libguile/pairs.c

   1 /* Copyright (C) 1995,1996,2000,2001, 2004, 2005, 2006, 2008 Free Software Foundation, Inc.
   2  *
   3  * This library is free software; you can redistribute it and/or
   4  * modify it under the terms of the GNU Lesser General Public
   5  * License as published by the Free Software Foundation; either
   6  * version 2.1 of the License, or (at your option) any later version.
   7  *
   8  * This library is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * Lesser General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU Lesser General Public
  14  * License along with this library; if not, write to the Free Software
  15  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  16  */
  17
  18
  19 \f
  20 #ifdef HAVE_CONFIG_H
  21 # include <config.h>
  22 #endif
  23
  24 #include "libguile/_scm.h"
  25 #include "libguile/validate.h"
  26
  27 #include "libguile/pairs.h"
  28
  29 \f
  30
  31 /* {Pairs}
  32  */
  33
  34 #if (SCM_DEBUG_PAIR_ACCESSES == 1)
  35
  36 #include "libguile/ports.h"
  37 #include "libguile/strings.h"
  38
  39 void scm_error_pair_access (SCM non_pair)
  40 {
  41   static unsigned int running = 0;
  42   SCM message = scm_from_locale_string ("Non-pair accessed with SCM_C[AD]R: `~S'\n");
  43
  44   if (!running)
  45     {
  46       running = 1;
  47       scm_simple_format (scm_current_error_port (),
  48                          message, scm_list_1 (non_pair));
  49       abort ();
  50     }
  51 }
  52
  53 #endif
  54
  55 SCM_DEFINE (scm_cons, "cons", 2, 0, 0,
  56             (SCM x, SCM y),
  57             "Return a newly allocated pair whose car is @var{x} and whose\n"
  58             "cdr is @var{y}.  The pair is guaranteed to be different (in the\n"
  59             "sense of @code{eq?}) from every previously existing object.")
  60 #define FUNC_NAME s_scm_cons
  61 {
  62   return scm_cell (SCM_UNPACK (x), SCM_UNPACK (y));
  63 }
  64 #undef FUNC_NAME
  65
  66
  67 SCM
  68 scm_cons2 (SCM w, SCM x, SCM y)
  69 {
  70   return scm_cons (w, scm_cons (x, y));
  71 }
  72
  73
  74 SCM_DEFINE (scm_pair_p, "pair?", 1, 0, 0,
  75             (SCM x),
  76             "Return @code{#t} if @var{x} is a pair; otherwise return\n"
  77             "@code{#f}.")
  78 #define FUNC_NAME s_scm_pair_p
  79 {
  80   return scm_from_bool (scm_is_pair (x));
  81 }
  82 #undef FUNC_NAME
  83
  84 SCM
  85 scm_car (SCM pair)
  86 {
  87   if (!scm_is_pair (pair))
  88     scm_wrong_type_arg_msg (NULL, 0, pair, "pair");
  89   return SCM_CAR (pair);
  90 }
  91
  92 SCM
  93 scm_cdr (SCM pair)
  94 {
  95   if (!scm_is_pair (pair))
  96     scm_wrong_type_arg_msg (NULL, 0, pair, "pair");
  97   return SCM_CDR (pair);
  98 }
  99
 100 SCM
 101 scm_i_chase_pairs (SCM tree, scm_t_uint32 pattern)
 102 {
 103   do
 104     {
 105       if (!scm_is_pair (tree))
 106         scm_wrong_type_arg_msg (NULL, 0, tree, "pair");
 107       tree = (pattern & 1) ? SCM_CAR (tree) : SCM_CDR (tree);
 108       pattern >>= 2;
 109     }
 110   while (pattern);
 111   return tree;
 112 }
 113
 114 SCM_DEFINE (scm_set_car_x, "set-car!", 2, 0, 0,
 115             (SCM pair, SCM value),
 116             "Stores @var{value} in the car field of @var{pair}.  The value returned\n"
 117             "by @code{set-car!} is unspecified.")
