term = t2;
  } else if (!IsStringTerm(t2)) {
    LOCAL_Error_TYPE = TYPE_ERROR_STRING;
    LOCAL_Error_Term = t2;
  } else {
    s = UStringOfTerm( t2 );
    t1 = Deref(ARG1);
    if (IsVarTerm(t1)) {
      LOCAL_Error_TYPE = INSTANTIATION_ERROR;
      LOCAL_Error_Term = t1;
    } else if (!IsIntegerTerm( t1 )) {
      LOCAL_Error_TYPE = TYPE_ERROR_INTEGER;
      LOCAL_Error_Term = t1;
    } else {
       unsigned char *ns = (unsigned char *)s;
      utf8proc_int32_t chr;
      Int indx = IntegerOfTerm( t1 );
      if (indx <= 0) {
	if (indx < 0) {
	  LOCAL_Error_TYPE = DOMAIN_ERROR_NOT_LESS_THAN_ZERO;
	  LOCAL_Error_Term = t1;
	} else {
	  return FALSE;
	}
      } else {
	indx -= 1;
	ns = skip_utf8((unsigned char *)s,indx);
	if (ns == NULL) {
	  return FALSE;
	} else {
	   get_utf8( ns, &chr);
	  if ( chr != '\0')  return Yap_unify(ARG3, MkIntegerTerm(chr));
	}
      }
      return FALSE; // replace by error code
    }
  }
  /* Error handling */
  if (LOCAL_Error_TYPE) {
    if (Yap_HandleError( "string_code/3" )) {
      goto restart_aux;
    } else {
      return FALSE;
    }
  }
  cut_fail();
}

static Int 
atom_concat2( USES_REGS1 )
{
  Term t1;
  Term *tailp;
  Int n;
 restart_aux:
  t1 = Deref(ARG1);
  n = Yap_SkipList(&t1, &tailp);
  if (*tailp != TermNil) {
    LOCAL_Error_TYPE = TYPE_ERROR_LIST;
  } else {
    seq_tv_t *inpv = (seq_tv_t *)malloc(n*sizeof(seq_tv_t)), out;
    int i = 0;
    Atom at;
    
    if (!inpv) {
      LOCAL_Error_TYPE = RESOURCE_ERROR_HEAP;
      free(inpv);
      goto error;
    }

    while (t1 != TermNil) {
      inpv[i].type = YAP_STRING_ATOM;
      inpv[i].val.t = HeadOfTerm(t1);
      i++;
      t1 = TailOfTerm(t1);
    }
    out.type = YAP_STRING_ATOM;
    if (!Yap_Concat_Text(n, inpv, &out PASS_REGS)) {
      free(inpv);
      goto error;
    }
    free(inpv);
    at =  out.val.a;
    if (at) return Yap_unify(ARG2, MkAtomTerm(at));
  }
 error:
  /* Error handling */
  if (LOCAL_Error_TYPE) {
    if (Yap_HandleError( "string_code/3" )) {
      goto restart_aux;
    } else {
      return FALSE;
    }
  }
  cut_fail();
}

static Int 
string_concat2( USES_REGS1 )
{
  Term t1;
  Term *tailp;
  Int n;
 restart_aux:
  t1 = Deref(ARG1);
  n = Yap_SkipList(&t1, &tailp);
  if (*tailp != TermNil) {
    LOCAL_Error_TYPE = TYPE_ERROR_LIST;
  } else {
    seq_tv_t *inpv = (seq_tv_t *)malloc(n*sizeof(seq_tv_t)), out;
    int i = 0;
    
    if (!inpv) {
      LOCAL_Error_TYPE = RESOURCE_ERROR_HEAP;
      free(inpv);
      goto error;
    }

    while (t1 != TermNil) {
      inpv[i].type = YAP_STRING_STRING;
      inpv[i].val.t = HeadOfTerm(t1);
      i++;
      t1 = TailOfTerm(t1);
    }
    out.type = YAP_STRING_STRING;
    if (!Yap_Concat_Text(n, inpv, &out PASS_REGS)) {
      free(inpv);
      goto error;
    }
    free(inpv);
    if (out.val.t) return Yap_unify(ARG2, out.val.t);
  }
 error:
  /* Error handling */
  if (LOCAL_Error_TYPE) {
    if (Yap_HandleError( "string_code/3" )) {
      goto restart_aux;
    } else {
      return FALSE;
    }
  }
  cut_fail();
}


static Int 
atomic_concat2( USES_REGS1 )
{
  Term t1;
  Term *tailp;
  Int n;
 restart_aux:
  t1 = Deref(ARG1);
  n = Yap_SkipList(&t1, &tailp);
  if (*tailp != TermNil) {
    LOCAL_Error_TYPE = TYPE_ERROR_LIST;
  } else {
    seq_tv_t *inpv = (seq_tv_t *)malloc(n*sizeof(seq_tv_t)), out;
    int i = 0;
    Atom at;
    
    if (!inpv) {
      LOCAL_Error_TYPE = RESOURCE_ERROR_HEAP;
      free(inpv);
      goto error;
    }

    while (t1 != TermNil) {
      inpv[i].type = YAP_STRING_STRING|YAP_STRING_ATOM|YAP_STRING_INT|YAP_STRING_FLOAT|YAP_STRING_BIG|YAP_STRING_TERM;
      inpv[i].val.t = HeadOfTerm(t1);
      i++;
      t1 = TailOfTerm(t1);
    }
    out.type = YAP_STRING_ATOM;
    if (!Yap_Concat_Text(n, inpv, &out PASS_REGS)) {
      free(inpv);
      goto error;
    }
    free(inpv);
    at =  out.val.a;
    if (at) return Yap_unify(ARG2, MkAtomTerm(at));
  }
 error:
  /* Error handling */
  if (LOCAL_Error_TYPE && Yap_HandleError( "atom_concat/3" )) {
    goto restart_aux;
  }
  return FALSE;
}

static Int 
atomics_to_string2( USES_REGS1 )
{
  Term t1;
  Term *tailp;
  Int n;
 restart_aux:
  t1 = Deref(ARG1);
  n = Yap_SkipList(&t1, &tailp);
  if (*tailp != TermNil) {
    LOCAL_Error_TYPE = TYPE_ERROR_LIST;
  } else {
    seq_tv_t *inpv = (seq_tv_t *)malloc(n*sizeof(seq_tv_t)), out;
    int i = 0;
    Atom at;
    
    if (!inpv) {
      LOCAL_Error_TYPE = RESOURCE_ERROR_HEAP;
      free(inpv);
      goto error;
    }

