libguile/variable.c

   1 /*      Copyright (C) 1995, 1996, 1997, 1998, 2000 Free Software Foundation, Inc.
   2  *
   3  * This program is free software; you can redistribute it and/or modify
   4  * it under the terms of the GNU General Public License as published by
   5  * the Free Software Foundation; either version 2, or (at your option)
   6  * any later version.
   7  *
   8  * This program 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
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License
  14  * along with this software; see the file COPYING.  If not, write to
  15  * the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
  16  * Boston, MA 02111-1307 USA
  17  *
  18  * As a special exception, the Free Software Foundation gives permission
  19  * for additional uses of the text contained in its release of GUILE.
  20  *
  21  * The exception is that, if you link the GUILE library with other files
  22  * to produce an executable, this does not by itself cause the
  23  * resulting executable to be covered by the GNU General Public License.
  24  * Your use of that executable is in no way restricted on account of
  25  * linking the GUILE library code into it.
  26  *
  27  * This exception does not however invalidate any other reasons why
  28  * the executable file might be covered by the GNU General Public License.
  29  *
  30  * This exception applies only to the code released by the
  31  * Free Software Foundation under the name GUILE.  If you copy
  32  * code from other Free Software Foundation releases into a copy of
  33  * GUILE, as the General Public License permits, the exception does
  34  * not apply to the code that you add in this way.  To avoid misleading
  35  * anyone as to the status of such modified files, you must delete
  36  * this exception notice from them.
  37  *
  38  * If you write modifications of your own for GUILE, it is your choice
  39  * whether to permit this exception to apply to your modifications.
  40  * If you do not wish that, delete this exception notice.  */
  41
  42 /* Software engineering face-lift by Greg J. Badros, 11-Dec-1999,
  43    gjb@cs.washington.edu, http://www.cs.washington.edu/homes/gjb */
  44
  45 \f
  46
  47 #include "libguile/_scm.h"
  48 #include "libguile/eq.h"
  49 #include "libguile/ports.h"
  50 #include "libguile/root.h"
  51 #include "libguile/smob.h"
  52
  53 #include "libguile/validate.h"
  54 #include "libguile/variable.h"
  55 \f
  56 scm_bits_t scm_tc16_variable;
  57
  58 static int
  59 variable_print (SCM exp, SCM port, scm_print_state *pstate)
  60 {
  61   scm_puts ("#<variable ", port);
  62   scm_intprint(SCM_UNPACK (exp), 16, port);
  63   {
  64     SCM val_cell;
  65     val_cell = SCM_CDR(exp);
  66     if (!SCM_UNBNDP (SCM_CAR (val_cell)))
  67       {
  68         scm_puts (" name: ", port);
  69         scm_iprin1 (SCM_CAR (val_cell), port, pstate);
  70       }
  71     scm_puts (" binding: ", port);
  72     scm_iprin1 (SCM_CDR (val_cell), port, pstate);
  73   }
  74   scm_putc('>', port);
  75   return 1;
  76 }
  77
  78 static SCM
  79 variable_equalp (SCM var1, SCM var2)
  80 {
  81   return scm_equal_p (SCM_CDR (var1), SCM_CDR (var2));
  82 }
  83 \f
  84
  85 SCM_SYMBOL (anonymous_variable_sym, "anonymous-variable");
  86
  87
  88 static SCM
  89 make_vcell_variable (SCM vcell)
  90 {
  91   SCM_RETURN_NEWSMOB (scm_tc16_variable, SCM_UNPACK (vcell));
  92 }
  93
  94 SCM_DEFINE (scm_make_variable, "make-variable", 1, 1, 0,
  95             (SCM init, SCM name_hint),
  96             "Return a variable object initialized to value @var{init}.\n"
  97             "If given, uses @var{name-hint} as its internal (debugging)\n"
  98             "name, otherwise just treat it as an anonymous variable.\n"
  99             "Remember, of course, that multiple bindings to the same\n"
 100             "variable may exist, so @var{name-hint} is just that---a hint.\n")
 101 #define FUNC_NAME s_scm_make_variable
 102 {
 103   SCM val_cell;
 104
 105   if (SCM_UNBNDP (name_hint))
 106     name_hint = anonymous_variable_sym;
 107
 108   SCM_NEWCELL(val_cell);
 109   SCM_DEFER_INTS;
 110   SCM_SETCAR (val_cell, name_hint);
 111   SCM_SETCDR (val_cell, init);
 112   SCM_ALLOW_INTS;
 113   return make_vcell_variable (val_cell);
 114 }
 115 #undef FUNC_NAME
 116
 117
 118 SCM_DEFINE (scm_make_undefined_variable, "make-undefined-variable", 0, 1, 0,
 119             (SCM name_hint),
 120             "Return a variable object initialized to an undefined value.\n"
 121             "If given, uses @var{name-hint} as its internal (debugging)\n"
 122             "name, otherwise just treat it as an anonymous variable.\n"
 123             "Remember, of course, that multiple bindings to the same\n"
 124             "variable may exist, so @var{name-hint} is just that---a hint.\n")
 125 #define FUNC_NAME s_scm_make_undefined_variable
 126 {
 127   SCM vcell;
 128
 129   if (SCM_UNBNDP (name_hint))
 130     name_hint = anonymous_variable_sym;
 131
 132   SCM_NEWCELL (vcell);
 133   SCM_DEFER_INTS;
 134   SCM_SETCAR (vcell, name_hint);
 135   SCM_SETCDR (vcell, SCM_UNDEFINED);
 136   SCM_ALLOW_INTS;
 137   return make_vcell_variable (vcell);
 138 }
 139 #undef FUNC_NAME
 140
 141
 142 SCM_DEFINE (scm_variable_p, "variable?", 1, 0, 0,
 143             (SCM obj),
 144             "Return @code{#t} iff @var{obj} is a variable object, else\n"
 145             "return @code{#f}\n")
 146 #define FUNC_NAME s_scm_variable_p
 147 {
 148   return SCM_BOOL (SCM_VARIABLEP (obj));
 149 }
 150 #undef FUNC_NAME
 151
 152
 153 SCM_DEFINE (scm_variable_ref, "variable-ref", 1, 0, 0,
 154             (SCM var),
 155             "Dereference @var{var} and return its value.\n"
 156             "@var{var} must be a variable object; see @code{make-variable}\n"
 157             "and @code{make-undefined-variable}.")
