parser-bottom-up.c

     
   1  //! @file parser-bottom-up.c
   2  //! @author J. Marcel van der Veer
   3  
   4  //! @section Copyright
   5  //!
   6  //! This file is part of Algol68G - an Algol 68 compiler-interpreter.
   7  //! Copyright 2001-2023 J. Marcel van der Veer [algol68g@xs4all.nl].
   8  
   9  //! @section License
  10  //!
  11  //! This program is free software; you can redistribute it and/or modify it 
  12  //! under the terms of the GNU General Public License as published by the 
  13  //! Free Software Foundation; either version 3 of the License, or 
  14  //! (at your option) any later version.
  15  //!
  16  //! This program is distributed in the hope that it will be useful, but 
  17  //! WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
  18  //! or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for 
  19  //! more details. You should have received a copy of the GNU General Public 
  20  //! License along with this program. If not, see [http://www.gnu.org/licenses/].
  21  
  22  //! @section Synopsis 
  23  //!
  24  //! Hand-coded bottom-up parser for Algol 68.
  25  
  26  // This code constitutes an effective "Algol 68 VW parser"; a pragmatic
  27  // approach was chosen since in the early days of Algol 68, many "ab initio" 
  28  // implementations failed.
  29  // 
  30  // This is a Mailloux-type parser, in the sense that it scans a "phrase" for
  31  // definitions needed for parsing, and therefore allows for tags to be used
  32  // before they are defined, which gives some freedom in top-down programming.
  33  // 
  34  //    B. J. Mailloux. On the implementation of Algol 68.
  35  //    Thesis, Universiteit van Amsterdam (Mathematisch Centrum) [1968].
  36  // 
  37  // Technically, Mailloux's approach renders the two-level grammar LALR.
  38  // 
  39  // This is the bottom-up parser that resolves the structure of the program.
  40  
  41  #include "a68g.h"
  42  #include "a68g-parser.h"
  43  #include "a68g-prelude.h"
  44  
  45  // Bottom-up parser, reduces all constructs.
  46  
  47  //! @brief Whether a series is serial or collateral.
  48  
  49  int serial_or_collateral (NODE_T * p)
  50  {
  51    int semis = 0, commas = 0, exits = 0;
  52    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
  53      if (IS (q, COMMA_SYMBOL)) {
  54        commas++;
  55      } else if (IS (q, SEMI_SYMBOL)) {
  56        semis++;
  57      } else if (IS (q, EXIT_SYMBOL)) {
  58        exits++;
  59      }
  60    }
  61    if (semis == 0 && exits == 0 && commas > 0) {
  62      return COLLATERAL_CLAUSE;
  63    } else if ((semis > 0 || exits > 0) && commas == 0) {
  64      return SERIAL_CLAUSE;
  65    } else if (semis == 0 && exits == 0 && commas == 0) {
  66      return SERIAL_CLAUSE;
  67    } else {
  68  // Heuristic guess to give intelligible error message.
  69      return (semis + exits) >= (commas ? SERIAL_CLAUSE : COLLATERAL_CLAUSE);
  70    }
  71  }
  72  
  73  //! @brief Insert a node with attribute "a" after "p".
  74  
  75  void pad_node (NODE_T * p, int a)
  76  {
  77  // This is used to fill information that Algol 68 does not require to be present.
  78  // Filling in gives one format for such construct; this helps later passes.
  79    NODE_T *z = new_node ();
  80    *z = *p;
  81    if (GINFO (p) != NO_GINFO) {
  82      GINFO (z) = new_genie_info ();
  83    }
  84    PREVIOUS (z) = p;
  85    SUB (z) = NO_NODE;
  86    ATTRIBUTE (z) = a;
  87    MOID (z) = NO_MOID;
  88    if (NEXT (z) != NO_NODE) {
  89      PREVIOUS (NEXT (z)) = z;
  90    }
  91    NEXT (p) = z;
  92  }
  93  
  94  //! @brief Diagnose extensions.
  95  
  96  void a68_extension (NODE_T * p)
  97  {
  98    if (OPTION_PORTCHECK (&A68_JOB)) {
  99      diagnostic (A68_WARNING | A68_FORCE_DIAGNOSTICS, p, WARNING_EXTENSION);
 100    } else {
 101      diagnostic (A68_WARNING, p, WARNING_EXTENSION);
 102    }
 103  }
 104  
 105  //! @brief Diagnose for clauses not yielding a value.
