src/getargs.c

   1 /* Parse command line arguments for Bison.
   2
   3    Copyright (C) 1984, 1986, 1989, 1992, 2000-2013 Free Software
   4    Foundation, Inc.
   5
   6    This file is part of Bison, the GNU Compiler Compiler.
   7
   8    This program is free software: you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation, either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  20
  21 #include <config.h>
  22 #include "system.h"
  23 #include "output.h"
  24
  25 #include <argmatch.h>
  26 #include <c-strcase.h>
  27 #include <configmake.h>
  28 #include <error.h>
  29 #include <getopt.h>
  30 #include <progname.h>
  31
  32 #include "complain.h"
  33 #include "files.h"
  34 #include "getargs.h"
  35 #include "muscle-tab.h"
  36 #include "quote.h"
  37 #include "uniqstr.h"
  38
  39 bool defines_flag;
  40 bool graph_flag;
  41 bool xml_flag;
  42 bool no_lines_flag;
  43 bool token_table_flag;
  44 bool yacc_flag; /* for -y */
  45
  46 bool nondeterministic_parser = false;
  47 bool glr_parser = false;
  48
  49 int feature_flag = feature_caret;
  50 int report_flag = report_none;
  51 int trace_flag = trace_none;
  52
  53 static struct bison_language const valid_languages[] = {
  54   { "c", "c-skel.m4", ".c", ".h", true },
  55   { "c++", "c++-skel.m4", ".cc", ".hh", true },
  56   { "java", "java-skel.m4", ".java", ".java", false },
  57   { "", "", "", "", false }
  58 };
  59
  60 int skeleton_prio = default_prio;
  61 const char *skeleton = NULL;
  62 int language_prio = default_prio;
  63 struct bison_language const *language = &valid_languages[0];
  64 const char *include = NULL;
  65
  66 /** Decode an option's key.
  67  *
  68  *  \param option   option being decoded.
  69  *  \param keys     array of valid subarguments.
  70  *  \param values   array of corresponding (int) values.
  71  *  \param all      the all value.
  72  *  \param flags    the flags to update
  73  *  \param arg      the subarguments to decode.
  74  *                  If null, then activate all the flags.
  75  *  \param no       length of the potential "no-" prefix.
  76  *                  Can be 0 or 3. If 3, negate the action of the subargument.
  77  *
  78  *  If VALUE != 0 then KEY sets flags and no-KEY clears them.
  79  *  If VALUE == 0 then KEY clears all flags from \c all and no-KEY sets all
  80  *  flags from \c all.  Thus no-none = all and no-all = none.
  81  */
  82 static void
  83 flag_argmatch (const char *option,
  84                const char * const keys[], const int values[],
  85                int all, int *flags, char *arg, size_t no)
  86 {
  87   int value = XARGMATCH (option, arg + no, keys, values);
  88
  89   /* -rnone == -rno-all, and -rno-none == -rall.  */
  90   if (!value)
  91     {
  92       value = all;
  93       no = !no;
  94     }
  95
  96   if (no)
  97     *flags &= ~value;
  98   else
  99     *flags |= value;
 100 }
 101
 102 /** Decode an option's set of keys.
 103  *
 104  *  \param option   option being decoded.
 105  *  \param keys     array of valid subarguments.
 106  *  \param values   array of corresponding (int) values.
 107  *  \param all      the all value.
 108  *  \param flags    the flags to update
 109  *  \param args     comma separated list of effective subarguments to decode.
 110  *                  If 0, then activate all the flags.
 111  */
 112 static void
 113 flags_argmatch (const char *option,
 114                 const char * const keys[], const int values[],
 115                 int all, int *flags, char *args)
 116 {
 117   if (args)
 118     for (args = strtok (args, ","); args; args = strtok (NULL, ","))
 119       {
 120         size_t no = STRPREFIX_LIT ("no-", args) ? 3 : 0;
 121         flag_argmatch (option, keys,
 122                        values, all, flags, args, no);
 123       }
 124   else
 125     *flags |= all;
 126 }
 127
 128
 129 /** Decode a set of sub arguments.
 130  *
 131  *  \param FlagName  the flag familly to update.
 132  *  \param Args      the effective sub arguments to decode.
