libguile/read.c

   1 /*      Copyright (C) 1995,1996,1997, 1999 Free Software Foundation, Inc.
   2  *
   3  * This program is free software; you can redistribute it and/or modify
   4  * it under the terms of the GNU General Public License as published by
   5  * the Free Software Foundation; either version 2, or (at your option)
   6  * any later version.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License
  14  * along with this software; see the file COPYING.  If not, write to
  15  * the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
  16  * Boston, MA 02111-1307 USA
  17  *
  18  * As a special exception, the Free Software Foundation gives permission
  19  * for additional uses of the text contained in its release of GUILE.
  20  *
  21  * The exception is that, if you link the GUILE library with other files
  22  * to produce an executable, this does not by itself cause the
  23  * resulting executable to be covered by the GNU General Public License.
  24  * Your use of that executable is in no way restricted on account of
  25  * linking the GUILE library code into it.
  26  *
  27  * This exception does not however invalidate any other reasons why
  28  * the executable file might be covered by the GNU General Public License.
  29  *
  30  * This exception applies only to the code released by the
  31  * Free Software Foundation under the name GUILE.  If you copy
  32  * code from other Free Software Foundation releases into a copy of
  33  * GUILE, as the General Public License permits, the exception does
  34  * not apply to the code that you add in this way.  To avoid misleading
  35  * anyone as to the status of such modified files, you must delete
  36  * this exception notice from them.
  37  *
  38  * If you write modifications of your own for GUILE, it is your choice
  39  * whether to permit this exception to apply to your modifications.
  40  * If you do not wish that, delete this exception notice.  */
  41
  42 /* Software engineering face-lift by Greg J. Badros, 11-Dec-1999,
  43    gjb@cs.washington.edu, http://www.cs.washington.edu/homes/gjb */
  44
  45 \f
  46
  47 #include <stdio.h>
  48 #include "_scm.h"
  49 #include "chars.h"
  50 #include "genio.h"
  51 #include "eval.h"
  52 #include "unif.h"
  53 #include "keywords.h"
  54 #include "alist.h"
  55 #include "srcprop.h"
  56 #include "hashtab.h"
  57 #include "hash.h"
  58
  59 #include "validate.h"
  60 #include "read.h"
  61
  62 \f
  63
  64 SCM_SYMBOL (scm_keyword_prefix, "prefix");
  65
  66 scm_option scm_read_opts[] = {
  67   { SCM_OPTION_BOOLEAN, "copy", 0,
  68     "Copy source code expressions." },
  69   { SCM_OPTION_BOOLEAN, "positions", 0,
  70     "Record positions of source code expressions." },
  71   { SCM_OPTION_BOOLEAN, "case-insensitive", 0,
  72     "Convert symbols to lower case."},
  73   { SCM_OPTION_SCM, "keywords", SCM_ASWORD (SCM_BOOL_F),
  74     "Style of keyword recognition: #f or 'prefix"}
  75 };
  76
  77 SCM_DEFINE (scm_read_options, "read-options-interface", 0, 1, 0,
  78             (SCM setting),
  79 "")
  80 #define FUNC_NAME s_scm_read_options
  81 {
  82   SCM ans = scm_options (setting,
  83                          scm_read_opts,
  84                          SCM_N_READ_OPTIONS,
  85                          FUNC_NAME);
  86   if (SCM_COPY_SOURCE_P)
  87     SCM_RECORD_POSITIONS_P = 1;
  88   return ans;
  89 }
  90 #undef FUNC_NAME
  91
  92 /* An association list mapping extra hash characters to procedures.  */
  93 static SCM *scm_read_hash_procedures;
  94
  95 SCM_DEFINE (scm_read, "read", 0, 1, 0,
