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   1 /*
   2  * Copyright © 2016 Keith Packard <keithp@keithp.com>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation, either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program 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  * General Public License for more details.
  13  */
  14
  15 #include "ao_scheme.h"
  16 #include "ao_scheme_read.h"
  17 #include <math.h>
  18 #include <stdlib.h>
  19
  20 static const uint16_t   lex_classes[128] = {
  21         IGNORE,         /* ^@ */
  22         IGNORE,         /* ^A */
  23         IGNORE,         /* ^B */
  24         IGNORE,         /* ^C */
  25         IGNORE,         /* ^D */
  26         IGNORE,         /* ^E */
  27         IGNORE,         /* ^F */
  28         IGNORE,         /* ^G */
  29         IGNORE,         /* ^H */
  30         WHITE,          /* ^I */
  31         WHITE,          /* ^J */
  32         WHITE,          /* ^K */
  33         WHITE,          /* ^L */
  34         WHITE,          /* ^M */
  35         IGNORE,         /* ^N */
  36         IGNORE,         /* ^O */
  37         IGNORE,         /* ^P */
  38         IGNORE,         /* ^Q */
  39         IGNORE,         /* ^R */
  40         IGNORE,         /* ^S */
  41         IGNORE,         /* ^T */
  42         IGNORE,         /* ^U */
  43         IGNORE,         /* ^V */
  44         IGNORE,         /* ^W */
  45         IGNORE,         /* ^X */
  46         IGNORE,         /* ^Y */
  47         IGNORE,         /* ^Z */
  48         IGNORE,         /* ^[ */
  49         IGNORE,         /* ^\ */
  50         IGNORE,         /* ^] */
  51         IGNORE,         /* ^^ */
  52         IGNORE,         /* ^_ */
  53         PRINTABLE|WHITE,        /*    */
  54         PRINTABLE,              /* ! */
  55         PRINTABLE|STRINGC,      /* " */
  56         PRINTABLE|POUND,        /* # */
  57         PRINTABLE,              /* $ */
  58         PRINTABLE,              /* % */
  59         PRINTABLE,              /* & */
  60         PRINTABLE|SPECIAL,      /* ' */
  61         PRINTABLE|SPECIAL,      /* ( */
  62         PRINTABLE|SPECIAL,      /* ) */
  63         PRINTABLE,              /* * */
  64         PRINTABLE|SIGN,         /* + */
  65         PRINTABLE|SPECIAL_QUASI,        /* , */
  66         PRINTABLE|SIGN,         /* - */
  67         PRINTABLE|DOTC|FLOATC,  /* . */
  68         PRINTABLE,              /* / */
  69         PRINTABLE|DIGIT,        /* 0 */
  70         PRINTABLE|DIGIT,        /* 1 */
  71         PRINTABLE|DIGIT,        /* 2 */
  72         PRINTABLE|DIGIT,        /* 3 */
  73         PRINTABLE|DIGIT,        /* 4 */
  74         PRINTABLE|DIGIT,        /* 5 */
  75         PRINTABLE|DIGIT,        /* 6 */
  76         PRINTABLE|DIGIT,        /* 7 */
  77         PRINTABLE|DIGIT,        /* 8 */
  78         PRINTABLE|DIGIT,        /* 9 */
  79         PRINTABLE,              /* : */
  80         PRINTABLE|COMMENT,      /* ; */
  81         PRINTABLE,              /* < */
  82         PRINTABLE,              /* = */
  83         PRINTABLE,              /* > */
  84         PRINTABLE,              /* ? */
  85         PRINTABLE,              /*  @ */
  86         PRINTABLE|HEX_LETTER,   /*  A */
  87         PRINTABLE|HEX_LETTER,   /*  B */
  88         PRINTABLE|HEX_LETTER,   /*  C */
  89         PRINTABLE|HEX_LETTER,   /*  D */
  90         PRINTABLE|FLOATC|HEX_LETTER,/*  E */
  91         PRINTABLE|HEX_LETTER,   /*  F */
  92         PRINTABLE,              /*  G */
  93         PRINTABLE,              /*  H */
  94         PRINTABLE,              /*  I */
  95         PRINTABLE,              /*  J */
  96         PRINTABLE,              /*  K */
  97         PRINTABLE,              /*  L */
  98         PRINTABLE,              /*  M */
  99         PRINTABLE,              /*  N */
 100         PRINTABLE,              /*  O */
 101         PRINTABLE,              /*  P */
 102         PRINTABLE,              /*  Q */
 103         PRINTABLE,              /*  R */
 104         PRINTABLE,              /*  S */
 105         PRINTABLE,              /*  T */
 106         PRINTABLE,              /*  U */
 107         PRINTABLE,              /*  V */
 108         PRINTABLE,              /*  W */
 109         PRINTABLE,              /*  X */