 133  *  \param All       the "all" value.
 134  *
 135  *  \arg FlagName_args   the list of keys.
 136  *  \arg FlagName_types  the list of values.
 137  *  \arg FlagName_flag   the flag to update.
 138  */
 139 #define FLAGS_ARGMATCH(FlagName, Args, All)                             \
 140   flags_argmatch ("--" #FlagName, FlagName ## _args, FlagName ## _types, \
 141                   All, &FlagName ## _flag, Args)
 142
 143
 144 /*----------------------.
 145 | --report's handling.  |
 146 `----------------------*/
 147
 148 static const char * const report_args[] =
 149 {
 150   /* In a series of synonyms, present the most meaningful first, so
 151      that argmatch_valid be more readable.  */
 152   "none",
 153   "state", "states",
 154   "itemset", "itemsets",
 155   "lookahead", "lookaheads", "look-ahead",
 156   "solved",
 157   "all",
 158   0
 159 };
 160
 161 static const int report_types[] =
 162 {
 163   report_none,
 164   report_states, report_states,
 165   report_states | report_itemsets, report_states | report_itemsets,
 166   report_states | report_lookahead_tokens,
 167   report_states | report_lookahead_tokens,
 168   report_states | report_lookahead_tokens,
 169   report_states | report_solved_conflicts,
 170   report_all
 171 };
 172
 173 ARGMATCH_VERIFY (report_args, report_types);
 174
 175
 176 /*---------------------.
 177 | --trace's handling.  |
 178 `---------------------*/
 179
 180 static const char * const trace_args[] =
 181 {
 182   "none       - no traces",
 183   "scan       - grammar scanner traces",
 184   "parse      - grammar parser traces",
 185   "automaton  - construction of the automaton",
 186   "bitsets    - use of bitsets",
 187   "grammar    - reading, reducing the grammar",
 188   "resource   - memory consumption (where available)",
 189   "sets       - grammar sets: firsts, nullable etc.",
 190   "muscles    - m4 definitions passed to the skeleton",
 191   "tools      - m4 invocation",
 192   "m4         - m4 traces",
 193   "skeleton   - skeleton postprocessing",
 194   "time       - time consumption",
 195   "ielr       - IELR conversion",
 196   "all        - all of the above",
 197   0
 198 };
 199
 200 static const int trace_types[] =
 201 {
 202   trace_none,
 203   trace_scan,
 204   trace_parse,
 205   trace_automaton,
 206   trace_bitsets,
 207   trace_grammar,
 208   trace_resource,
 209   trace_sets,
 210   trace_muscles,
 211   trace_tools,
 212   trace_m4,
 213   trace_skeleton,
 214   trace_time,
 215   trace_ielr,
 216   trace_all
 217 };
 218
 219 ARGMATCH_VERIFY (trace_args, trace_types);
 220
 221
 222 /*-----------------------.
 223 | --feature's handling.  |
 224 `-----------------------*/
 225
 226 static const char * const feature_args[] =
 227 {
 228   "none",
 229   "caret", "diagnostics-show-caret",
 230   "all",
 231   0
 232 };
 233
 234 static const int feature_types[] =
 235 {
 236   feature_none,
 237   feature_caret, feature_caret,
 238   feature_all
 239 };
 240
 241 ARGMATCH_VERIFY (feature_args, feature_types);
 242
 243 /*-------------------------------------------.
 244 | Display the help message and exit STATUS.  |
 245 `-------------------------------------------*/
 246
 247 static void usage (int) ATTRIBUTE_NORETURN;
 248
 249 static void
 250 usage (int status)
 251 {
 252   if (status != 0)
 253     fprintf (stderr, _("Try '%s --help' for more information.\n"),
 254              program_name);
 255   else
 256     {
 257       /* For ../build-aux/cross-options.pl to work, use the format:
 258                 ^  -S, --long[=ARGS] (whitespace)
