#ifndef SCM_PAIRS_H
#define SCM_PAIRS_H

/* Copyright 1995-1996,2000-2001,2004,2006,2008-2010,2012,2018,2025
     Free Software Foundation, Inc.

   This file is part of Guile.

   Guile is free software: you can redistribute it and/or modify it
   under the terms of the GNU Lesser General Public License as published
   by the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   Guile is distributed in the hope that it will be useful, but WITHOUT
   ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
   License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with Guile.  If not, see
   <https://www.gnu.org/licenses/>.  */



#include "libguile/error.h"
#include "libguile/gc.h"
#include "libguile/inline.h"




/*
 * Use scm_is_null_and_not_nil if it's important (for correctness)
 * that #nil must NOT be considered null.
 */
#define scm_is_null_and_not_nil(x)     (scm_is_eq ((x), SCM_EOL))

/*
 * Use scm_is_null_assume_not_nil if 
#nil will never be tested,
 * for increased efficiency.
 */
#define scm_is_null_assume_not_nil(x)  (scm_is_eq ((x), SCM_EOL))

/*
 * See the comments preceeding the definitions of SCM_BOOL_F and
 * SCM_MATCHES_BITS_IN_COMMON in scm.h for more information on how the
 * following macro works.
 */
#define scm_is_null_or_nil(x)  \
  (SCM_MATCHES_BITS_IN_COMMON ((x), SCM_ELISP_NIL, SCM_EOL))




/* Older spellings for these null, nil, and pair predicates. */
#define SCM_NILP(x) (scm_is_eq ((x), SCM_ELISP_NIL))
#define SCM_NULL_OR_NIL_P(x) (scm_is_null_or_nil (x))
#define SCM_NULLP(x) (scm_is_null (x))
#define SCM_NNULLP(x) (!scm_is_null (x))
#define SCM_CONSP(x)            (scm_is_pair (x))
#define SCM_NCONSP(x)           (!SCM_CONSP (x))




/* #nil is null. */
#define scm_is_null(x)		(scm_is_null_or_nil(x))

struct scm_pair
{
  SCM car;
  SCM cdr;
};

static inline int
scm_is_pair (SCM x)
{
  return SCM_I_CONSP (x);
}

static inline struct scm_pair *
scm_to_pair (SCM x)
{
  if (!scm_is_pair (x))
    abort ();
  return (struct scm_pair *) SCM_UNPACK_POINTER (x);
}

static inline SCM
scm_from_pair (struct scm_pair *pair)
{
  return SCM_PACK_POINTER (pair);
}

static inline SCM
scm_pair_car (struct scm_pair *pair)
{
  return pair->car;
}

static inline SCM
scm_pair_cdr (struct scm_pair *pair)
{
  return pair->cdr;
}

static inline void
scm_pair_set_car_x (struct scm_pair *pair, SCM car)
{
  pair->car = car;
}

static inline void
scm_pair_set_cdr_x (struct scm_pair *pair, SCM cdr)
{
  pair->cdr = cdr;
}

static inline SCM*
scm_pair_car_loc (struct scm_pair *pair)
{
  return &pair->car;
}

static inline SCM*
scm_pair_cdr_loc (struct scm_pair *pair)
{
  return &pair->cdr;
}

#define SCM_CAR(x) (scm_pair_car (scm_to_pair (x)))
#define SCM_CDR(x) (scm_pair_cdr (scm_to_pair (x)))

#define SCM_SETCAR(x, v) (scm_pair_set_car_x (scm_to_pair (x), v))
#define SCM_SETCDR(x, v) (scm_pair_set_cdr_x (scm_to_pair (x), v))

#define SCM_CARLOC(x) (scm_pair_car_loc (scm_to_pair (x)))
#define SCM_CDRLOC(x) (scm_pair_cdr_loc (scm_to_pair (x)))

#define SCM_CAAR(OBJ)		SCM_CAR (SCM_CAR (OBJ))
#define SCM_CDAR(OBJ)		SCM_CDR (SCM_CAR (OBJ))
#define SCM_CADR(OBJ)		SCM_CAR (SCM_CDR (OBJ))
#define SCM_CDDR(OBJ)		SCM_CDR (SCM_CDR (OBJ))

#define SCM_CAAAR(OBJ)		SCM_CAR (SCM_CAR (SCM_CAR (OBJ)))
#define SCM_CDAAR(OBJ)		SCM_CDR (SCM_CAR (SCM_CAR (OBJ)))
#define SCM_CADAR(OBJ)		SCM_CAR (SCM_CDR (SCM_CAR (OBJ)))
#define SCM_CDDAR(OBJ)		SCM_CDR (SCM_CDR (SCM_CAR (OBJ)))
#define SCM_CAADR(OBJ)		SCM_CAR (SCM_CAR (SCM_CDR (OBJ)))
#define SCM_CDADR(OBJ)		SCM_CDR (SCM_CAR (SCM_CDR (OBJ)))
#define SCM_CADDR(OBJ)		SCM_CAR (SCM_CDR (SCM_CDR (OBJ)))
#define SCM_CDDDR(OBJ)		SCM_CDR (SCM_CDR (SCM_CDR (OBJ)))