    while (t1 != TermNil) {
      inpv[i].type = YAP_STRING_STRING|YAP_STRING_ATOM|YAP_STRING_INT|YAP_STRING_FLOAT|YAP_STRING_BIG|YAP_STRING_TERM;
      inpv[i].val.t = HeadOfTerm(t1);
      i++;
      t1 = TailOfTerm(t1);
    }
    out.type = YAP_STRING_STRING;
    if (!Yap_Concat_Text(n, inpv, &out PASS_REGS)) {
      free(inpv);
      goto error;
    }
    free(inpv);
    at =  out.val.a;
    if (at) return Yap_unify(ARG2, MkAtomTerm(at));
  }
 error:
  /* Error handling */
  if (LOCAL_Error_TYPE && Yap_HandleError( "atomics_to_string/2" )) {
    goto restart_aux;
  }
  return FALSE;
}

static Int 
atomics_to_string3( USES_REGS1 )
{
  Term t1, t2;
  Term *tailp;
  Int n;
 restart_aux:
  t1 = Deref(ARG1);
  t2 = Deref(ARG2);
  n = Yap_SkipList(&t1, &tailp);
  if (*tailp != TermNil) {
    LOCAL_Error_TYPE = TYPE_ERROR_LIST;
  } else {
    seq_tv_t *inpv = (seq_tv_t *)malloc((n*2-1)*sizeof(seq_tv_t)), out;
    int i = 0;
    Atom at;
    
    if (!inpv) {
      LOCAL_Error_TYPE = RESOURCE_ERROR_HEAP;
      free(inpv);
      goto error;
    }

    while (t1 != TermNil) {
      inpv[i].type = YAP_STRING_STRING|YAP_STRING_ATOM|YAP_STRING_INT|YAP_STRING_FLOAT|YAP_STRING_BIG|YAP_STRING_TERM;
      inpv[i].val.t = HeadOfTerm(t1);
      i++;
      inpv[i].type = YAP_STRING_STRING|YAP_STRING_ATOM|YAP_STRING_INT|YAP_STRING_FLOAT|YAP_STRING_BIG|YAP_STRING_TERM;
      inpv[i].val.t = t2;
      i++;
      t1 = TailOfTerm(t1);
    }
    out.type = YAP_STRING_STRING;
    if (!Yap_Concat_Text(2*n-1, inpv, &out PASS_REGS)) {
      free(inpv);
      goto error;
    }
    free(inpv);
    at =  out.val.a;
    if (at) return Yap_unify(ARG3, MkAtomTerm(at));
  }
 error:
  /* Error handling */
  if (LOCAL_Error_TYPE && Yap_HandleError( "atomics_to_string/3" )) {
    goto restart_aux;
  }
  return FALSE;
}

static Int 
atom_length( USES_REGS1 )
{
  Term t1 = Deref(ARG1);;
  Term t2 = Deref(ARG2);
  ssize_t len;

  if (!Yap_IsGroundTerm(t1)) {
      Yap_Error(INSTANTIATION_ERROR, t1, "atom_length/2");
      return(FALSE);
  } else if (!IsAtomTerm(t1)) {
      Yap_Error(TYPE_ERROR_ATOM, t1, "atom_length/2");
      return(FALSE);
  }

  if (Yap_IsGroundTerm(t2)) {

    if (!IsIntegerTerm(t2)) {
      Yap_Error(TYPE_ERROR_INTEGER, t2, "atom_length/2");
      return(FALSE);
    } else if ((len = IntegerOfTerm(t2)) < 0) {
      Yap_Error(DOMAIN_ERROR_NOT_LESS_THAN_ZERO, t2, "atom_length/2");
      return(FALSE);
    }
  }
restart_aux:
  len = Yap_AtomicToLength(t1 PASS_REGS);
  if (len != (size_t)-1)
    return Yap_unify( ARG2, MkIntegerTerm(len) );
  /* error handling */
  if (LOCAL_Error_TYPE && Yap_HandleError( "atom_length/2" )) {
    goto restart_aux;
  }
  return FALSE;
}

static Int
atomic_length( USES_REGS1 )
{
  Term t1 = Deref(ARG1);
  Term t2 = Deref(ARG2);
  ssize_t len;

  if (!Yap_IsGroundTerm(t1)) {
      Yap_Error(INSTANTIATION_ERROR, t1, "atomic_length/2");
      return(FALSE);
  } else if (!IsAtomicTerm(t1)) {
      Yap_Error(TYPE_ERROR_ATOM, t1, "atomic_length/2");
      return(FALSE);
  }

  if (Yap_IsGroundTerm(t2)) {

    if (!IsIntegerTerm(t2)) {
      Yap_Error(TYPE_ERROR_INTEGER, t2, "atomic_length/2");
      return(FALSE);
    }
    if ((len = IntegerOfTerm(t2)) < 0) {
      Yap_Error(DOMAIN_ERROR_NOT_LESS_THAN_ZERO, t2, "atomic_length/2");
      return(FALSE);
    }
  }
restart_aux:
  len = Yap_AtomicToLength(t1 PASS_REGS);
  if (len != (size_t)-1)
    return Yap_unify( ARG2, MkIntegerTerm(len) );
  /* error handling */
  if (LOCAL_Error_TYPE && Yap_HandleError( "atomic_length/2" )) {
    goto restart_aux;
  }
  return FALSE;
}

static Int
string_length( USES_REGS1 )
{
  Term t1;
  Term t2 = Deref(ARG2);
  ssize_t len;

  if (Yap_IsGroundTerm(t2)) {

    if (!IsIntegerTerm(t2)) {
      Yap_Error(TYPE_ERROR_INTEGER, t2, "string_length/2");
      return(FALSE);
    }
    if (FALSE && (len = IntegerOfTerm(t2)) < 0) {
      Yap_Error(DOMAIN_ERROR_NOT_LESS_THAN_ZERO, t2, "string_length/2");
      return(FALSE);
    }
  }
restart_aux:
  t1  = Deref(ARG1);
  len = Yap_AtomicToLength(t1 PASS_REGS);
  if (len != (size_t)-1)
    return Yap_unify( ARG2, MkIntegerTerm(len) );
  /* error handling */
  if (LOCAL_Error_TYPE && Yap_HandleError( "string_length/2" )) {
    goto restart_aux;
  }
  return FALSE;
}


static int
is_wide(wchar_t *s)
{
  wchar_t ch;

  while ((ch = *s++)) {
    if (ch > MAX_ISO_LATIN1)
      return TRUE;
  }
  return FALSE;
}

