libguile/memoize.c

   1 /* Copyright (C) 1995,1996,1997,1998,1999,2000,2001,2002,2003,2004,2005,2006,2007,2008,2009,2010
   2  * Free Software Foundation, Inc.
   3  *
   4  * This library is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU Lesser General Public License
   6  * as published by the Free Software Foundation; either version 3 of
   7  * the License, or (at your option) any later version.
   8  *
   9  * This library is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * Lesser General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Lesser General Public
  15  * License along with this library; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  17  * 02110-1301 USA
  18  */
  19
  20 \f
  21
  22 #ifdef HAVE_CONFIG_H
  23 #  include <config.h>
  24 #endif
  25
  26 #include "libguile/__scm.h"
  27 #include "libguile/_scm.h"
  28 #include "libguile/continuations.h"
  29 #include "libguile/eq.h"
  30 #include "libguile/list.h"
  31 #include "libguile/macros.h"
  32 #include "libguile/memoize.h"
  33 #include "libguile/modules.h"
  34 #include "libguile/srcprop.h"
  35 #include "libguile/ports.h"
  36 #include "libguile/print.h"
  37 #include "libguile/strings.h"
  38 #include "libguile/throw.h"
  39 #include "libguile/validate.h"
  40
  41
  42 \f
  43
  44
  45 #if 0
  46 #define CAR(x)   SCM_CAR(x)
  47 #define CDR(x)   SCM_CDR(x)
  48 #define CAAR(x)  SCM_CAAR(x)
  49 #define CADR(x)  SCM_CADR(x)
  50 #define CDAR(x)  SCM_CDAR(x)
  51 #define CDDR(x)  SCM_CDDR(x)
  52 #define CADDR(x) SCM_CADDR(x)
  53 #define CDDDR(x) SCM_CDDDR(x)
  54 #define CADDDR(x) SCM_CDDDR(x)
  55 #else
  56 #define CAR(x)   scm_car(x)
  57 #define CDR(x)   scm_cdr(x)
  58 #define CAAR(x)  scm_caar(x)
  59 #define CADR(x)  scm_cadr(x)
  60 #define CDAR(x)  scm_cdar(x)
  61 #define CDDR(x)  scm_cddr(x)
  62 #define CADDR(x) scm_caddr(x)
  63 #define CDDDR(x) scm_cdddr(x)
  64 #define CADDDR(x) scm_cadddr(x)
  65 #endif
  66
  67
  68 static const char s_bad_expression[] = "Bad expression";
  69 static const char s_expression[] = "Missing or extra expression in";
  70 static const char s_missing_expression[] = "Missing expression in";
  71 static const char s_extra_expression[] = "Extra expression in";
  72 static const char s_empty_combination[] = "Illegal empty combination";
  73 static const char s_missing_body_expression[] = "Missing body expression in";
  74 static const char s_mixed_body_forms[] = "Mixed definitions and expressions in";
  75 static const char s_bad_define[] = "Bad define placement";
  76 static const char s_missing_clauses[] = "Missing clauses";
  77 static const char s_misplaced_else_clause[] = "Misplaced else clause";
  78 static const char s_bad_case_clause[] = "Bad case clause";
  79 static const char s_bad_case_labels[] = "Bad case labels";
  80 static const char s_duplicate_case_label[] = "Duplicate case label";
  81 static const char s_bad_cond_clause[] = "Bad cond clause";
  82 static const char s_missing_recipient[] = "Missing recipient in";
  83 static const char s_bad_variable[] = "Bad variable";
  84 static const char s_bad_bindings[] = "Bad bindings";
  85 static const char s_bad_binding[] = "Bad binding";
  86 static const char s_duplicate_binding[] = "Duplicate binding";
  87 static const char s_bad_exit_clause[] = "Bad exit clause";
  88 static const char s_bad_formals[] = "Bad formals";
  89 static const char s_bad_formal[] = "Bad formal";
  90 static const char s_duplicate_formal[] = "Duplicate formal";
  91 static const char s_splicing[] = "Non-list result for unquote-splicing";
  92 static const char s_bad_slot_number[] = "Bad slot number";
  93
  94
  95 /* Signal a syntax error.  We distinguish between the form that caused the
  96  * error and the enclosing expression.  The error message will print out as
  97  * shown in the following pattern.  The file name and line number are only
  98  * given when they can be determined from the erroneous form or from the
  99  * enclosing expression.
 100  *
 101  * <filename>: In procedure memoization:
 102  * <filename>: In file <name>, line <nr>: <error-message> in <expression>.  */
 103
 104 SCM_SYMBOL (syntax_error_key, "syntax-error");
 105
 106 /* The prototype is needed to indicate that the function does not return.  */
 107 static void
 108 syntax_error (const char* const, const SCM, const SCM) SCM_NORETURN;
 109
 110 static void
 111 syntax_error (const char* const msg, const SCM form, const SCM expr)
 112 {
 113   SCM msg_string = scm_from_locale_string (msg);
 114   SCM filename = SCM_BOOL_F;
 115   SCM linenr = SCM_BOOL_F;
 116   const char *format;
 117   SCM args;
 118
 119   if (scm_is_pair (form))
 120     {
 121       filename = scm_source_property (form, scm_sym_filename);
 122       linenr = scm_source_property (form, scm_sym_line);
 123     }
 124
 125   if (scm_is_false (filename) && scm_is_false (linenr) && scm_is_pair (expr))
 126     {
 127       filename = scm_source_property (expr, scm_sym_filename);
 128       linenr = scm_source_property (expr, scm_sym_line);
 129     }
 130
 131   if (!SCM_UNBNDP (expr))
 132     {
 133       if (scm_is_true (filename))
 134         {
 135           format = "In file ~S, line ~S: ~A ~S in expression ~S.";
 136           args = scm_list_5 (filename, linenr, msg_string, form, expr);
 137         }
 138       else if (scm_is_true (linenr))
 139         {
 140           format = "In line ~S: ~A ~S in expression ~S.";
 141           args = scm_list_4 (linenr, msg_string, form, expr);
 142         }
 143       else
 144         {
 145           format = "~A ~S in expression ~S.";
 146           args = scm_list_3 (msg_string, form, expr);
 147         }
 148     }
 149   else
 150     {
 151       if (scm_is_true (filename))
 152         {
 153           format = "In file ~S, line ~S: ~A ~S.";