#define SCM_CAAAAR(OBJ)		SCM_CAR (SCM_CAR (SCM_CAR (SCM_CAR (OBJ))))
#define SCM_CDAAAR(OBJ)		SCM_CDR (SCM_CAR (SCM_CAR (SCM_CAR (OBJ))))
#define SCM_CADAAR(OBJ)		SCM_CAR (SCM_CDR (SCM_CAR (SCM_CAR (OBJ))))
#define SCM_CDDAAR(OBJ)		SCM_CDR (SCM_CDR (SCM_CAR (SCM_CAR (OBJ))))
#define SCM_CAADAR(OBJ)		SCM_CAR (SCM_CAR (SCM_CDR (SCM_CAR (OBJ))))
#define SCM_CDADAR(OBJ)		SCM_CDR (SCM_CAR (SCM_CDR (SCM_CAR (OBJ))))
#define SCM_CADDAR(OBJ)		SCM_CAR (SCM_CDR (SCM_CDR (SCM_CAR (OBJ))))
#define SCM_CDDDAR(OBJ)		SCM_CDR (SCM_CDR (SCM_CDR (SCM_CAR (OBJ))))
#define SCM_CAAADR(OBJ)		SCM_CAR (SCM_CAR (SCM_CAR (SCM_CDR (OBJ))))
#define SCM_CDAADR(OBJ)		SCM_CDR (SCM_CAR (SCM_CAR (SCM_CDR (OBJ))))
#define SCM_CADADR(OBJ)		SCM_CAR (SCM_CDR (SCM_CAR (SCM_CDR (OBJ))))
#define SCM_CDDADR(OBJ)		SCM_CDR (SCM_CDR (SCM_CAR (SCM_CDR (OBJ))))
#define SCM_CAADDR(OBJ)		SCM_CAR (SCM_CAR (SCM_CDR (SCM_CDR (OBJ))))
#define SCM_CDADDR(OBJ)		SCM_CDR (SCM_CAR (SCM_CDR (SCM_CDR (OBJ))))
#define SCM_CADDDR(OBJ)		SCM_CAR (SCM_CDR (SCM_CDR (SCM_CDR (OBJ))))
#define SCM_CDDDDR(OBJ)		SCM_CDR (SCM_CDR (SCM_CDR (SCM_CDR (OBJ))))




#define SCM_VALIDATE_NULL(pos, scm) \
  SCM_I_MAKE_VALIDATE_MSG2 (pos, scm, scm_is_null, "empty list")

#define SCM_VALIDATE_NULL_OR_NIL(pos, scm) \
  SCM_MAKE_VALIDATE_MSG (pos, scm, NULL_OR_NIL_P, "empty list")

#define SCM_VALIDATE_CONS(pos, scm) \
  SCM_I_MAKE_VALIDATE_MSG2 (pos, scm, scm_is_pair, "pair")

#ifdef BUILDING_LIBGUILE
#define SCM_VALIDATE_MUTABLE_PAIR(pos, scm) \
  SCM_I_MAKE_VALIDATE_MSG2 (pos, scm, scm_is_mutable_pair, "mutable pair")
#endif /* BUILDING_LIBGUILE */

#define SCM_VALIDATE_NULLORCONS(pos, env) \
  do { \
    SCM_ASSERT (scm_is_null (env) || scm_is_pair (env), env, pos, FUNC_NAME); \
  } while (0)




SCM_API SCM scm_cons (SCM x, SCM y);
SCM_API SCM scm_car (SCM x);
SCM_API SCM scm_cdr (SCM x);

SCM_INTERNAL int scm_is_mutable_pair (SCM x);

SCM_API SCM scm_cons2 (SCM w, SCM x, SCM y);
SCM_API SCM scm_pair_p (SCM x);
SCM_API SCM scm_set_car_x (SCM pair, SCM value);
SCM_API SCM scm_set_cdr_x (SCM pair, SCM value);

SCM_API SCM scm_cddr (SCM x);
SCM_API SCM scm_cdar (SCM x);
SCM_API SCM scm_cadr (SCM x);
SCM_API SCM scm_caar (SCM x);
SCM_API SCM scm_cdddr (SCM x);
SCM_API SCM scm_cddar (SCM x);
SCM_API SCM scm_cdadr (SCM x);
SCM_API SCM scm_cdaar (SCM x);
SCM_API SCM scm_caddr (SCM x);
SCM_API SCM scm_cadar (SCM x);
SCM_API SCM scm_caadr (SCM x);
SCM_API SCM scm_caaar (SCM x);
SCM_API SCM scm_cddddr (SCM x);
SCM_API SCM scm_cdddar (SCM x);
SCM_API SCM scm_cddadr (SCM x);
SCM_API SCM scm_cddaar (SCM x);
SCM_API SCM scm_cdaddr (SCM x);
SCM_API SCM scm_cdadar (SCM x);
SCM_API SCM scm_cdaadr (SCM x);
SCM_API SCM scm_cdaaar (SCM x);
SCM_API SCM scm_cadddr (SCM x);
SCM_API SCM scm_caddar (SCM x);
SCM_API SCM scm_cadadr (SCM x);
SCM_API SCM scm_cadaar (SCM x);
SCM_API SCM scm_caaddr (SCM x);
SCM_API SCM scm_caadar (SCM x);
SCM_API SCM scm_caaadr (SCM x);
SCM_API SCM scm_caaaar (SCM x);

SCM_INTERNAL void scm_init_pairs (void);

#endif  /* SCM_PAIRS_H */