 110         PRINTABLE,              /*  Y */
 111         PRINTABLE,              /*  Z */
 112         PRINTABLE,              /*  [ */
 113         PRINTABLE|BACKSLASH,    /*  \ */
 114         PRINTABLE,              /*  ] */
 115         PRINTABLE,              /*  ^ */
 116         PRINTABLE,              /*  _ */
 117         PRINTABLE|SPECIAL_QUASI,        /*  ` */
 118         PRINTABLE|HEX_LETTER,   /*  a */
 119         PRINTABLE|HEX_LETTER,   /*  b */
 120         PRINTABLE|HEX_LETTER,   /*  c */
 121         PRINTABLE|HEX_LETTER,   /*  d */
 122         PRINTABLE|FLOATC|HEX_LETTER,/*  e */
 123         PRINTABLE|HEX_LETTER,   /*  f */
 124         PRINTABLE,              /*  g */
 125         PRINTABLE,              /*  h */
 126         PRINTABLE,              /*  i */
 127         PRINTABLE,              /*  j */
 128         PRINTABLE,              /*  k */
 129         PRINTABLE,              /*  l */
 130         PRINTABLE,              /*  m */
 131         PRINTABLE,              /*  n */
 132         PRINTABLE,              /*  o */
 133         PRINTABLE,              /*  p */
 134         PRINTABLE,              /*  q */
 135         PRINTABLE,              /*  r */
 136         PRINTABLE,              /*  s */
 137         PRINTABLE,              /*  t */
 138         PRINTABLE,              /*  u */
 139         PRINTABLE,              /*  v */
 140         PRINTABLE,              /*  w */
 141         PRINTABLE,              /*  x */
 142         PRINTABLE,              /*  y */
 143         PRINTABLE,              /*  z */
 144         PRINTABLE,              /*  { */
 145         PRINTABLE,              /*  | */
 146         PRINTABLE,              /*  } */
 147         PRINTABLE,              /*  ~ */
 148         IGNORE,                 /*  ^? */
 149 };
 150
 151 static int lex_unget_c;
 152
 153 static inline int
 154 lex_get(void)
 155 {
 156         int     c;
 157         if (lex_unget_c) {
 158                 c = lex_unget_c;
 159                 lex_unget_c = 0;
 160         } else {
 161                 c = ao_scheme_getc();
 162         }
 163         return c;
 164 }
 165
 166 static inline void
 167 lex_unget(int c)
 168 {
 169         if (c != EOF)
 170                 lex_unget_c = c;
 171 }
 172
 173 static uint16_t lex_class;
 174
 175 static int
 176 lexc(void)
 177 {
 178         int     c;
 179         do {
 180                 c = lex_get();
 181                 if (c == EOF) {
 182                         c = 0;
 183                         lex_class = ENDOFFILE;
 184                 } else {
 185                         c &= 0x7f;
 186                         lex_class = lex_classes[c];
 187                 }
 188         } while (lex_class & IGNORE);
 189         return c;
 190 }
 191
 192 static int
 193 lex_quoted(void)
 194 {
 195         int     c;
 196         int     v;
 197         int     count;
 198
 199         c = lex_get();
 200         if (c == EOF) {
 201                 lex_class = ENDOFFILE;
 202                 return 0;
 203         }
 204         lex_class = 0;
 205         c &= 0x7f;
 206         switch (c) {
 207         case 'n':
 208                 return '\n';
 209         case 'f':
 210                 return '\f';
 211         case 'b':
 212                 return '\b';
 213         case 'r':
 214                 return '\r';
 215         case 'v':
 216                 return '\v';
 217         case 't':
 218                 return '\t';
 219         case '0':
 220         case '1':
 221         case '2':
 222         case '3':
 223         case '4':
 224         case '5':
 225         case '6':
 226         case '7':
 227                 v = c - '0';
 228                 count = 1;
 229                 while (count <= 3) {
 230                         c = lex_get();
 231                         if (c == EOF)
 232                                 return EOF;
 233                         c &= 0x7f;
 234                         if (c < '0' || '7' < c) {
 235                                 lex_unget(c);
 236                                 break;
 237                         }
 238                         v = (v << 3) + c - '0';
 239                         ++count;
 240                 }
 241                 return v;
 242         default:
 243                 return c;
 244         }
 245 }
 246