 154           args = scm_list_4 (filename, linenr, msg_string, form);
 155         }
 156       else if (scm_is_true (linenr))
 157         {
 158           format = "In line ~S: ~A ~S.";
 159           args = scm_list_3 (linenr, msg_string, form);
 160         }
 161       else
 162         {
 163           format = "~A ~S.";
 164           args = scm_list_2 (msg_string, form);
 165         }
 166     }
 167
 168   scm_error (syntax_error_key, "memoization", format, args, SCM_BOOL_F);
 169 }
 170
 171
 172 /* Shortcut macros to simplify syntax error handling. */
 173 #define ASSERT_SYNTAX(cond, message, form)              \
 174   { if (SCM_UNLIKELY (!(cond)))                 \
 175       syntax_error (message, form, SCM_UNDEFINED); }
 176 #define ASSERT_SYNTAX_2(cond, message, form, expr)      \
 177   { if (SCM_UNLIKELY (!(cond)))                 \
 178       syntax_error (message, form, expr); }
 179
 180 \f
 181
 182
 183 /* {Evaluator memoized expressions}
 184  */
 185
 186 scm_t_bits scm_tc16_memoized;
 187
 188 #define MAKMEMO(n, args)        (scm_cell (scm_tc16_memoized | ((n) << 16), (scm_t_bits)(args)))
 189
 190 #define MAKMEMO_BEGIN(exps) \
 191   MAKMEMO (SCM_M_BEGIN, exps)
 192 #define MAKMEMO_IF(test, then, else_) \
 193   MAKMEMO (SCM_M_IF, scm_cons (test, scm_cons (then, else_)))
 194 #define MAKMEMO_LAMBDA(nreq, rest, body) \
 195   MAKMEMO (SCM_M_LAMBDA, scm_cons (SCM_I_MAKINUM (nreq), scm_cons (rest, body)))
 196 #define MAKMEMO_LET(inits, body) \
 197   MAKMEMO (SCM_M_LET, scm_cons (inits, body))
 198 #define MAKMEMO_QUOTE(exp) \
 199   MAKMEMO (SCM_M_QUOTE, exp)
 200 #define MAKMEMO_DEFINE(var, val) \
 201   MAKMEMO (SCM_M_DEFINE, scm_cons (var, val))
 202 #define MAKMEMO_DYNWIND(in, expr, out) \
 203   MAKMEMO (SCM_M_DYNWIND, scm_cons (in, scm_cons (expr, out)))
 204 #define MAKMEMO_APPLY(exp) \
 205   MAKMEMO (SCM_M_APPLY, exp)
 206 #define MAKMEMO_CONT(proc) \
 207   MAKMEMO (SCM_M_CONT, proc)
 208 #define MAKMEMO_CALL_WITH_VALUES(prod, cons) \
 209   MAKMEMO (SCM_M_CALL_WITH_VALUES, scm_cons (prod, cons))
 210 #define MAKMEMO_CALL(proc, nargs, args) \
 211   MAKMEMO (SCM_M_CALL, scm_cons (proc, scm_cons (SCM_I_MAKINUM (nargs), args)))
 212 #define MAKMEMO_LEX_REF(n) \
 213   MAKMEMO (SCM_M_LEXICAL_REF, SCM_I_MAKINUM (n))
 214 #define MAKMEMO_LEX_SET(n, val) \
 215   MAKMEMO (SCM_M_LEXICAL_SET, scm_cons (SCM_I_MAKINUM (n), val))
 216 #define MAKMEMO_TOP_REF(var) \
 217   MAKMEMO (SCM_M_TOPLEVEL_REF, var)
 218 #define MAKMEMO_TOP_SET(var, val) \
 219   MAKMEMO (SCM_M_TOPLEVEL_SET, scm_cons (var, val))
 220 #define MAKMEMO_MOD_REF(mod, var, public) \
 221   MAKMEMO (SCM_M_MODULE_REF, scm_cons (mod, scm_cons (var, public)))
 222 #define MAKMEMO_MOD_SET(val, mod, var, public) \
 223   MAKMEMO (SCM_M_MODULE_SET, scm_cons (val, scm_cons (mod, scm_cons (var, public))))
 224
 225 \f
 226
 227 /* This table must agree with the list of M_ constants in memoize.h */
 228 static const char *const memoized_tags[] =
 229 {
 230   "begin",
 231   "if",
 232   "lambda",
 233   "let",
 234   "quote",
 235   "define",
 236   "dynwind",
 237   "apply",
 238   "call/cc",
 239   "call-with-values",
 240   "call",
 241   "lexical-ref",
 242   "lexical-set!",
 243   "toplevel-ref",
 244   "toplevel-set!",
 245   "module-ref",
 246   "module-set!",
 247 };
 248
 249 static int
 250 scm_print_memoized (SCM memoized, SCM port, scm_print_state *pstate)
 251 {
 252   scm_puts ("#<memoized ", port);
 253   scm_write (scm_unmemoize_expression (memoized), port);
 254   scm_puts (">", port);
 255   return 1;
 256 }
 257
 258 static SCM scm_m_at (SCM xorig, SCM env);
 259 static SCM scm_m_atat (SCM xorig, SCM env);
 260 static SCM scm_m_and (SCM xorig, SCM env);
 261 static SCM scm_m_apply (SCM xorig, SCM env);
 262 static SCM scm_m_begin (SCM xorig, SCM env);
 263 static SCM scm_m_cont (SCM xorig, SCM env);
 264 static SCM scm_m_at_call_with_values (SCM xorig, SCM env);
 265 static SCM scm_m_cond (SCM xorig, SCM env);
 266 static SCM scm_m_define (SCM x, SCM env);
 267 static SCM scm_m_at_dynamic_wind (SCM xorig, SCM env);
 268 static SCM scm_m_eval_when (SCM xorig, SCM env);
 269 static SCM scm_m_if (SCM xorig, SCM env);
 270 static SCM scm_m_lambda (SCM xorig, SCM env);
 271 static SCM scm_m_let (SCM xorig, SCM env);
 272 static SCM scm_m_letrec (SCM xorig, SCM env);
 273 static SCM scm_m_letstar (SCM xorig, SCM env);
 274 static SCM scm_m_or (SCM xorig, SCM env);
 275 static SCM scm_m_quote (SCM xorig, SCM env);
 276 static SCM scm_m_set_x (SCM xorig, SCM env);
 277
 278
 279 \f
 280
 281
 282 static scm_t_macro_primitive
 283 memoize_env_ref_transformer (SCM env, SCM x)
 284 {
 285   SCM var;
 286   for (; scm_is_pair (env); env = CDR (env))
 287     if (scm_is_eq (x, CAR (env)))
 288       return NULL; /* lexical */
 289
 290   var = scm_module_variable (env, x);
 291   if (scm_is_true (var) && scm_is_true (scm_variable_bound_p (var))
 292       && scm_is_true (scm_macro_p (scm_variable_ref (var))))
 293     return scm_i_macro_primitive (scm_variable_ref (var));
 294   else
 295     return NULL; /* anything else */
 296 }
 297
 298 static int
 299 memoize_env_var_is_free (SCM env, SCM x)
 300 {
 301   for (; scm_is_pair (env); env = CDR (env))
 302     if (scm_is_eq (x, CAR (env)))
 303       return 0; /* bound */
 304   return 1; /* free */
 305 }
 306
 307 static int
 308 memoize_env_lexical_index (SCM env, SCM x)
 309 {
 310   int i = 0;
 311   for (; scm_is_pair (env); env = CDR (env), i++)
 312     if (scm_is_eq (x, CAR (env)))
 313       return i; /* bound */
 314   return -1; /* free */
 315 }
 316
 317 static SCM
 318 memoize_env_extend (SCM env, SCM vars)
 319 {
 320   return scm_append (scm_list_2 (vars, env));
 321 }
 322
 323 static SCM
 324 memoize (SCM exp, SCM env)
 325 {
 326   if (scm_is_pair (exp))
 327     {
 328       SCM CAR;
 329       scm_t_macro_primitive trans;
 330