 118 #define FUNC_NAME s_scm_set_car_x
 119 {
 120   SCM_VALIDATE_CONS (1, pair);
 121   SCM_SETCAR (pair, value);
 122   return SCM_UNSPECIFIED;
 123 }
 124 #undef FUNC_NAME
 125
 126
 127 SCM_DEFINE (scm_set_cdr_x, "set-cdr!", 2, 0, 0,
 128             (SCM pair, SCM value),
 129             "Stores @var{value} in the cdr field of @var{pair}.  The value returned\n"
 130             "by @code{set-cdr!} is unspecified.")
 131 #define FUNC_NAME s_scm_set_cdr_x
 132 {
 133   SCM_VALIDATE_CONS (1, pair);
 134   SCM_SETCDR (pair, value);
 135   return SCM_UNSPECIFIED;
 136 }
 137 #undef FUNC_NAME
 138
 139 \f
 140
 141 /* Every cxr-pattern is made up of pairs of bits, starting with the two least
 142  * significant bits.  If in a pair of bits the least significant of the two
 143  * bits is 0, this means CDR, otherwise CAR.  The most significant bits of the
 144  * two bits is only needed to indicate when cxr-ing is ready.  This is the
 145  * case, when all remaining pairs of bits equal 00.  */
 146
 147 typedef struct {
 148   const char *name;
 149   unsigned char pattern;
 150 } t_cxr;
 151
 152 static const t_cxr cxrs[] =
 153 {
 154   {"cdr",    0x02}, /* 00000010 */
 155   {"car",    0x03}, /* 00000011 */
 156   {"cddr",   0x0a}, /* 00001010 */
 157   {"cdar",   0x0b}, /* 00001011 */
 158   {"cadr",   0x0e}, /* 00001110 */
 159   {"caar",   0x0f}, /* 00001111 */
 160   {"cdddr",  0x2a}, /* 00101010 */
 161   {"cddar",  0x2b}, /* 00101011 */
 162   {"cdadr",  0x2e}, /* 00101110 */
 163   {"cdaar",  0x2f}, /* 00101111 */
 164   {"caddr",  0x3a}, /* 00111010 */
 165   {"cadar",  0x3b}, /* 00111011 */
 166   {"caadr",  0x3e}, /* 00111110 */
 167   {"caaar",  0x3f}, /* 00111111 */
 168   {"cddddr", 0xaa}, /* 10101010 */
 169   {"cdddar", 0xab}, /* 10101011 */
 170   {"cddadr", 0xae}, /* 10101110 */
 171   {"cddaar", 0xaf}, /* 10101111 */
 172   {"cdaddr", 0xba}, /* 10111010 */
 173   {"cdadar", 0xbb}, /* 10111011 */
 174   {"cdaadr", 0xbe}, /* 10111110 */
 175   {"cdaaar", 0xbf}, /* 10111111 */
 176   {"cadddr", 0xea}, /* 11101010 */
 177   {"caddar", 0xeb}, /* 11101011 */
 178   {"cadadr", 0xee}, /* 11101110 */
 179   {"cadaar", 0xef}, /* 11101111 */
 180   {"caaddr", 0xfa}, /* 11111010 */
 181   {"caadar", 0xfb}, /* 11111011 */
 182   {"caaadr", 0xfe}, /* 11111110 */
 183   {"caaaar", 0xff}, /* 11111111 */
 184   {0, 0}
 185 };
 186
 187 \f
 188
 189 void
 190 scm_init_pairs ()
 191 {
 192   unsigned int subnr = 0;
 193
 194   for (subnr = 0; cxrs[subnr].name; subnr++)
 195     {
 196       SCM (*pattern) () = (SCM (*) ()) (scm_t_bits) cxrs[subnr].pattern;
 197       scm_c_define_subr (cxrs[subnr].name, scm_tc7_cxr, pattern);
 198     }
 199
 200 #include "libguile/pairs.x"
 201 }
 202
 203
 204 /*
 205   Local Variables:
 206   c-file-style: "gnu"
 207   End:
 208 */