/*************************************************************************
*									 *
*	 YAP Prolog 							 *
*									 *
*	Yap Prolog was developed at NCCUP - Universidade do Porto	 *
*									 *
* Copyright L.Damas, V.S.Costa and Universidade do Porto 1985-1997	 *
*									 *
**************************************************************************
*									 *
* File:		cmppreds.c						 *
* Last rev:								 *
* mods:									 *
* comments:	comparing two prolog terms				 *
*									 *
*************************************************************************/
///    @file cmppreds.c



#ifdef SCCS
static char     SccsId[] = "%W% %G%";
#endif

#include "Yap.h"
#include "Yatom.h"
#include "YapHeap.h"
#include "eval.h"
#if HAVE_STRING_H
#include <string.h>
#endif
#include <wchar.h>

static Int compare(Term, Term);
static Int p_compare( USES_REGS1 );
static Int p_acomp( USES_REGS1 );
static Int a_eq(Term,Term);
static Int a_dif(Term,Term);
static Int a_gt(Term, Term);
static Int a_ge(Term,Term);
static Int a_lt(Term,Term);
static Int a_le(Term,Term);
static Int a_noteq(Term,Term);
static Int a_gen_lt(Term,Term);
static Int a_gen_le(Term,Term);
static Int a_gen_gt(Term,Term);
static Int a_gen_ge(Term,Term);

#define rfloat(X)	( X > 0.0 ? 1 : ( X == 0.0 ? 0 : -1))

static int
cmp_atoms(Atom a1, Atom a2)
{
  if (IsWideAtom(a1)) {
    if (IsWideAtom(a2)) {
      return wcscmp((wchar_t *)RepAtom(a1)->StrOfAE,(wchar_t *)RepAtom(a2)->StrOfAE);
    } else {
      /* The standard does not seem to have nothing on this */
      unsigned char *s1 = (unsigned char *)RepAtom(a1)->StrOfAE;
      wchar_t *s2 = (wchar_t *)RepAtom(a2)->StrOfAE;

      while (*s1 == *s2) {
	if (!*s1) return 0;
	s1++;
	s2++;
      }
      return *s1-*s2;
    }
  } else if (IsWideAtom(a2)) {
    /* The standard does not seem to have nothing on this */
    wchar_t *s1 = (wchar_t *)RepAtom(a1)->StrOfAE;
    unsigned char *s2 = (unsigned char *)RepAtom(a2)->StrOfAE;

    while (*s1 == *s2) {
      if (!*s1) return 0;
      s1++;
      s2++;
    }
    return *s1-*s2;
  } else {
    return strcmp(RepAtom(a1)->StrOfAE,RepAtom(a2)->StrOfAE);
  }
}

static int compare_complex(register CELL *pt0, register CELL *pt0_end, register
		   CELL *pt1)
{
  CACHE_REGS
  register CELL **to_visit = (CELL **)HR;
  register int out = 0;