 158 #define FUNC_NAME s_scm_variable_ref
 159 {
 160   SCM_VALIDATE_VARIABLE (1, var);
 161   return SCM_CDR (SCM_CDR (var));
 162 }
 163 #undef FUNC_NAME
 164
 165
 166
 167 SCM_DEFINE (scm_variable_set_x, "variable-set!", 2, 0, 0,
 168             (SCM var, SCM val),
 169             "Set the value of the variable @var{var} to @var{val}.\n"
 170             "@var{var} must be a variable object, @var{val} can be any\n"
 171             "value. Return an unspecified value.\n")
 172 #define FUNC_NAME s_scm_variable_set_x
 173 {
 174   SCM_VALIDATE_VARIABLE (1,var);
 175   SCM_SETCDR (SCM_CDR (var), val);
 176   return SCM_UNSPECIFIED;
 177 }
 178 #undef FUNC_NAME
 179
 180
 181 SCM_DEFINE (scm_builtin_variable, "builtin-variable", 1, 0, 0,
 182             (SCM name),
 183             "Return the built-in variable with the name @var{name}.\n"
 184             "@var{name} must be a symbol (not a string).\n"
 185             "Then use @code{variable-ref} to access its value.\n")
 186 #define FUNC_NAME s_scm_builtin_variable
 187 {
 188   SCM vcell;
 189   SCM var_slot;
 190
 191   SCM_VALIDATE_SYMBOL (1,name);
 192   vcell = scm_sym2vcell (name, SCM_BOOL_F, SCM_BOOL_T);
 193   if (SCM_FALSEP (vcell))
 194     return SCM_BOOL_F;
 195
 196   scm_intern_symbol (scm_symhash_vars, name);
 197   var_slot = scm_sym2ovcell (name, scm_symhash_vars);
 198
 199   SCM_DEFER_INTS;
 200   if (SCM_IMP (SCM_CDR (var_slot))
 201       || !SCM_EQ_P (SCM_VARVCELL (var_slot), vcell))
 202     SCM_SETCDR (var_slot, make_vcell_variable (vcell));
 203   SCM_ALLOW_INTS;
 204
 205   return SCM_CDR (var_slot);
 206 }
 207 #undef FUNC_NAME
 208
 209
 210 SCM_DEFINE (scm_variable_bound_p, "variable-bound?", 1, 0, 0,
 211             (SCM var),
 212             "Return @code{#t} iff @var{var} is bound to a value.\n"
 213             "Throws an error if @var{var} is not a variable object.\n")
 214 #define FUNC_NAME s_scm_variable_bound_p
 215 {
 216   SCM_VALIDATE_VARIABLE (1,var);
 217   return SCM_NEGATE_BOOL(SCM_UNBNDP (SCM_CDR (SCM_VARVCELL (var))));
 218 }
 219 #undef FUNC_NAME
 220
 221
 222
 223
 224 void
 225 scm_init_variable ()
 226 {
 227   scm_tc16_variable = scm_make_smob_type ("variable", 0);
 228   scm_set_smob_mark (scm_tc16_variable, scm_markcdr);
 229   scm_set_smob_print (scm_tc16_variable, variable_print);
 230   scm_set_smob_equalp (scm_tc16_variable, variable_equalp);
 231
 232 #ifndef SCM_MAGIC_SNARFER
 233 #include "libguile/variable.x"
 234 #endif
 235 }
 236
 237
 238 /*
 239   Local Variables:
 240   c-file-style: "gnu"
 241   End:
 242 */