 106  
 107  void empty_clause (NODE_T * p)
 108  {
 109    diagnostic (A68_SYNTAX_ERROR, p, ERROR_CLAUSE_WITHOUT_VALUE);
 110  }
 111  
 112  #if !defined (BUILD_PARALLEL_CLAUSE)
 113  
 114  //! @brief Diagnose for parallel clause.
 115  
 116  void par_clause (NODE_T * p)
 117  {
 118    diagnostic (A68_SYNTAX_ERROR, p, ERROR_NO_PARALLEL_CLAUSE);
 119  }
 120  
 121  #endif
 122  
 123  //! @brief Diagnose for missing symbol.
 124  
 125  void strange_tokens (NODE_T * p)
 126  {
 127    NODE_T *q = ((p != NO_NODE && NEXT (p) != NO_NODE) ? NEXT (p) : p);
 128    diagnostic (A68_SYNTAX_ERROR, q, ERROR_SYNTAX_STRANGE_TOKENS);
 129  }
 130  
 131  //! @brief Diagnose for strange separator.
 132  
 133  void strange_separator (NODE_T * p)
 134  {
 135    NODE_T *q = ((p != NO_NODE && NEXT (p) != NO_NODE) ? NEXT (p) : p);
 136    diagnostic (A68_SYNTAX_ERROR, q, ERROR_SYNTAX_STRANGE_SEPARATOR);
 137  }
 138  
 139  //! @brief If match then reduce a sentence, the core BU parser routine.
 140  
 141  void reduce (NODE_T * p, void (*a) (NODE_T *), BOOL_T * z, ...)
 142  {
 143    va_list list;
 144    va_start (list, z);
 145    int result = va_arg (list, int), expect;
 146    NODE_T *head = p, *tail = NO_NODE;
 147    while ((expect = va_arg (list, int)) != STOP)
 148    {
 149      BOOL_T keep_matching;
 150      if (p == NO_NODE) {
 151        keep_matching = A68_FALSE;
 152      } else if (expect == WILDCARD) {
 153  // WILDCARD matches any Algol68G non terminal, but no keyword.
 154        keep_matching = (BOOL_T) (non_terminal_string (A68 (edit_line), ATTRIBUTE (p)) != NO_TEXT);
 155      } else {
 156        if (expect == SKIP) {
 157  // Stray "~" matches expected SKIP.
 158          if (IS (p, OPERATOR) && IS_LITERALLY (p, "~")) {
 159            ATTRIBUTE (p) = SKIP;
 160          }
 161        }
 162        if (expect >= 0) {
 163          keep_matching = (BOOL_T) (expect == ATTRIBUTE (p));
 164        } else {
 165          keep_matching = (BOOL_T) (expect != ATTRIBUTE (p));
 166        }
 167      }
 168      if (keep_matching) {
 169        tail = p;
 170        FORWARD (p);
 171      } else {
 172        va_end (list);
 173        return;
 174      }
 175    }
 176  // Print parser reductions.
 177    if (head != NO_NODE && OPTION_REDUCTIONS (&A68_JOB) && LINE_NUMBER (head) > 0) {
 178      A68_PARSER (reductions)++;
 179      WIS (head);
 180      ASSERT (snprintf (A68 (output_line), SNPRINTF_SIZE, "\nReduction %d: %s<-", A68_PARSER (reductions), non_terminal_string (A68 (edit_line), result)) >= 0);
 181      WRITE (A68_STDOUT, A68 (output_line));
 182      int count = 0;
 183      for (NODE_T *q = head; q != NO_NODE && tail != NO_NODE && q != NEXT (tail); FORWARD (q), count++) {
 184        int gatt = ATTRIBUTE (q);
 185        char *str = non_terminal_string (A68 (input_line), gatt);
 186        if (count > 0) {
 187          WRITE (A68_STDOUT, ", ");
 188        }
 189        if (str != NO_TEXT) {
 190          WRITE (A68_STDOUT, str);
 191          if (gatt == IDENTIFIER || gatt == OPERATOR || gatt == DENOTATION || gatt == INDICANT) {
 192            ASSERT (snprintf (A68 (output_line), SNPRINTF_SIZE, " \"%s\"", NSYMBOL (q)) >= 0);
 193            WRITE (A68_STDOUT, A68 (output_line));
 194          }
 195        } else {
 196          WRITE (A68_STDOUT, NSYMBOL (q));
 197        }
 198      }
 199    }
 200  // Make reduction.
 201    if (a != NO_NOTE) {
 202      a (head);
 203    }
 204    make_sub (head, tail, result);
 205    va_end (list);
 206    if (z != NO_TICK) {
 207      *z = A68_TRUE;
 208    }
 209  }
 210  
 211  //! @brief Graciously ignore extra semicolons.
