/*************************************************************************
 *									 *
 *	 YAP Prolog 	%W% %G% 					 *
 *	Yap Prolog was developed at NCCUP - Universidade do Porto	 *
 *									 *
 * Copyright L.Damas, V.S.Costa and Universidade do Porto 1985-2012	 *
 *									 *
 **************************************************************************
 *									 *
 * File:		YapCompounTerm.h *
 * mods: *
 * comments:	main header file for YAP				 *
 * version:      $Id: Yap.h,v 1.38 2008-06-18 10:02:27 vsc Exp $	 *
 *************************************************************************/

/*************************************************************************************************
                           High level macros to access arguments
*************************************************************************************************/

#ifndef YAPCOMPOUNDTERM_H

#define YAPCOMPOUNDTERM_H 1

#include "inline-only.h"

EXTERN bool Yap_unify(Term a, Term b);

INLINE_ONLY Term Deref(Term a);

INLINE_ONLY Term Deref(Term a) {
  while (IsVarTerm(a)) {
    Term *b = (Term *)a;
    a = *b;
    if (a == ((Term)b))
      return a;
  }
  return (a);
}

INLINE_ONLY CELL *GetTermAdress(Term a);

INLINE_ONLY Term Derefa(CELL *b);

INLINE_ONLY Term Derefa(CELL *b) {
  Term a = *b;
restart:
  if (!IsVarTerm(a)) {
    return (a);
  } else if (a == (CELL)b) {
    return (a);
  } else {
    b = (CELL *)a;
    a = *b;
    goto restart;
  }
}

INLINE_ONLY Term ArgOfTerm(int i, Term t);

INLINE_ONLY Term ArgOfTerm(int i, Term t)

{
  return (Term)(Derefa(RepAppl(t) + (i)));
}

INLINE_ONLY Term HeadOfTerm(Term);

INLINE_ONLY Term HeadOfTerm(Term t) {
  return (Term)(Derefa(RepPair(t)));
}

INLINE_ONLY Term TailOfTerm(Term);

INLINE_ONLY Term TailOfTerm(Term t) {
  return (Term)(Derefa(RepPair(t) + 1));
}

INLINE_ONLY Term ArgOfTermCell(int i, Term t);

INLINE_ONLY Term ArgOfTermCell(int i, Term t) {
  return (Term)((CELL)(RepAppl(t) + (i)));
}

INLINE_ONLY Term HeadOfTermCell(Term);

INLINE_ONLY Term HeadOfTermCell(Term t) {
  return (Term)((CELL)(RepPair(t)));
}

INLINE_ONLY Term TailOfTermCell(Term);

INLINE_ONLY Term TailOfTermCell(Term t) {
  return (Term)((CELL)(RepPair(t) + 1));
}

#endif /* YAPCOMPOUNDTERM_H */