libguile/objects.c

   1 /*      Copyright (C) 1995, 1996, 1999 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 /* This file and objects.h contains those minimal pieces of the Guile
  48  * Object Oriented Programming System which need to be included in
  49  * libguile.  See the comments in objects.h.
  50  */
  51
  52 #include "_scm.h"
  53
  54 #include "struct.h"
  55 #include "procprop.h"
  56 #include "chars.h"
  57 #include "keywords.h"
  58 #include "smob.h"
  59 #include "eval.h"
  60 #include "alist.h"
  61
  62 #include "validate.h"
  63 #include "objects.h"
  64 \f
  65
  66 SCM scm_metaclass_standard;
  67 SCM scm_metaclass_operator;
  68
  69 /* These variables are filled in by the object system when loaded. */
  70 SCM scm_class_boolean, scm_class_char, scm_class_pair;
  71 SCM scm_class_procedure, scm_class_string, scm_class_symbol;
  72 SCM scm_class_procedure_with_setter, scm_class_primitive_generic;
  73 SCM scm_class_vector, scm_class_null;
  74 SCM scm_class_integer, scm_class_real, scm_class_complex;
  75 SCM scm_class_unknown;
  76
  77 SCM *scm_port_class = 0;
  78 SCM *scm_smob_class = 0;
  79
  80 SCM scm_no_applicable_method;
  81
  82 SCM (*scm_make_extended_class) (char *type_name);
  83 void (*scm_make_port_classes) (int ptobnum, char *type_name);
  84 void (*scm_change_object_class) (SCM, SCM, SCM);
  85
  86 /* This function is used for efficient type dispatch.  */
  87 SCM
  88 scm_class_of (SCM x)
  89 {
  90   switch (SCM_ITAG3 (x))
  91     {
  92     case scm_tc3_int_1:
  93     case scm_tc3_int_2:
  94       return scm_class_integer;
  95
  96     case scm_tc3_imm24:
  97       if (SCM_CHARP (x))
  98         return scm_class_char;
  99       else
 100         {
 101           switch (SCM_ISYMNUM (x))
 102             {
 103             case SCM_ISYMNUM (SCM_BOOL_F):
 104             case SCM_ISYMNUM (SCM_BOOL_T):
 105               return scm_class_boolean;
 106             case SCM_ISYMNUM (SCM_EOL):
 107               return scm_class_null;
 108             default:
 109               return scm_class_unknown;
 110             }
 111         }
 112
 113     case scm_tc3_cons:
 114       switch (SCM_TYP7 (x))
 115         {
 116         case scm_tcs_cons_nimcar:
 117           return scm_class_pair;
 118         case scm_tcs_closures:
 119           return scm_class_procedure;
 120         case scm_tcs_symbols:
 121           return scm_class_symbol;
 122         case scm_tc7_vector:
 123         case scm_tc7_wvect:
 124 #ifdef HAVE_ARRAYS
 125         case scm_tc7_bvect:
 126         case scm_tc7_byvect:
 127         case scm_tc7_svect:
 128         case scm_tc7_ivect:
 129         case scm_tc7_uvect:
 130         case scm_tc7_fvect:
 131         case scm_tc7_dvect:
 132         case scm_tc7_cvect:
 133 #endif
 134           return scm_class_vector;
 135         case scm_tc7_string:
 136         case scm_tc7_substring:
 137           return scm_class_string;
 138         case scm_tc7_asubr:
 139         case scm_tc7_subr_0:
 140         case scm_tc7_subr_1:
 141         case scm_tc7_cxr:
 142         case scm_tc7_subr_3:
 143         case scm_tc7_subr_2:
 144         case scm_tc7_rpsubr:
 145         case scm_tc7_subr_1o:
 146         case scm_tc7_subr_2o:
 147         case scm_tc7_lsubr_2:
 148         case scm_tc7_lsubr:
 149           if (SCM_SUBR_GENERIC (x) && *SCM_SUBR_GENERIC (x))