/* split an atom into two sub-atoms */
static Int 
atom_split( USES_REGS1 )
{
  Term t1 = Deref(ARG1);
  Term t2 = Deref(ARG2);
  size_t len;
  int i;
  Term to1, to2;
  Atom at;

  if (IsVarTerm(t1)) {
    Yap_Error(INSTANTIATION_ERROR, t1, "$atom_split/4");
    return(FALSE);		
  }
  if (!IsAtomTerm(t1)) {
    Yap_Error(TYPE_ERROR_ATOM, t1, "$atom_split/4");
    return(FALSE);
  }
  if (IsVarTerm(t2)) {
    Yap_Error(INSTANTIATION_ERROR, t2, "$atom_split/4");
    return(FALSE);		
  }
  if (!IsIntTerm(t2)) {
    Yap_Error(TYPE_ERROR_INTEGER, t2, "$atom_split/4");
    return(FALSE);
  }
  if ((Int)(len = IntOfTerm(t2)) < 0) {
    Yap_Error(DOMAIN_ERROR_NOT_LESS_THAN_ZERO, t2, "$atom_split/4");
    return(FALSE);
  }
  at  = AtomOfTerm(t1);
  if (IsWideAtom(at)) {
    wchar_t *ws, *ws1 = (wchar_t *)HR;
    unsigned char *s1 = (unsigned char *)HR;
    size_t wlen;

    ws = (wchar_t *)RepAtom(at)->StrOfAE;
    wlen = wcslen(ws);
    if (len > wlen) return FALSE;
    if (s1+len > (unsigned char *)LCL0-1024)
      Yap_Error(RESOURCE_ERROR_STACK,t1,"$atom_split/4");
    for (i = 0; i< len; i++) {
      if (ws[i] > MAX_ISO_LATIN1) {
	break;
      }
      s1[i] = ws[i];
    }
    if (ws1[i] > MAX_ISO_LATIN1) {
      /* first sequence is wide */
      if (ws1+len > (wchar_t *)ASP-1024)
	Yap_Error(RESOURCE_ERROR_STACK,t1,"$atom_split/4");
      ws = (wchar_t *)RepAtom(at)->StrOfAE;
      for (i = 0; i< len; i++) {
	ws1[i] = ws[i];
      }
      ws1[len] = '\0';
      to1 = MkAtomTerm(Yap_LookupWideAtom(ws1));
      /* we don't know if the rest of the string is wide or not */
      if (is_wide(ws+len)) {
	to2 = MkAtomTerm(Yap_LookupWideAtom(ws+len)); 
      } else {
	char *s2 = (char *)HR;
	if (s2+(wlen-len) > (char *)ASP-1024)
	  Yap_Error(RESOURCE_ERROR_STACK,t1,"$atom_split/4");
	ws += len;
	while ((*s2++ = *ws++));
	to2 = MkAtomTerm(Yap_LookupAtom(( char *)HR));
      }
    } else {
      s1[len] = '\0';
      to1 = MkAtomTerm(Yap_ULookupAtom(s1));
      /* second atom must be wide, if first wasn't */
      to2 = MkAtomTerm(Yap_LookupWideAtom(ws+len)); 
    }
  } else {
    unsigned char *s, *s1 = (unsigned char *)HR;

    s = RepAtom(at)->UStrOfAE;
    if (len > (Int)strlen((char *)s)) return(FALSE);
    if (s1+len > (unsigned char *)ASP-1024)
      Yap_Error(RESOURCE_ERROR_STACK,t1,"$atom_split/4");
    for (i = 0; i< len; i++) {
      s1[i] = s[i];
    }
    s1[len] = '\0';
    to1 = MkAtomTerm(Yap_ULookupAtom(s1));
    to2 = MkAtomTerm(Yap_ULookupAtom(s+len));
  }
  return(Yap_unify_constant(ARG3,to1) && Yap_unify_constant(ARG4,to2));
}

static Int 
atom_number( USES_REGS1 )
{
  Term t1;
 restart_aux:
  t1  = Deref(ARG1);
  if (Yap_IsGroundTerm(t1)) {
    Term tf = Yap_AtomToNumber(t1 PASS_REGS);
    if (tf)
      return Yap_unify( ARG2, tf );
  } else {
    /* ARG1 unbound */
    Term   t = Deref(ARG2);
    Atom af = Yap_NumberToAtom(t PASS_REGS);
    if (af)
      return Yap_unify( ARG1, MkAtomTerm(af) );
  }
  /* error handling */
  if (LOCAL_Error_TYPE && Yap_HandleError( "atom_number/2" )) {
    t1 = Deref(ARG1);
    goto restart_aux;
  }
  return FALSE;
}


static Int 
string_number( USES_REGS1 )
{
  Term t1;
 restart_aux:
  t1  = Deref(ARG1);
  if (Yap_IsGroundTerm(t1)) {
    Term tf = Yap_StringToNumber(t1 PASS_REGS);
    if (tf)
      return Yap_unify( ARG2, tf );
  } else {
    /* ARG1 unbound */
    Term   t = Deref(ARG2);
    Term tf = Yap_NumberToString(t PASS_REGS);
    if (tf)
      return Yap_unify( ARG1, tf );
  }
  /* error handling */
  if (LOCAL_Error_TYPE && Yap_HandleError( "string_number/2" )) {
    t1 = Deref(ARG1);
    goto restart_aux;
  }
  return FALSE;
}


#define SUB_ATOM_HAS_MIN    1
#define SUB_ATOM_HAS_SIZE   2
#define SUB_ATOM_HAS_AFTER  4
#define SUB_ATOM_HAS_VAL    8
#define SUB_ATOM_HAS_WIDE  16
#define SUB_ATOM_HAS_UTF8  32

static void *
alloc_tmp_stack(size_t sz USES_REGS) {
  void *pt = (void *)HR;
  while (HR > ASP-(1044+sz/sizeof(CELL))) {
    if (!Yap_gc(5, ENV, gc_P(P,CP))) {
      Yap_Error(RESOURCE_ERROR_STACK, TermNil, "sub_atom/5");
      return(NULL);
    }
  }
  return pt;
}

static Term
build_new_atomic(int mask, wchar_t *wp, const unsigned char *p, size_t min, size_t len USES_REGS)
{
  Atom nat;
  if (mask & SUB_ATOM_HAS_WIDE) {
    wchar_t *src = wp+min;
    wchar_t *d = alloc_tmp_stack((len+1)*sizeof(wchar_t) PASS_REGS);
    if (!d) return NIL;
    
    wcsncpy(d, src, len);
    d[len] = '\0';
    nat = Yap_LookupMaybeWideAtom(d);
    if (nat)
      return MkAtomTerm(nat);
  } else if (!(mask & SUB_ATOM_HAS_UTF8)) {
    const unsigned char *src = p+min;
    unsigned char *d = alloc_tmp_stack((len+1)*sizeof(char) PASS_REGS);
    if (!d) return NIL;
    
    strncpy((char *)d, (char *)src, len);
    d[len] = '\0';
    nat = Yap_ULookupAtom(d);
    if (nat)
      return MkAtomTerm(nat);
  } else {
    const unsigned char *src = p;
    unsigned char *buf;
    Term t = init_tstring( PASS_REGS1  );
    src = skip_utf8((unsigned char *)src, min);
    const unsigned char *cp = src;

