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