 loop:
  while (pt0 < pt0_end) {
    register CELL d0, d1;
    ++ pt0;
    ++ pt1;
    d0 = Derefa(pt0);
    d1 = Derefa(pt1);
    if (IsVarTerm(d0)) {
      if (IsVarTerm(d1)) {
	out = Signed(d0) - Signed(d1);
	if (out) goto done;
      }
      else {
	out = -1;
	goto done;
      }
    } else if (IsVarTerm(d1)) {
      out = 1;
      goto done;
    } else {
      if (d0 == d1) continue;
      else if (IsAtomTerm(d0)) {
	if (IsAtomTerm(d1))
	  out = cmp_atoms(AtomOfTerm(d0), AtomOfTerm(d1));
	else if (IsPrimitiveTerm(d1))
	  out = 1;
	else out = -1;
	/* I know out must be != 0 */
	goto done;
      }
      else if (IsIntTerm(d0)) {
	if (IsIntTerm(d1))
	  out = IntOfTerm(d0) - IntOfTerm(d1);
	else if (IsFloatTerm(d1)) {
	  out = 1;
	} else if (IsLongIntTerm(d1)) {
	  out = IntOfTerm(d0) - LongIntOfTerm(d1);
#ifdef USE_GMP
	} else if (IsBigIntTerm(d1)) {
	  out = Yap_gmp_tcmp_int_big(IntOfTerm(d0), d1);
#endif
	} else if (IsRefTerm(d1))
		out = 1 ;
	else out = -1;
	if (out != 0)
	  goto done;
      } else if (IsFloatTerm(d0)) {
	if (IsFloatTerm(d1)){
	  out = rfloat(FloatOfTerm(d0) - FloatOfTerm(d1));
	} else if (IsRefTerm(d1)) {
	  out = 1;
	} else {
	  out = -1;
	}
	if (out != 0)
	  goto done;
      } else if (IsStringTerm(d0)) {
	if (IsStringTerm(d1)){
	  out = strcmp(StringOfTerm(d0) , StringOfTerm(d1));
	} else if (IsIntTerm(d1))
	  out = 1;
	else if (IsFloatTerm(d1)) {
	  out = 1;
	} else if (IsLongIntTerm(d1)) {
	  out = 1;
#ifdef USE_GMP
	} else if (IsBigIntTerm(d1)) {
	  out = 1;
#endif
	} else if (IsRefTerm(d1)) {
	  out = 1 ;
	} else {
	  out = -1;
	}
	if (out != 0)
	  goto done;
      } else if (IsLongIntTerm(d0)) {
	if (IsIntTerm(d1))
	  out = LongIntOfTerm(d0) - IntOfTerm(d1);
	else if (IsFloatTerm(d1)) {
	  out = 1;
	} else if (IsLongIntTerm(d1)) {
	  out = LongIntOfTerm(d0) - LongIntOfTerm(d1);
#ifdef USE_GMP
	} else if (IsBigIntTerm(d1)) {
	  out = Yap_gmp_tcmp_int_big(LongIntOfTerm(d0), d1);
#endif
	} else if (IsRefTerm(d1)) {
	  out = 1 ;
	} else {
	  out = -1;
	}
	if (out != 0)
	  goto done;
      }
#ifdef USE_GMP
      else if (IsBigIntTerm(d0)) {
	if (IsIntTerm(d1)) {
	  out = Yap_gmp_tcmp_int_big(d0, IntOfTerm(d1));
	} else if (IsFloatTerm(d1)) {
	  out = 1;
	} else if (IsLongIntTerm(d1)) {
	  out = Yap_gmp_tcmp_int_big(d0, LongIntOfTerm(d1));
	} else if (IsBigIntTerm(d1)) {
	  out = Yap_gmp_tcmp_big_big(d0, d1);
	} else if (IsRefTerm(d1))
	  out = 1 ;
	else out = -1;
	if (out != 0)
	  goto done;
      }
#endif
      else if (IsPairTerm(d0)) {
	if (!IsPairTerm(d1)) {
	  if (IsApplTerm(d1)) {
	    Functor f = FunctorOfTerm(d1);
	    if (IsExtensionFunctor(f))
	      out = 1;
	    else if (!(out = 2-ArityOfFunctor(f)))
	       out = strcmp(".",RepAtom(NameOfFunctor(f))->StrOfAE);
	  } else out = 1;
	  goto done;
	}
#ifdef RATIONAL_TREES
	to_visit[0] = pt0;
	to_visit[1] = pt0_end;
	to_visit[2] = pt1;
	to_visit[3] = (CELL *)*pt0;
	to_visit += 4;
	*pt0 = d1;
#else
	/* store the terms to visit */
	if (pt0 < pt0_end) {
	  to_visit[0] = pt0;
	  to_visit[1] = pt0_end;
	  to_visit[2] = pt1;
	  to_visit += 3;
	}
#endif
	pt0 = RepPair(d0) - 1;
	pt0_end = RepPair(d0) + 1;
	pt1 = RepPair(d1) - 1;
	continue;
      }
      else if (IsRefTerm(d0)) {
	if (IsRefTerm(d1))
	  out = Unsigned(RefOfTerm(d1)) -
	    Unsigned(RefOfTerm(d0));
	else out = -1;
	goto done;
      } else if (IsApplTerm(d0)) {
	register Functor f;
	register CELL *ap2, *ap3;
	if (!IsApplTerm(d1)) {
	  out = 1 ;
	  goto done;
	} else {
	  /* store the terms to visit */
	  Functor f2;
	  ap2 = RepAppl(d0);
	  ap3 = RepAppl(d1);
	  f = (Functor)(*ap2);
	  if (IsExtensionFunctor(f)) {
	    out = 1;
	    goto done;
	  }
	  f2 = (Functor)(*ap3);	
	  if (IsExtensionFunctor(f2)) {
	    out = -1;
	    goto done;
	  }
	  /* compare functors */
	  if (f != (Functor)*ap3) {
	    if (!(out = ArityOfFunctor(f)-ArityOfFunctor(f2)))
	       out = cmp_atoms(NameOfFunctor(f), NameOfFunctor(f2));
	    goto done;
	  }
#ifdef RATIONAL_TREES
	to_visit[0] = pt0;
	to_visit[1] = pt0_end;
	to_visit[2] = pt1;
	to_visit[3] = (CELL *)*pt0;
	to_visit += 4;
	*pt0 = d1;
#else
	  /* store the terms to visit */
	  if (pt0 < pt0_end) {
	    to_visit[0] = pt0;
	    to_visit[1] = pt0_end;
	    to_visit[2] = pt1;
	    to_visit += 3;
	  }
#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 **)HR) {
#ifdef RATIONAL_TREES
    to_visit -= 4;
    pt0 = to_visit[0];
    pt0_end = to_visit[1];
    pt1 = to_visit[2];
    *pt0 = (CELL)to_visit[3];
#else
    to_visit -= 3;
    pt0 = to_visit[0];
    pt0_end = to_visit[1];
    pt1 = to_visit[2];
#endif
    goto loop;
  }