    LOCAL_TERM_ERROR( t, 4*(len+1) );
    buf = buf_from_tstring(HR);
    while (len) {
      utf8proc_int32_t  chr;
      cp +=  get_utf8((unsigned char *)cp,  &chr);
      buf += put_utf8((unsigned char *)buf, chr);
      len--;
    }
    *buf++ = '\0';
    
    close_tstring( buf  PASS_REGS );
    return t;
  }
  return 0L;
}

static Int wcsstrcmp(wchar_t *p, char *p2, size_t len)
{
  while (len--) {
    Int d = *p++-*p2++;
    if (d) return d;
  }
  return 0;
}

static int
check_sub_atom_at(int min, Atom at, Atom nat)
{
  if (IsWideAtom(nat)) {
    wchar_t *p1, *p2;
    wchar_t c1;
    if (!IsWideAtom(at)) return FALSE;
    p1 = RepAtom(at)->WStrOfAE+min;
    p2 = RepAtom(nat)->WStrOfAE;
    while ( (c1 = *p1++) == *p2++ && c1);
    return c1 == 0;
  } else {
    if (IsWideAtom(at)) {
      wchar_t *p1;
      unsigned char *p2;
      wchar_t c1;
      p1 = RepAtom(at)->WStrOfAE+min;
      p2 = RepAtom(nat)->UStrOfAE;
      while ( (c1 = *p1++) == *p2++ && c1);
      return c1 == 0;
    } else {
      unsigned char *p1, *p2;
      char c1;
      p1 = RepAtom(at)->UStrOfAE+min;
      p2 = RepAtom(nat)->UStrOfAE;
      while ( (c1 = *p1++) == *p2++ && c1);
      return c1 == 0;
    }
  }
}

static int
check_sub_string_at(int min, const unsigned char *p1, const unsigned char *p2, size_t len)
{
  p1 = skip_utf8((unsigned char *)p1, min);
  return cmpn_utf8( p1, p2, len ) == 0;
}

static int
check_sub_atom_bef(int max, Atom at, Atom nat)
{
  if (IsWideAtom(nat)) {
    wchar_t *p1, *p2;
    wchar_t c1;

    size_t len = wcslen(RepAtom(nat)->WStrOfAE);
    int min = max- len;
    if (min < 0) return FALSE;
    if (!IsWideAtom(at)) return FALSE;
    p1 = RepAtom(at)->WStrOfAE+min;
    p2 = RepAtom(nat)->WStrOfAE;
    while ( (c1 = *p1++) == *p2++ && c1);
    return c1 == 0;
  } else {
    size_t len = strlen((char *)RepAtom(nat)->StrOfAE);
    int min = max- len;
    if ((Int)(min - len) < 0) return FALSE;
    if (IsWideAtom(at)) {
      wchar_t *p1;
      unsigned char *p2;
      wchar_t c1;
      p1 = RepAtom(at)->WStrOfAE+min;
      p2 = RepAtom(nat)->UStrOfAE;
      while ( (c1 = *p1++) == *p2++ && c1);
      return c1 == 0;
    } else {
      unsigned char *p1, *p2;
      char c1;
      p1 = RepAtom(at)->UStrOfAE+min;
      p2 = RepAtom(nat)->UStrOfAE;
      while ( (c1 = *p1++) == *p2++ && c1);
      return c1 == 0;
    }
  }
}

static int
check_sub_string_bef(int max, Term at, Term nat)
{
  size_t len = strlen_utf8(UStringOfTerm(nat));
  int min = max- len;
  const unsigned char *p1, *p2;
  int c1;

  if ((Int)(min - len) < 0) return FALSE;

  p1 = skip_utf8((unsigned char *)UStringOfTerm(at),min);
  p2 = UStringOfTerm(nat);
  while ( (c1 = *p1++) == *p2++ && c1);
  return c1 == 0;
}

static Int
cont_sub_atomic( USES_REGS1 )
{
  Term tat1= Deref(ARG1);
  Atom at = NULL;
  int mask;
  size_t min, len, after, sz;
  wchar_t *wp = NULL;
  const unsigned char *p = NULL;
  Term nat;
  int sub_atom = TRUE;

  mask = IntegerOfTerm(EXTRA_CBACK_ARG(5,1));
  min = IntegerOfTerm(EXTRA_CBACK_ARG(5,2));
  len = IntegerOfTerm(EXTRA_CBACK_ARG(5,3));
  after = IntegerOfTerm(EXTRA_CBACK_ARG(5,4));
  sz = IntegerOfTerm(EXTRA_CBACK_ARG(5,5));

