libguile/objects.c

   1 /* Copyright (C) 1995,1996,1999,2000,2001 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 /* 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 "libguile/_scm.h"
  53
  54 #include "libguile/struct.h"
  55 #include "libguile/procprop.h"
  56 #include "libguile/chars.h"
  57 #include "libguile/keywords.h"
  58 #include "libguile/smob.h"
  59 #include "libguile/eval.h"
  60 #include "libguile/alist.h"
  61 #include "libguile/ports.h"
  62 #include "libguile/strings.h"
  63 #include "libguile/vectors.h"
  64
  65 #include "libguile/validate.h"
  66 #include "libguile/objects.h"
  67 \f
  68
  69 SCM scm_metaclass_standard;
  70 SCM scm_metaclass_operator;
  71
  72 /* These variables are filled in by the object system when loaded. */
  73 SCM scm_class_boolean, scm_class_char, scm_class_pair;
  74 SCM scm_class_procedure, scm_class_string, scm_class_symbol;
  75 SCM scm_class_procedure_with_setter, scm_class_primitive_generic;
  76 SCM scm_class_vector, scm_class_null;
  77 SCM scm_class_integer, scm_class_real, scm_class_complex;
  78 SCM scm_class_unknown;
  79
  80 SCM *scm_port_class = 0;
  81 SCM *scm_smob_class = 0;
  82
  83 SCM scm_no_applicable_method;
  84
  85 /* This function is used for efficient type dispatch.  */
  86 SCM_DEFINE (scm_class_of, "class-of", 1, 0, 0,
  87             (SCM x),
  88             "Return the class of @var{x}.")
  89 #define FUNC_NAME s_scm_class_of
  90 {
  91   switch (SCM_ITAG3 (x))
  92     {
  93     case scm_tc3_int_1:
  94     case scm_tc3_int_2:
  95       return scm_class_integer;
  96
  97     case scm_tc3_imm24:
  98       if (SCM_CHARP (x))
  99         return scm_class_char;
 100       else
 101         {
 102           switch (SCM_ISYMNUM (x))
 103             {
 104             case SCM_ISYMNUM (SCM_BOOL_F):
 105             case SCM_ISYMNUM (SCM_BOOL_T):
 106               return scm_class_boolean;
 107             case SCM_ISYMNUM (SCM_EOL):
 108               return scm_class_null;
 109             default:
 110               return scm_class_unknown;
 111             }
 112         }
 113
 114     case scm_tc3_cons:
 115       switch (SCM_TYP7 (x))
 116         {
 117         case scm_tcs_cons_nimcar:
 118           return scm_class_pair;
 119         case scm_tcs_closures:
 120           return scm_class_procedure;
 121         case scm_tc7_symbol:
 122           return scm_class_symbol;
 123         case scm_tc7_vector:
 124         case scm_tc7_wvect:
 125 #ifdef HAVE_ARRAYS
 126         case scm_tc7_bvect:
 127         case scm_tc7_byvect:
 128         case scm_tc7_svect:
 129         case scm_tc7_ivect:
 130         case scm_tc7_uvect:
 131         case scm_tc7_fvect:
 132         case scm_tc7_dvect:
 133         case scm_tc7_cvect:
 134 #endif
 135           return scm_class_vector;
 136         case scm_tc7_string:
 137         case scm_tc7_substring:
 138           return scm_class_string;
 139         case scm_tc7_asubr:
 140         case scm_tc7_subr_0:
 141         case scm_tc7_subr_1:
 142         case scm_tc7_cxr:
 143         case scm_tc7_subr_3:
 144         case scm_tc7_subr_2:
 145         case scm_tc7_rpsubr:
 146         case scm_tc7_subr_1o:
 147         case scm_tc7_subr_2o:
 148         case scm_tc7_lsubr_2:
 149         case scm_tc7_lsubr:
 150           if (SCM_SUBR_GENERIC (x) && *SCM_SUBR_GENERIC (x))
 151             return scm_class_primitive_generic;
 152           else
 153             return scm_class_procedure;
 154         case scm_tc7_cclo:
 155           return scm_class_procedure;
 156         case scm_tc7_pws:
 157           return scm_class_procedure_with_setter;
 158
 159         case scm_tc7_smob:
 160           {
 161             scm_t_bits type = SCM_TYP16 (x);
 162             if (type != scm_tc16_port_with_ps)
 163               return scm_smob_class[SCM_TC2SMOBNUM (type)];
 164             x = SCM_PORT_WITH_PS_PORT (x);
 165             /* fall through to ports */
 166           }
 167         case scm_tc7_port:
 168           return scm_port_class[(SCM_WRTNG & SCM_CELL_WORD_0 (x)
 169                                  ? (SCM_RDNG & SCM_CELL_WORD_0 (x)
 170                                     ? SCM_INOUT_PCLASS_INDEX | SCM_PTOBNUM (x)
 171                                     : SCM_OUT_PCLASS_INDEX | SCM_PTOBNUM (x))