 done:
  /* failure */
#ifdef RATIONAL_TREES
  while (to_visit > (CELL **)HR) {
    to_visit -= 4;
    pt0 = to_visit[0];
    pt0_end = to_visit[1];
    pt1 = to_visit[2];
    *pt0 = (CELL)to_visit[3];
  }
#endif
  return(out);
}

inline static Int 
compare(Term t1, Term t2) /* compare terms t1 and t2	 */
{

  if (t1 == t2)
    return 0;
  if (IsVarTerm(t1)) {
    if (IsVarTerm(t2))
      return Signed(t1) - Signed(t2);
    return -1;
  } else if (IsVarTerm(t2)) {
    /* get rid of variables */
    return 1;
  }
  if (IsAtomOrIntTerm(t1)) {
    if (IsAtomTerm(t1)) {
      if (IsAtomTerm(t2))
	return cmp_atoms(AtomOfTerm(t1),AtomOfTerm(t2));
      if (IsPrimitiveTerm(t2))
	return 1;
      if (IsStringTerm(t2))
	return 1;
      return -1;
    } else {
      if (IsIntTerm(t2)) {
	return IntOfTerm(t1) - IntOfTerm(t2);
      }
      if (IsApplTerm(t2)) {
	Functor fun2 = FunctorOfTerm(t2);
	switch ((CELL)fun2) {
	case double_e:
	  return 1;
	case long_int_e:
	  return IntOfTerm(t1) - LongIntOfTerm(t2);
#ifdef USE_GMP
	case big_int_e:
	  return Yap_gmp_tcmp_int_big(IntOfTerm(t1), t2);
#endif
	case db_ref_e:
	  return 1;
	case string_e:
	  return -1;
	}
      }
      return -1;
    }
  } else if (IsPairTerm(t1)) {
    if (IsApplTerm(t2)) {
      Functor f = FunctorOfTerm(t2);
      if (IsExtensionFunctor(f))
	return 1;
      else {
	int out;
	if (!(out = 2-ArityOfFunctor(f)))
	  out = strcmp(".",RepAtom(NameOfFunctor(f))->StrOfAE);
	return(out);
      }
    }
    if (IsPairTerm(t2)) {
      return(compare_complex(RepPair(t1)-1,
			     RepPair(t1)+1,
			     RepPair(t2)-1));
    }
    else return 1;
  } else {
    /* compound term */
    Functor fun1 = FunctorOfTerm(t1);