 212  
 213  void ignore_superfluous_semicolons (NODE_T * p)
 214  {
 215  // This routine relaxes the parser a bit with respect to superfluous semicolons,
 216  // for instance "FI; OD". These provoke only a warning.
 217    for (; p != NO_NODE; FORWARD (p)) {
 218      ignore_superfluous_semicolons (SUB (p));
 219      if (NEXT (p) != NO_NODE && IS (NEXT (p), SEMI_SYMBOL) && NEXT_NEXT (p) == NO_NODE) {
 220        diagnostic (A68_WARNING | A68_FORCE_DIAGNOSTICS, NEXT (p), WARNING_SKIPPED_SUPERFLUOUS, ATTRIBUTE (NEXT (p)));
 221        NEXT (p) = NO_NODE;
 222      } else if (IS (p, SEMI_SYMBOL) && is_semicolon_less (NEXT (p))) {
 223        diagnostic (A68_WARNING | A68_FORCE_DIAGNOSTICS, p, WARNING_SKIPPED_SUPERFLUOUS, ATTRIBUTE (p));
 224        if (PREVIOUS (p) != NO_NODE) {
 225          NEXT (PREVIOUS (p)) = NEXT (p);
 226        }
 227        PREVIOUS (NEXT (p)) = PREVIOUS (p);
 228      }
 229    }
 230  }
 231  
 232  //! @brief Driver for the bottom-up parser.
 233  
 234  void bottom_up_parser (NODE_T * p)
 235  {
 236    if (p != NO_NODE) {
 237      if (!setjmp (A68_PARSER (bottom_up_crash_exit))) {
 238        NODE_T *q;
 239        int error_count_0 = ERROR_COUNT (&A68_JOB);
 240        ignore_superfluous_semicolons (p);
 241  // A program is "label sequence; particular program".
 242        extract_labels (p, SERIAL_CLAUSE);
 243  // Parse the program itself.
 244        for (q = p; q != NO_NODE; FORWARD (q)) {
 245          BOOL_T siga = A68_TRUE;
 246          if (SUB (q) != NO_NODE) {
 247            reduce_branch (q, SOME_CLAUSE);
 248          }
 249          while (siga) {
 250            siga = A68_FALSE;
 251            reduce (q, NO_NOTE, &siga, LABEL, DEFINING_IDENTIFIER, COLON_SYMBOL, STOP);
 252            reduce (q, NO_NOTE, &siga, LABEL, LABEL, DEFINING_IDENTIFIER, COLON_SYMBOL, STOP);
 253          }
 254        }
 255  // Determine the encompassing enclosed clause.
 256        for (q = p; q != NO_NODE; FORWARD (q)) {
 257  #if defined (BUILD_PARALLEL_CLAUSE)
 258          reduce (q, NO_NOTE, NO_TICK, PARALLEL_CLAUSE, PAR_SYMBOL, COLLATERAL_CLAUSE, STOP);
 259  #else
 260          reduce (q, par_clause, NO_TICK, PARALLEL_CLAUSE, PAR_SYMBOL, COLLATERAL_CLAUSE, STOP);
 261  #endif
 262          reduce (q, NO_NOTE, NO_TICK, ENCLOSED_CLAUSE, PARALLEL_CLAUSE, STOP);
 263          reduce (q, NO_NOTE, NO_TICK, ENCLOSED_CLAUSE, CLOSED_CLAUSE, STOP);
 264          reduce (q, NO_NOTE, NO_TICK, ENCLOSED_CLAUSE, COLLATERAL_CLAUSE, STOP);
 265          reduce (q, NO_NOTE, NO_TICK, ENCLOSED_CLAUSE, CONDITIONAL_CLAUSE, STOP);
 266          reduce (q, NO_NOTE, NO_TICK, ENCLOSED_CLAUSE, CASE_CLAUSE, STOP);
 267          reduce (q, NO_NOTE, NO_TICK, ENCLOSED_CLAUSE, CONFORMITY_CLAUSE, STOP);
 268          reduce (q, NO_NOTE, NO_TICK, ENCLOSED_CLAUSE, LOOP_CLAUSE, STOP);
 269        }
 270  // Try reducing the particular program.