 259          A --long option is required.
 260          Otherwise, add exceptions to ../build-aux/cross-options.pl.  */
 261
 262       printf (_("Usage: %s [OPTION]... FILE\n"), program_name);
 263       fputs (_("\
 264 Generate a deterministic LR or generalized LR (GLR) parser employing\n\
 265 LALR(1), IELR(1), or canonical LR(1) parser tables.  IELR(1) and\n\
 266 canonical LR(1) support is experimental.\n\
 267 \n\
 268 "), stdout);
 269
 270       fputs (_("\
 271 Mandatory arguments to long options are mandatory for short options too.\n\
 272 "), stdout);
 273       fputs (_("\
 274 The same is true for optional arguments.\n\
 275 "), stdout);
 276
 277       fputs (_("\
 278 \n\
 279 Operation modes:\n\
 280   -h, --help                 display this help and exit\n\
 281   -V, --version              output version information and exit\n\
 282       --print-localedir      output directory containing locale-dependent data\n\
 283       --print-datadir        output directory containing skeletons and XSLT\n\
 284   -y, --yacc                 emulate POSIX Yacc\n\
 285   -W, --warnings[=CATEGORY]  report the warnings falling in CATEGORY\n\
 286   -f, --feature[=FEATURE]    activate miscellaneous features\n\
 287 \n\
 288 "), stdout);
 289
 290       fputs (_("\
 291 Parser:\n\
 292   -L, --language=LANGUAGE          specify the output programming language\n\
 293   -S, --skeleton=FILE              specify the skeleton to use\n\
 294   -t, --debug                      instrument the parser for tracing\n\
 295                                    same as '-Dparse.trace'\n\
 296       --locations                  enable location support\n\
 297   -D, --define=NAME[=VALUE]        similar to '%define NAME \"VALUE\"'\n\
 298   -F, --force-define=NAME[=VALUE]  override '%define NAME \"VALUE\"'\n\
 299   -p, --name-prefix=PREFIX         prepend PREFIX to the external symbols\n\
 300                                    deprecated by '-Dapi.prefix=PREFIX'\n\
 301   -l, --no-lines                   don't generate '#line' directives\n\
 302   -k, --token-table                include a table of token names\n\
 303 "), stdout);
 304       putc ('\n', stdout);
 305
 306       /* Keep -d and --defines separate so that ../build-aux/cross-options.pl
 307        * won't assume that -d also takes an argument.  */
 308       fputs (_("\
 309 Output:\n\
 310       --defines[=FILE]       also produce a header file\n\
 311   -d                         likewise but cannot specify FILE (for POSIX Yacc)\n\
 312   -r, --report=THINGS        also produce details on the automaton\n\
 313       --report-file=FILE     write report to FILE\n\
 314   -v, --verbose              same as '--report=state'\n\
 315   -b, --file-prefix=PREFIX   specify a PREFIX for output files\n\
 316   -o, --output=FILE          leave output to FILE\n\
 317   -g, --graph[=FILE]         also output a graph of the automaton\n\
 318   -x, --xml[=FILE]           also output an XML report of the automaton\n\
 319                              (the XML schema is experimental)\n\
 320 "), stdout);
 321       putc ('\n', stdout);
 322
 323       fputs (_("\
 324 Warning categories include:\n\
 325   'midrule-values'    unset or unused midrule values\n\
 326   'yacc'              incompatibilities with POSIX Yacc\n\
 327   'conflicts-sr'      S/R conflicts (enabled by default)\n\
 328   'conflicts-rr'      R/R conflicts (enabled by default)\n\
 329   'deprecated'        obsolete constructs\n\
 330   'empty-rule'        empty rules without %empty\n\
 331   'precedence'        useless precedence and associativity\n\
 332   'other'             all other warnings (enabled by default)\n\
 333   'all'               all the warnings\n\
 334   'no-CATEGORY'       turn off warnings in CATEGORY\n\
 335   'none'              turn off all the warnings\n\
 336   'error[=CATEGORY]'  treat warnings as errors\n\
 337 "), stdout);
 338       putc ('\n', stdout);
 339
 340       fputs (_("\
 341 THINGS is a list of comma separated words that can include:\n\
 342   'state'        describe the states\n\
 343   'itemset'      complete the core item sets with their closure\n\
 344   'lookahead'    explicitly associate lookahead tokens to items\n\
 345   'solved'       describe shift/reduce conflicts solving\n\
 346   'all'          include all the above information\n\
 347   'none'         disable the report\n\
 348 "), stdout);
 349       putc ('\n', stdout);
 350
 351       fputs (_("\
 352 FEATURE is a list of comma separated words that can include:\n\
 353   'caret'        show errors with carets\n\
 354   'all'          all of the above\n\
 355   'none'         disable all of the above\n\
 356   "), stdout);
 357
 358       putc ('\n', stdout);
 359       printf (_("Report bugs to <%s>.\n"), PACKAGE_BUGREPORT);
 360       printf (_("%s home page: <%s>.\n"), PACKAGE_NAME, PACKAGE_URL);
 361       fputs (_("General help using GNU software: "
 362                "<http://www.gnu.org/gethelp/>.\n"),
 363              stdout);
 364       /* Don't output this redundant message for English locales.