    if (IsExtensionFunctor(fun1)) {
      /* float, long, big, dbref */
      switch ((CELL)fun1) {
      case double_e:
	{
	  if (IsFloatTerm(t2))
	    return(rfloat(FloatOfTerm(t1) - FloatOfTerm(t2)));
	  if (IsRefTerm(t2))
	    return 1;
	  return -1;
	}
      case long_int_e:
	{
	  if (IsIntTerm(t2))
	    return LongIntOfTerm(t1) - IntOfTerm(t2);
	  if (IsFloatTerm(t2)) {
	    return 1;
	  }
	  if (IsLongIntTerm(t2))
	    return LongIntOfTerm(t1) - LongIntOfTerm(t2);
#ifdef USE_GMP
	  if (IsBigIntTerm(t2)) {
	    return Yap_gmp_tcmp_int_big(LongIntOfTerm(t1), t2);
	  }
#endif
	  if (IsRefTerm(t2))
	    return 1;
	  return -1;
	}
#ifdef USE_GMP
      case big_int_e:
	{
	  if (IsIntTerm(t2))
	    return Yap_gmp_tcmp_big_int(t1, IntOfTerm(t2));
	  if (IsFloatTerm(t2)) {
	    return 1;
	  }
	  if (IsLongIntTerm(t2))
	    return Yap_gmp_tcmp_big_int(t1, LongIntOfTerm(t2));
	  if (IsBigIntTerm(t2)) {
	    return Yap_gmp_tcmp_big_big(t1, t2);
	  }
	  if (IsRefTerm(t2))
	    return 1;
	  return -1;
	}
#endif
      case string_e:
	{
	  if (IsApplTerm(t2)) {
	    Functor fun2 = FunctorOfTerm(t2);
	    switch ((CELL)fun2) {
	    case double_e:
	      return 1;
	    case long_int_e:
	      return 1;
#ifdef USE_GMP
	    case big_int_e:
	      return 1;
#endif
	    case db_ref_e:
	      return 1;
	    case string_e:
	      return strcmp(StringOfTerm(t1), StringOfTerm(t2));
	    }
	    return -1;
	  }
	  return -1;
	}
      case db_ref_e:
	if (IsRefTerm(t2))
	  return Unsigned(RefOfTerm(t2)) -
	    Unsigned(RefOfTerm(t1));
	return -1;
      }
    }
    if (!IsApplTerm(t2)) {
      if (IsPairTerm(t2)) {
	Int out;
	Functor f = FunctorOfTerm(t1);

	if (!(out = ArityOfFunctor(f))-2)
	  out = strcmp(RepAtom(NameOfFunctor(f))->StrOfAE,".");
	return out;
      }
      return 1;
    } else {
      Functor fun2 = FunctorOfTerm(t2);
      Int r;

      if (IsExtensionFunctor(fun2)) {
	return 1;
      }
      r = ArityOfFunctor(fun1) - ArityOfFunctor(fun2);
      if (r)
	return r;
      r = cmp_atoms(NameOfFunctor(fun1), NameOfFunctor(fun2));
      if (r)
	return r;
      else
	return(compare_complex(RepAppl(t1),
			       RepAppl(t1)+ArityOfFunctor(fun1),
			       RepAppl(t2)));
    }
  }
}

Int Yap_compare_terms(Term d0, Term d1)
{
  return compare(Deref(d0),Deref(d1));
}

static Int 
p_compare( USES_REGS1 )
{				/* compare(?Op,?T1,?T2)	 */
  Int             r = compare(Deref(ARG2), Deref(ARG3));
  Atom            p;

  if (r < 0)
    p = AtomLT;
  else if (r > 0)
    p = AtomGT;
  else
    p = AtomEQ;
  return Yap_unify_constant(ARG1, MkAtomTerm(p));
}

inline static Int
int_cmp(Int dif)
{
  return dif;
}

inline static Int
flt_cmp(Float dif)
{
  if (dif < 0.0)
    return -1;
  if (dif > 0.0)
    return 1;
  return dif = 0.0;
}