 331       CAR = CAR (exp);
 332       if (scm_is_symbol (CAR))
 333         trans = memoize_env_ref_transformer (env, CAR);
 334       else
 335         trans = NULL;
 336
 337       if (trans)
 338         return trans (exp, env);
 339       else
 340         {
 341           SCM proc;
 342           SCM args = SCM_EOL;
 343           int nargs = 0;
 344           proc = memoize (CAR (exp), env);
 345           for (exp = CDR (exp); scm_is_pair (exp); exp = CDR (exp), nargs++)
 346             args = scm_cons (memoize (CAR (exp), env), args);
 347           if (scm_is_null (exp))
 348             return MAKMEMO_CALL (proc, nargs,
 349                                  scm_reverse_x (args, SCM_UNDEFINED));
 350           else
 351             syntax_error ("expected a proper list", exp, SCM_UNDEFINED);
 352         }
 353     }
 354   else if (scm_is_symbol (exp))
 355     {
 356       int i = memoize_env_lexical_index (env, exp);
 357       if (i < 0)
 358         return MAKMEMO_TOP_REF (exp);
 359       else
 360         return MAKMEMO_LEX_REF (i);
 361     }
 362   else
 363     return MAKMEMO_QUOTE (exp);
 364 }
 365
 366 static SCM
 367 memoize_exprs (SCM forms, const SCM env)
 368 {
 369   SCM ret = SCM_EOL;
 370
 371   for (; !scm_is_null (forms); forms = CDR (forms))
 372     ret = scm_cons (memoize (CAR (forms), env), ret);
 373   return scm_reverse_x (ret, SCM_UNDEFINED);
 374 }
 375
 376 static SCM
 377 memoize_sequence (const SCM forms, const SCM env)
 378 {
 379   ASSERT_SYNTAX (scm_ilength (forms) >= 1, s_bad_expression,
 380                  scm_cons (scm_sym_begin, forms));
 381   return MAKMEMO_BEGIN (memoize_exprs (forms, env));
 382 }
 383
 384
 385 \f
 386 /* Memoization.  */
 387
 388 #define SCM_SYNTAX(RANAME, STR, CFN)  \
 389 SCM_SNARF_HERE(static const char RANAME[]=STR)\
 390 SCM_SNARF_INIT(scm_c_define (RANAME, scm_i_make_primitive_macro (RANAME, CFN)))
 391
 392 SCM_SYNTAX (s_at, "@", scm_m_at);
 393 SCM_SYNTAX (s_atat, "@@", scm_m_atat);
 394 SCM_SYNTAX (s_and, "and", scm_m_and);
 395 SCM_SYNTAX (s_begin, "begin", scm_m_begin);
 396 SCM_SYNTAX (s_atcall_cc, "@call-with-current-continuation", scm_m_cont);
 397 SCM_SYNTAX (s_at_call_with_values, "@call-with-values", scm_m_at_call_with_values);
 398 SCM_SYNTAX (s_cond, "cond", scm_m_cond);
 399 SCM_SYNTAX (s_define, "define", scm_m_define);
 400 SCM_SYNTAX (s_at_dynamic_wind, "@dynamic-wind", scm_m_at_dynamic_wind);
 401 SCM_SYNTAX (s_eval_when, "eval-when", scm_m_eval_when);
 402 SCM_SYNTAX (s_if, "if", scm_m_if);
 403 SCM_SYNTAX (s_lambda, "lambda", scm_m_lambda);
 404 SCM_SYNTAX (s_let, "let", scm_m_let);
 405 SCM_SYNTAX (s_letrec, "letrec", scm_m_letrec);
 406 SCM_SYNTAX (s_letstar, "let*", scm_m_letstar);
 407 SCM_SYNTAX (s_or, "or", scm_m_or);
 408 SCM_SYNTAX (s_quote, "quote", scm_m_quote);
 409 SCM_SYNTAX (s_set_x, "set!", scm_m_set_x);
 410 SCM_SYNTAX (s_atapply, "@apply", scm_m_apply);
 411
 412
 413 SCM_GLOBAL_SYMBOL (scm_sym_apply, "apply");
 414 SCM_GLOBAL_SYMBOL (scm_sym_arrow, "=>");
 415 SCM_GLOBAL_SYMBOL (scm_sym_at, "@");
 416 SCM_GLOBAL_SYMBOL (scm_sym_atat, "@@");
 417 SCM_GLOBAL_SYMBOL (scm_sym_at_call_with_values, "@call-with-values");
 418 SCM_GLOBAL_SYMBOL (scm_sym_atapply, "@apply");
 419 SCM_GLOBAL_SYMBOL (scm_sym_atcall_cc, "@call-with-current-continuation");
 420 SCM_GLOBAL_SYMBOL (scm_sym_begin, "begin");
 421 SCM_GLOBAL_SYMBOL (scm_sym_case, "case");
 422 SCM_GLOBAL_SYMBOL (scm_sym_cond, "cond");
 423 SCM_GLOBAL_SYMBOL (scm_sym_define, "define");
 424 SCM_GLOBAL_SYMBOL (scm_sym_at_dynamic_wind, "@dynamic-wind");
 425 SCM_GLOBAL_SYMBOL (scm_sym_else, "else");
 426 SCM_GLOBAL_SYMBOL (scm_sym_eval_when, "eval-when");
 427 SCM_GLOBAL_SYMBOL (scm_sym_if, "if");
 428 SCM_GLOBAL_SYMBOL (scm_sym_lambda, "lambda");
 429 SCM_GLOBAL_SYMBOL (scm_sym_let, "let");
 430 SCM_GLOBAL_SYMBOL (scm_sym_letrec, "letrec");
 431 SCM_GLOBAL_SYMBOL (scm_sym_letstar, "let*");
 432 SCM_GLOBAL_SYMBOL (scm_sym_or, "or");
 433 SCM_GLOBAL_SYMBOL (scm_sym_quote, "quote");
 434 SCM_GLOBAL_SYMBOL (scm_sym_set_x, "set!");
 435 SCM_SYMBOL (sym_eval, "eval");
 436 SCM_SYMBOL (sym_load, "load");
 437
 438 SCM_GLOBAL_SYMBOL (scm_sym_unquote, "unquote");
 439 SCM_GLOBAL_SYMBOL (scm_sym_quasiquote, "quasiquote");
 440 SCM_GLOBAL_SYMBOL (scm_sym_uq_splicing, "unquote-splicing");
 441
 442
 443 static SCM
 444 scm_m_at (SCM expr, SCM env SCM_UNUSED)
 445 {
 446   ASSERT_SYNTAX (scm_ilength (expr) == 3, s_bad_expression, expr);
 447   ASSERT_SYNTAX (scm_ilength (CADR (expr)) > 0, s_bad_expression, expr);
 448   ASSERT_SYNTAX (scm_is_symbol (CADDR (expr)), s_bad_expression, expr);
 449
 450   return MAKMEMO_MOD_REF (CADR (expr), CADDR (expr), SCM_BOOL_T);
 451 }
 452
 453 static SCM
 454 scm_m_atat (SCM expr, SCM env SCM_UNUSED)
 455 {
 456   ASSERT_SYNTAX (scm_ilength (expr) == 3, s_bad_expression, expr);
 457   ASSERT_SYNTAX (scm_ilength (CADR (expr)) > 0, s_bad_expression, expr);
 458   ASSERT_SYNTAX (scm_is_symbol (CADDR (expr)), s_bad_expression, expr);
 459
 460   return MAKMEMO_MOD_REF (CADR (expr), CADDR (expr), SCM_BOOL_F);
 461 }
 462
 463 static SCM
 464 scm_m_and (SCM expr, SCM env)
 465 {
 466   const SCM cdr_expr = CDR (expr);
 467
 468   if (scm_is_null (cdr_expr))
 469     return MAKMEMO_QUOTE (SCM_BOOL_T);
 470   ASSERT_SYNTAX (scm_is_pair (cdr_expr), s_bad_expression, expr);
 471
 472   if (scm_is_null (CDR (cdr_expr)))
 473     return memoize (CAR (cdr_expr), env);
 474   else
 475     return MAKMEMO_IF (memoize (CAR (cdr_expr), env),
 476                        scm_m_and (cdr_expr, env),
 477                        MAKMEMO_QUOTE (SCM_BOOL_F));
 478 }
 479
 480 static SCM
 481 scm_m_apply (SCM expr, SCM env)
 482 {
 483   const SCM cdr_expr = CDR (expr);
 484   ASSERT_SYNTAX (scm_ilength (cdr_expr) >= 0, s_bad_expression, expr);
 485   ASSERT_SYNTAX (scm_ilength (cdr_expr) == 2, s_missing_expression, expr);