 172                                  : SCM_IN_PCLASS_INDEX | SCM_PTOBNUM (x))];
 173         case scm_tcs_cons_gloc:
 174           /* must be a struct */
 175           if (SCM_OBJ_CLASS_FLAGS (x) & SCM_CLASSF_GOOPS_VALID)
 176             return SCM_CLASS_OF (x);
 177           else if (SCM_OBJ_CLASS_FLAGS (x) & SCM_CLASSF_GOOPS)
 178             {
 179               /* Goops object */
 180               if (! SCM_FALSEP (SCM_OBJ_CLASS_REDEF (x)))
 181                 scm_change_object_class (x,
 182                                          SCM_CLASS_OF (x),         /* old */
 183                                          SCM_OBJ_CLASS_REDEF (x)); /* new */
 184               return SCM_CLASS_OF (x);
 185             }
 186           else
 187             {
 188               /* ordinary struct */
 189               SCM handle = scm_struct_create_handle (SCM_STRUCT_VTABLE (x));
 190               if (!SCM_FALSEP (SCM_STRUCT_TABLE_CLASS (SCM_CDR (handle))))
 191                 return SCM_STRUCT_TABLE_CLASS (SCM_CDR (handle));
 192               else
 193                 {
 194                   SCM name = SCM_STRUCT_TABLE_NAME (SCM_CDR (handle));
 195                   SCM class = scm_make_extended_class (!SCM_FALSEP (name)
 196                                                        ? SCM_SYMBOL_CHARS (name)
 197                                                        : 0);
 198                   SCM_SET_STRUCT_TABLE_CLASS (SCM_CDR (handle), class);
 199                   return class;
 200                 }
 201             }
 202         default:
 203           if (SCM_CONSP (x))
 204             return scm_class_pair;
 205           else
 206             return scm_class_unknown;
 207         }
 208
 209     case scm_tc3_cons_gloc:
 210     case scm_tc3_tc7_1:
 211     case scm_tc3_tc7_2:
 212     case scm_tc3_closure:
 213       /* Never reached */
 214       break;
 215     }
 216   return scm_class_unknown;
 217 }
 218 #undef FUNC_NAME
 219
 220 /* The cache argument for scm_mcache_lookup_cmethod has one of two possible
 221  * formats:
 222  *
 223  * Format #1:
 224  * (SCM_IM_DISPATCH ARGS N-SPECIALIZED
 225  *   #((TYPE1 ... ENV FORMALS FORM ...) ...)
 226  *   GF)
 227  *
 228  * Format #2:
 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   long 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_INUMP (methods))
 265     {
 266       /* cache format #2: compute a hash value */
 267       long hashset = SCM_INUM (methods);
 268       long j = n;
 269       z = SCM_CDDR (z);
 270       mask = SCM_INUM (SCM_CAR (z));
 271       methods = SCM_CADR (z);
 272       i = 0;
 273       ls = args;
 274       if (!SCM_NULLP (ls))
 275         do
 276           {
 277             i += SCM_STRUCT_DATA (scm_class_of (SCM_CAR (ls)))
 278                  [scm_si_hashsets + hashset];
 279             ls = SCM_CDR (ls);
 280           }
 281         while (j-- && !SCM_NULLP (ls));
 282       i &= mask;
 283       end = i;
 284     }
 285   else /* SCM_VECTORP (methods) */
 286     {
 287       /* cache format #1: prepare for linear search */
 288       mask = -1;
 289       i = 0;
 290       end = SCM_VECTOR_LENGTH (methods);
 291     }
 292
 293   /* Search for match  */
 294   do
 295     {
 296       long j = n;
 297       z = SCM_VELTS (methods)[i];
 298       ls = args; /* list of arguments */
 299       if (!SCM_NULLP (ls))
 300         do
 301           {
 302             /* More arguments than specifiers => CLASS != ENV */
 303             if (! SCM_EQ_P (scm_class_of (SCM_CAR (ls)), SCM_CAR (z)))
 304               goto next_method;
 305             ls = SCM_CDR (ls);
 306             z = SCM_CDR (z);
 307           }
 308         while (j-- && !SCM_NULLP (ls));
 309       /* Fewer arguments than specifiers => CAR != ENV */
 310       if (SCM_NULLP (SCM_CAR (z)) || SCM_CONSP (SCM_CAR (z)))
 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_FALSEP (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_list_1 (a1));
 348 }
 349
 350 SCM
 351 scm_call_generic_2 (SCM gf, SCM a1, SCM a2)
 352 {
 353   return scm_apply_generic (gf, scm_list_2 (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_list_3 (a1, a2, a3));
 360 }
 361
 362 SCM_DEFINE (scm_entity_p, "entity?", 1, 0, 0,
 363             (SCM obj),
 364             "Return @code{#t} if @var{obj} is an entity.")