  96             (SCM port),
  97 "")
  98 #define FUNC_NAME s_scm_read
  99 {
 100   int c;
 101   SCM tok_buf, copy;
 102
 103   if (SCM_UNBNDP (port))
 104     port = scm_cur_inp;
 105   SCM_VALIDATE_OPINPORT (1,port);
 106
 107   c = scm_flush_ws (port, (char *) NULL);
 108   if (EOF == c)
 109     return SCM_EOF_VAL;
 110   scm_ungetc (c, port);
 111
 112   tok_buf = scm_makstr (30L, 0);
 113   return scm_lreadr (&tok_buf, port, &copy);
 114 }
 115 #undef FUNC_NAME
 116
 117
 118
 119 char *
 120 scm_grow_tok_buf (SCM *tok_buf)
 121 {
 122   scm_vector_set_length_x (*tok_buf, SCM_MAKINUM (2 * SCM_LENGTH (*tok_buf)));
 123   return SCM_CHARS (*tok_buf);
 124 }
 125
 126
 127
 128 int
 129 scm_flush_ws (SCM port, const char *eoferr)
 130 {
 131   register int c;
 132   while (1)
 133     switch (c = scm_getc (port))
 134       {
 135       case EOF:
 136       goteof:
 137         if (eoferr)
 138           scm_wta (SCM_UNDEFINED, "end of file in ", eoferr);
 139         return c;
 140       case ';':
 141       lp:
 142         switch (c = scm_getc (port))
 143           {
 144           case EOF:
 145             goto goteof;
 146           default:
 147             goto lp;
 148           case SCM_LINE_INCREMENTORS:
 149             break;
 150           }
 151         break;
 152       case SCM_LINE_INCREMENTORS:
 153       case SCM_SINGLE_SPACES:
 154       case '\t':
 155         break;
 156       default:
 157         return c;
 158       }
 159 }
 160
 161
 162
 163 int
 164 scm_casei_streq (char *s1, char *s2)
 165 {
 166   while (*s1 && *s2)
 167     if (scm_downcase((int)*s1) != scm_downcase((int)*s2))
 168       return 0;
 169     else
 170       {
 171         ++s1;
 172         ++s2;
 173       }
 174   return !(*s1 || *s2);
 175 }
 176
 177
 178 /* recsexpr is used when recording expressions
 179  * constructed by read:sharp.
 180  */
 181 #ifndef DEBUG_EXTENSIONS
 182 #define recsexpr(obj, line, column, filename) (obj)
 183 #else
 184 static SCM
 185 recsexpr (SCM obj,int line,int column,SCM filename)
 186 {
 187   if (SCM_IMP (obj) || SCM_NCONSP(obj))
 188     return obj;
 189   {
 190     SCM tmp = obj, copy;
 191     /* If this sexpr is visible in the read:sharp source, we want to
 192        keep that information, so only record non-constant cons cells
 193        which haven't previously been read by the reader. */
 194     if (SCM_FALSEP (scm_whash_lookup (scm_source_whash, obj)))
 195       {
 196         if (SCM_COPY_SOURCE_P)
 197           {
 198             copy = scm_cons (recsexpr (SCM_CAR (obj), line, column, filename),
 199                              SCM_UNDEFINED);
 200             while ((tmp = SCM_CDR (tmp)) && SCM_CONSP (tmp))
 201               {
 202                 SCM_SETCDR (copy, scm_cons (recsexpr (SCM_CAR (tmp),
 203                                                       line,
 204                                                       column,
 205                                                       filename),
 206                                             SCM_UNDEFINED));
 207                 copy = SCM_CDR (copy);
 208               }
 209             SCM_SETCDR (copy, tmp);
 210           }
 211         else
 212           {
 213             recsexpr (SCM_CAR (obj), line, column, filename);
 214             while ((tmp = SCM_CDR (tmp)) && SCM_CONSP (tmp))
 215               recsexpr (SCM_CAR (tmp), line, column, filename);
 216             copy = SCM_UNDEFINED;
 217           }
 218         scm_whash_insert (scm_source_whash,
 219                           obj,
 220                           scm_make_srcprops (line,