static inline Int
a_cmp(Term t1, Term t2 USES_REGS)
{
  LOCAL_ArithError = FALSE;
  if (IsVarTerm(t1)) {
    LOCAL_ArithError = TRUE;
    Yap_Error(INSTANTIATION_ERROR, t1, "=:=/2");
    return FALSE;
  }
  if (IsVarTerm(t2)) {
    LOCAL_ArithError = TRUE;
    Yap_Error(INSTANTIATION_ERROR, t2, "=:=/2");
    return FALSE;
  }
  if (IsFloatTerm(t1) && IsFloatTerm(t2)) {
    return flt_cmp(FloatOfTerm(t1)-FloatOfTerm(t2));
  }
  if (IsIntegerTerm(t1) && IsIntegerTerm(t2)) {
    return int_cmp(IntegerOfTerm(t1)-IntegerOfTerm(t2));
  }
  t1 = Yap_Eval(t1);
  if (!t1) {
    return FALSE;
  }
  if (IsIntegerTerm(t1)) {
    Int i1 = IntegerOfTerm(t1);
    t2 = Yap_Eval(t2);

    if (IsIntegerTerm(t2)) {
      Int i2 = IntegerOfTerm(t2);
      return int_cmp(i1-i2);
    } else if (IsFloatTerm(t2)) {
      Float f2 = FloatOfTerm(t2);
#if HAVE_ISNAN
      if (isnan(f2)) {
	LOCAL_Error_TYPE = EVALUATION_ERROR_UNDEFINED;
	LOCAL_Error_Term = t2;
	LOCAL_ErrorMessage = "trying to evaluate nan";
	LOCAL_ArithError = TRUE;
      }
#endif      
      return flt_cmp(i1-f2);
#ifdef USE_GMP
    } else if (IsBigIntTerm(t2)) {
      return Yap_gmp_cmp_int_big(i1,t2);
#endif
    } else {
      return FALSE;
    }
  } else if (IsFloatTerm(t1)) {
    Float f1 = FloatOfTerm(t1);
#if HAVE_ISNAN
    if (isnan(f1)) {
      LOCAL_Error_TYPE = EVALUATION_ERROR_UNDEFINED;
      LOCAL_Error_Term = t1;
      LOCAL_ErrorMessage = "trying to evaluate nan";
      LOCAL_ArithError = TRUE;
    }
#endif      
    t2 = Yap_Eval(t2);
#if HAVE_ISNAN
      if (isnan(f1))
	return -1;
#endif      

    if (IsIntegerTerm(t2)) {
      Int i2 = IntegerOfTerm(t2);
      return flt_cmp(f1-i2);
    } else if (IsFloatTerm(t2)) {
      Float f2 = FloatOfTerm(t2);
#if HAVE_ISNAN
      if (isnan(f2)) {
	LOCAL_Error_TYPE = EVALUATION_ERROR_UNDEFINED;
	LOCAL_Error_Term = t2;
	LOCAL_ErrorMessage = "trying to evaluate nan";
	LOCAL_ArithError = TRUE;
      }
#endif      
      return flt_cmp(f1-f2);
#ifdef USE_GMP
    } else if (IsBigIntTerm(t2)) {
      return Yap_gmp_cmp_float_big(f1,t2);
#endif
    } else {
      return FALSE;
    }
#ifdef USE_GMP
  } else if (IsBigIntTerm(t1)) {
    {
      t2 = Yap_Eval(t2);

      if (IsIntegerTerm(t2)) {
	return Yap_gmp_cmp_big_int(t1, IntegerOfTerm(t2));
      } else if (IsFloatTerm(t2)) {
	Float f2 = FloatOfTerm(t2);
#if HAVE_ISNAN
	if (isnan(f2)) {
	  LOCAL_Error_TYPE = EVALUATION_ERROR_UNDEFINED;
	  LOCAL_Error_Term = t2;
	  LOCAL_ErrorMessage = "trying to evaluate nan";
	  LOCAL_ArithError = TRUE;
	}
#endif      
	return Yap_gmp_cmp_big_float(t1, f2);
      } else if (IsBigIntTerm(t2)) {
	return Yap_gmp_cmp_big_big(t1, t2);
      } else {
	return FALSE;
      }
    }
#endif
  } else {
    return FALSE;
  }
}

/**

   @defgroup arithmetic_cmps Arithmetic Comparison Predicates
   @ingroup arithmetic

   Comparison of Numeric Expressions. Both arguments must be valid ground expressions at time of call.