 247 #ifndef AO_SCHEME_TOKEN_MAX
 248 #define AO_SCHEME_TOKEN_MAX     128
 249 #endif
 250
 251 static char     token_string[AO_SCHEME_TOKEN_MAX];
 252 static int32_t  token_int;
 253 static int      token_len;
 254
 255 static inline void add_token(int c) {
 256         if (c && token_len < AO_SCHEME_TOKEN_MAX - 1)
 257                 token_string[token_len++] = c;
 258 }
 259
 260 static inline void del_token(void) {
 261         if (token_len > 0)
 262                 token_len--;
 263 }
 264
 265 static inline void end_token(void) {
 266         token_string[token_len] = '\0';
 267 }
 268
 269 #ifdef AO_SCHEME_FEATURE_FLOAT
 270 static float    token_float;
 271
 272 struct namedfloat {
 273         const char      *name;
 274         float           value;
 275 };
 276
 277 static const struct namedfloat namedfloats[] = {
 278         { .name = "+inf.0", .value = INFINITY },
 279         { .name = "-inf.0", .value = -INFINITY },
 280         { .name = "+nan.0", .value = NAN },
 281         { .name = "-nan.0", .value = NAN },
 282 };
 283
 284 #define NUM_NAMED_FLOATS        (sizeof namedfloats / sizeof namedfloats[0])
 285 #endif
 286
 287 static int
 288 parse_int(int base)
 289 {
 290         int     cval;
 291         int     c;
 292
 293         token_int = 0;
 294         for (;;) {
 295                 c = lexc();
 296                 if ((lex_class & HEX_DIGIT) == 0) {
 297                         lex_unget(c);
 298                         end_token();
 299                         return NUM;
 300                 }
 301                 add_token(c);
 302                 if ('0' <= c && c <= '9')
 303                         cval = c - '0';
 304                 else
 305                         cval = (c | ('a' - 'A')) - 'a' + 10;
 306                 token_int = token_int * base + cval;
 307         }
 308         return NUM;
 309 }
 310
 311 static int
 312 _lex(void)
 313 {
 314         int     c;
 315
 316         token_len = 0;
 317         for (;;) {
 318                 c = lexc();
 319                 if (lex_class & ENDOFFILE)
 320                         return END;
 321
 322                 if (lex_class & WHITE)
 323                         continue;
 324
 325                 if (lex_class & COMMENT) {
 326                         while ((c = lexc()) != '\n') {
 327                                 if (lex_class & ENDOFFILE)
 328                                         return END;
 329                         }
 330                         continue;
 331                 }
 332
 333                 if (lex_class & (SPECIAL|DOTC)) {
 334                         add_token(c);
 335                         end_token();
 336                         switch (c) {
 337                         case '(':
 338                         case '[':
 339                                 return OPEN;
 340                         case ')':
 341                         case ']':
 342                                 return CLOSE;
 343                         case '\'':
 344                                 return QUOTE;
 345                         case '.':
 346                                 return DOT;
 347 #ifdef AO_SCHEME_FEATURE_QUASI
 348                         case '`':
 349                                 return QUASIQUOTE;
 350                         case ',':
 351                                 c = lexc();
 352                                 if (c == '@') {
 353                                         add_token(c);
 354                                         end_token();
 355                                         return UNQUOTE_SPLICING;
 356                                 } else {
 357                                         lex_unget(c);
 358                                         return UNQUOTE;
 359                                 }
 360 #endif
 361                         }
 362                 }
 363                 if (lex_class & POUND) {
 364                         c = lexc();
 365                         switch (c) {
 366                         case 't':
 367                                 add_token(c);
 368                                 end_token();
 369                                 return BOOL;
 370                         case 'f':
 371                                 add_token(c);
 372                                 end_token();