 271        q = p;
 272        reduce (q, NO_NOTE, NO_TICK, PARTICULAR_PROGRAM, LABEL, ENCLOSED_CLAUSE, STOP);
 273        reduce (q, NO_NOTE, NO_TICK, PARTICULAR_PROGRAM, ENCLOSED_CLAUSE, STOP);
 274        if (SUB (p) == NO_NODE || NEXT (p) != NO_NODE) {
 275          recover_from_error (p, PARTICULAR_PROGRAM, (BOOL_T) ((ERROR_COUNT (&A68_JOB) - error_count_0) > MAX_ERRORS));
 276        }
 277      }
 278    }
 279  }
 280  
 281  //! @brief Reduce code clause.
 282  
 283  void reduce_code_clause (NODE_T * p)
 284  {
 285    BOOL_T siga = A68_TRUE;
 286    while (siga) {
 287      siga = A68_FALSE;
 288      for (NODE_T *u = p; u != NO_NODE; FORWARD (u)) {
 289        reduce (u, NO_NOTE, &siga, CODE_LIST, CODE_SYMBOL, ROW_CHAR_DENOTATION, STOP);
 290        reduce (u, NO_NOTE, &siga, CODE_LIST, CODE_LIST, ROW_CHAR_DENOTATION, STOP);
 291        reduce (u, NO_NOTE, &siga, CODE_LIST, CODE_LIST, COMMA_SYMBOL, ROW_CHAR_DENOTATION, STOP);
 292        reduce (u, NO_NOTE, &siga, CODE_CLAUSE, CODE_LIST, EDOC_SYMBOL, STOP);
 293      }
 294    }
 295  }
 296  
 297  //! @brief Reduce the sub-phrase that starts one level down.
 298  
 299  void reduce_branch (NODE_T * q, int expect)
 300  {
 301  // If unsuccessful then the routine will at least copy the resulting attribute
 302  // as the parser can repair some faults. This gives less spurious diagnostics.
 303    if (q != NO_NODE && SUB (q) != NO_NODE) {
 304      NODE_T *p = SUB (q), *u = NO_NODE;
 305      int error_count_0 = ERROR_COUNT (&A68_JOB), error_count_02;
 306      BOOL_T declarer_pack = A68_FALSE, no_error;
 307      switch (expect) {
 308      case STRUCTURE_PACK:
 309      case PARAMETER_PACK:
 310      case FORMAL_DECLARERS:
 311      case UNION_PACK:
 312      case SPECIFIER: {
 313          declarer_pack = A68_TRUE;
 314        }
 315      default: {
 316          declarer_pack = A68_FALSE;
 317        }
 318      }
 319  // Sample all info needed to decide whether a bold tag is operator or indicant.
 320  // Find the meaning of bold tags and quit in case of extra errors.
 321      extract_indicants (p);
 322      if (!declarer_pack) {
 323        extract_priorities (p);
 324        extract_operators (p);
 325      }
 326      error_count_02 = ERROR_COUNT (&A68_JOB);
 327      elaborate_bold_tags (p);
 328      if ((ERROR_COUNT (&A68_JOB) - error_count_02) > 0) {
 329        longjmp (A68_PARSER (bottom_up_crash_exit), 1);
 330      }
 331  // Now we can reduce declarers, knowing which bold tags are indicants.
 332      reduce_declarers (p, expect);
 333  // Parse the phrase, as appropriate.
 334      if (expect == CODE_CLAUSE) {
 335        reduce_code_clause (p);
 336      } else if (declarer_pack == A68_FALSE) {
 337        error_count_02 = ERROR_COUNT (&A68_JOB);
 338        extract_declarations (p);
 339        if ((ERROR_COUNT (&A68_JOB) - error_count_02) > 0) {
 340          longjmp (A68_PARSER (bottom_up_crash_exit), 1);
 341        }
 342        extract_labels (p, expect);
 343        for (u = p; u != NO_NODE; FORWARD (u)) {
 344          if (SUB (u) != NO_NODE) {
 345            if (IS (u, FORMAT_DELIMITER_SYMBOL)) {
 346              reduce_branch (u, FORMAT_TEXT);
 347            } else if (IS (u, FORMAT_OPEN_SYMBOL)) {
 348              reduce_branch (u, FORMAT_TEXT);
 349            } else if (IS (u, OPEN_SYMBOL)) {
 350              if (NEXT (u) != NO_NODE && IS (NEXT (u), THEN_BAR_SYMBOL)) {
 351                reduce_branch (u, ENQUIRY_CLAUSE);
 352              } else if (PREVIOUS (u) != NO_NODE && IS (PREVIOUS (u), PAR_SYMBOL)) {
 353                reduce_branch (u, COLLATERAL_CLAUSE);
 354              }