 221                                              column,
 222                                              filename,
 223                                              copy,
 224                                              SCM_EOL));
 225       }
 226     return obj;
 227   }
 228 }
 229 #endif
 230
 231 /* Consume an SCSH-style block comment.  Assume that we've already
 232    read the initial `#!', and eat characters until we get a
 233    newline/exclamation-point/sharp-sign/newline sequence.  */
 234
 235 static void
 236 skip_scsh_block_comment (SCM port)
 237 {
 238   /* Is this portable?  Dear God, spare me from the non-eight-bit
 239      characters.  But is it tasteful?  */
 240   long history = 0;
 241
 242   for (;;)
 243     {
 244       int c = scm_getc (port);
 245
 246       if (c == EOF)
 247         scm_wta (SCM_UNDEFINED,
 248                  "unterminated `#! ... !#' comment", "read");
 249       history = ((history << 8) | (c & 0xff)) & 0xffffffff;
 250
 251       /* Were the last four characters read "\n!#\n"?  */
 252       if (history == (('\n' << 24) | ('!' << 16) | ('#' << 8) | '\n'))
 253         return;
 254     }
 255 }
 256
 257 static SCM scm_get_hash_procedure(int c);
 258
 259 static char s_list[]="list";
 260
 261 SCM
 262 scm_lreadr (SCM *tok_buf,SCM port,SCM *copy)
 263 {
 264   int c;
 265   scm_sizet j;
 266   SCM p;
 267
 268 tryagain:
 269   c = scm_flush_ws (port, s_scm_read);
 270 tryagain_no_flush_ws:
 271   switch (c)
 272     {
 273     case EOF:
 274       return SCM_EOF_VAL;
 275
 276     case '(':
 277       return SCM_RECORD_POSITIONS_P
 278              ? scm_lreadrecparen (tok_buf, port, s_list, copy)
 279              : scm_lreadparen (tok_buf, port, s_list, copy);
 280     case ')':
 281       scm_wta (SCM_UNDEFINED, "unexpected \")\"", "read");
 282       goto tryagain;
 283
 284     case '\'':
 285       p = scm_sym_quote;
 286       goto recquote;
 287     case '`':
 288       p = scm_sym_quasiquote;
 289       goto recquote;
 290     case ',':
 291       c = scm_getc (port);
 292       if ('@' == c)
 293         p = scm_sym_uq_splicing;
 294       else
 295         {
 296           scm_ungetc (c, port);
 297           p = scm_sym_unquote;
 298         }
 299     recquote:
 300       p = scm_cons2 (p,
 301                      scm_lreadr (tok_buf, port, copy),
 302                      SCM_EOL);
 303       if (SCM_RECORD_POSITIONS_P)
 304         scm_whash_insert (scm_source_whash,
 305                           p,
 306                           scm_make_srcprops (SCM_LINUM (port),
 307                                              SCM_COL (port) - 1,
 308                                              SCM_FILENAME (port),
 309                                              SCM_COPY_SOURCE_P
 310                                              ? (*copy = scm_cons2 (SCM_CAR (p),
 311                                                                    SCM_CAR (SCM_CDR (p)),
 312                                                                    SCM_EOL))
 313                                              : SCM_UNDEFINED,
 314                                              SCM_EOL));
 315       return p;
 316     case '#':
 317       c = scm_getc (port);
 318       switch (c)
 319         {
 320         case '(':
 321           p = scm_lreadparen (tok_buf, port, "vector", copy);
 322           return SCM_NULLP (p) ? scm_nullvect : scm_vector (p);
 323
 324         case 't':
 325         case 'T':
 326           return SCM_BOOL_T;
 327         case 'f':
 328         case 'F':