 150             return scm_class_primitive_generic;
 151           else
 152             return scm_class_procedure;
 153         case scm_tc7_cclo:
 154           return scm_class_procedure;
 155         case scm_tc7_pws:
 156           return scm_class_procedure_with_setter;
 157
 158         case scm_tc7_smob:
 159           {
 160             long type = SCM_TYP16 (x);
 161             if (type == scm_tc16_flo)
 162               {
 163                 if (SCM_CARW (x) & SCM_IMAG_PART)
 164                   return scm_class_complex;
 165                 else
 166                   return scm_class_real;
 167               }
 168             else if (type != scm_tc16_port_with_ps)
 169               return scm_smob_class[SCM_TC2SMOBNUM (type)];
 170             x = SCM_PORT_WITH_PS_PORT (x);
 171             /* fall through to ports */
 172           }
 173         case scm_tc7_port:
 174           return scm_port_class[(SCM_WRTNG & SCM_CARW (x)
 175                                  ? (SCM_RDNG & SCM_CARW (x)
 176                                     ? SCM_INOUT_PCLASS_INDEX | SCM_PTOBNUM (x)
 177                                     : SCM_OUT_PCLASS_INDEX | SCM_PTOBNUM (x))
 178                                  : SCM_IN_PCLASS_INDEX | SCM_PTOBNUM (x))];
 179         case scm_tcs_cons_gloc:
 180           /* must be a struct */
 181           if (SCM_OBJ_CLASS_FLAGS (x) & SCM_CLASSF_GOOPS_VALID)
 182             return SCM_CLASS_OF (x);
 183           else if (SCM_OBJ_CLASS_FLAGS (x) & SCM_CLASSF_GOOPS)
 184             {
 185               /* Goops object */
 186               if (SCM_OBJ_CLASS_REDEF (x) != SCM_BOOL_F)
 187                 scm_change_object_class (x,
 188                                          SCM_CLASS_OF (x),         /* old */
 189                                          SCM_OBJ_CLASS_REDEF (x)); /* new */
 190               return SCM_CLASS_OF (x);
 191             }
 192           else
 193             {
 194               /* ordinary struct */
 195               SCM handle = scm_struct_create_handle (SCM_STRUCT_VTABLE (x));
 196               if (SCM_NFALSEP (SCM_STRUCT_TABLE_CLASS (SCM_CDR (handle))))
 197                 return SCM_STRUCT_TABLE_CLASS (SCM_CDR (handle));
 198               else
 199                 {
 200                   SCM name = SCM_STRUCT_TABLE_NAME (SCM_CDR (handle));
 201                   SCM class = scm_make_extended_class (SCM_NFALSEP (name)
 202                                                        ? SCM_ROCHARS (name)
 203                                                        : 0);
 204                   SCM_SET_STRUCT_TABLE_CLASS (SCM_CDR (handle), class);
 205                   return class;
 206                 }
 207             }
 208         default:
 209           if (SCM_CONSP (x))
 210             return scm_class_pair;
 211           else
 212             return scm_class_unknown;
 213         }
 214
 215     case scm_tc3_cons_gloc:
 216     case scm_tc3_tc7_1:
 217     case scm_tc3_tc7_2:
 218     case scm_tc3_closure:
 219       /* Never reached */
 220       break;
 221     }
 222   return scm_class_unknown;
 223 }
 224
 225 /* (SCM_IM_DISPATCH ARGS N-SPECIALIZED
 226  *   #((TYPE1 ... ENV FORMALS FORM ...) ...)
 227  *   GF)
 228  *
 229  * (SCM_IM_HASH_DISPATCH ARGS N-SPECIALIZED HASHSET MASK
 230  *   #((TYPE1 ... ENV FORMALS FORM ...) ...)