  if (mask & SUB_ATOM_HAS_UTF8) {
    sub_atom = FALSE;
    p = UStringOfTerm(tat1);
  } else if (mask & SUB_ATOM_HAS_WIDE) {
    at = AtomOfTerm(tat1);
    wp = RepAtom(at)->WStrOfAE;
  } else {
    at = AtomOfTerm(tat1);
    p = RepAtom(at)->UStrOfAE;
  }
  /* we can have one of two cases: A5 bound or unbound */
  if (mask & SUB_ATOM_HAS_VAL) {
    int found = FALSE;
    nat = Deref(ARG5);
    if (mask & SUB_ATOM_HAS_WIDE) {
      wp = RepAtom(at)->WStrOfAE;
      if (IsWideAtom(AtomOfTerm(nat))) {
	while (!found) {
	  if (wcsncmp(wp+min, AtomOfTerm(nat)->WStrOfAE, len) == 0) {
	    Yap_unify(ARG2, MkIntegerTerm(min));
	    Yap_unify(ARG3, MkIntegerTerm(len));
	    Yap_unify(ARG4, MkIntegerTerm(after));
	    found = TRUE;
	    /* found one, check if there is any left */
	    while (min <= sz-len) {
	      after--;
	      min++;
	      if (wcsncmp(wp+min, AtomOfTerm(nat)->WStrOfAE, len) == 0)
		break;
	    }
	  } else {
	    if (min == sz-len) break;
	    after--;
	    min++;
	  }
	}
      } else {
	while (!found) {
	  if (wcsstrcmp(wp+min, (char *)AtomOfTerm(nat)->StrOfAE, len) == 0) {
	    Yap_unify(ARG2, MkIntegerTerm(min));
	    Yap_unify(ARG3, MkIntegerTerm(len));
	    Yap_unify(ARG4, MkIntegerTerm(after));
	    found = TRUE;
	    /* found one, check if there is any left */
	    while (min <= sz-len) {
	      after--;
	      min++;
	      if (wcsstrcmp(wp+min, (char *)AtomOfTerm(nat)->StrOfAE, len) == 0)
		break;
	    }
	  } else {
	    if (min == sz-len) break;
	    after--;
	    min++;
	  }
	} 
      }     
    } else if (sub_atom) {
      p = RepAtom(at)->UStrOfAE;
      while (!found) {
	if (strncmp((char *)p+min, (char *)AtomOfTerm(nat)->StrOfAE, len) == 0) {
	  Yap_unify(ARG2, MkIntegerTerm(min));
	  Yap_unify(ARG3, MkIntegerTerm(len));
	  Yap_unify(ARG4, MkIntegerTerm(after));
	  found = TRUE;
	  /* found one, check if there is any left */
	  while (min <= sz-len) {
	    after--;
	    min++;
	    if (strncmp((char *)p+min, (char *)AtomOfTerm(nat)->StrOfAE, len) == 0)
	      break;
	  }
	} else {
	  if (min == sz-len) break;
	  after--;
	  min++;
	}
      }
    } else {
      const unsigned char *p = UStringOfTerm( Deref(ARG1) ), *p1 = p;
      const unsigned char *p5 = UStringOfTerm( Deref(ARG5) );

      while (!found) {
	p = skip_utf8((unsigned char *)p1, min);
        if (cmpn_utf8(p, p5, len) == 0) {
          Yap_unify(ARG2, MkIntegerTerm(min));
          Yap_unify(ARG3, MkIntegerTerm(len));
          Yap_unify(ARG4, MkIntegerTerm(after));
          found = TRUE;
          /* found one, check if there is any left */
          while (min <= sz-len) {
	    int chr;
	    p +=  get_utf8((unsigned char *)p, &chr);
            after--;
            min++;
            if (cmpn_utf8(p, UStringOfTerm(nat), len) == 0)
              break;
          }
        } else {
          if (min == sz-len) break;
          after--;
          min++;
        }
      }
    }
    if (found) {
      if (min > sz-len) cut_succeed();
    } else {
      cut_fail();
    }
  } else if (mask & SUB_ATOM_HAS_SIZE) {
    nat = build_new_atomic(mask, wp, p, min, len PASS_REGS);
    Yap_unify(ARG2, MkIntegerTerm(min));
    Yap_unify(ARG4, MkIntegerTerm(after));
    Yap_unify(ARG5, nat);
    min++;
    if (after-- == 0) cut_succeed();
  } else if (mask & SUB_ATOM_HAS_MIN) {
    after = sz-(min+len);
    nat = build_new_atomic(mask, wp, p, min, len PASS_REGS);
    Yap_unify(ARG3, MkIntegerTerm(len));
    Yap_unify(ARG4, MkIntegerTerm(after));
    Yap_unify(ARG5, nat);
    len++;
    if (after-- == 0) cut_succeed();    
  } else if (mask & SUB_ATOM_HAS_AFTER) {
    len = sz-(min+after);
    nat = build_new_atomic(mask, wp, p, min, len PASS_REGS);
    Yap_unify(ARG2, MkIntegerTerm(min));
    Yap_unify(ARG3, MkIntegerTerm(len));
    Yap_unify(ARG5, nat);
    min++;
    if (len-- == 0) cut_succeed();    
  } else {
    nat = build_new_atomic(mask, wp, p, min, len PASS_REGS);
    Yap_unify(ARG2, MkIntegerTerm(min));
    Yap_unify(ARG3, MkIntegerTerm(len));
    Yap_unify(ARG4, MkIntegerTerm(after));
    Yap_unify(ARG5, nat);
    len++;
    if (after-- == 0) {
      if (min == sz) cut_succeed();
      min++;
      len = 0;
      after = sz-min;
    }
  }
  EXTRA_CBACK_ARG(5,1) = MkIntegerTerm(mask);
  EXTRA_CBACK_ARG(5,2) = MkIntegerTerm(min);
  EXTRA_CBACK_ARG(5,3) = MkIntegerTerm(len);
  EXTRA_CBACK_ARG(5,4) = MkIntegerTerm(after);   
  EXTRA_CBACK_ARG(5,5) = MkIntegerTerm(sz); 
  return TRUE;
}

static Int
sub_atomic( int sub_atom USES_REGS )
{
  Term tat1, tbef, tsize, tafter, tout;
  int mask = 0;
  size_t min, len, after, sz;
  wchar_t *wp = NULL;
  unsigned char *p = NULL;
  int bnds = 0;
  Term nat = 0L;
  Atom at = NULL;