 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             "Return @code{#t} if @var{obj} is an operator.")
 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 /* XXX - What code requires the object procedure to be only of certain
 383          types? */
 384
 385 SCM_DEFINE (scm_valid_object_procedure_p, "valid-object-procedure?", 1, 0, 0,
 386             (SCM proc),
 387             "Return @code{#t} iff @var{proc} is a procedure that can be used "
 388             "with @code{set-object-procedure}.  It is always valid to use "
 389             "a closure constructed by @code{lambda}.")
 390 #define FUNC_NAME s_scm_valid_object_procedure_p
 391 {
 392   if (SCM_IMP (proc))
 393     return SCM_BOOL_F;
 394   switch (SCM_TYP7 (proc))
 395     {
 396     default:
 397       return SCM_BOOL_F;
 398     case scm_tcs_closures:
 399     case scm_tc7_subr_1:
 400     case scm_tc7_subr_2:
 401     case scm_tc7_subr_3:
 402     case scm_tc7_lsubr_2:
 403       return SCM_BOOL_T;
 404     }
 405 }
 406 #undef FUNC_NAME
 407
 408 SCM_DEFINE (scm_set_object_procedure_x, "set-object-procedure!", 2, 0, 0,
 409             (SCM obj, SCM proc),
 410             "Set the object procedure of @var{obj} to @var{proc}.\n"
 411             "@var{obj} must be either an entity or an operator.")
 412 #define FUNC_NAME s_scm_set_object_procedure_x
 413 {
 414   SCM_ASSERT (SCM_STRUCTP (obj)
 415               && ((SCM_CLASS_FLAGS (obj) & SCM_CLASSF_OPERATOR)
 416                   || (SCM_I_ENTITYP (obj)
 417                       && !(SCM_OBJ_CLASS_FLAGS (obj)
 418                            & SCM_CLASSF_PURE_GENERIC))),
 419               obj,
 420               SCM_ARG1,
 421               FUNC_NAME);
 422   SCM_ASSERT (scm_valid_object_procedure_p (proc), proc, SCM_ARG2, FUNC_NAME);
 423   if (SCM_I_ENTITYP (obj))
 424     SCM_SET_ENTITY_PROCEDURE (obj, proc);
 425   else
 426     SCM_OPERATOR_CLASS (obj)->procedure = proc;
 427   return SCM_UNSPECIFIED;
 428 }
 429 #undef FUNC_NAME
 430
 431 #ifdef GUILE_DEBUG
 432 SCM_DEFINE (scm_object_procedure, "object-procedure", 1, 0, 0,
 433             (SCM obj),
 434             "Return the object procedure of @var{obj}. @var{obj} must be\n"
 435             "an entity or an operator.")
 436 #define FUNC_NAME s_scm_object_procedure
 437 {
 438   SCM_ASSERT (SCM_STRUCTP (obj)
 439               && ((SCM_CLASS_FLAGS (obj) & SCM_CLASSF_OPERATOR)
 440                   || SCM_I_ENTITYP (obj)),
 441               obj, SCM_ARG1, FUNC_NAME);
 442   return (SCM_I_ENTITYP (obj)
 443           ? SCM_ENTITY_PROCEDURE (obj)
 444           : SCM_OPERATOR_CLASS (obj)->procedure);
 445 }
 446 #undef FUNC_NAME
 447 #endif /* GUILE_DEBUG */
 448
 449 /* The following procedures are not a part of Goops but a minimal
 450  * object system built upon structs.  They are here for those who
 451  * want to implement their own object system.