 329           return SCM_BOOL_F;
 330
 331         case 'b':
 332         case 'B':
 333         case 'o':
 334         case 'O':
 335         case 'd':
 336         case 'D':
 337         case 'x':
 338         case 'X':
 339         case 'i':
 340         case 'I':
 341         case 'e':
 342         case 'E':
 343           scm_ungetc (c, port);
 344           c = '#';
 345           goto num;
 346
 347         case '!':
 348           /* start of a shell script.  Parse as a block comment,
 349              terminated by !#, just like SCSH.  */
 350           skip_scsh_block_comment (port);
 351           /* EOF is not an error here */
 352           c = scm_flush_ws (port, (char *)NULL);
 353           goto tryagain_no_flush_ws;
 354
 355 #ifdef HAVE_ARRAYS
 356         case '*':
 357           j = scm_read_token (c, tok_buf, port, 0);
 358           p = scm_istr2bve (SCM_CHARS (*tok_buf) + 1, (long) (j - 1));
 359           if (SCM_NFALSEP (p))
 360             return p;
 361           else
 362             goto unkshrp;
 363 #endif
 364
 365         case '{':
 366           j = scm_read_token (c, tok_buf, port, 1);
 367           p = scm_intern (SCM_CHARS (*tok_buf), j);
 368           return SCM_CAR (p);
 369
 370         case '\\':
 371           c = scm_getc (port);
 372           j = scm_read_token (c, tok_buf, port, 0);
 373           if (j == 1)
 374             return SCM_MAKE_CHAR (c);
 375           if (c >= '0' && c < '8')
 376             {
 377               p = scm_istr2int (SCM_CHARS (*tok_buf), (long) j, 8);
 378               if (SCM_NFALSEP (p))
 379                 return SCM_MAKE_CHAR (SCM_INUM (p));
 380             }
 381           for (c = 0; c < scm_n_charnames; c++)
 382             if (scm_charnames[c]
 383                 && (scm_casei_streq (scm_charnames[c], SCM_CHARS (*tok_buf))))
 384               return SCM_MAKE_CHAR (scm_charnums[c]);
 385           scm_wta (SCM_UNDEFINED, "unknown # object: #\\", SCM_CHARS (*tok_buf));
 386
 387           /* #:SYMBOL is a syntax for keywords supported in all contexts.  */
 388         case ':':
 389           j = scm_read_token ('-', tok_buf, port, 0);
 390           p = scm_intern (SCM_CHARS (*tok_buf), j);
 391           return scm_make_keyword_from_dash_symbol (SCM_CAR (p));
 392
 393         default:
 394         callshrp:
 395           {
 396             SCM sharp = scm_get_hash_procedure (c);
 397
 398             if (SCM_NIMP (sharp))
 399               {
 400                 int line = SCM_LINUM (port);
 401                 int column = SCM_COL (port) - 2;
 402                 SCM got;
 403
 404                 got = scm_apply (sharp,
 405                                  SCM_MAKE_CHAR (c),
 406                                  scm_acons (port, SCM_EOL, SCM_EOL));
 407                 if (SCM_UNSPECIFIED == got)
 408                   goto unkshrp;
 409                 if (SCM_RECORD_POSITIONS_P)
 410                   return *copy = recsexpr (got, line, column,
 411                                            SCM_FILENAME (port));
 412                 else
 413                   return got;
 414               }
 415           }
 416         unkshrp:
 417           scm_misc_error (s_scm_read, "Unknown # object: ~S",
 418                           scm_listify (SCM_MAKE_CHAR (c), SCM_UNDEFINED));
 419         }
 420
 421     case '"':
 422       j = 0;
 423       while ('"' != (c = scm_getc (port)))
 424         {
 425           SCM_ASSERT (EOF != c, SCM_UNDEFINED, "end of file in ", "string");
 426
 427           while (j + 2 >= SCM_LENGTH (*tok_buf))