 373                                 return BOOL;
 374 #ifdef AO_SCHEME_FEATURE_VECTOR
 375                         case '(':
 376                                 return OPEN_VECTOR;
 377 #endif
 378                         case '\\':
 379                                 for (;;) {
 380                                         int alphabetic;
 381                                         c = lexc();
 382                                         alphabetic = (('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z'));
 383                                         if (token_len == 0) {
 384                                                 add_token(c);
 385                                                 if (!alphabetic)
 386                                                         break;
 387                                         } else {
 388                                                 if (alphabetic)
 389                                                         add_token(c);
 390                                                 else {
 391                                                         lex_unget(c);
 392                                                         break;
 393                                                 }
 394                                         }
 395                                 }
 396                                 end_token();
 397                                 if (token_len == 1)
 398                                         token_int = token_string[0];
 399                                 else if (!strcmp(token_string, "space"))
 400                                         token_int = ' ';
 401                                 else if (!strcmp(token_string, "newline"))
 402                                         token_int = '\n';
 403                                 else if (!strcmp(token_string, "tab"))
 404                                         token_int = '\t';
 405                                 else if (!strcmp(token_string, "return"))
 406                                         token_int = '\r';
 407                                 else if (!strcmp(token_string, "formfeed"))
 408                                         token_int = '\f';
 409                                 else {
 410                                         ao_scheme_error(AO_SCHEME_INVALID, "invalid character token #\\%s", token_string);
 411                                         continue;
 412                                 }
 413                                 return NUM;
 414                         case 'x':
 415                                 return parse_int(16);
 416                         case 'o':
 417                                 return parse_int(8);
 418                         case 'b':
 419                                 return parse_int(2);
 420                         }
 421                 }
 422                 if (lex_class & STRINGC) {
 423                         for (;;) {
 424                                 c = lexc();
 425                                 if (lex_class & BACKSLASH)
 426                                         c = lex_quoted();
 427                                 if (lex_class & (STRINGC|ENDOFFILE)) {
 428                                         end_token();
 429                                         return STRING;
 430                                 }
 431                                 add_token(c);
 432                         }
 433                 }
 434                 if (lex_class & PRINTABLE) {
 435 #ifdef AO_SCHEME_FEATURE_FLOAT
 436                         int     isfloat = 1;
 437                         int     epos = 0;
 438 #endif
 439                         int     hasdigit = 0;
 440                         int     isneg = 0;
 441                         int     isint = 1;
 442
 443                         token_int = 0;
 444                         for (;;) {
 445                                 if (!(lex_class & NUMBER)) {
 446                                         isint = 0;
 447 #ifdef AO_SCHEME_FEATURE_FLOAT
 448                                         isfloat = 0;
 449 #endif
 450                                 } else {
 451 #ifdef AO_SCHEME_FEATURE_FLOAT
 452                                         if (!(lex_class & INTEGER))
 453                                                 isint = 0;