 486
 487   return MAKMEMO_APPLY (memoize_exprs (cdr_expr, env));
 488 }
 489
 490 static SCM
 491 scm_m_begin (SCM expr, SCM env)
 492 {
 493   const SCM cdr_expr = CDR (expr);
 494   ASSERT_SYNTAX (scm_ilength (cdr_expr) >= 1, s_bad_expression, expr);
 495   return MAKMEMO_BEGIN (memoize_exprs (cdr_expr, env));
 496 }
 497
 498 static SCM
 499 scm_m_cont (SCM expr, SCM env)
 500 {
 501   const SCM cdr_expr = CDR (expr);
 502   ASSERT_SYNTAX (scm_ilength (cdr_expr) >= 0, s_bad_expression, expr);
 503   ASSERT_SYNTAX (scm_ilength (cdr_expr) == 1, s_expression, expr);
 504
 505   return MAKMEMO_CONT (memoize (CADR (expr), env));
 506 }
 507
 508 static SCM
 509 scm_m_at_call_with_values (SCM expr, SCM env)
 510 {
 511   const SCM cdr_expr = CDR (expr);
 512   ASSERT_SYNTAX (scm_ilength (cdr_expr) >= 0, s_bad_expression, expr);
 513   ASSERT_SYNTAX (scm_ilength (cdr_expr) == 2, s_expression, expr);
 514
 515   return MAKMEMO_CALL_WITH_VALUES (memoize (CADR (expr), env),
 516                                    memoize (CADDR (expr), env));
 517 }
 518
 519 static SCM
 520 scm_m_cond (SCM expr, SCM env)
 521 {
 522   /* Check, whether 'else or '=> is a literal, i. e. not bound to a value. */
 523   const int else_literal_p = memoize_env_var_is_free (env, scm_sym_else);
 524   const int arrow_literal_p = memoize_env_var_is_free (env, scm_sym_arrow);
 525
 526   const SCM clauses = CDR (expr);
 527   SCM clause_idx;
 528   SCM ret, loc;
 529
 530   ASSERT_SYNTAX (scm_ilength (clauses) >= 0, s_bad_expression, expr);
 531   ASSERT_SYNTAX (scm_ilength (clauses) >= 1, s_missing_clauses, expr);
 532
 533   ret = scm_cons (SCM_UNDEFINED, MAKMEMO_QUOTE (SCM_UNSPECIFIED));
 534   loc = ret;
 535
 536   for (clause_idx = clauses;
 537        !scm_is_null (clause_idx);
 538        clause_idx = CDR (clause_idx))
 539     {
 540       SCM test;
 541
 542       const SCM clause = CAR (clause_idx);
 543       const long length = scm_ilength (clause);
 544       ASSERT_SYNTAX_2 (length >= 1, s_bad_cond_clause, clause, expr);
 545
 546       test = CAR (clause);
 547       if (scm_is_eq (test, scm_sym_else) && else_literal_p)
 548         {
 549           const int last_clause_p = scm_is_null (CDR (clause_idx));
 550           ASSERT_SYNTAX_2 (length >= 2,
 551                            s_bad_cond_clause, clause, expr);
 552           ASSERT_SYNTAX_2 (last_clause_p,
 553                            s_misplaced_else_clause, clause, expr);
 554           SCM_SETCDR (loc,
 555                       memoize (scm_cons (scm_sym_begin, CDR (clause)), env));
 556         }
 557       else if (length >= 2
 558                && scm_is_eq (CADR (clause), scm_sym_arrow)
 559                && arrow_literal_p)
 560         {
 561           SCM tmp = scm_gensym (scm_from_locale_string ("cond "));
 562           SCM i;
 563           SCM new_env = scm_cons (tmp, env);
 564           ASSERT_SYNTAX_2 (length > 2, s_missing_recipient, clause, expr);
 565           ASSERT_SYNTAX_2 (length == 3, s_extra_expression, clause, expr);
 566           i = MAKMEMO_IF (MAKMEMO_LEX_REF (0),
 567                           MAKMEMO_CALL (memoize (CADDR (clause),
 568                                                  scm_cons (tmp, new_env)),
 569                                         1,
 570                                         scm_list_1 (MAKMEMO_LEX_REF (0))),
 571                           MAKMEMO_QUOTE (SCM_UNSPECIFIED));
 572           SCM_SETCDR (loc,
 573                       MAKMEMO_LET (scm_list_1 (memoize (CAR (clause), env)),
 574                                    i));
 575           env = new_env;
 576           loc = scm_last_pair (SCM_MEMOIZED_ARGS (i));
 577         }
 578       /* FIXME length == 1 case */
 579       else
 580         {
 581           SCM i = MAKMEMO_IF (memoize (CAR (clause), env),
 582                               memoize (scm_cons (scm_sym_begin, CDR (clause)), env),
 583                               MAKMEMO_QUOTE (SCM_UNSPECIFIED));
 584           SCM_SETCDR (loc, i);
 585           loc = scm_last_pair (SCM_MEMOIZED_ARGS (i));
 586         }
 587     }
 588
 589   return CDR (ret);
 590 }
 591
 592 /* According to Section 5.2.1 of R5RS we first have to make sure that the
 593    variable is bound, and then perform the `(set! variable expression)'
 594    operation.  However, EXPRESSION _can_ be evaluated before VARIABLE is
 595    bound.  This means that EXPRESSION won't necessarily be able to assign
 596    values to VARIABLE as in `(define foo (begin (set! foo 1) (+ foo 1)))'.  */
 597 static SCM
 598 scm_m_define (SCM expr, SCM env)
 599 {
 600   const SCM cdr_expr = CDR (expr);
 601   SCM body;
 602   SCM variable;
 603
 604   ASSERT_SYNTAX (scm_ilength (cdr_expr) >= 0, s_bad_expression, expr);
 605   ASSERT_SYNTAX (scm_ilength (cdr_expr) >= 2, s_missing_expression, expr);
 606   ASSERT_SYNTAX (!scm_is_pair (env), s_bad_define, expr);
 607
 608   body = CDR (cdr_expr);
 609   variable = CAR (cdr_expr);
 610
 611   if (scm_is_pair (variable))
 612     {
 613       ASSERT_SYNTAX_2 (scm_is_symbol (CAR (variable)), s_bad_variable, variable, expr);
 614       return MAKMEMO_DEFINE (CAR (variable),
 615                              memoize (scm_cons (scm_sym_lambda,
 616                                                 scm_cons (CDR (variable), body)),
 617                                       env));
 618     }
 619   ASSERT_SYNTAX_2 (scm_is_symbol (variable), s_bad_variable, variable, expr);
 620   ASSERT_SYNTAX (scm_ilength (body) == 1, s_expression, expr);
 621   return MAKMEMO_DEFINE (variable, memoize (CAR (body), env));
 622 }
 623
 624 static SCM
 625 scm_m_at_dynamic_wind (SCM expr, SCM env)
 626 {
 627   const SCM cdr_expr = CDR (expr);
 628   ASSERT_SYNTAX (scm_ilength (cdr_expr) == 3, s_bad_expression, expr);
 629
 630   return MAKMEMO_DYNWIND (memoize (CADR (expr), env),