 231  *   GF)
 232  *
 233  * ARGS is either a list of expressions, in which case they
 234  * are interpreted as the arguments of an application, or
 235  * a non-pair, which is interpreted as a single expression
 236  * yielding all arguments.
 237  *
 238  * SCM_IM_DISPATCH expressions in generic functions always
 239  * have ARGS = the symbol `args' or the iloc #@0-0.
 240  *
 241  * Need FORMALS in order to support varying arity.  This
 242  * also avoids the need for renaming of bindings.
 243  *
 244  * We should probably not complicate this mechanism by
 245  * introducing "optimizations" for getters and setters or
 246  * primitive methods.  Getters and setter will normally be
 247  * compiled into @slot-[ref|set!] or a procedure call.
 248  * They rely on the dispatch performed before executing
 249  * the code which contains them.
 250  *
 251  * We might want to use a more efficient representation of
 252  * this form in the future, perhaps after we have introduced
 253  * low-level support for syntax-case macros.
 254  */
 255
 256 SCM
 257 scm_mcache_lookup_cmethod (SCM cache, SCM args)
 258 {
 259   int i, n, end, mask;
 260   SCM ls, methods, z = SCM_CDDR (cache);
 261   n = SCM_INUM (SCM_CAR (z)); /* maximum number of specializers */
 262   methods = SCM_CADR (z);
 263
 264   if (SCM_NIMP (methods))
 265     {
 266       /* Prepare for linear search */
 267       mask = -1;
 268       i = 0;
 269       end = SCM_LENGTH (methods);
 270     }
 271   else
 272     {
 273       /* Compute a hash value */
 274       int hashset = SCM_INUM (methods);
 275       int j = n;
 276       mask = SCM_INUM (SCM_CAR (z = SCM_CDDR (z)));
 277       methods = SCM_CADR (z);
 278       i = 0;
 279       ls = args;
 280       if (SCM_NIMP (ls))
 281         do
 282           {
 283             i += SCM_ASWORD (SCM_STRUCT_DATA (scm_class_of (SCM_CAR (ls)))
 284                   [scm_si_hashsets + hashset]);
 285             ls = SCM_CDR (ls);
 286           }
 287         while (--j && SCM_NIMP (ls));
 288       i &= mask;
 289       end = i;
 290     }
 291
 292   /* Search for match  */
 293   do
 294     {
 295       int j = n;
 296       z = SCM_VELTS (methods)[i];
 297       ls = args; /* list of arguments */
 298       if (SCM_NIMP (ls))
 299         do
 300           {
 301             /* More arguments than specifiers => CLASS != ENV */
 302             if (scm_class_of (SCM_CAR (ls)) != SCM_CAR (z))
 303               goto next_method;
 304             ls = SCM_CDR (ls);
 305             z = SCM_CDR (z);
 306           }
 307         while (--j && SCM_NIMP (ls));
 308       /* Fewer arguments than specifiers => CAR != ENV */
 309       if (!(SCM_IMP (SCM_CAR (z)) || SCM_CONSP (SCM_CAR (z))))
 310         goto next_method;
 311       return z;
 312     next_method:
 313       i = (i + 1) & mask;
 314     } while (i != end);
 315   return SCM_BOOL_F;
 316 }
 317
 318 SCM
 319 scm_mcache_compute_cmethod (SCM cache, SCM args)
 320 {
 321   SCM cmethod = scm_mcache_lookup_cmethod (cache, args);
 322   if (SCM_IMP (cmethod))
 323     /* No match - memoize */