 454                                         if (token_len != epos &&
 455                                             (lex_class & SIGN))
 456                                         {
 457                                                 isint = 0;
 458                                                 isfloat = 0;
 459                                         }
 460 #endif
 461                                         if (c == '-')
 462                                                 isneg = 1;
 463 #ifdef AO_SCHEME_FEATURE_FLOAT
 464                                         if (c == '.' && epos != 0)
 465                                                 isfloat = 0;
 466                                         if (c == 'e' || c == 'E') {
 467                                                 if (token_len == 0)
 468                                                         isfloat = 0;
 469                                                 else
 470                                                         epos = token_len + 1;
 471                                         }
 472 #endif
 473                                         if (lex_class & DIGIT) {
 474                                                 hasdigit = 1;
 475                                                 if (isint)
 476                                                         token_int = token_int * 10 + c - '0';
 477                                         }
 478                                 }
 479                                 add_token (c);
 480                                 c = lexc ();
 481                                 if ((lex_class & (NOTNAME))
 482 #ifdef AO_SCHEME_FEATURE_FLOAT
 483                                     && (c != '.' || !isfloat)
 484 #endif
 485                                         ) {
 486 #ifdef AO_SCHEME_FEATURE_FLOAT
 487                                         unsigned int u;
 488 #endif
 489 //                                      if (lex_class & ENDOFFILE)
 490 //                                              clearerr (f);
 491                                         lex_unget(c);
 492                                         end_token ();
 493                                         if (isint && hasdigit) {
 494                                                 if (isneg)
 495                                                         token_int = -token_int;
 496                                                 return NUM;
 497                                         }
 498 #ifdef AO_SCHEME_FEATURE_FLOAT
 499                                         if (isfloat && hasdigit) {
 500                                                 token_float = strtof(token_string, NULL);
 501                                                 return FLOAT;
 502                                         }
 503                                         for (u = 0; u < NUM_NAMED_FLOATS; u++)
 504                                                 if (!strcmp(namedfloats[u].name, token_string)) {
 505                                                         token_float = namedfloats[u].value;
 506                                                         return FLOAT;
 507                                                 }
 508 #endif
 509                                         return NAME;
 510                                 }
 511                         }
 512                 }
 513         }
 514 }
 515
 516 static inline int lex(void)
 517 {
 518         int     parse_token = _lex();
 519         RDBGI("token %d (%s)\n", parse_token, token_string);
 520         return parse_token;
 521 }
 522
 523 static int parse_token;
 524
 525 int                     ao_scheme_read_list;
 526 struct ao_scheme_cons   *ao_scheme_read_cons;
 527 struct ao_scheme_cons   *ao_scheme_read_cons_tail;
 528 struct ao_scheme_cons   *ao_scheme_read_stack;
 529 static int              ao_scheme_read_state;
 530
 531 #define READ_IN_QUOTE   0x01
 532 #define READ_SAW_DOT    0x02
 533 #define READ_DONE_DOT   0x04
 534 #define READ_SAW_VECTOR 0x08
 535
 536 static int
 537 push_read_stack(int read_state)
 538 {
 539         RDBGI("push read stack %p 0x%x\n", ao_scheme_read_cons, read_state);
 540         RDBG_IN();
 541         if (ao_scheme_read_list) {
 542                 ao_scheme_read_stack = ao_scheme_cons_cons(ao_scheme_cons_poly(ao_scheme_read_cons),