 428             scm_grow_tok_buf (tok_buf);
 429
 430           if (c == '\\')
 431             switch (c = scm_getc (port))
 432               {
 433               case '\n':
 434                 continue;
 435               case '0':
 436                 c = '\0';
 437                 break;
 438               case 'f':
 439                 c = '\f';
 440                 break;
 441               case 'n':
 442                 c = '\n';
 443                 break;
 444               case 'r':
 445                 c = '\r';
 446                 break;
 447               case 't':
 448                 c = '\t';
 449                 break;
 450               case 'a':
 451                 c = '\007';
 452                 break;
 453               case 'v':
 454                 c = '\v';
 455                 break;
 456               }
 457           SCM_CHARS (*tok_buf)[j] = c;
 458           ++j;
 459         }
 460       if (j == 0)
 461         return scm_nullstr;
 462       SCM_CHARS (*tok_buf)[j] = 0;
 463       {
 464         SCM str;
 465         str = scm_makfromstr (SCM_CHARS (*tok_buf), j, 0);
 466         return str;
 467       }
 468
 469     case'0':case '1':case '2':case '3':case '4':
 470     case '5':case '6':case '7':case '8':case '9':
 471     case '.':
 472     case '-':
 473     case '+':
 474     num:
 475       j = scm_read_token (c, tok_buf, port, 0);
 476       p = scm_istring2number (SCM_CHARS (*tok_buf), (long) j, 10L);
 477       if (SCM_NFALSEP (p))
 478         return p;
 479       if (c == '#')
 480         {
 481           if ((j == 2) && (scm_getc (port) == '('))
 482             {
 483               scm_ungetc ('(', port);
 484               c = SCM_CHARS (*tok_buf)[1];
 485               goto callshrp;
 486             }
 487           scm_wta (SCM_UNDEFINED, "unknown # object", SCM_CHARS (*tok_buf));
 488         }
 489       goto tok;
 490
 491     case ':':
 492       if (SCM_ASSCM (SCM_KEYWORD_STYLE) == scm_keyword_prefix)
 493         {
 494           j = scm_read_token ('-', tok_buf, port, 0);
 495           p = scm_intern (SCM_CHARS (*tok_buf), j);
 496           return scm_make_keyword_from_dash_symbol (SCM_CAR (p));
 497         }
 498       /* fallthrough */
 499     default:
 500       j = scm_read_token (c, tok_buf, port, 0);
 501       /* fallthrough */
 502
 503     tok:
 504       p = scm_intern (SCM_CHARS (*tok_buf), j);
 505       return SCM_CAR (p);
 506     }
 507 }
 508
 509 #ifdef _UNICOS
 510 _Pragma ("noopt");              /* # pragma _CRI noopt */
 511 #endif
 512
 513 scm_sizet
 514 scm_read_token (int ic, SCM *tok_buf, SCM port, int weird)
 515 {
 516   register scm_sizet j;
 517   register int c;
 518   register char *p;
 519
 520   c = (SCM_CASE_INSENSITIVE_P ? scm_downcase(ic) : ic);
 521   p = SCM_CHARS (*tok_buf);
 522
 523   if (weird)
 524     j = 0;
 525   else
 526     {
 527       j = 0;
 528       while (j + 2 >= SCM_LENGTH (*tok_buf))
 529         p = scm_grow_tok_buf (tok_buf);
 530       p[j] = c;
 531       ++j;
 532     }
 533
 534   while (1)
 535     {
 536       while (j + 2 >= SCM_LENGTH (*tok_buf))
 537         p = scm_grow_tok_buf (tok_buf);
 538       c = scm_getc (port);
 539       switch (c)
 540         {
 541         case '(':
 542         case ')':
 543         case '"':
 544         case ';':
 545         case SCM_WHITE_SPACES:
 546         case SCM_LINE_INCREMENTORS:
 547           if (weird)
 548             goto default_case;
 549
 550           scm_ungetc (c, port);
 551         case EOF:
 552         eof_case:
 553           p[j] = 0;
 554           return j;