 324     return scm_memoize_method (cache, args);
 325   return cmethod;
 326 }
 327
 328 SCM
 329 scm_apply_generic (SCM gf, SCM args)
 330 {
 331   SCM cmethod = scm_mcache_compute_cmethod (SCM_ENTITY_PROCEDURE (gf), args);
 332   return scm_eval_body (SCM_CDR (SCM_CMETHOD_CODE (cmethod)),
 333                         SCM_EXTEND_ENV (SCM_CAR (SCM_CMETHOD_CODE (cmethod)),
 334                                         args,
 335                                         SCM_CMETHOD_ENV (cmethod)));
 336 }
 337
 338 SCM
 339 scm_call_generic_0 (SCM gf)
 340 {
 341   return scm_apply_generic (gf, SCM_EOL);
 342 }
 343
 344 SCM
 345 scm_call_generic_1 (SCM gf, SCM a1)
 346 {
 347   return scm_apply_generic (gf, SCM_LIST1 (a1));
 348 }
 349
 350 SCM
 351 scm_call_generic_2 (SCM gf, SCM a1, SCM a2)
 352 {
 353   return scm_apply_generic (gf, SCM_LIST2 (a1, a2));
 354 }
 355
 356 SCM
 357 scm_call_generic_3 (SCM gf, SCM a1, SCM a2, SCM a3)
 358 {
 359   return scm_apply_generic (gf, SCM_LIST3 (a1, a2, a3));
 360 }
 361
 362 SCM_DEFINE (scm_entity_p, "entity?", 1, 0, 0,
 363             (SCM obj),
 364 "")
 365 #define FUNC_NAME s_scm_entity_p
 366 {
 367   return SCM_BOOL(SCM_STRUCTP (obj) && SCM_I_ENTITYP (obj));
 368 }
 369 #undef FUNC_NAME
 370
 371 SCM_DEFINE (scm_operator_p, "operator?", 1, 0, 0,
 372             (SCM obj),
 373 "")
 374 #define FUNC_NAME s_scm_operator_p
 375 {
 376   return SCM_BOOL(SCM_STRUCTP (obj)
 377                   && SCM_I_OPERATORP (obj)
 378                   && !SCM_I_ENTITYP (obj));
 379 }
 380 #undef FUNC_NAME
 381
 382 SCM_DEFINE (scm_set_object_procedure_x, "set-object-procedure!", 2, 0, 0,
 383             (SCM obj, SCM proc),
 384 "")
 385 #define FUNC_NAME s_scm_set_object_procedure_x
 386 {
 387   SCM_ASSERT (SCM_STRUCTP (obj)
 388               && ((SCM_CLASS_FLAGS (obj) & SCM_CLASSF_OPERATOR)
 389                   || (SCM_I_ENTITYP (obj)
 390                       && !(SCM_OBJ_CLASS_FLAGS (obj)
 391                            & SCM_CLASSF_PURE_GENERIC))),
 392               obj,
 393               SCM_ARG1,
 394               FUNC_NAME);
 395   SCM_VALIDATE_PROC (2,proc);
 396   if (SCM_I_ENTITYP (obj))
 397     SCM_ENTITY_PROCEDURE (obj) = proc;
 398   else
 399     SCM_OPERATOR_CLASS (obj)->procedure = proc;
 400   return SCM_UNSPECIFIED;
 401 }
 402 #undef FUNC_NAME
 403
 404 #ifdef GUILE_DEBUG
 405 SCM_DEFINE (scm_object_procedure, "object-procedure", 1, 0, 0,
 406             (SCM obj),
 407 "")
 408 #define FUNC_NAME s_scm_object_procedure
 409 {
 410   SCM_ASSERT (SCM_STRUCTP (obj)
 411               && ((SCM_CLASS_FLAGS (obj) & SCM_CLASSF_OPERATOR)
 412                   || SCM_I_ENTITYP (obj)),
 413               obj, SCM_ARG1, FUNC_NAME);
 414   return (SCM_I_ENTITYP (obj)
 415           ? SCM_ENTITY_PROCEDURE (obj)
 416           : SCM_OPERATOR_CLASS (obj)->procedure);
 417 }
 418 #undef FUNC_NAME
 419 #endif /* GUILE_DEBUG */
 420
 421 /* The following procedures are not a part of Goops but a minimal
 422  * object system built upon structs.  They are here for those who
 423  * want to implement their own object system.