 631                           memoize (CADDR (expr), env),
 632                           memoize (CADDDR (expr), env));
 633 }
 634
 635 static SCM
 636 scm_m_eval_when (SCM expr, SCM env)
 637 {
 638   ASSERT_SYNTAX (scm_ilength (expr) >= 3, s_bad_expression, expr);
 639   ASSERT_SYNTAX (scm_ilength (CADR (expr)) > 0, s_bad_expression, expr);
 640
 641   if (scm_is_true (scm_memq (sym_eval, CADR (expr)))
 642       || scm_is_true (scm_memq (sym_load, CADR (expr))))
 643     return MAKMEMO_BEGIN (memoize_exprs (CDDR (expr), env));
 644   else
 645     return MAKMEMO_QUOTE (SCM_UNSPECIFIED);
 646 }
 647
 648 static SCM
 649 scm_m_if (SCM expr, SCM env SCM_UNUSED)
 650 {
 651   const SCM cdr_expr = CDR (expr);
 652   const long length = scm_ilength (cdr_expr);
 653   ASSERT_SYNTAX (length == 2 || length == 3, s_expression, expr);
 654   return MAKMEMO_IF (memoize (CADR (expr), env),
 655                      memoize (CADDR (expr), env),
 656                      ((length == 3)
 657                       ? memoize (CADDDR (expr), env)
 658                       : MAKMEMO_QUOTE (SCM_UNSPECIFIED)));
 659 }
 660
 661 /* A helper function for memoize_lambda to support checking for duplicate
 662  * formal arguments: Return true if OBJ is `eq?' to one of the elements of
 663  * LIST or to the CDR of the last cons.  Therefore, LIST may have any of the
 664  * forms that a formal argument can have:
 665  *   <rest>, (<arg1> ...), (<arg1> ...  .  <rest>) */
 666 static int
 667 c_improper_memq (SCM obj, SCM list)
 668 {
 669   for (; scm_is_pair (list); list = CDR (list))
 670     {
 671       if (scm_is_eq (CAR (list), obj))
 672         return 1;
 673     }
 674   return scm_is_eq (list, obj);
 675 }
 676
 677 static SCM
 678 scm_m_lambda (SCM expr, SCM env SCM_UNUSED)
 679 {
 680   SCM formals;
 681   SCM formals_idx;
 682   SCM formal_vars = SCM_EOL;
 683   int nreq = 0;
 684
 685   const SCM cdr_expr = CDR (expr);
 686   const long length = scm_ilength (cdr_expr);
 687   ASSERT_SYNTAX (length >= 0, s_bad_expression, expr);
 688   ASSERT_SYNTAX (length >= 2, s_missing_expression, expr);
 689
 690   /* Before iterating the list of formal arguments, make sure the formals
 691    * actually are given as either a symbol or a non-cyclic list.  */
 692   formals = CAR (cdr_expr);
 693   if (scm_is_pair (formals))
 694     {
 695       /* Dirk:FIXME:: We should check for a cyclic list of formals, and if
 696        * detected, report a 'Bad formals' error.  */
 697     }
 698   else
 699     {
 700       ASSERT_SYNTAX_2 (scm_is_symbol (formals) || scm_is_null (formals),
 701                        s_bad_formals, formals, expr);
 702     }
 703
 704   /* Now iterate the list of formal arguments to check if all formals are
 705    * symbols, and that there are no duplicates.  */
 706   formals_idx = formals;
 707   while (scm_is_pair (formals_idx))
 708     {
 709       const SCM formal = CAR (formals_idx);
 710       const SCM next_idx = CDR (formals_idx);
 711       ASSERT_SYNTAX_2 (scm_is_symbol (formal), s_bad_formal, formal, expr);
 712       ASSERT_SYNTAX_2 (!c_improper_memq (formal, next_idx),
 713                        s_duplicate_formal, formal, expr);
 714       nreq++;
 715       formal_vars = scm_cons (formal, formal_vars);
 716       formals_idx = next_idx;
 717     }
 718   ASSERT_SYNTAX_2 (scm_is_null (formals_idx) || scm_is_symbol (formals_idx),
 719                    s_bad_formal, formals_idx, expr);
 720   if (scm_is_symbol (formals_idx))
 721     formal_vars = scm_cons (formals_idx, formal_vars);
 722   return MAKMEMO_LAMBDA (nreq, scm_symbol_p (formals_idx),
 723                          memoize_sequence (CDDR (expr),
 724                                            memoize_env_extend (env, formal_vars)));
 725 }
 726
 727 /* Check if the format of the bindings is ((<symbol> <init-form>) ...).  */
 728 static void
 729 check_bindings (const SCM bindings, const SCM expr)
 730 {
 731   SCM binding_idx;
 732
 733   ASSERT_SYNTAX_2 (scm_ilength (bindings) >= 0,
 734                    s_bad_bindings, bindings, expr);
 735
 736   binding_idx = bindings;
 737   for (; !scm_is_null (binding_idx); binding_idx = CDR (binding_idx))
 738     {
 739       SCM name;         /* const */
 740
 741       const SCM binding = CAR (binding_idx);
 742       ASSERT_SYNTAX_2 (scm_ilength (binding) == 2,
 743                        s_bad_binding, binding, expr);
 744
 745       name = CAR (binding);
 746       ASSERT_SYNTAX_2 (scm_is_symbol (name), s_bad_variable, name, expr);
 747     }
 748 }
 749
 750 /* The bindings, which must have the format ((v1 i1) (v2 i2) ... (vn in)), are
 751  * transformed to the lists (vn .. v2 v1) and (i1 i2 ... in). If a duplicate
 752  * variable name is detected, an error is signalled. */
 753 static int
 754 transform_bindings (const SCM bindings, const SCM expr,
 755                     SCM *const rvarptr, SCM *const initptr)
 756 {
 757   SCM rvariables = SCM_EOL;
 758   SCM rinits = SCM_EOL;
 759   SCM binding_idx = bindings;
 760   int n = 0;
 761   for (; !scm_is_null (binding_idx); binding_idx = CDR (binding_idx))
 762     {
 763       const SCM binding = CAR (binding_idx);
 764       const SCM CDR_binding = CDR (binding);
 765       const SCM name = CAR (binding);
 766       ASSERT_SYNTAX_2 (scm_is_false (scm_c_memq (name, rvariables)),
 767                        s_duplicate_binding, name, expr);
 768       rvariables = scm_cons (name, rvariables);
 769       rinits = scm_cons (CAR (CDR_binding), rinits);
 770       n++;
 771     }
 772   *rvarptr = rvariables;
 773   *initptr = scm_reverse_x (rinits, SCM_UNDEFINED);
 774   return n;
 775 }
 776
 777 /* This function is a helper function for memoize_let.  It transforms
 778  * (let name ((var init) ...) body ...) into
 779  * ((letrec ((name (lambda (var ...) body ...))) name) init ...)