 365          Note we still output for 'C' so that it gets included in the
 366          man page.  */
 367       const char *lc_messages = setlocale (LC_MESSAGES, NULL);
 368       if (lc_messages && !STREQ (lc_messages, "en_"))
 369         /* TRANSLATORS: Replace LANG_CODE in this URL with your language
 370            code <http://translationproject.org/team/LANG_CODE.html> to
 371            form one of the URLs at http://translationproject.org/team/.
 372            Otherwise, replace the entire URL with your translation team's
 373            email address.  */
 374         fputs (_("Report translation bugs to "
 375                  "<http://translationproject.org/team/>.\n"), stdout);
 376       fputs (_("For complete documentation, run: info bison.\n"), stdout);
 377     }
 378
 379   exit (status);
 380 }
 381
 382
 383 /*------------------------------.
 384 | Display the version message.  |
 385 `------------------------------*/
 386
 387 static void
 388 version (void)
 389 {
 390   /* Some efforts were made to ease the translators' task, please
 391      continue.  */
 392   printf (_("bison (GNU Bison) %s"), VERSION);
 393   putc ('\n', stdout);
 394   fputs (_("Written by Robert Corbett and Richard Stallman.\n"), stdout);
 395   putc ('\n', stdout);
 396
 397   fprintf (stdout,
 398            _("Copyright (C) %d Free Software Foundation, Inc.\n"),
 399            PACKAGE_COPYRIGHT_YEAR);
 400
 401   fputs (_("\
 402 This is free software; see the source for copying conditions.  There is NO\n\
 403 warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n\
 404 "),
 405          stdout);
 406 }
 407
 408
 409 /*-------------------------------------.
 410 | --skeleton and --language handling.  |
 411 `--------------------------------------*/
 412
 413 void
 414 skeleton_arg (char const *arg, int prio, location loc)
 415 {
 416   if (prio < skeleton_prio)
 417     {
 418       skeleton_prio = prio;
 419       skeleton = arg;
 420     }
 421   else if (prio == skeleton_prio)
 422     complain (&loc, complaint,
 423               _("multiple skeleton declarations are invalid"));
 424 }
 425
 426 void
 427 language_argmatch (char const *arg, int prio, location loc)
 428 {
 429   char const *msg;
 430
 431   if (prio < language_prio)
 432     {
 433       int i;
 434       for (i = 0; valid_languages[i].language[0]; i++)
 435         if (c_strcasecmp (arg, valid_languages[i].language) == 0)
 436           {
 437             language_prio = prio;
 438             language = &valid_languages[i];
 439             return;
 440           }
 441       msg = _("%s: invalid language");
 442     }
 443   else if (language_prio == prio)
 444     msg = _("multiple language declarations are invalid");
 445   else
 446     return;
 447
 448   complain (&loc, complaint, msg, quotearg_colon (arg));
 449 }
 450
 451 /*----------------------.
 452 | Process the options.  |
 453 `----------------------*/
 454
 455 /* Shorts options.