  tat1 = Deref(ARG1);  
  EXTRA_CBACK_ARG(5,3) = MkIntegerTerm(0);
  if (IsVarTerm(tat1)) {
    Yap_Error(INSTANTIATION_ERROR, tat1, "sub_atom/5: first argument");
    return FALSE;
  } else if (sub_atom && !IsAtomTerm(tat1)) {
    Yap_Error(TYPE_ERROR_ATOM, tat1, "sub_atom/5");
    return FALSE;
  } else if (!sub_atom && !IsStringTerm(tat1)) {
    Yap_Error(TYPE_ERROR_STRING, tat1, "sub_string/5");
    return FALSE;
  }
  tbef = Deref(ARG2);  
  if (IsVarTerm(tbef)) {
    min = 0;
  } else if (!IsIntegerTerm(tbef)) {
    Yap_Error(TYPE_ERROR_INTEGER, tbef, "sub_string/5");
    return FALSE;
  } else {
    min = IntegerOfTerm(tbef);
	if ((Int)min < 0) {
	    Yap_Error(DOMAIN_ERROR_NOT_LESS_THAN_ZERO, tbef, "sub_string/5");
	    return FALSE;
	};
    mask |= SUB_ATOM_HAS_MIN;
    bnds++;
  }
  if (IsVarTerm(tsize = Deref(ARG3))) {
    len = 0;
  } else if (!IsIntegerTerm(tsize)) {
    Yap_Error(TYPE_ERROR_INTEGER, tsize, "sub_string/5");
    return FALSE;
  } else {
    len = IntegerOfTerm(tsize);
	if ((Int)len < 0) {
	    Yap_Error(DOMAIN_ERROR_NOT_LESS_THAN_ZERO, tsize, "sub_string/5");
	    return FALSE;
	};
    mask |= SUB_ATOM_HAS_SIZE;
    bnds++;
  }
  if (IsVarTerm(tafter = Deref(ARG4))) {
    after = 0;
  } else if (!IsIntegerTerm(tafter)) {
    Yap_Error(TYPE_ERROR_INTEGER, tafter, "sub_string/5");
    return FALSE;
  } else {
    after = IntegerOfTerm(tafter);
	if ((Int)after < 0) {
	    Yap_Error(DOMAIN_ERROR_NOT_LESS_THAN_ZERO, tafter, "sub_string/5");
	    return FALSE;
	};
    mask |= SUB_ATOM_HAS_AFTER;
    bnds++;
  }
  if (!IsVarTerm(tout = Deref(ARG5))) {
    if (sub_atom) {
      if (!IsAtomTerm(tout)) {
	Yap_Error(TYPE_ERROR_ATOM, tout, "sub_atom/5");
	return FALSE;
      } else {
	Atom oat;
	mask |= SUB_ATOM_HAS_VAL|SUB_ATOM_HAS_SIZE;
	oat = AtomOfTerm(tout);
	if (IsWideAtom(oat)) 
	  len = wcslen(RepAtom(oat)->WStrOfAE);
	else
	  len = strlen((const char *)RepAtom(oat)->StrOfAE);
      }
    } else {
      if (!IsStringTerm(tout)) {
	Yap_Error(TYPE_ERROR_STRING, tout, "sub_string/5");
	return FALSE;
      } else {
	mask |= SUB_ATOM_HAS_VAL|SUB_ATOM_HAS_SIZE;
	len = strlen_utf8( UStringOfTerm(tout) );
      }
    }
    if (!Yap_unify(ARG3, MkIntegerTerm(len)))
      cut_fail();
    bnds+=2;
  }
  if (sub_atom) {
    at = AtomOfTerm(tat1);
    if (IsWideAtom(at)) {
      mask |= SUB_ATOM_HAS_WIDE;
      wp = RepAtom(at)->WStrOfAE;
      sz = wcslen(wp);
    } else {
      p = RepAtom(at)->UStrOfAE;
      sz = strlen((const char *)p);
    }
  } else {
      mask |= SUB_ATOM_HAS_UTF8;
      p = (unsigned char *)StringOfTerm(tat1);
      sz = strlen_utf8(p);
  }
  /* the problem is deterministic if we have two cases */
  if (bnds > 1) {
    int out = FALSE;

    if ((mask & (SUB_ATOM_HAS_MIN|SUB_ATOM_HAS_SIZE)) ==
	(SUB_ATOM_HAS_MIN|SUB_ATOM_HAS_SIZE)) {
      if (min+len > sz) cut_fail();
      if ((Int)(after = (sz-(min+len))) < 0) cut_fail();
      nat = build_new_atomic(mask, wp, p, min, len PASS_REGS);
      if (!nat) cut_fail();
      out = Yap_unify(ARG4,MkIntegerTerm(after)) &&
	Yap_unify(ARG5, nat);
    } else if ((mask & (SUB_ATOM_HAS_MIN|SUB_ATOM_HAS_AFTER)) ==
	       (SUB_ATOM_HAS_MIN|SUB_ATOM_HAS_AFTER)) {
      if (sz < min+after) cut_fail();
      len = sz-(min+after);
      nat = build_new_atomic(mask, wp, p, min, len PASS_REGS);
      if (!nat) cut_fail();
      out = Yap_unify(ARG3,MkIntegerTerm(len)) &&
	Yap_unify(ARG5, nat);
    } else if ((mask & (SUB_ATOM_HAS_SIZE|SUB_ATOM_HAS_AFTER)) ==
	      (SUB_ATOM_HAS_SIZE|SUB_ATOM_HAS_AFTER) ) {
      if (len+after > sz) cut_fail();
      min = sz-(len+after);
      nat = build_new_atomic(mask, wp, p, min, len PASS_REGS);
      if (!nat) cut_fail();
      out = Yap_unify(ARG2,MkIntegerTerm(min)) &&
	Yap_unify(ARG5, nat);
    } else if ((mask & (SUB_ATOM_HAS_MIN|SUB_ATOM_HAS_VAL)) ==
	       (SUB_ATOM_HAS_MIN|SUB_ATOM_HAS_VAL)) {
      if (sub_atom)
	out = check_sub_atom_at(min, at, AtomOfTerm(nat));
      else
	out = check_sub_string_at(min, p, UStringOfTerm( nat ), len);
    } else if ((mask & (SUB_ATOM_HAS_AFTER|SUB_ATOM_HAS_VAL)) ==
	       (SUB_ATOM_HAS_AFTER|SUB_ATOM_HAS_VAL)) {
      if (sub_atom)
	out = check_sub_atom_bef(sz - after, at, AtomOfTerm(nat));
      else
	out = check_sub_string_bef(sz - after, tat1, tout);
    } else if ((mask & (SUB_ATOM_HAS_SIZE|SUB_ATOM_HAS_VAL)) ==
	        (SUB_ATOM_HAS_SIZE|SUB_ATOM_HAS_VAL)) {
      if (!sub_atom) {
	out = (strlen_utf8(UStringOfTerm(tout)) == len);
	if (!out) cut_fail();
      } else if (IsWideAtom(AtomOfTerm(tout))) {
	if (!(mask & SUB_ATOM_HAS_VAL)) {
	  cut_fail();
	}
	/* just check length, they may still be several occurrences :( */
	out = (wcslen(RepAtom(AtomOfTerm(tout))->WStrOfAE) == len);
      } else {
	out = (strlen((const char *)RepAtom(AtomOfTerm(tout))->StrOfAE) == len);
	if (!out) cut_fail();
      }
      if (len == sz) {
	out =  out && 
	  Yap_unify(ARG1, ARG5) &&
	  Yap_unify(ARG2, MkIntegerTerm(0)) &&
	  Yap_unify(ARG4, MkIntegerTerm(0));
      } else if (len > sz) {
	cut_fail();
      } else {
	mask |= SUB_ATOM_HAS_SIZE;
	min = 0;
	after = sz-len;
	goto backtrackable;
      }
    }
    if (out) cut_succeed();
    cut_fail();
  } else {
    if (!(mask & SUB_ATOM_HAS_MIN)) min = 0;
    if (!(mask & SUB_ATOM_HAS_SIZE)) len = 0;
    if (!(mask & SUB_ATOM_HAS_AFTER)) after = sz-(len+min);
  }
 backtrackable:
  EXTRA_CBACK_ARG(5,1) = MkIntegerTerm(mask);
  EXTRA_CBACK_ARG(5,2) = MkIntegerTerm(min);
  EXTRA_CBACK_ARG(5,3) = MkIntegerTerm(len);
  EXTRA_CBACK_ARG(5,4) = MkIntegerTerm(after);   
  EXTRA_CBACK_ARG(5,5) = MkIntegerTerm(sz); 
  return cont_sub_atomic( PASS_REGS1 );
}