 355            } else if (is_one_of (u, IF_SYMBOL, ELIF_SYMBOL, CASE_SYMBOL, OUSE_SYMBOL, WHILE_SYMBOL, UNTIL_SYMBOL, ELSE_BAR_SYMBOL, ACCO_SYMBOL, STOP)) {
 356              reduce_branch (u, ENQUIRY_CLAUSE);
 357            } else if (IS (u, BEGIN_SYMBOL)) {
 358              reduce_branch (u, SOME_CLAUSE);
 359            } else if (is_one_of (u, THEN_SYMBOL, ELSE_SYMBOL, OUT_SYMBOL, DO_SYMBOL, ALT_DO_SYMBOL, STOP)) {
 360              reduce_branch (u, SERIAL_CLAUSE);
 361            } else if (IS (u, IN_SYMBOL)) {
 362              reduce_branch (u, COLLATERAL_CLAUSE);
 363            } else if (IS (u, THEN_BAR_SYMBOL)) {
 364              reduce_branch (u, SOME_CLAUSE);
 365            } else if (IS (u, LOOP_CLAUSE)) {
 366              reduce_branch (u, ENCLOSED_CLAUSE);
 367            } else if (is_one_of (u, FOR_SYMBOL, FROM_SYMBOL, BY_SYMBOL, TO_SYMBOL, DOWNTO_SYMBOL, STOP)) {
 368              reduce_branch (u, UNIT);
 369            }
 370          }
 371        }
 372        reduce_primary_parts (p, expect);
 373        if (expect != ENCLOSED_CLAUSE) {
 374          reduce_primaries (p, expect);
 375          if (expect == FORMAT_TEXT) {
 376            reduce_format_texts (p);
 377          } else {
 378            reduce_secondaries (p);
 379            reduce_formulae (p);
 380            reduce_tertiaries (p);
 381          }
 382        }
 383        for (u = p; u != NO_NODE; FORWARD (u)) {
 384          if (SUB (u) != NO_NODE) {
 385            if (IS (u, CODE_SYMBOL)) {
 386              reduce_branch (u, CODE_CLAUSE);
 387            }
 388          }
 389        }
 390        reduce_right_to_left_constructs (p);
 391  // Reduce units and declarations.
 392        reduce_basic_declarations (p);
 393        reduce_units (p);
 394        reduce_erroneous_units (p);
 395        if (expect != UNIT) {
 396          if (expect == GENERIC_ARGUMENT) {
 397            reduce_generic_arguments (p);
 398          } else if (expect == BOUNDS) {
 399            reduce_bounds (p);
 400          } else {
 401            reduce_declaration_lists (p);
 402            if (expect != DECLARATION_LIST) {
 403              for (u = p; u != NO_NODE; FORWARD (u)) {
 404                reduce (u, NO_NOTE, NO_TICK, LABELED_UNIT, LABEL, UNIT, STOP);
 405                reduce (u, NO_NOTE, NO_TICK, SPECIFIED_UNIT, SPECIFIER, COLON_SYMBOL, UNIT, STOP);
 406              }
 407              if (expect == SOME_CLAUSE) {
 408                expect = serial_or_collateral (p);
 409              }
 410              if (expect == SERIAL_CLAUSE) {
 411                reduce_serial_clauses (p);
 412              } else if (expect == ENQUIRY_CLAUSE) {
 413                reduce_enquiry_clauses (p);
 414              } else if (expect == COLLATERAL_CLAUSE) {
 415                reduce_collateral_clauses (p);
 416              } else if (expect == ARGUMENT) {
 417                reduce_arguments (p);
 418              }
 419            }
 420          }
 421        }
 422        reduce_enclosed_clauses (p, expect);
 423      }
 424  // Do something if parsing failed.
 425      if (SUB (p) == NO_NODE || NEXT (p) != NO_NODE) {
 426        recover_from_error (p, expect, (BOOL_T) ((ERROR_COUNT (&A68_JOB) - error_count_0) > MAX_ERRORS));
 427        no_error = A68_FALSE;
 428      } else {
 429        no_error = A68_TRUE;
 430      }
 431      ATTRIBUTE (q) = ATTRIBUTE (p);
 432      if (no_error) {
 433        SUB (q) = SUB (p);
 434      }
 435    }
 436  }
 437  
 438  //! @brief Driver for reducing declarers.
 439  
 440  void reduce_declarers (NODE_T * p, int expect)
 441  {
 442    NODE_T *q; BOOL_T siga; // Must be in this scope.
 443  // Reduce lengtheties.