 543                                                        ao_scheme_cons(ao_scheme_int_poly(read_state),
 544                                                                      ao_scheme_cons_poly(ao_scheme_read_stack)));
 545                 if (!ao_scheme_read_stack)
 546                         return 0;
 547         } else
 548                 ao_scheme_read_state = read_state;
 549         ao_scheme_read_cons = NULL;
 550         ao_scheme_read_cons_tail = NULL;
 551         return 1;
 552 }
 553
 554 static int
 555 pop_read_stack(void)
 556 {
 557         int     read_state = 0;
 558         if (ao_scheme_read_list) {
 559                 ao_scheme_read_cons = ao_scheme_poly_cons(ao_scheme_read_stack->car);
 560                 ao_scheme_read_stack = ao_scheme_poly_cons(ao_scheme_read_stack->cdr);
 561                 read_state = ao_scheme_poly_int(ao_scheme_read_stack->car);
 562                 ao_scheme_read_stack = ao_scheme_poly_cons(ao_scheme_read_stack->cdr);
 563                 for (ao_scheme_read_cons_tail = ao_scheme_read_cons;
 564                      ao_scheme_read_cons_tail && ao_scheme_read_cons_tail->cdr;
 565                      ao_scheme_read_cons_tail = ao_scheme_poly_cons(ao_scheme_read_cons_tail->cdr))
 566                         ;
 567         } else {
 568                 ao_scheme_read_cons = 0;
 569                 ao_scheme_read_cons_tail = 0;
 570                 ao_scheme_read_stack = 0;
 571                 read_state = ao_scheme_read_state;
 572         }
 573         RDBG_OUT();
 574         RDBGI("pop read stack %p %d\n", ao_scheme_read_cons, read_state);
 575         return read_state;
 576 }
 577
 578 #ifdef AO_SCHEME_FEATURE_VECTOR
 579 #define is_open(t) ((t) == OPEN || (t) == OPEN_VECTOR)
 580 #else
 581 #define is_open(t) ((t) == OPEN)
 582 #endif
 583
 584 ao_poly
 585 ao_scheme_read(void)
 586 {
 587         struct ao_scheme_atom   *atom;
 588         struct ao_scheme_string *string;
 589         int                     read_state;
 590         ao_poly                 v = AO_SCHEME_NIL;
 591
 592         ao_scheme_read_list = 0;
 593         read_state = 0;
 594         ao_scheme_read_cons = ao_scheme_read_cons_tail = ao_scheme_read_stack = 0;
 595         for (;;) {
 596                 parse_token = lex();
 597                 while (is_open(parse_token)) {
 598 #ifdef AO_SCHEME_FEATURE_VECTOR
 599                         if (parse_token == OPEN_VECTOR)
 600                                 read_state |= READ_SAW_VECTOR;
 601 #endif
 602                         if (!push_read_stack(read_state))
 603                                 return AO_SCHEME_NIL;
 604                         ao_scheme_read_list++;
 605                         read_state = 0;
 606                         parse_token = lex();
 607                 }
 608
 609                 switch (parse_token) {
 610                 case END:
 611                 default:
 612                         if (ao_scheme_read_list)
 613                                 ao_scheme_error(AO_SCHEME_EOF, "unexpected end of file");
 614                         return _ao_scheme_atom_eof;
 615                         break;
 616                 case NAME:
 617                         atom = ao_scheme_atom_intern(token_string);
 618                         if (atom)
 619                                 v = ao_scheme_atom_poly(atom);
 620                         else
 621                                 v = AO_SCHEME_NIL;
 622                         break;
 623                 case NUM:
 624                         v = ao_scheme_integer_poly(token_int);
 625                         break;
 626 #ifdef AO_SCHEME_FEATURE_FLOAT
 627                 case FLOAT:
 628                         v = ao_scheme_float_get(token_float);
 629                         break;
 630 #endif
 631                 case BOOL:
 632                         if (token_string[0] == 't')
 633                                 v = _ao_scheme_bool_true;
 634                         else
 635                                 v = _ao_scheme_bool_false;
 636                         break;
 637                 case STRING:
 638                         string = ao_scheme_string_make(token_string);
 639                         if (string)
 640                                 v = ao_scheme_string_poly(string);