 780  * and memoizes the expression.  It is assumed that the caller has checked
 781  * that name is a symbol and that there are bindings and a body.  */
 782 static SCM
 783 memoize_named_let (const SCM expr, SCM env)
 784 {
 785   SCM rvariables;
 786   SCM inits;
 787   int nreq;
 788
 789   const SCM cdr_expr = CDR (expr);
 790   const SCM name = CAR (cdr_expr);
 791   const SCM cddr_expr = CDR (cdr_expr);
 792   const SCM bindings = CAR (cddr_expr);
 793   check_bindings (bindings, expr);
 794
 795   nreq = transform_bindings (bindings, expr, &rvariables, &inits);
 796
 797   env = scm_cons (name, env);
 798   return MAKMEMO_LET
 799     (scm_list_1 (MAKMEMO_QUOTE (SCM_UNDEFINED)),
 800      MAKMEMO_BEGIN
 801      (scm_list_2 (MAKMEMO_LEX_SET
 802                   (0,
 803                    MAKMEMO_LAMBDA
 804                    (nreq, SCM_BOOL_F,
 805                     memoize_sequence (CDDDR (expr),
 806                                       memoize_env_extend (env, rvariables)))),
 807                   MAKMEMO_CALL (MAKMEMO_LEX_REF (0),
 808                                 nreq,
 809                                 memoize_exprs (inits, env)))));
 810 }
 811
 812 /* (let ((v1 i1) (v2 i2) ...) body) with variables v1 .. vn and initializers
 813  * i1 .. in is transformed to (#@let (vn ... v2 v1) (i1 i2 ...) body).  */
 814 static SCM
 815 scm_m_let (SCM expr, SCM env)
 816 {
 817   SCM bindings;
 818
 819   const SCM cdr_expr = CDR (expr);
 820   const long length = scm_ilength (cdr_expr);
 821   ASSERT_SYNTAX (length >= 0, s_bad_expression, expr);
 822   ASSERT_SYNTAX (length >= 2, s_missing_expression, expr);
 823
 824   bindings = CAR (cdr_expr);
 825   if (scm_is_symbol (bindings))
 826     {
 827       ASSERT_SYNTAX (length >= 3, s_missing_expression, expr);
 828       return memoize_named_let (expr, env);
 829     }
 830
 831   check_bindings (bindings, expr);
 832   if (scm_is_null (bindings))
 833     return memoize_sequence (CDDR (expr), env);
 834   else
 835     {
 836       SCM rvariables;
 837       SCM inits;
 838       transform_bindings (bindings, expr, &rvariables, &inits);
 839       return MAKMEMO_LET (memoize_exprs (inits, env),
 840                           memoize_sequence (CDDR (expr),
 841                                             memoize_env_extend (env, rvariables)));
 842     }
 843 }
 844
 845 static SCM
 846 scm_m_letrec (SCM expr, SCM env)
 847 {
 848   SCM bindings;
 849
 850   const SCM cdr_expr = CDR (expr);
 851   ASSERT_SYNTAX (scm_ilength (cdr_expr) >= 0, s_bad_expression, expr);
 852   ASSERT_SYNTAX (scm_ilength (cdr_expr) >= 2, s_missing_expression, expr);
 853
 854   bindings = CAR (cdr_expr);
 855   if (scm_is_null (bindings))
 856     return memoize_sequence (CDDR (expr), env);
 857   else
 858     {
 859       SCM rvariables;
 860       SCM inits;
 861       SCM v, i;
 862       SCM undefs = SCM_EOL;
 863       SCM vals = SCM_EOL;
 864       SCM sets = SCM_EOL;
 865       SCM new_env;
 866       int offset;
 867       int n = transform_bindings (bindings, expr, &rvariables, &inits);
 868       offset = n;
 869       new_env = memoize_env_extend (env, rvariables);
 870       for (v = scm_reverse (rvariables), i = inits; scm_is_pair (v);
 871            v = CDR (v), i = CDR (i), n--)
 872         {
 873           undefs = scm_cons (MAKMEMO_QUOTE (SCM_UNDEFINED), undefs);
 874           vals = scm_cons (memoize (CAR (i), new_env), vals);
 875           sets = scm_cons (MAKMEMO_LEX_SET ((n-1) + offset,
 876                                             MAKMEMO_LEX_REF (n-1)),
 877                            sets);
 878         }
 879       return MAKMEMO_LET
 880         (undefs,
 881          MAKMEMO_BEGIN (scm_list_2 (MAKMEMO_LET (scm_reverse (vals),
 882                                                  MAKMEMO_BEGIN (sets)),
 883                                     memoize_sequence (CDDR (expr),
 884                                                       new_env))));
 885     }
 886 }
 887
 888 static SCM
 889 scm_m_letstar (SCM expr, SCM env SCM_UNUSED)
 890 {
 891   SCM bindings;
 892
 893   const SCM cdr_expr = CDR (expr);
 894   ASSERT_SYNTAX (scm_ilength (cdr_expr) >= 0, s_bad_expression, expr);
 895   ASSERT_SYNTAX (scm_ilength (cdr_expr) >= 2, s_missing_expression, expr);
 896
 897   bindings = CAR (cdr_expr);
 898   if (scm_is_null (bindings))
 899     return memoize_sequence (CDDR (expr), env);
 900   else
 901     {
 902       SCM rvariables;
 903       SCM variables;
 904       SCM inits;
 905       SCM ret, loc;
 906       transform_bindings (bindings, expr, &rvariables, &inits);
 907       variables = scm_reverse (rvariables);
 908       ret = scm_cons (SCM_UNDEFINED, SCM_UNSPECIFIED);
 909       loc = ret;
 910       for (; scm_is_pair (variables);
 911            variables = CDR (variables), inits = CDR (inits))
 912         { SCM x = MAKMEMO_LET (scm_list_1 (memoize (CAR (inits), env)),
 913                                MAKMEMO_QUOTE (SCM_UNSPECIFIED));
 914           SCM_SETCDR (loc, x);
 915           loc = scm_last_pair (SCM_MEMOIZED_ARGS (x));
 916           env = scm_cons (CAR (variables), env);
 917         }
 918       SCM_SETCDR (loc, memoize_sequence (CDDR (expr), env));
 919       return CDR (ret);
 920     }
 921 }
 922
 923 static SCM
 924 scm_m_or (SCM expr, SCM env SCM_UNUSED)
 925 {
 926   SCM tail = CDR (expr);
 927   SCM ret, loc;
 928   const long length = scm_ilength (tail);
 929
 930   ASSERT_SYNTAX (length >= 0, s_bad_expression, expr);
 931
 932   ret = scm_cons (SCM_UNDEFINED, SCM_UNSPECIFIED);
 933   loc = ret;
 934   for (; scm_is_pair (tail); tail = CDR (tail))
 935     {
 936       SCM tmp = scm_gensym (scm_from_locale_string ("cond "));
 937       SCM x = MAKMEMO_IF (MAKMEMO_LEX_REF (0),
 938                           MAKMEMO_LEX_REF (0),
 939                           MAKMEMO_QUOTE (SCM_UNSPECIFIED));
 940       SCM new_env = scm_cons (tmp, env);
 941       SCM_SETCDR (loc, MAKMEMO_LET (scm_list_1 (memoize (CAR (tail),
 942                                                          env)),
 943                                     x));
 944       env = new_env;
 945       loc = scm_last_pair (SCM_MEMOIZED_ARGS (x));
 946     }