 555         case '\\':
 556           if (!weird)
 557             goto default_case;
 558           else
 559             {
 560               c = scm_getc (port);
 561               if (c == EOF)
 562                 goto eof_case;
 563               else
 564                 goto default_case;
 565             }
 566         case '}':
 567           if (!weird)
 568             goto default_case;
 569
 570           c = scm_getc (port);
 571           if (c == '#')
 572             {
 573               p[j] = 0;
 574               return j;
 575             }
 576           else
 577             {
 578               scm_ungetc (c, port);
 579               c = '}';
 580               goto default_case;
 581             }
 582
 583         default:
 584         default_case:
 585           {
 586             c = (SCM_CASE_INSENSITIVE_P ? scm_downcase(c) : c);
 587             p[j] = c;
 588             ++j;
 589           }
 590
 591         }
 592     }
 593 }
 594
 595 #ifdef _UNICOS
 596 _Pragma ("opt");                /* # pragma _CRI opt */
 597 #endif
 598
 599 SCM
 600 scm_lreadparen (SCM *tok_buf, SCM port, char *name, SCM *copy)
 601 {
 602   SCM tmp;
 603   SCM tl;
 604   SCM ans;
 605   int c;
 606
 607   c = scm_flush_ws (port, name);
 608   if (')' == c)
 609     return SCM_EOL;
 610   scm_ungetc (c, port);
 611   if (scm_sym_dot == (tmp = scm_lreadr (tok_buf, port, copy)))
 612     {
 613       ans = scm_lreadr (tok_buf, port, copy);
 614     closeit:
 615       if (')' != (c = scm_flush_ws (port, name)))
 616         scm_wta (SCM_UNDEFINED, "missing close paren", "");
 617       return ans;
 618     }
 619   ans = tl = scm_cons (tmp, SCM_EOL);
 620   while (')' != (c = scm_flush_ws (port, name)))
 621     {
 622       scm_ungetc (c, port);
 623       if (scm_sym_dot == (tmp = scm_lreadr (tok_buf, port, copy)))
 624         {
 625           SCM_SETCDR (tl, scm_lreadr (tok_buf, port, copy));
 626           goto closeit;
 627         }
 628       SCM_SETCDR (tl, scm_cons (tmp, SCM_EOL));
 629       tl = SCM_CDR (tl);
 630     }
 631   return ans;
 632 }
 633
 634
 635 SCM
 636 scm_lreadrecparen (SCM *tok_buf, SCM port, char *name, SCM *copy)
 637 {
 638   register int c;
 639   register SCM tmp;
 640   register SCM tl, tl2 = SCM_EOL;
 641   SCM ans, ans2 = SCM_EOL;
 642   /* Need to capture line and column numbers here. */
 643   int line = SCM_LINUM (port);
 644   int column = SCM_COL (port) - 1;
 645
 646   c = scm_flush_ws (port, name);
 647   if (')' == c)
 648     return SCM_EOL;
 649   scm_ungetc (c, port);
 650   if (scm_sym_dot == (tmp = scm_lreadr (tok_buf, port, copy)))
 651     {
 652       ans = scm_lreadr (tok_buf, port, copy);
 653       if (')' != (c = scm_flush_ws (port, name)))
 654         scm_wta (SCM_UNDEFINED, "missing close paren", "");
 655       return ans;
 656     }
 657   /* Build the head of the list structure. */
 658   ans = tl = scm_cons (tmp, SCM_EOL);
 659   if (SCM_COPY_SOURCE_P)
 660     ans2 = tl2 = scm_cons (SCM_CONSP (tmp)
 661                            ? *copy
 662                            : tmp,
 663                            SCM_EOL);
 664   while (')' != (c = scm_flush_ws (port, name)))
 665     {
 666       scm_ungetc (c, port);
 667       if (scm_sym_dot == (tmp = scm_lreadr (tok_buf, port, copy)))
 668         {
 669           SCM_SETCDR (tl, tmp = scm_lreadr (tok_buf, port, copy));
 670           if (SCM_COPY_SOURCE_P)
 671             SCM_SETCDR (tl2, scm_cons (SCM_CONSP (tmp)
 672                                        ? *copy
 673                                        : tmp,
