libguile/variable.c

   1 /* Copyright (C) 1995,1996,1997,1998,2000,2001 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 vcell = SCM_VARVCELL (exp);
  65     if (!SCM_UNBNDP (SCM_CAR (vcell)))
  66       {
  67         scm_puts (" name: ", port);
  68         scm_iprin1 (SCM_CAR (vcell), port, pstate);
  69       }
  70     scm_puts (" binding: ", port);
  71     scm_iprin1 (SCM_CDR (vcell), port, pstate);
  72   }
  73   scm_putc('>', port);
  74   return 1;
  75 }
  76
  77 static SCM
  78 variable_equalp (SCM var1, SCM var2)
  79 {
  80   return scm_equal_p (SCM_VARVCELL (var1), SCM_VARVCELL (var2));
  81 }
  82 \f
  83
  84 SCM_SYMBOL (anonymous_variable_sym, "anonymous-variable");
  85
  86
  87 static SCM
  88 make_vcell_variable (SCM vcell)
  89 {
  90   SCM_RETURN_NEWSMOB (scm_tc16_variable, SCM_UNPACK (vcell));
  91 }
  92
  93 SCM_DEFINE (scm_make_variable, "make-variable", 1, 1, 0,
  94             (SCM init, SCM name_hint),
  95             "Return a variable object initialized to value @var{init}.\n"
  96             "If given, uses @var{name-hint} as its internal (debugging)\n"
  97             "name, otherwise just treat it as an anonymous variable.\n"
  98             "Remember, of course, that multiple bindings to the same\n"
  99             "variable may exist, so @var{name-hint} is just that---a hint.\n")
 100 #define FUNC_NAME s_scm_make_variable
 101 {
 102   SCM vcell;
 103
 104   if (SCM_UNBNDP (name_hint))
 105     name_hint = anonymous_variable_sym;
 106
 107   vcell = scm_cons (name_hint, init);
 108   return make_vcell_variable (vcell);
 109 }
 110 #undef FUNC_NAME
 111
 112
 113 SCM_DEFINE (scm_make_undefined_variable, "make-undefined-variable", 0, 1, 0,
 114             (SCM name_hint),
 115             "Return a variable object initialized to an undefined value.\n"
 116             "If given, uses @var{name-hint} as its internal (debugging)\n"
 117             "name, otherwise just treat it as an anonymous variable.\n"
 118             "Remember, of course, that multiple bindings to the same\n"
 119             "variable may exist, so @var{name-hint} is just that---a hint.\n")
 120 #define FUNC_NAME s_scm_make_undefined_variable
 121 {
 122   SCM vcell;
 123
 124   if (SCM_UNBNDP (name_hint))
 125     name_hint = anonymous_variable_sym;
 126
 127   vcell = scm_cons (name_hint, SCM_UNDEFINED);
 128   return make_vcell_variable (vcell);
 129 }
 130 #undef FUNC_NAME
 131
 132
 133 SCM_DEFINE (scm_variable_p, "variable?", 1, 0, 0,
 134             (SCM obj),
 135             "Return @code{#t} iff @var{obj} is a variable object, else\n"
 136             "return @code{#f}\n")
 137 #define FUNC_NAME s_scm_variable_p
 138 {
 139   return SCM_BOOL (SCM_VARIABLEP (obj));
 140 }
 141 #undef FUNC_NAME
 142
 143
 144 SCM_DEFINE (scm_variable_ref, "variable-ref", 1, 0, 0,
 145             (SCM var),
 146             "Dereference @var{var} and return its value.\n"
 147             "@var{var} must be a variable object; see @code{make-variable}\n"
 148             "and @code{make-undefined-variable}.")
 149 #define FUNC_NAME s_scm_variable_ref
 150 {
 151   SCM_VALIDATE_VARIABLE (1, var);
 152   return SCM_CDR (SCM_VARVCELL (var));
 153 }
 154 #undef FUNC_NAME
 155
 156
 157
 158 SCM_DEFINE (scm_variable_set_x, "variable-set!", 2, 0, 0,
 159             (SCM var, SCM val),
 160             "Set the value of the variable @var{var} to @var{val}.\n"
 161             "@var{var} must be a variable object, @var{val} can be any\n"
 162             "value. Return an unspecified value.\n")
 163 #define FUNC_NAME s_scm_variable_set_x
 164 {
 165   SCM_VALIDATE_VARIABLE (1, var);
 166   SCM_SETCDR (SCM_VARVCELL (var), val);
 167   return SCM_UNSPECIFIED;
 168 }
 169 #undef FUNC_NAME
 170
 171
 172 SCM_DEFINE (scm_builtin_variable, "builtin-variable", 1, 0, 0,
 173             (SCM name),
 174             "Return the built-in variable with the name @var{name}.\n"
 175             "@var{name} must be a symbol (not a string).\n"
 176             "Then use @code{variable-ref} to access its value.\n")
 177 #define FUNC_NAME s_scm_builtin_variable
 178 {
 179   SCM vcell;
 180   SCM var_slot;
 181
 182   SCM_VALIDATE_SYMBOL (1,name);
 183   vcell = scm_sym2vcell (name, SCM_BOOL_F, SCM_BOOL_T);
 184   if (SCM_FALSEP (vcell))
 185     return SCM_BOOL_F;
 186
 187   scm_intern_symbol (scm_symhash_vars, name);
 188   var_slot = scm_sym2ovcell (name, scm_symhash_vars);
 189
 190   SCM_DEFER_INTS;
 191   if (SCM_IMP (SCM_CDR (var_slot))
 192       || !SCM_EQ_P (SCM_VARVCELL (var_slot), vcell))
 193     SCM_SETCDR (var_slot, make_vcell_variable (vcell));
 194   SCM_ALLOW_INTS;
 195
 196   return SCM_CDR (var_slot);
 197 }
 198 #undef FUNC_NAME
 199
 200
 201 SCM_DEFINE (scm_variable_bound_p, "variable-bound?", 1, 0, 0,
 202             (SCM var),
 203             "Return @code{#t} iff @var{var} is bound to a value.\n"
 204             "Throws an error if @var{var} is not a variable object.\n")
 205 #define FUNC_NAME s_scm_variable_bound_p
 206 {
 207   SCM_VALIDATE_VARIABLE (1, var);
 208   return SCM_BOOL (!SCM_UNBNDP (SCM_CDR (SCM_VARVCELL (var))));
 209 }
 210 #undef FUNC_NAME
 211
 212
 213
 214
 215 void
 216 scm_init_variable ()
 217 {
 218   scm_tc16_variable = scm_make_smob_type ("variable", 0);
 219   scm_set_smob_mark (scm_tc16_variable, scm_markcdr);
 220   scm_set_smob_print (scm_tc16_variable, variable_print);
 221   scm_set_smob_equalp (scm_tc16_variable, variable_equalp);
 222
 223 #ifndef SCM_MAGIC_SNARFER
 224 #include "libguile/variable.x"
 225 #endif
 226 }
 227
 228
 229 /*
 230   Local Variables:
 231   c-file-style: "gnu"
 232   End:
 233 */