 424  */
 425
 426 SCM
 427 scm_i_make_class_object (SCM meta,
 428                          SCM layout_string,
 429                          unsigned long flags)
 430 {
 431   SCM c;
 432   SCM layout = scm_make_struct_layout (layout_string);
 433   c = scm_make_struct (meta,
 434                        SCM_INUM0,
 435                        SCM_LIST4 (layout, SCM_BOOL_F, SCM_EOL, SCM_EOL));
 436   SCM_SET_CLASS_FLAGS (c, flags);
 437   return c;
 438 }
 439
 440 SCM_DEFINE (scm_make_class_object, "make-class-object", 2, 0, 0,
 441             (SCM metaclass, SCM layout),
 442 "")
 443 #define FUNC_NAME s_scm_make_class_object
 444 {
 445   unsigned long flags = 0;
 446   SCM_VALIDATE_STRUCT (1,metaclass);
 447   SCM_VALIDATE_STRING (2,layout);
 448   if (metaclass == scm_metaclass_operator)
 449     flags = SCM_CLASSF_OPERATOR;
 450   return scm_i_make_class_object (metaclass, layout, flags);
 451 }
 452 #undef FUNC_NAME
 453
 454 SCM_DEFINE (scm_make_subclass_object, "make-subclass-object", 2, 0, 0,
 455             (SCM class, SCM layout),
 456 "")
 457 #define FUNC_NAME s_scm_make_subclass_object
 458 {
 459   SCM pl;
 460   SCM_VALIDATE_STRUCT (1,class);
 461   SCM_VALIDATE_STRING (2,layout);
 462   pl = SCM_STRUCT_DATA (class)[scm_vtable_index_layout];
 463   /* Convert symbol->string */
 464   pl = scm_makfromstr (SCM_CHARS (pl), (scm_sizet) SCM_LENGTH (pl), 0);
 465   return scm_i_make_class_object (SCM_STRUCT_VTABLE (class),
 466                                   scm_string_append (SCM_LIST2 (pl, layout)),
 467                                   SCM_CLASS_FLAGS (class));
 468 }
 469 #undef FUNC_NAME
 470
 471 void
 472 scm_init_objects ()
 473 {
 474   SCM ms = scm_makfrom0str (SCM_METACLASS_STANDARD_LAYOUT);
 475   SCM ml = scm_make_struct_layout (ms);
 476   SCM mt = scm_make_vtable_vtable (ml, SCM_INUM0,
 477                                    SCM_LIST3 (SCM_BOOL_F, SCM_EOL, SCM_EOL));
 478
 479   SCM os = scm_makfrom0str (SCM_METACLASS_OPERATOR_LAYOUT);
 480   SCM ol = scm_make_struct_layout (os);
 481   SCM ot = scm_make_vtable_vtable (ol, SCM_INUM0,
 482                                    SCM_LIST3 (SCM_BOOL_F, SCM_EOL, SCM_EOL));
 483
 484   SCM es = scm_makfrom0str (SCM_ENTITY_LAYOUT);
 485   SCM el = scm_make_struct_layout (es);
 486   SCM et = scm_make_struct (mt, SCM_INUM0,
 487                             SCM_LIST4 (el, SCM_BOOL_F, SCM_EOL, SCM_EOL));
 488
 489   scm_sysintern ("<class>", mt);
 490   scm_metaclass_standard = mt;
 491   scm_sysintern ("<operator-class>", ot);
 492   scm_metaclass_operator = ot;
 493   SCM_SET_CLASS_FLAGS (et, SCM_CLASSF_OPERATOR | SCM_CLASSF_ENTITY);
 494   SCM_SET_CLASS_DESTRUCTOR (et, scm_struct_free_entity);
 495   scm_sysintern ("<entity>", et);
 496
 497 #include "objects.x"
 498 }