/** @pred  sub_atom(+ _A_,? _Bef_, ? _Size_, ? _After_, ? _At_out_) is iso 


True when  _A_ and  _At_out_ are atoms such that the name of
 _At_out_ has size  _Size_ and is a sub-string of the name of
 _A_, such that  _Bef_ is the number of characters before and
 _After_ the number of characters afterwards.

Note that  _A_ must always be known, but  _At_out_ can be unbound when
calling this built-in. If all the arguments for sub_atom/5 but  _A_
are unbound, the built-in will backtrack through all possible
sub-strings of  _A_.
 
 */
static Int
sub_atom(  USES_REGS1 )
{
  return sub_atomic( TRUE PASS_REGS );
}

/** @pred  sub_string(+ _S_,? _Bef_, ? _Size_, ? _After_, ? _S_out_) is iso 


True when  _S_ and  _S_out_ are strings such that the 
 _S_out_ has size  _Size_ and is a sub-string of
 _S_,   _Bef_ is the number of characters before, and
 _After_ the number of characters afterwards.

Note that  _S_ must always be known, but  _S_out_ can be unbound when
calling this built-in. If all the arguments for sub_string/5 but  _S_
are unbound, the built-in will generate all possible
sub-strings of  _S_.
 
 */
static Int
sub_string(  USES_REGS1 )
{
  return sub_atomic( FALSE PASS_REGS );
}

static Int 
cont_current_atom( USES_REGS1 )
{
  Atom            catom;
  Int             i = IntOfTerm(EXTRA_CBACK_ARG(1,2));
  AtomEntry       *ap; /* nasty hack for gcc on hpux */

  /* protect current hash table line */
  if (IsAtomTerm(EXTRA_CBACK_ARG(1,1)))
    catom = AtomOfTerm(EXTRA_CBACK_ARG(1,1));
  else
    catom = NIL;
  if (catom == NIL){
    i++;
    /* move away from current hash table line */
    while (i < AtomHashTableSize) {
      READ_LOCK(HashChain[i].AERWLock);
      catom = HashChain[i].Entry;
      READ_UNLOCK(HashChain[i].AERWLock);
      if (catom != NIL) {
	break;
      }
      i++;
    }
    if (i == AtomHashTableSize) {
      cut_fail();
    }
  }
  ap = RepAtom(catom);
  if (Yap_unify_constant(ARG1, MkAtomTerm(catom))) {
    READ_LOCK(ap->ARWLock);
    if (ap->NextOfAE == NIL) {
      READ_UNLOCK(ap->ARWLock);
      i++;
      while (i < AtomHashTableSize) {
	READ_LOCK(HashChain[i].AERWLock);
	catom = HashChain[i].Entry;
	READ_UNLOCK(HashChain[i].AERWLock);
	if (catom != NIL) {
	  break;
	}
	i++;
      }
      if (i == AtomHashTableSize) {
	cut_fail();
      } else {
	EXTRA_CBACK_ARG(1,1) = MkAtomTerm(catom);
      }
    } else {
      EXTRA_CBACK_ARG(1,1) = MkAtomTerm(ap->NextOfAE);
      READ_UNLOCK(ap->ARWLock);
    }
    EXTRA_CBACK_ARG(1,2) = MkIntTerm(i);
    return TRUE;
  } else {
    return FALSE;
  }
}

static Int 
current_atom( USES_REGS1 )
{				/* current_atom(?Atom)		 */
  Term t1 = Deref(ARG1);
  if (!IsVarTerm(t1)) {
    if (IsAtomTerm(t1))
      cut_succeed();
    else
      cut_fail();
  }
  READ_LOCK(HashChain[0].AERWLock);
  if (HashChain[0].Entry != NIL) {
    EXTRA_CBACK_ARG(1,1) = MkAtomTerm(HashChain[0].Entry);
  } else {
    EXTRA_CBACK_ARG(1,1) = MkIntTerm(0);
  }
  READ_UNLOCK(HashChain[0].AERWLock);
  EXTRA_CBACK_ARG(1,2) = MkIntTerm(0);
  return (cont_current_atom( PASS_REGS1 ));
}


static Int 
cont_current_wide_atom( USES_REGS1 )
{
  Atom            catom;
  Int             i = IntOfTerm(EXTRA_CBACK_ARG(1,2));
  AtomEntry       *ap; /* nasty hack for gcc on hpux */

  /* protect current hash table line */
  if (IsAtomTerm(EXTRA_CBACK_ARG(1,1)))
    catom = AtomOfTerm(EXTRA_CBACK_ARG(1,1));
  else
    catom = NIL;
  if (catom == NIL){
    i++;
    /* move away from current hash table line */
    while (i < WideAtomHashTableSize) {
      READ_LOCK(WideHashChain[i].AERWLock);
      catom = WideHashChain[i].Entry;
      READ_UNLOCK(WideHashChain[i].AERWLock);
      if (catom != NIL) {
	break;
      }
      i++;
    }
    if (i == WideAtomHashTableSize) {
      cut_fail();
    }
  }
  ap = RepAtom(catom);
  if (Yap_unify_constant(ARG1, MkAtomTerm(catom))) {
    READ_LOCK(ap->ARWLock);
    if (ap->NextOfAE == NIL) {
      READ_UNLOCK(ap->ARWLock);
      i++;
      while (i < WideAtomHashTableSize) {
	READ_LOCK(WideHashChain[i].AERWLock);
	catom = WideHashChain[i].Entry;
	READ_UNLOCK(WideHashChain[i].AERWLock);
	if (catom != NIL) {
	  break;
	}
	i++;
      }
      if (i == WideAtomHashTableSize) {
	cut_fail();
      } else {
	EXTRA_CBACK_ARG(1,1) = MkAtomTerm(catom);
      }
    } else {
      EXTRA_CBACK_ARG(1,1) = MkAtomTerm(ap->NextOfAE);
      READ_UNLOCK(ap->ARWLock);
    }
    EXTRA_CBACK_ARG(1,2) = MkIntTerm(i);
    return TRUE;
  } else {
    return FALSE;
  }
}