 444    for (q = p; q != NO_NODE; FORWARD (q)) {
 445      siga = A68_TRUE;
 446      reduce (q, NO_NOTE, NO_TICK, LONGETY, LONG_SYMBOL, STOP);
 447      reduce (q, NO_NOTE, NO_TICK, SHORTETY, SHORT_SYMBOL, STOP);
 448      while (siga) {
 449        siga = A68_FALSE;
 450        reduce (q, NO_NOTE, &siga, LONGETY, LONGETY, LONG_SYMBOL, STOP);
 451        reduce (q, NO_NOTE, &siga, SHORTETY, SHORTETY, SHORT_SYMBOL, STOP);
 452      }
 453    }
 454  // Reduce indicants.
 455    for (q = p; q != NO_NODE; FORWARD (q)) {
 456      reduce (q, NO_NOTE, NO_TICK, INDICANT, INT_SYMBOL, STOP);
 457      reduce (q, NO_NOTE, NO_TICK, INDICANT, REAL_SYMBOL, STOP);
 458      reduce (q, NO_NOTE, NO_TICK, INDICANT, BITS_SYMBOL, STOP);
 459      reduce (q, NO_NOTE, NO_TICK, INDICANT, BYTES_SYMBOL, STOP);
 460      reduce (q, NO_NOTE, NO_TICK, INDICANT, COMPLEX_SYMBOL, STOP);
 461      reduce (q, NO_NOTE, NO_TICK, INDICANT, COMPL_SYMBOL, STOP);
 462      reduce (q, NO_NOTE, NO_TICK, INDICANT, BOOL_SYMBOL, STOP);
 463      reduce (q, NO_NOTE, NO_TICK, INDICANT, CHAR_SYMBOL, STOP);
 464      reduce (q, NO_NOTE, NO_TICK, INDICANT, FORMAT_SYMBOL, STOP);
 465      reduce (q, NO_NOTE, NO_TICK, INDICANT, STRING_SYMBOL, STOP);
 466      reduce (q, NO_NOTE, NO_TICK, INDICANT, FILE_SYMBOL, STOP);
 467      reduce (q, NO_NOTE, NO_TICK, INDICANT, CHANNEL_SYMBOL, STOP);
 468      reduce (q, NO_NOTE, NO_TICK, INDICANT, SEMA_SYMBOL, STOP);
 469      reduce (q, NO_NOTE, NO_TICK, INDICANT, PIPE_SYMBOL, STOP);
 470      reduce (q, NO_NOTE, NO_TICK, INDICANT, SOUND_SYMBOL, STOP);
 471    }
 472  // Reduce standard stuff.
 473    for (q = p; q != NO_NODE; FORWARD (q)) {
 474      if (whether (q, LONGETY, INDICANT, STOP)) {
 475        int a;
 476        if (SUB_NEXT (q) == NO_NODE) {
 477          diagnostic (A68_SYNTAX_ERROR, NEXT (q), ERROR_EXPECTED, INFO_APPROPRIATE_DECLARER);
 478          reduce (q, NO_NOTE, NO_TICK, DECLARER, LONGETY, INDICANT, STOP);
 479        } else {
 480          a = ATTRIBUTE (SUB_NEXT (q));
 481          if (a == INT_SYMBOL || a == REAL_SYMBOL || a == BITS_SYMBOL || a == BYTES_SYMBOL || a == COMPLEX_SYMBOL || a == COMPL_SYMBOL) {
 482            reduce (q, NO_NOTE, NO_TICK, DECLARER, LONGETY, INDICANT, STOP);
 483          } else {
 484            diagnostic (A68_SYNTAX_ERROR, NEXT (q), ERROR_EXPECTED, INFO_APPROPRIATE_DECLARER);
 485            reduce (q, NO_NOTE, NO_TICK, DECLARER, LONGETY, INDICANT, STOP);
 486          }
 487        }
 488      } else if (whether (q, SHORTETY, INDICANT, STOP)) {
 489        int a;
 490        if (SUB_NEXT (q) == NO_NODE) {
 491          diagnostic (A68_SYNTAX_ERROR, NEXT (q), ERROR_EXPECTED, INFO_APPROPRIATE_DECLARER);
 492          reduce (q, NO_NOTE, NO_TICK, DECLARER, SHORTETY, INDICANT, STOP);
 493        } else {
 494          a = ATTRIBUTE (SUB_NEXT (q));
 495          if (a == INT_SYMBOL || a == REAL_SYMBOL || a == BITS_SYMBOL || a == BYTES_SYMBOL || a == COMPLEX_SYMBOL || a == COMPL_SYMBOL) {
 496            reduce (q, NO_NOTE, NO_TICK, DECLARER, SHORTETY, INDICANT, STOP);
 497          } else {
 498            diagnostic (A68_SYNTAX_ERROR, NEXT (q), ERROR_EXPECTED, INFO_APPROPRIATE_DECLARER);
 499            reduce (q, NO_NOTE, NO_TICK, DECLARER, LONGETY, INDICANT, STOP);
 500          }
 501        }
 502      }
 503    }
 504    for (q = p; q != NO_NODE; FORWARD (q)) {
 505      reduce (q, NO_NOTE, NO_TICK, DECLARER, INDICANT, STOP);
 506    }
 507  // Reduce declarer lists.