 641                         else
 642                                 v = AO_SCHEME_NIL;
 643                         break;
 644                 case QUOTE:
 645 #ifdef AO_SCHEME_FEATURE_QUASI
 646                 case QUASIQUOTE:
 647                 case UNQUOTE:
 648                 case UNQUOTE_SPLICING:
 649 #endif
 650                         if (!push_read_stack(read_state))
 651                                 return AO_SCHEME_NIL;
 652                         ao_scheme_read_list++;
 653                         read_state = READ_IN_QUOTE;
 654                         switch (parse_token) {
 655                         case QUOTE:
 656                                 v = _ao_scheme_atom_quote;
 657                                 break;
 658 #ifdef AO_SCHEME_FEATURE_QUASI
 659                         case QUASIQUOTE:
 660                                 v = _ao_scheme_atom_quasiquote;
 661                                 break;
 662                         case UNQUOTE:
 663                                 v = _ao_scheme_atom_unquote;
 664                                 break;
 665                         case UNQUOTE_SPLICING:
 666                                 v = _ao_scheme_atom_unquote2dsplicing;
 667                                 break;
 668 #endif
 669                         }
 670                         break;
 671                 case CLOSE:
 672                         if (!ao_scheme_read_list) {
 673                                 v = AO_SCHEME_NIL;
 674                                 break;
 675                         }
 676                         v = ao_scheme_cons_poly(ao_scheme_read_cons);
 677                         --ao_scheme_read_list;
 678                         read_state = pop_read_stack();
 679 #ifdef AO_SCHEME_FEATURE_VECTOR
 680                         if (read_state & READ_SAW_VECTOR)
 681                                 v = ao_scheme_vector_poly(ao_scheme_list_to_vector(ao_scheme_poly_cons(v)));
 682 #endif
 683                         break;
 684                 case DOT:
 685                         if (!ao_scheme_read_list) {
 686                                 ao_scheme_error(AO_SCHEME_INVALID, ". outside of cons");
 687                                 return AO_SCHEME_NIL;
 688                         }
 689                         if (!ao_scheme_read_cons) {
 690                                 ao_scheme_error(AO_SCHEME_INVALID, ". first in cons");
 691                                 return AO_SCHEME_NIL;
 692                         }
 693                         read_state |= READ_SAW_DOT;
 694                         continue;
 695                 }
 696
 697                 /* loop over QUOTE ends */
 698                 for (;;) {
 699                         if (!ao_scheme_read_list)
 700                                 return v;
 701
 702                         if (read_state & READ_DONE_DOT) {
 703                                 ao_scheme_error(AO_SCHEME_INVALID, ". not last in cons");
 704                                 return AO_SCHEME_NIL;
 705                         }
 706
 707                         if (read_state & READ_SAW_DOT) {
 708                                 read_state |= READ_DONE_DOT;
 709                                 ao_scheme_read_cons_tail->cdr = v;
 710                         } else {
 711                                 struct ao_scheme_cons   *read = ao_scheme_cons_cons(v, AO_SCHEME_NIL);
 712                                 if (!read)
 713                                         return AO_SCHEME_NIL;
 714
 715                                 if (ao_scheme_read_cons_tail)
 716                                         ao_scheme_read_cons_tail->cdr = ao_scheme_cons_poly(read);
 717                                 else
 718                                         ao_scheme_read_cons = read;
 719                                 ao_scheme_read_cons_tail = read;
 720                         }
 721
 722                         if (!(read_state & READ_IN_QUOTE) || !ao_scheme_read_cons->cdr)
 723                                 break;
 724
 725                         v = ao_scheme_cons_poly(ao_scheme_read_cons);
 726                         --ao_scheme_read_list;
 727                         read_state = pop_read_stack();
 728                 }
 729         }
 730         return v;
 731 }