 456    Should be computed from long_options.  */
 457 static char const short_options[] =
 458   "D:"
 459   "F:"
 460   "L:"
 461   "S:"
 462   "T::"
 463   "V"
 464   "W::"
 465   "b:"
 466   "d"
 467   "f::"
 468   "e"
 469   "g::"
 470   "h"
 471   "k"
 472   "l"
 473   "n"
 474   "o:"
 475   "p:"
 476   "r:"
 477   "t"
 478   "v"
 479   "x::"
 480   "y"
 481   ;
 482
 483 /* Values for long options that do not have single-letter equivalents.  */
 484 enum
 485 {
 486   LOCATIONS_OPTION = CHAR_MAX + 1,
 487   PRINT_LOCALEDIR_OPTION,
 488   PRINT_DATADIR_OPTION,
 489   REPORT_FILE_OPTION
 490 };
 491
 492 static struct option const long_options[] =
 493 {
 494   /* Operation modes. */
 495   { "help",            no_argument,       0,   'h' },
 496   { "version",         no_argument,       0,   'V' },
 497   { "print-localedir", no_argument,       0,   PRINT_LOCALEDIR_OPTION },
 498   { "print-datadir",   no_argument,       0,   PRINT_DATADIR_OPTION   },
 499   { "warnings",        optional_argument, 0,   'W' },
 500
 501   /* Parser. */
 502   { "name-prefix",   required_argument,   0,   'p' },
 503   { "include",       required_argument,   0,   'I' },
 504
 505   /* Output. */
 506   { "file-prefix", required_argument,   0,   'b' },
 507   { "output",      required_argument,   0,   'o' },
 508   { "output-file", required_argument,   0,   'o' },
 509   { "graph",       optional_argument,   0,   'g' },
 510   { "xml",         optional_argument,   0,   'x' },
 511   { "report",      required_argument,   0,   'r' },
 512   { "report-file", required_argument,   0,   REPORT_FILE_OPTION },
 513   { "verbose",     no_argument,         0,   'v' },
 514
 515   /* Hidden. */
 516   { "trace",         optional_argument,   0,     'T' },
 517
 518   /* Output.  */
 519   { "defines",     optional_argument,   0,   'd' },
 520   { "feature",     optional_argument,   0,   'f' },
 521
 522   /* Operation modes.  */
 523   { "fixed-output-files", no_argument,  0,   'y' },
 524   { "yacc",               no_argument,  0,   'y' },
 525
 526   /* Parser.  */
 527   { "debug",          no_argument,               0,   't' },
 528   { "define",         required_argument,         0,   'D' },
 529   { "force-define",   required_argument,         0,   'F' },
 530   { "locations",      no_argument,               0, LOCATIONS_OPTION },
 531   { "no-lines",       no_argument,               0,   'l' },
 532   { "raw",            no_argument,               0,     0 },
 533   { "skeleton",       required_argument,         0,   'S' },
 534   { "language",       required_argument,         0,   'L' },
 535   { "token-table",    no_argument,               0,   'k' },
 536
 537   {0, 0, 0, 0}
 538 };
 539
 540 /* Under DOS, there is no difference on the case.  This can be
 541    troublesome when looking for `.tab' etc.  */
 542 #ifdef MSDOS
 543 # define AS_FILE_NAME(File) (strlwr (File), (File))
 544 #else
 545 # define AS_FILE_NAME(File) (File)
 546 #endif
 547
 548 /* Build a location for the current command line argument. */
 549 static
 550 location
 551 command_line_location (void)
 552 {
 553   location res;
 554   /* "<command line>" is used in GCC's messages about -D. */
 555   boundary_set (&res.start, uniqstr_new ("<command line>"), optind - 1, -1);
 556   res.end = res.start;
 557   return res;
 558 }
 559
 560
 561 void
 562 getargs (int argc, char *argv[])
 563 {
 564   int c;
 565
 566   while ((c = getopt_long (argc, argv, short_options, long_options, NULL))
 567          != -1)
 568     switch (c)
 569       {
 570         /* ASCII Sorting for short options (i.e., upper case then
 571            lower case), and then long-only options.  */
 572
 573       case 0:
 574         /* Certain long options cause getopt_long to return 0.  */
 575         break;
 576
 577       case 'D': /* -DNAME[=VALUE]. */
 578       case 'F': /* -FNAME[=VALUE]. */
 579         {
 580           char* name = optarg;
 581           char* value = strchr (optarg, '=');
 582           if (value)
 583             *value++ = 0;
 584           muscle_percent_define_insert (name, command_line_location (),
 585                                         value ? value : "",
