libguile/variable.c

   1 /*      Copyright (C) 1995, 1996, 1997, 1998 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 <stdio.h>
  48 #include "libguile/_scm.h"
  49 #include "libguile/eq.h"
  50 #include "libguile/ports.h"
  51 #include "libguile/root.h"
  52 #include "libguile/smob.h"
  53
  54 #include "libguile/validate.h"
  55 #include "libguile/variable.h"
  56 \f
  57
  58 static int
  59 prin_var (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
  79 static SCM
  80 scm_markvar (SCM ptr)
  81 {
  82   return SCM_CDR (ptr);
  83 }
  84
  85 static SCM
  86 var_equal (SCM var1, SCM var2)
  87 {
  88   return scm_equal_p (SCM_CDR (var1), SCM_CDR (var2));
  89 }
  90
  91 int scm_tc16_variable;
  92 \f
  93
  94 static SCM anonymous_variable_sym;
  95
  96
  97 static SCM
  98 make_vcell_variable (SCM vcell)
  99 {
 100   SCM_RETURN_NEWSMOB (scm_tc16_variable, SCM_UNPACK (vcell));
 101 }
 102
 103 SCM_DEFINE (scm_make_variable, "make-variable", 1, 1, 0,
 104             (SCM init, SCM name_hint),
 105             "Return a variable object initialized to value INIT.\n"
 106             "If given, uses NAME-HINT as its internal (debugging)\n"
 107             "name, otherwise just treat it as an anonymous variable.\n"
 108             "Remember, of course, that multiple bindings to the same\n"
 109             "variable may exist, so NAME-HINT is just that---a hint.\n")
 110 #define FUNC_NAME s_scm_make_variable
 111 {
 112   SCM val_cell;
 113
 114   if (SCM_UNBNDP (name_hint))
 115     name_hint = anonymous_variable_sym;
 116
 117   SCM_NEWCELL(val_cell);
 118   SCM_DEFER_INTS;
 119   SCM_SETCAR (val_cell, name_hint);
 120   SCM_SETCDR (val_cell, init);
 121   SCM_ALLOW_INTS;
 122   return make_vcell_variable (val_cell);
 123 }
 124 #undef FUNC_NAME
 125
 126
 127 SCM_DEFINE (scm_make_undefined_variable, "make-undefined-variable", 0, 1, 0,
 128             (SCM name_hint),
 129             "Return a variable object initialized to an undefined value.\n"
 130             "If given, uses NAME-HINT as its internal (debugging)\n"
 131             "name, otherwise just treat it as an anonymous variable.\n"
 132             "Remember, of course, that multiple bindings to the same\n"
 133             "variable may exist, so NAME-HINT is just that---a hint.\n")
 134 #define FUNC_NAME s_scm_make_undefined_variable
 135 {
 136   SCM vcell;
 137
 138   if (SCM_UNBNDP (name_hint))
 139     name_hint = anonymous_variable_sym;
 140
 141   SCM_NEWCELL (vcell);
 142   SCM_DEFER_INTS;
 143   SCM_SETCAR (vcell, name_hint);
 144   SCM_SETCDR (vcell, SCM_UNDEFINED);
 145   SCM_ALLOW_INTS;
 146   return make_vcell_variable (vcell);
 147 }
 148 #undef FUNC_NAME
 149
 150
 151 SCM_DEFINE (scm_variable_p, "variable?", 1, 0, 0,
 152             (SCM obj),
 153             "Return #t iff OBJ is a variable object, else return #f\n")
 154 #define FUNC_NAME s_scm_variable_p
 155 {
 156   return SCM_BOOL(SCM_VARIABLEP (obj));
 157 }
 158 #undef FUNC_NAME
 159
 160
 161 SCM_DEFINE (scm_variable_ref, "variable-ref", 1, 0, 0,
 162             (SCM var),
 163             "Dereference VAR and return its value.\n"
 164             "VAR must be a variable object;  see `make-variable' and\n"
 165             "`make-undefined-variable'")
 166 #define FUNC_NAME s_scm_variable_ref
 167 {
 168   SCM_VALIDATE_VARIABLE (1,var);
 169   return SCM_CDR (SCM_CDR (var));
 170 }
 171 #undef FUNC_NAME
 172
 173
 174
 175 SCM_DEFINE (scm_variable_set_x, "variable-set!", 2, 0, 0,
 176             (SCM var, SCM val),
 177             "Set the value of the variable VAR to VAL.\n"
 178             "VAR must be a variable object, VAL can be any value.\n"
 179             "Returns an unspecified value.\n")
 180 #define FUNC_NAME s_scm_variable_set_x
 181 {
 182   SCM_VALIDATE_VARIABLE (1,var);
 183   SCM_SETCDR (SCM_CDR (var), val);
 184   return SCM_UNSPECIFIED;
 185 }
 186 #undef FUNC_NAME
 187
 188
 189 SCM_DEFINE (scm_builtin_variable, "builtin-variable", 1, 0, 0,
 190             (SCM name),
 191             "Return the built-in variable with the name NAME.\n"
 192             "NAME must be a symbol (not a string).\n"
 193             "Then use `variable-ref' to access its value.\n")
 194 #define FUNC_NAME s_scm_builtin_variable
 195 {
 196   SCM vcell;
 197   SCM var_slot;
 198
 199   SCM_VALIDATE_SYMBOL (1,name);
 200   vcell = scm_sym2vcell (name, SCM_BOOL_F, SCM_BOOL_T);
 201   if (SCM_FALSEP (vcell))
 202     return SCM_BOOL_F;
 203
 204   scm_intern_symbol (scm_symhash_vars, name);
 205   var_slot = scm_sym2ovcell (name, scm_symhash_vars);
 206
 207   SCM_DEFER_INTS;
 208   if (SCM_IMP (SCM_CDR (var_slot))
 209       || !SCM_EQ_P (SCM_VARVCELL (var_slot), vcell))
 210     SCM_SETCDR (var_slot, make_vcell_variable (vcell));
 211   SCM_ALLOW_INTS;
 212
 213   return SCM_CDR (var_slot);
 214 }
 215 #undef FUNC_NAME
 216
 217
 218 SCM_DEFINE (scm_variable_bound_p, "variable-bound?", 1, 0, 0,
 219             (SCM var),
 220             "Return #t iff VAR is bound to a value.\n"
 221             "Throws an error if VAR is not a variable object.\n")
 222 #define FUNC_NAME s_scm_variable_bound_p
 223 {
 224   SCM_VALIDATE_VARIABLE (1,var);
 225   return SCM_NEGATE_BOOL(SCM_UNBNDP (SCM_CDR (SCM_VARVCELL (var))));
 226 }
 227 #undef FUNC_NAME
 228
 229
 230
 231
 232 void
 233 scm_init_variable ()
 234 {
 235   scm_tc16_variable = scm_make_smob_type_mfpe ("variable", 0,
 236                                               scm_markvar, NULL, prin_var, var_equal);
 237   anonymous_variable_sym = SCM_CAR (scm_sysintern ("anonymous-variable", SCM_UNDEFINED));
 238 #include "libguile/variable.x"
 239 }
 240
 241
 242 /*
 243   Local Variables:
 244   c-file-style: "gnu"
 245   End:
 246 */