 674                                        SCM_EOL));
 675           if (')' != (c = scm_flush_ws (port, name)))
 676             scm_wta (SCM_UNDEFINED, "missing close paren", "");
 677           goto exit;
 678         }
 679       tl = SCM_SETCDR (tl, scm_cons (tmp, SCM_EOL));
 680       if (SCM_COPY_SOURCE_P)
 681         tl2 = SCM_SETCDR (tl2, scm_cons (SCM_CONSP (tmp)
 682                                          ? *copy
 683                                          : tmp,
 684                                          SCM_EOL));
 685     }
 686 exit:
 687   scm_whash_insert (scm_source_whash,
 688                     ans,
 689                     scm_make_srcprops (line,
 690                                        column,
 691                                        SCM_FILENAME (port),
 692                                        SCM_COPY_SOURCE_P
 693                                        ? *copy = ans2
 694                                        : SCM_UNDEFINED,
 695                                        SCM_EOL));
 696   return ans;
 697 }
 698
 699
 700 \f
 701
 702 /* Manipulate the read-hash-procedures alist.  This could be written in
 703    Scheme, but maybe it will also be used by C code during initialisation.  */
 704 SCM_DEFINE (scm_read_hash_extend, "read-hash-extend", 2, 0, 0,
 705             (SCM chr, SCM proc),
 706 "")
 707 #define FUNC_NAME s_scm_read_hash_extend
 708 {
 709   SCM this;
 710   SCM prev;
 711
 712   SCM_VALIDATE_CHAR (1,chr);
 713   SCM_ASSERT (SCM_FALSEP (proc) || SCM_NIMP(proc), proc, SCM_ARG2,
 714               FUNC_NAME);
 715
 716   /* Check if chr is already in the alist.  */
 717   this = *scm_read_hash_procedures;
 718   prev = SCM_BOOL_F;
 719   while (1)
 720     {
 721       if (SCM_NULLP (this))
 722         {
 723           /* not found, so add it to the beginning.  */
 724           if (SCM_NFALSEP (proc))
 725             {
 726               *scm_read_hash_procedures =
 727                 scm_cons (scm_cons (chr, proc), *scm_read_hash_procedures);
 728             }
 729           break;
 730         }
 731       if (chr == SCM_CAAR (this))
 732         {
 733           /* already in the alist.  */
 734           if (SCM_FALSEP (proc))
 735             {
 736               /* remove it.  */
 737               if (prev == SCM_BOOL_F)
 738                 {
 739                   *scm_read_hash_procedures =
 740                     SCM_CDR (*scm_read_hash_procedures);
 741                 }
 742               else
 743                 scm_set_cdr_x (prev, SCM_CDR (this));
 744             }
 745           else
 746             {
 747               /* replace it.  */
 748               scm_set_cdr_x (SCM_CAR (this), proc);
 749             }
 750           break;
 751         }
 752       prev = this;
 753       this = SCM_CDR (this);
 754     }
 755
 756   return SCM_UNSPECIFIED;
 757 }
 758 #undef FUNC_NAME
 759
 760 /* Recover the read-hash procedure corresponding to char c.  */
 761 static SCM
 762 scm_get_hash_procedure (int c)
 763 {
 764   SCM rest = *scm_read_hash_procedures;
 765
 766   while (1)
 767     {
 768       if (SCM_NULLP (rest))
 769         return SCM_BOOL_F;
 770
 771       if (SCM_CHAR (SCM_CAAR (rest)) == c)
 772         return SCM_CDAR (rest);
 773
 774       rest = SCM_CDR (rest);
 775     }
 776 }
 777
 778 void
 779 scm_init_read ()
 780 {
 781   scm_read_hash_procedures =
 782     SCM_CDRLOC (scm_sysintern ("read-hash-procedures", SCM_EOL));
 783
 784   scm_init_opts (scm_read_options, scm_read_opts, SCM_N_READ_OPTIONS);
 785 #include "read.x"
 786 }