   @{
*/


Int
Yap_acmp(Term t1, Term t2 USES_REGS)
{
  Int out = a_cmp(t1, t2 PASS_REGS);
  if (LOCAL_ArithError) { Yap_Error(LOCAL_Error_TYPE, LOCAL_Error_Term, LOCAL_ErrorMessage); return FALSE; }
  return out;
}

static Int 
p_acomp( USES_REGS1 )
{				/* $a_compare(?R,+X,+Y) */
  Term t1 = Deref(ARG1);
  Term t2 = Deref(ARG2);
  Int out;

  out = a_cmp(t1, t2 PASS_REGS);
  if (LOCAL_ArithError) { Yap_Error(LOCAL_Error_TYPE, LOCAL_Error_Term, LOCAL_ErrorMessage); return FALSE; }
  return out;
}

/**
   @class arith_eq_2
   @brief  =:=/2: Equality of arithmetic expressions

   <b>+ _X_ =:= + _Y_ [ISO]</b><p> @anchor ar_eq_2


   The value of the expression  _X_ is less than the value of expression _Y_.
 */
static Int 
a_eq(Term t1, Term t2)
{
  CACHE_REGS
  /* A =:= B		 */
  int out;

  if (IsVarTerm(t1)) {
    Yap_Error(INSTANTIATION_ERROR, t1, "=:=/2");
    return(FALSE);
  }
  if (IsVarTerm(t2)) {
    Yap_Error(INSTANTIATION_ERROR, t2, "=:=/2");
    return(FALSE);
  }
  if (IsFloatTerm(t1)) {
    if (IsFloatTerm(t2))
      return (FloatOfTerm(t1) == FloatOfTerm(t2));
    else if (IsIntegerTerm(t2)) {
      return (FloatOfTerm(t1) == IntegerOfTerm(t2));
    }
  }
  if (IsIntegerTerm(t1)) {
    if (IsIntegerTerm(t2)) {
      return (IntegerOfTerm(t1) == IntegerOfTerm(t2));
    } else if (IsFloatTerm(t2)) {
      return (FloatOfTerm(t2) == IntegerOfTerm(t1));
    }
  }
  out = a_cmp(t1,t2 PASS_REGS);
  if (LOCAL_ArithError) { Yap_Error(LOCAL_Error_TYPE, LOCAL_Error_Term, LOCAL_ErrorMessage); return FALSE; }
  return out == 0;
}

/**
   @class arith_dif_2
   @brief  =\\=/2: Difference of arithmetic expressions

   <b>+ _X_ =\\= + _Y_ [ISO]</b><p> @anchor ar_dif_2


   The value of the expression  _X_ is different from the value of expression _Y_.
 */
static Int 
a_dif(Term t1, Term t2)
{
  CACHE_REGS
  Int out = a_cmp(Deref(t1),Deref(t2) PASS_REGS);
  if (LOCAL_ArithError) { Yap_Error(LOCAL_Error_TYPE, LOCAL_Error_Term, LOCAL_ErrorMessage); return FALSE; }
  return out != 0;
}

/**
   @class arith_gt_2
   @brief \>/2: Greater than arithmetic expressions

  <b>+ _X_ \> + _Y_ [ISO]</b><p> @anchor qQlg_2


  The value of the expression  _X_ is less than or equal to the value
  of expression  _Y_.
*/
static Int 
a_gt(Term t1, Term t2)
{				/* A > B		 */
  CACHE_REGS
  Int out = a_cmp(Deref(t1),Deref(t2) PASS_REGS);
  if (LOCAL_ArithError) { Yap_Error(LOCAL_Error_TYPE, LOCAL_Error_Term, LOCAL_ErrorMessage); return FALSE; }
  return out > 0;
}