 452  */
 453
 454 SCM
 455 scm_i_make_class_object (SCM meta,
 456                          SCM layout_string,
 457                          unsigned long flags)
 458 {
 459   SCM c;
 460   SCM layout = scm_make_struct_layout (layout_string);
 461   c = scm_make_struct (meta,
 462                        SCM_INUM0,
 463                        scm_list_4 (layout, SCM_BOOL_F, SCM_EOL, SCM_EOL));
 464   SCM_SET_CLASS_FLAGS (c, flags);
 465   return c;
 466 }
 467
 468 SCM_DEFINE (scm_make_class_object, "make-class-object", 2, 0, 0,
 469             (SCM metaclass, SCM layout),
 470             "Create a new class object of class @var{metaclass}, with the\n"
 471             "slot layout specified by @var{layout}.")
 472 #define FUNC_NAME s_scm_make_class_object
 473 {
 474   unsigned long flags = 0;
 475   SCM_VALIDATE_STRUCT (1,metaclass);
 476   SCM_VALIDATE_STRING (2,layout);
 477   if (SCM_EQ_P (metaclass, scm_metaclass_operator))
 478     flags = SCM_CLASSF_OPERATOR;
 479   return scm_i_make_class_object (metaclass, layout, flags);
 480 }
 481 #undef FUNC_NAME
 482
 483 SCM_DEFINE (scm_make_subclass_object, "make-subclass-object", 2, 0, 0,
 484             (SCM class, SCM layout),
 485             "Create a subclass object of @var{class}, with the slot layout\n"
 486             "specified by @var{layout}.")
 487 #define FUNC_NAME s_scm_make_subclass_object
 488 {
 489   SCM pl;
 490   SCM_VALIDATE_STRUCT (1,class);
 491   SCM_VALIDATE_STRING (2,layout);
 492   pl = SCM_PACK (SCM_STRUCT_DATA (class) [scm_vtable_index_layout]);
 493   /* Convert symbol->string */
 494   pl = scm_mem2string (SCM_SYMBOL_CHARS (pl), SCM_SYMBOL_LENGTH (pl));
 495   return scm_i_make_class_object (SCM_STRUCT_VTABLE (class),
 496                                   scm_string_append (scm_list_2 (pl, layout)),
 497                                   SCM_CLASS_FLAGS (class));
 498 }
 499 #undef FUNC_NAME
 500
 501 void
 502 scm_init_objects ()
 503 {
 504   SCM ms = scm_makfrom0str (SCM_METACLASS_STANDARD_LAYOUT);
 505   SCM mt = scm_make_vtable_vtable (ms, SCM_INUM0,
 506                                    scm_list_3 (SCM_BOOL_F, SCM_EOL, SCM_EOL));
 507
 508   SCM os = scm_makfrom0str (SCM_METACLASS_OPERATOR_LAYOUT);
 509   SCM ot = scm_make_vtable_vtable (os, SCM_INUM0,
 510                                    scm_list_3 (SCM_BOOL_F, SCM_EOL, SCM_EOL));
 511
 512   SCM es = scm_makfrom0str (SCM_ENTITY_LAYOUT);
 513   SCM el = scm_make_struct_layout (es);
 514   SCM et = scm_make_struct (mt, SCM_INUM0,
 515                             scm_list_4 (el, SCM_BOOL_F, SCM_EOL, SCM_EOL));
 516
 517   scm_c_define ("<class>", mt);
 518   scm_metaclass_standard = mt;
 519   scm_c_define ("<operator-class>", ot);
 520   scm_metaclass_operator = ot;
 521   SCM_SET_CLASS_FLAGS (et, SCM_CLASSF_OPERATOR | SCM_CLASSF_ENTITY);
 522   SCM_SET_CLASS_DESTRUCTOR (et, scm_struct_free_entity);
 523   scm_c_define ("<entity>", et);
 524
 525 #ifndef SCM_MAGIC_SNARFER
 526 #include "libguile/objects.x"
 527 #endif
 528 }
 529
 530 /*
 531   Local Variables:
 532   c-file-style: "gnu"
 533   End:
 534 */