 947   SCM_SETCDR (loc, MAKMEMO_QUOTE (SCM_BOOL_F));
 948   return CDR (ret);
 949 }
 950
 951 static SCM
 952 scm_m_quote (SCM expr, SCM env SCM_UNUSED)
 953 {
 954   SCM quotee;
 955
 956   const SCM cdr_expr = CDR (expr);
 957   ASSERT_SYNTAX (scm_ilength (cdr_expr) >= 0, s_bad_expression, expr);
 958   ASSERT_SYNTAX (scm_ilength (cdr_expr) == 1, s_expression, expr);
 959   quotee = CAR (cdr_expr);
 960   return MAKMEMO_QUOTE (quotee);
 961 }
 962
 963 static SCM
 964 scm_m_set_x (SCM expr, SCM env)
 965 {
 966   SCM variable;
 967   SCM vmem;
 968
 969   const SCM cdr_expr = CDR (expr);
 970   ASSERT_SYNTAX (scm_ilength (cdr_expr) >= 0, s_bad_expression, expr);
 971   ASSERT_SYNTAX (scm_ilength (cdr_expr) == 2, s_expression, expr);
 972   variable = CAR (cdr_expr);
 973   vmem = memoize (variable, env);
 974
 975   switch (SCM_MEMOIZED_TAG (vmem))
 976     {
 977     case SCM_M_LEXICAL_REF:
 978       return MAKMEMO_LEX_SET (SCM_I_INUM (SCM_MEMOIZED_ARGS (vmem)),
 979                               memoize (CADDR (expr), env));
 980     case SCM_M_TOPLEVEL_REF:
 981       return MAKMEMO_TOP_SET (variable,
 982                               memoize (CADDR (expr), env));
 983     case SCM_M_MODULE_REF:
 984       return MAKMEMO_MOD_SET (memoize (CADDR (expr), env),
 985                               CAR (SCM_MEMOIZED_ARGS (vmem)),
 986                               CADR (SCM_MEMOIZED_ARGS (vmem)),
 987                               CDDR (SCM_MEMOIZED_ARGS (vmem)));
 988     default:
 989       syntax_error (s_bad_variable, variable, expr);
 990     }
 991 }
 992
 993
 994 \f
 995
 996 SCM_DEFINE (scm_memoize_expression, "memoize-expression", 1, 0, 0,
 997             (SCM exp),
 998             "Memoize the expression @var{exp}.")
 999 #define FUNC_NAME s_scm_memoize_expression
1000 {
1001   return memoize (exp, scm_current_module ());
1002 }
1003 #undef FUNC_NAME
1004
1005 \f
1006
1007
1008 SCM_SYMBOL (sym_placeholder, "_");
1009
1010 static SCM unmemoize (SCM expr);
1011
1012 static SCM
1013 unmemoize_exprs (SCM exprs)
1014 {
1015   SCM ret, tail;
1016   if (scm_is_null (exprs))
1017     return SCM_EOL;
1018   ret = scm_list_1 (unmemoize (CAR (exprs)));
1019   tail = ret;
1020   for (exprs = CDR (exprs); !scm_is_null (exprs); exprs = CDR (exprs))
1021     {
1022       SCM_SETCDR (tail, scm_list_1 (unmemoize (CAR (exprs))));
1023       tail = CDR (tail);
1024     }
1025   return ret;
1026 }
1027
1028 static SCM
1029 unmemoize_bindings (SCM inits)
1030 {
1031   SCM ret, tail;
1032   if (scm_is_null (inits))
1033     return SCM_EOL;
1034   ret = scm_list_1 (scm_list_2 (sym_placeholder, unmemoize (CAR (inits))));
1035   tail = ret;
1036   for (inits = CDR (inits); !scm_is_null (inits); inits = CDR (inits))
1037     {
1038       SCM_SETCDR (tail, scm_list_1 (scm_list_2 (sym_placeholder,
1039                                                 unmemoize (CAR (inits)))));
1040       tail = CDR (tail);
1041     }
1042   return ret;
1043 }
1044
1045 static SCM
1046 unmemoize_lexical (SCM n)
1047 {
1048   char buf[16];
1049   buf[15] = 0;
1050   snprintf (buf, 15, "<%u>", scm_to_uint32 (n));
1051   return scm_from_locale_symbol (buf);
1052 }
1053
1054 static SCM
1055 unmemoize (const SCM expr)
1056 {
1057   SCM args;
1058
1059   if (!SCM_MEMOIZED_P (expr))
1060     abort ();
1061
1062   args = SCM_MEMOIZED_ARGS (expr);
1063   switch (SCM_MEMOIZED_TAG (expr))
1064     {
1065     case SCM_M_APPLY:
1066       return scm_cons (scm_sym_atapply, unmemoize_exprs (args));
1067     case SCM_M_BEGIN:
1068       return scm_cons (scm_sym_begin, unmemoize_exprs (args));
1069     case SCM_M_CALL:
1070       return scm_cons (unmemoize (CAR (args)), unmemoize_exprs (CDDR (args)));
1071     case SCM_M_CONT:
1072       return scm_list_2 (scm_sym_atcall_cc, unmemoize (args));
1073     case SCM_M_CALL_WITH_VALUES:
1074       return scm_list_3 (scm_sym_at_call_with_values,
1075                          unmemoize (CAR (args)), unmemoize (CDR (args)));
1076     case SCM_M_DEFINE:
1077       return scm_list_3 (scm_sym_define, CAR (args), unmemoize (CDR (args)));
1078     case SCM_M_DYNWIND:
1079       return scm_list_4 (scm_sym_at_dynamic_wind,
1080                          unmemoize (CAR (args)),
1081                          unmemoize (CADR (args)),
1082                          unmemoize (CDDR (args)));
1083     case SCM_M_IF:
1084       return scm_list_4 (scm_sym_if, unmemoize (scm_car (args)),
1085                          unmemoize (scm_cadr (args)), unmemoize (scm_cddr (args)));
1086     case SCM_M_LAMBDA:
1087       return scm_list_3 (scm_sym_lambda,
1088                          scm_make_list (CAR (args), sym_placeholder),
1089                          unmemoize (CDDR (args)));
1090     case SCM_M_LET:
1091       return scm_list_3 (scm_sym_let,
1092                          unmemoize_bindings (CAR (args)),
1093                          unmemoize (CDR (args)));
1094     case SCM_M_QUOTE:
1095       return scm_list_2 (scm_sym_quote, args);
1096     case SCM_M_LEXICAL_REF:
1097       return unmemoize_lexical (args);
1098     case SCM_M_LEXICAL_SET:
1099       return scm_list_3 (scm_sym_set_x, unmemoize_lexical (CAR (args)),
1100                          unmemoize (CDR (args)));
1101     case SCM_M_TOPLEVEL_REF:
1102       return args;
1103     case SCM_M_TOPLEVEL_SET:
1104       return scm_list_3 (scm_sym_set_x, CAR (args), unmemoize (CDR (args)));
1105     case SCM_M_MODULE_REF:
1106       return scm_list_3 (scm_is_true (CDDR (args)) ? scm_sym_at : scm_sym_atat,
1107                          scm_i_finite_list_copy (CAR (args)),
1108                          CADR (args));
1109     case SCM_M_MODULE_SET:
1110       return scm_list_3 (scm_sym_set_x,
1111                          scm_list_3 (scm_is_true (CDDDR (args))
1112                                      ? scm_sym_at : scm_sym_atat,
1113                                      scm_i_finite_list_copy (CADR (args)),
1114                                      CADDR (args)),
1115                          unmemoize (CAR (args)));
1116     default:
1117       abort ();
1118     }
1119 }
1120
1121 SCM_DEFINE (scm_memoized_p, "memoized?", 1, 0, 0,
1122             (SCM obj),
1123             "Return @code{#t} if @var{obj} is memoized.")