 508    for (q = p; q != NO_NODE; FORWARD (q)) {
 509      if (NEXT (q) != NO_NODE && SUB_NEXT (q) != NO_NODE) {
 510        if (IS (q, STRUCT_SYMBOL)) {
 511          reduce_branch (NEXT (q), STRUCTURE_PACK);
 512          reduce (q, NO_NOTE, NO_TICK, DECLARER, STRUCT_SYMBOL, STRUCTURE_PACK, STOP);
 513        } else if (IS (q, UNION_SYMBOL)) {
 514          reduce_branch (NEXT (q), UNION_PACK);
 515          reduce (q, NO_NOTE, NO_TICK, DECLARER, UNION_SYMBOL, UNION_PACK, STOP);
 516        } else if (IS (q, PROC_SYMBOL)) {
 517          if (whether (q, PROC_SYMBOL, OPEN_SYMBOL, STOP)) {
 518            if (!is_formal_bounds (SUB_NEXT (q))) {
 519              reduce_branch (NEXT (q), FORMAL_DECLARERS);
 520            }
 521          }
 522        } else if (IS (q, OP_SYMBOL)) {
 523          if (whether (q, OP_SYMBOL, OPEN_SYMBOL, STOP)) {
 524            if (!is_formal_bounds (SUB_NEXT (q))) {
 525              reduce_branch (NEXT (q), FORMAL_DECLARERS);
 526            }
 527          }
 528        }
 529      }
 530    }
 531  // Reduce row, proc or op declarers.
 532    siga = A68_TRUE;
 533    while (siga) {
 534      siga = A68_FALSE;
 535      for (q = p; q != NO_NODE; FORWARD (q)) {
 536  // FLEX DECL.
 537        if (whether (q, FLEX_SYMBOL, DECLARER, STOP)) {
 538          reduce (q, NO_NOTE, &siga, DECLARER, FLEX_SYMBOL, DECLARER, STOP);
 539        }
 540  // FLEX [] DECL.
 541        if (whether (q, FLEX_SYMBOL, SUB_SYMBOL, DECLARER, STOP) && SUB_NEXT (q) != NO_NODE) {
 542          reduce_branch (NEXT (q), BOUNDS);
 543          reduce (q, NO_NOTE, &siga, DECLARER, FLEX_SYMBOL, BOUNDS, DECLARER, STOP);
 544          reduce (q, NO_NOTE, &siga, DECLARER, FLEX_SYMBOL, FORMAL_BOUNDS, DECLARER, STOP);
 545        }
 546  // FLEX () DECL.
 547        if (whether (q, FLEX_SYMBOL, OPEN_SYMBOL, DECLARER, STOP) && SUB_NEXT (q) != NO_NODE) {
 548          if (!whether (q, FLEX_SYMBOL, OPEN_SYMBOL, DECLARER, COLON_SYMBOL, STOP)) {
 549            reduce_branch (NEXT (q), BOUNDS);
 550            reduce (q, NO_NOTE, &siga, DECLARER, FLEX_SYMBOL, BOUNDS, DECLARER, STOP);
 551            reduce (q, NO_NOTE, &siga, DECLARER, FLEX_SYMBOL, FORMAL_BOUNDS, DECLARER, STOP);
 552          }
 553        }
 554  // [] DECL.
 555        if (whether (q, SUB_SYMBOL, DECLARER, STOP) && SUB (q) != NO_NODE) {
 556          reduce_branch (q, BOUNDS);
 557          reduce (q, NO_NOTE, &siga, DECLARER, BOUNDS, DECLARER, STOP);
 558          reduce (q, NO_NOTE, &siga, DECLARER, FORMAL_BOUNDS, DECLARER, STOP);
 559        }
 560  // () DECL.
 561        if (whether (q, OPEN_SYMBOL, DECLARER, STOP) && SUB (q) != NO_NODE) {
 562          if (whether (q, OPEN_SYMBOL, DECLARER, COLON_SYMBOL, STOP)) {
 563  // Catch e.g. (INT i) () INT:.