/**
   @class arith_ge_2
   @brief  \>=/2: Greater than or equal to arithmetic expressions

   <b>+ _X_ \>= + _Y_ [ISO]</b><p> @anchor gGqQ_2


   The value of the expression  _X_ is greater than or equal to the
   value of expression  _Y_.
*/
static Int 
a_ge(Term t1, Term t2)
{				/* A >= B		 */
  CACHE_REGS
  Int out = a_cmp(Deref(t1),Deref(t2) PASS_REGS);
  if (LOCAL_ArithError) { Yap_Error(LOCAL_Error_TYPE, LOCAL_Error_Term, LOCAL_ErrorMessage); return FALSE; }
  return out >= 0;
}

/**
   @class arith_lt_2
   @brief \</2: Lesser than arithmetic expressions

   <b>+ _X_ \< + _Y_ [ISO]</b><p> @anchor sS_2


   The value of the expression  _X_ is less than the value of expression
   _Y_.
*/
static Int 
a_lt(Term t1, Term t2)
{				/* A < B       */
  CACHE_REGS
  Int out = a_cmp(Deref(t1),Deref(t2) PASS_REGS);
  if (LOCAL_ArithError) { Yap_Error(LOCAL_Error_TYPE, LOCAL_Error_Term, LOCAL_ErrorMessage); return FALSE; }
  return out < 0;
}

/**
 *
 @class arith_le_2
 @brief =\</2: Lesser than or equal to arithmetic expressions

 <b>+ _X_ =\< + _Y_ [ISO]</b><p> @anchor qQsS_2


 The value of the expression  _X_ is less than or equal to the value
 of expression  _Y_.
*/
static Int 
a_le(Term t1, Term t2)
{				/* A <= B */
  CACHE_REGS
  Int out = a_cmp(Deref(t1),Deref(t2) PASS_REGS);
  if (LOCAL_ArithError) { Yap_Error(LOCAL_Error_TYPE, LOCAL_Error_Term, LOCAL_ErrorMessage); return FALSE; }
  return out <= 0;
}

/// @}

static Int 
a_noteq(Term t1, Term t2)
{
  return (compare(t1, t2) != 0);
}

static Int 
a_gen_lt(Term t1, Term t2)
{
  return (compare(t1, t2) < 0);
}

static Int 
a_gen_le(Term t1, Term t2)
{
  return (compare(t1, t2) <= 0);
}

static Int 
a_gen_gt(Term t1, Term t2)
{
  return compare(t1, t2) > 0;
}

static Int 
a_gen_ge(Term t1, Term t2)
{
  return compare(t1, t2) >= 0;
}


void 
Yap_InitCmpPreds(void)
{
  Yap_InitCmpPred("=:=", 2, a_eq, SafePredFlag | BinaryPredFlag);
  Yap_InitCmpPred("=\\=", 2, a_dif, SafePredFlag | BinaryPredFlag);
  Yap_InitCmpPred(">", 2, a_gt,  SafePredFlag | BinaryPredFlag);
  Yap_InitCmpPred("=<", 2, a_le, SafePredFlag | BinaryPredFlag);
  Yap_InitCmpPred("<", 2, a_lt, SafePredFlag | BinaryPredFlag);
  Yap_InitCmpPred(">=", 2, a_ge, SafePredFlag | BinaryPredFlag);
  Yap_InitCPred("$a_compare", 3, p_acomp, TestPredFlag | SafePredFlag);
  Yap_InitCmpPred("\\==", 2, a_noteq, BinaryPredFlag | SafePredFlag);
  Yap_InitCmpPred("@<", 2, a_gen_lt, BinaryPredFlag | SafePredFlag);
  Yap_InitCmpPred("@=<", 2, a_gen_le, BinaryPredFlag | SafePredFlag);
  Yap_InitCmpPred("@>", 2, a_gen_gt, BinaryPredFlag | SafePredFlag);
  Yap_InitCmpPred("@>=", 2, a_gen_ge, BinaryPredFlag | SafePredFlag);
  Yap_InitCPred("compare", 3, p_compare, TestPredFlag | SafePredFlag);
}