1124 #define FUNC_NAME s_scm_memoized_p
1125 {
1126   return scm_from_bool (SCM_MEMOIZED_P (obj));
1127 }
1128 #undef FUNC_NAME
1129
1130 SCM_DEFINE (scm_unmemoize_expression, "unmemoize-expression", 1, 0, 0,
1131             (SCM m),
1132             "Unmemoize the memoized expression @var{m}.")
1133 #define FUNC_NAME s_scm_unmemoize_expression
1134 {
1135   SCM_VALIDATE_MEMOIZED (1, m);
1136   return unmemoize (m);
1137 }
1138 #undef FUNC_NAME
1139
1140 SCM_DEFINE (scm_memoized_expression_typecode, "memoized-expression-typecode", 1, 0, 0,
1141             (SCM m),
1142             "Return the typecode from the memoized expression @var{m}.")
1143 #define FUNC_NAME s_scm_memoized_expression_typecode
1144 {
1145   SCM_VALIDATE_MEMOIZED (1, m);
1146   return scm_from_uint16 (SCM_MEMOIZED_TAG (m));
1147 }
1148 #undef FUNC_NAME
1149
1150 SCM_DEFINE (scm_memoized_expression_data, "memoized-expression-data", 1, 0, 0,
1151             (SCM m),
1152             "Return the data from the memoized expression @var{m}.")
1153 #define FUNC_NAME s_scm_memoized_expression_data
1154 {
1155   SCM_VALIDATE_MEMOIZED (1, m);
1156   return SCM_MEMOIZED_ARGS (m);
1157 }
1158 #undef FUNC_NAME
1159
1160 SCM_DEFINE (scm_memoized_typecode, "memoized-typecode", 1, 0, 0,
1161             (SCM sym),
1162             "Return the memoized typecode corresponding to the symbol @var{sym}.")
1163 #define FUNC_NAME s_scm_memoized_typecode
1164 {
1165   int i;
1166
1167   SCM_VALIDATE_SYMBOL (1, sym);
1168
1169   for (i = 0; i < sizeof(memoized_tags)/sizeof(const char*); i++)
1170     if (strcmp (scm_i_symbol_chars (sym), memoized_tags[i]) == 0)
1171       return scm_from_int32 (i);
1172
1173   return SCM_BOOL_F;
1174 }
1175 #undef FUNC_NAME
1176
1177 SCM_SYMBOL (scm_unbound_variable_key, "unbound-variable");
1178 static void error_unbound_variable (SCM symbol) SCM_NORETURN;
1179 static void error_unbound_variable (SCM symbol)
1180 {
1181   scm_error (scm_unbound_variable_key, NULL, "Unbound variable: ~S",
1182              scm_list_1 (symbol), SCM_BOOL_F);
1183 }
1184
1185 SCM_DEFINE (scm_memoize_variable_access_x, "memoize-variable-access!", 2, 0, 0,
1186             (SCM m, SCM mod),
1187             "Look up and cache the variable that @var{m} will access, returning the variable.")
1188 #define FUNC_NAME s_scm_memoize_variable_access_x
1189 {
1190   SCM mx;
1191   SCM_VALIDATE_MEMOIZED (1, m);
1192   mx = SCM_MEMOIZED_ARGS (m);
1193   switch (SCM_MEMOIZED_TAG (m))
1194     {
1195     case SCM_M_TOPLEVEL_REF:
1196       if (SCM_VARIABLEP (mx))
1197         return mx;
1198       else
1199         {
1200           SCM var = scm_module_variable (mod, mx);
1201           if (scm_is_false (var) || scm_is_false (scm_variable_bound_p (var)))
1202             error_unbound_variable (mx);
1203           SCM_SET_SMOB_OBJECT (m, var);
1204           return var;
1205         }
1206
1207     case SCM_M_TOPLEVEL_SET:
1208       {
1209         SCM var = CAR (mx);
1210         if (SCM_VARIABLEP (var))
1211           return var;
1212         else
1213           {
1214             var = scm_module_variable (mod, var);
1215             if (scm_is_false (var))
1216               error_unbound_variable (CAR (mx));
1217             SCM_SETCAR (mx, var);
1218             return var;
1219           }
1220       }
1221
1222     case SCM_M_MODULE_REF:
1223       if (SCM_VARIABLEP (mx))
1224         return mx;
1225       else
1226         {
1227           SCM var;
1228           mod = scm_resolve_module (CAR (mx));
1229           if (scm_is_true (CDDR (mx)))
1230             mod = scm_module_public_interface (mod);
1231           var = scm_module_lookup (mod, CADR (mx));
1232           if (scm_is_false (scm_variable_bound_p (var)))
1233             error_unbound_variable (CADR (mx));
1234           SCM_SET_SMOB_OBJECT (m, var);
1235           return var;
1236         }
1237
1238     case SCM_M_MODULE_SET:
1239       /* FIXME: not quite threadsafe */
1240       if (SCM_VARIABLEP (CDR (mx)))
1241         return CDR (mx);
1242       else
1243         {
1244           SCM var;
1245           mod = scm_resolve_module (CADR (mx));
1246           if (scm_is_true (CDDDR (mx)))
1247             mod = scm_module_public_interface (mod);
1248           var = scm_module_lookup (mod, CADDR (mx));
1249           SCM_SETCDR (mx, var);
1250           return var;
1251         }
1252
1253     default:
1254       scm_wrong_type_arg (FUNC_NAME, 1, m);
1255       return SCM_BOOL_F;
1256     }
1257 }
1258 #undef FUNC_NAME
1259
1260
1261 \f
1262
1263 void
1264 scm_init_memoize ()
1265 {
1266   scm_tc16_memoized = scm_make_smob_type ("%memoized", 0);
1267   scm_set_smob_mark (scm_tc16_memoized, scm_markcdr);
1268   scm_set_smob_print (scm_tc16_memoized, scm_print_memoized);
1269
1270 #include "libguile/memoize.x"
1271 }
1272
1273 /*
1274   Local Variables:
1275   c-file-style: "gnu"
1276   End:
1277 */