static Int 
current_wide_atom( USES_REGS1 )
{				/* current_atom(?Atom)		 */
  Term t1 = Deref(ARG1);
  if (!IsVarTerm(t1)) {
    if (IsAtomTerm(t1))
      cut_succeed();
    else
      cut_fail();
  }
  READ_LOCK(WideHashChain[0].AERWLock);
  if (WideHashChain[0].Entry != NIL) {
    EXTRA_CBACK_ARG(1,1) = MkAtomTerm(WideHashChain[0].Entry);
  } else {
    EXTRA_CBACK_ARG(1,1) = MkIntTerm(0);
  }
  READ_UNLOCK(WideHashChain[0].AERWLock);
  EXTRA_CBACK_ARG(1,2) = MkIntTerm(0);
  return (cont_current_wide_atom( PASS_REGS1 ));
}

void
Yap_InitBackAtoms(void)
{
  Yap_InitCPredBack("$current_atom", 1, 2, current_atom, cont_current_atom,SafePredFlag|SyncPredFlag);
  Yap_InitCPredBack("$current_wide_atom", 1, 2, current_wide_atom,cont_current_wide_atom,SafePredFlag|SyncPredFlag);
  Yap_InitCPredBack("atom_concat", 3, 2, atom_concat3, cont_atom_concat3, 0);
  Yap_InitCPredBack("atomic_concat", 3, 2, atomic_concat3, cont_atomic_concat3, 0);
  Yap_InitCPredBack("string_concat", 3, 2, string_concat3, cont_string_concat3, 0);
  Yap_InitCPredBack("sub_atom", 5, 5, sub_atom, cont_sub_atomic, 0);
  Yap_InitCPredBack("sub_string", 5, 5, sub_string, cont_sub_atomic, 0);
  Yap_InitCPredBack("string_code", 3, 1, string_code3, cont_string_code3, 0);

}

void
Yap_InitAtomPreds(void)
{
  Yap_InitCPred("name", 2, name, 0);
/** @pred  name( _A_, _L_) 


The predicate holds when at least one of the arguments is ground
(otherwise, an error message will be displayed). The argument  _A_ will
be unified with an atomic symbol and  _L_ with the list of the ASCII
codes for the characters of the external representation of  _A_.

~~~~~{.prolog}
 name(yap,L).
~~~~~
will return:

~~~~~{.prolog}
 L = [121,97,112].
~~~~~
and

~~~~~{.prolog}
 name(3,L).
~~~~~
will return:

~~~~~{.prolog}
 L = [51].
~~~~~

 
*/
  Yap_InitCPred("string_to_atom", 2, string_to_atom, 0);
  Yap_InitCPred("atom_string", 2, atom_string, 0);
  Yap_InitCPred("string_to_atomic", 2, string_to_atomic, 0);
  Yap_InitCPred("string_to_list", 2, string_to_list, 0);
  Yap_InitCPred("char_code", 2, char_code, SafePredFlag);
/** @pred  char_code(? _A_,? _I_) is iso 


The built-in succeeds with  _A_ bound to character represented as an
atom, and  _I_ bound to the character code represented as an
integer. At least, one of either  _A_ or  _I_ must be bound before
the call.

 
*/
  Yap_InitCPred("atom_chars", 2, atom_chars, 0);
/** @pred  atom_chars(? _A_,? _L_) is iso 


The predicate holds when at least one of the arguments is ground
(otherwise, an error message will be displayed). The argument  _A_ must
be unifiable with an atom, and the argument  _L_ with the list of the
characters of  _A_.

 
*/
  Yap_InitCPred("atom_codes", 2, atom_codes, 0);
  Yap_InitCPred("string_codes", 2, string_codes, 0);
  Yap_InitCPred("string_chars", 2, string_chars, 0);
  Yap_InitCPred("atom_length", 2, atom_length, SafePredFlag);
/** @pred  atom_length(+ _A_,? _I_) is iso 


The predicate holds when the first argument is an atom, and the second
unifies with the number of characters forming that atom.

 
*/
  Yap_InitCPred("atomic_length", 2, atomic_length, SafePredFlag);
  Yap_InitCPred("string_length", 2, string_length, SafePredFlag);
  Yap_InitCPred("$atom_split", 4, atom_split, SafePredFlag);
  Yap_InitCPred("number_chars", 2, number_chars, 0);
  Yap_InitCPred("number_atom", 2, number_atom, 0);
/** @pred  number_atom(? _I_,? _L_) 



The predicate holds when at least one of the arguments is ground
(otherwise, an error message will be displayed). The argument  _I_ must
be unifiable with a number, and the argument  _L_ must be unifiable
with an atom representing the number.

 
*/
  Yap_InitCPred("number_string", 2, number_string, 0);
  Yap_InitCPred("number_codes", 2, number_codes, 0);
  Yap_InitCPred("atom_number", 2, atom_number, 0);
/** @pred  atom_number(? _Atom_,? _Number_) 


The predicate holds when at least one of the arguments is ground
(otherwise, an error message will be displayed). If the argument
 _Atom_ is an atom,  _Number_ must be the number corresponding
to the characters in  _Atom_, otherwise the characters in
 _Atom_ must encode a number  _Number_.

 
*/
  Yap_InitCPred("string_number", 2, string_number, 0);
  Yap_InitCPred("$atom_concat", 2, atom_concat2, 0);
  Yap_InitCPred("$string_concat", 2, string_concat2, 0);
  Yap_InitCPred("atomic_concat", 2, atomic_concat2, 0);
/** @pred  atomic_concat(+ _As_,? _A_) 


The predicate holds when the first argument is a list of atomic terms, and
the second unifies with the atom obtained by concatenating all the
atomic terms in the first list. The first argument thus may contain
atoms or numbers.

 
*/
  Yap_InitCPred("atomics_to_string", 2, atomics_to_string2, 0);
  Yap_InitCPred("atomics_to_string", 3, atomics_to_string3, 0);
  Yap_InitCPred("get_string_code", 3, get_string_code3, 0);
  /* hiding and unhiding some predicates */
  Yap_InitCPred("hide", 1, hide, SafePredFlag|SyncPredFlag);
  Yap_InitCPred("unhide", 1, unhide, SafePredFlag|SyncPredFlag);
  Yap_InitCPred("$hidden", 1, hidden, HiddenPredFlag|SafePredFlag|SyncPredFlag);
}

/**
@}
*/