 586                                         c == 'D' ? MUSCLE_PERCENT_DEFINE_D
 587                                                  : MUSCLE_PERCENT_DEFINE_F);
 588         }
 589         break;
 590
 591       case 'I':
 592         include = AS_FILE_NAME (optarg);
 593         break;
 594
 595       case 'L':
 596         language_argmatch (optarg, command_line_prio,
 597                            command_line_location ());
 598         break;
 599
 600       case 'S':
 601         skeleton_arg (AS_FILE_NAME (optarg), command_line_prio,
 602                       command_line_location ());
 603         break;
 604
 605       case 'T':
 606         FLAGS_ARGMATCH (trace, optarg, trace_all);
 607         break;
 608
 609       case 'V':
 610         version ();
 611         exit (EXIT_SUCCESS);
 612
 613       case 'f':
 614         FLAGS_ARGMATCH (feature, optarg, feature_all);
 615         break;
 616
 617       case 'W':
 618         warnings_argmatch (optarg);
 619         break;
 620
 621       case 'b':
 622         spec_file_prefix = AS_FILE_NAME (optarg);
 623         break;
 624
 625       case 'd':
 626         /* Here, the -d and --defines options are differentiated.  */
 627         defines_flag = true;
 628         if (optarg)
 629           {
 630             free (spec_defines_file);
 631             spec_defines_file = xstrdup (AS_FILE_NAME (optarg));
 632           }
 633         break;
 634
 635       case 'g':
 636         graph_flag = true;
 637         if (optarg)
 638           {
 639             free (spec_graph_file);
 640             spec_graph_file = xstrdup (AS_FILE_NAME (optarg));
 641           }
 642         break;
 643
 644       case 'h':
 645         usage (EXIT_SUCCESS);
 646
 647       case 'k':
 648         token_table_flag = true;
 649         break;
 650
 651       case 'l':
 652         no_lines_flag = true;
 653         break;
 654
 655       case 'o':
 656         spec_outfile = AS_FILE_NAME (optarg);
 657         break;
 658
 659       case 'p':
 660         spec_name_prefix = optarg;
 661         break;
 662
 663       case 'r':
 664         FLAGS_ARGMATCH (report, optarg, report_all);
 665         break;
 666
 667       case 't':
 668         muscle_percent_define_insert ("parse.trace",
 669                                       command_line_location (), "",
 670                                       MUSCLE_PERCENT_DEFINE_D);
 671         break;
 672
 673       case 'v':
 674         report_flag |= report_states;
 675         break;
 676
 677       case 'x':
 678         xml_flag = true;
 679         if (optarg)
 680           {
 681             free (spec_xml_file);
 682             spec_xml_file = xstrdup (AS_FILE_NAME (optarg));
 683           }
 684         break;
 685
 686       case 'y':
 687         warning_argmatch ("error=yacc", 0, 6);
 688         yacc_flag = true;
 689         break;
 690
 691       case LOCATIONS_OPTION:
 692         muscle_percent_define_ensure ("locations",
 693                                       command_line_location (), true);
 694         break;
 695
 696       case PRINT_LOCALEDIR_OPTION:
 697         printf ("%s\n", LOCALEDIR);
 698         exit (EXIT_SUCCESS);
 699
 700       case PRINT_DATADIR_OPTION:
 701         printf ("%s\n", pkgdatadir ());
 702         exit (EXIT_SUCCESS);
 703
 704       case REPORT_FILE_OPTION:
 705         free (spec_verbose_file);
 706         spec_verbose_file = xstrdup (AS_FILE_NAME (optarg));
 707         break;
 708
 709       default:
 710         usage (EXIT_FAILURE);
 711       }
 712
 713   if (argc - optind != 1)
 714     {
 715       if (argc - optind < 1)
 716         error (0, 0, _("%s: missing operand"), quotearg_colon (argv[argc - 1]));
 717       else
 718         error (0, 0, _("extra operand %s"), quote (argv[optind + 1]));
 719       usage (EXIT_FAILURE);
 720     }
 721
 722   current_file = grammar_file = uniqstr_new (argv[optind]);
 723   MUSCLE_INSERT_C_STRING ("file_name", grammar_file);
 724 }
 725
 726 void
 727 tr (char *s, char from, char to)
 728 {
 729   for (; *s; s++)
 730     if (*s == from)
 731       *s = to;
 732 }