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 "_scm.h"
  49 #include "eq.h"
  50 #include "genio.h"
  51 #include "smob.h"
  52
  53 #include "validate.h"
  54 #include "variable.h"
  55 \f
  56
  57 static int
  58 prin_var (SCM exp,SCM port,scm_print_state *pstate)
  59 {
  60   scm_puts ("#<variable ", port);
  61   scm_intprint((int) exp, 16, port);
  62   {
  63     SCM val_cell;
  64     val_cell = SCM_CDR(exp);
  65     if (SCM_CAR (val_cell) != SCM_UNDEFINED)
  66       {
  67         scm_puts (" name: ", port);
  68         scm_iprin1 (SCM_CAR (val_cell), port, pstate);
  69       }
  70     scm_puts (" binding: ", port);
  71     scm_iprin1 (SCM_CDR (val_cell), port, pstate);
  72   }
  73   scm_putc('>', port);
  74   return 1;
  75 }
  76
  77
  78 static SCM
  79 scm_markvar (SCM ptr)
  80 {
  81   return SCM_CDR (ptr);
  82 }
  83
  84 static SCM
  85 var_equal (SCM var1, SCM var2)
  86 {
  87   return scm_equal_p (SCM_CDR (var1), SCM_CDR (var2));
  88 }
  89
  90 int scm_tc16_variable;
  91 \f
  92
  93 static SCM anonymous_variable_sym;
  94
  95
  96 static SCM
  97 make_vcell_variable (SCM vcell)
  98 {
  99   SCM_RETURN_NEWSMOB (scm_tc16_variable, vcell);
 100 }
 101
 102 SCM_DEFINE (scm_make_variable, "make-variable", 1, 1, 0,
 103             (SCM init, SCM name_hint),
 104             "Return a variable object initialized to value INIT.\n"
 105             "If given, uses NAME-HINT as its internal (debugging)\n"
 106             "name, otherwise just treat it as an anonymous variable.\n"
 107             "Remember, of course, that multiple bindings to the same\n"
 108             "variable may exist, so NAME-HINT is just that---a hint.\n")
 109 #define FUNC_NAME s_scm_make_variable
 110 {
 111   SCM val_cell;
 112
 113   if (name_hint == SCM_UNDEFINED)
 114     name_hint = anonymous_variable_sym;
 115
 116   SCM_NEWCELL(val_cell);
 117   SCM_DEFER_INTS;
 118   SCM_SETCAR (val_cell, name_hint);
 119   SCM_SETCDR (val_cell, init);
 120   SCM_ALLOW_INTS;
 121   return make_vcell_variable (val_cell);
 122 }
 123 #undef FUNC_NAME
 124
 125
 126 SCM_DEFINE (scm_make_undefined_variable, "make-undefined-variable", 0, 1, 0,
 127             (SCM name_hint),
 128             "Return a variable object initialized to an undefined value.\n"
 129             "If given, uses NAME-HINT as its internal (debugging)\n"
 130             "name, otherwise just treat it as an anonymous variable.\n"
 131             "Remember, of course, that multiple bindings to the same\n"
 132             "variable may exist, so NAME-HINT is just that---a hint.\n")
 133 #define FUNC_NAME s_scm_make_undefined_variable
 134 {
 135   SCM vcell;
 136
 137   if (name_hint == SCM_UNDEFINED)
 138     name_hint = anonymous_variable_sym;
 139
 140   SCM_NEWCELL (vcell);
 141   SCM_DEFER_INTS;
 142   SCM_SETCAR (vcell, name_hint);
 143   SCM_SETCDR (vcell, SCM_UNDEFINED);
 144   SCM_ALLOW_INTS;
 145   return make_vcell_variable (vcell);
 146 }
 147 #undef FUNC_NAME
 148
 149
 150 SCM_DEFINE (scm_variable_p, "variable?", 1, 0, 0,
 151             (SCM obj),
 152             "Return #t iff OBJ is a variable object, else return #f\n")
 153 #define FUNC_NAME s_scm_variable_p
 154 {
 155   return SCM_BOOL(SCM_VARIABLEP (obj));
 156 }
 157 #undef FUNC_NAME
 158
 159
 160 SCM_DEFINE (scm_variable_ref, "variable-ref", 1, 0, 0,
 161             (SCM var),
 162             "Dereference VAR and return its value.\n"
 163             "VAR must be a variable object;  see `make-variable' and\n"
 164             "`make-undefined-variable'")
 165 #define FUNC_NAME s_scm_variable_ref
 166 {
 167   SCM_VALIDATE_VARIABLE (1,var);
 168   return SCM_CDR (SCM_CDR (var));
 169 }
 170 #undef FUNC_NAME
 171
 172
 173
 174 SCM_DEFINE (scm_variable_set_x, "variable-set!", 2, 0, 0,
 175             (SCM var, SCM val),
 176             "Set the value of the variable VAR to VAL.\n"
 177             "VAR must be a variable object, VAL can be any value.\n"
 178             "Returns an unspecified value.\n")
 179 #define FUNC_NAME s_scm_variable_set_x
 180 {
 181   SCM_VALIDATE_VARIABLE (1,var);
 182   SCM_SETCDR (SCM_CDR (var), val);
 183   return SCM_UNSPECIFIED;
 184 }
 185 #undef FUNC_NAME
 186
 187
 188 SCM_DEFINE (scm_builtin_variable, "builtin-variable", 1, 0, 0,
 189             (SCM name),
 190             "Return the built-in variable with the name NAME.\n"
 191             "NAME must be a symbol (not a string).\n"
 192             "Then use `variable-ref' to access its value.\n")
 193 #define FUNC_NAME s_scm_builtin_variable
 194 {
 195   SCM vcell;
 196   SCM var_slot;
 197
 198   SCM_VALIDATE_SYMBOL (1,name);
 199   vcell = scm_sym2vcell (name, SCM_BOOL_F, SCM_BOOL_T);
 200   if (vcell == SCM_BOOL_F)
 201     return SCM_BOOL_F;
 202
 203   scm_intern_symbol (scm_symhash_vars, name);
 204   var_slot = scm_sym2ovcell (name, scm_symhash_vars);
 205
 206   SCM_DEFER_INTS;
 207   if (   SCM_IMP (SCM_CDR (var_slot))
 208       || (SCM_VARVCELL (var_slot) != vcell))
 209     SCM_SETCDR (var_slot, make_vcell_variable (vcell));
 210   SCM_ALLOW_INTS;
 211
 212   return SCM_CDR (var_slot);
 213 }
 214 #undef FUNC_NAME
 215
 216
 217 SCM_DEFINE (scm_variable_bound_p, "variable-bound?", 1, 0, 0,
 218             (SCM var),
 219             "Return #t iff VAR is bound to a value.\n"
 220             "Throws an error if VAR is not a variable object.\n")
 221 #define FUNC_NAME s_scm_variable_bound_p
 222 {
 223   SCM_VALIDATE_VARIABLE (1,var);
 224   return SCM_NEGATE_BOOL(SCM_UNBNDP (SCM_CDR (SCM_VARVCELL (var))));
 225 }
 226 #undef FUNC_NAME
 227
 228
 229
 230
 231 void
 232 scm_init_variable ()
 233 {
 234   scm_tc16_variable = scm_make_smob_type_mfpe ("variable", 0,
 235                                               scm_markvar, NULL, prin_var, var_equal);
 236   anonymous_variable_sym = SCM_CAR (scm_sysintern ("anonymous-variable", SCM_UNDEFINED));
 237 #include "variable.x"
 238 }
 239