 564            if (is_formal_bounds (SUB (q))) {
 565              reduce_branch (q, BOUNDS);
 566              reduce (q, NO_NOTE, &siga, DECLARER, BOUNDS, DECLARER, STOP);
 567              reduce (q, NO_NOTE, &siga, DECLARER, FORMAL_BOUNDS, DECLARER, STOP);
 568            }
 569          } else {
 570            reduce_branch (q, BOUNDS);
 571            reduce (q, NO_NOTE, &siga, DECLARER, BOUNDS, DECLARER, STOP);
 572            reduce (q, NO_NOTE, &siga, DECLARER, FORMAL_BOUNDS, DECLARER, STOP);
 573          }
 574        }
 575      }
 576  // PROC DECL, PROC () DECL, OP () DECL.
 577      for (q = p; q != NO_NODE; FORWARD (q)) {
 578        int a = ATTRIBUTE (q);
 579        if (a == REF_SYMBOL) {
 580          reduce (q, NO_NOTE, &siga, DECLARER, REF_SYMBOL, DECLARER, STOP);
 581        } else if (a == PROC_SYMBOL) {
 582          reduce (q, NO_NOTE, &siga, DECLARER, PROC_SYMBOL, DECLARER, STOP);
 583          reduce (q, NO_NOTE, &siga, DECLARER, PROC_SYMBOL, FORMAL_DECLARERS, DECLARER, STOP);
 584          reduce (q, NO_NOTE, &siga, DECLARER, PROC_SYMBOL, VOID_SYMBOL, STOP);
 585          reduce (q, NO_NOTE, &siga, DECLARER, PROC_SYMBOL, FORMAL_DECLARERS, VOID_SYMBOL, STOP);
 586        } else if (a == OP_SYMBOL) {
 587          reduce (q, NO_NOTE, &siga, OPERATOR_PLAN, OP_SYMBOL, FORMAL_DECLARERS, DECLARER, STOP);
 588          reduce (q, NO_NOTE, &siga, OPERATOR_PLAN, OP_SYMBOL, FORMAL_DECLARERS, VOID_SYMBOL, STOP);
 589        }
 590      }
 591    }
 592  // Reduce packs etcetera.
 593    if (expect == STRUCTURE_PACK) {
 594      for (q = p; q != NO_NODE; FORWARD (q)) {
 595        siga = A68_TRUE;
 596        while (siga) {
 597          siga = A68_FALSE;
 598          reduce (q, NO_NOTE, &siga, STRUCTURED_FIELD, DECLARER, IDENTIFIER, STOP);
 599          reduce (q, NO_NOTE, &siga, STRUCTURED_FIELD, STRUCTURED_FIELD, COMMA_SYMBOL, IDENTIFIER, STOP);
 600        }
 601      }
 602      for (q = p; q != NO_NODE; FORWARD (q)) {
 603        siga = A68_TRUE;
 604        while (siga) {
 605          siga = A68_FALSE;
 606          reduce (q, NO_NOTE, &siga, STRUCTURED_FIELD_LIST, STRUCTURED_FIELD, STOP);
 607          reduce (q, NO_NOTE, &siga, STRUCTURED_FIELD_LIST, STRUCTURED_FIELD_LIST, COMMA_SYMBOL, STRUCTURED_FIELD, STOP);
 608          reduce (q, strange_separator, &siga, STRUCTURED_FIELD_LIST, STRUCTURED_FIELD_LIST, STRUCTURED_FIELD, STOP);
 609          reduce (q, strange_separator, &siga, STRUCTURED_FIELD_LIST, STRUCTURED_FIELD_LIST, SEMI_SYMBOL, STRUCTURED_FIELD, STOP);
 610        }
 611      }
 612      q = p;
 613      reduce (q, NO_NOTE, NO_TICK, STRUCTURE_PACK, OPEN_SYMBOL, STRUCTURED_FIELD_LIST, CLOSE_SYMBOL, STOP);
 614    } else if (expect == PARAMETER_PACK) {
 615      for (q = p; q != NO_NODE; FORWARD (q)) {
 616        siga = A68_TRUE;
 617        while (siga) {
 618          siga = A68_FALSE;
 619          reduce (q, NO_NOTE, &siga, PARAMETER, DECLARER, IDENTIFIER, STOP);
 620          reduce (q, NO_NOTE, &siga, PARAMETER, PARAMETER, COMMA_SYMBOL, IDENTIFIER, STOP);
 621        }
 622      }
 623      for (q = p; q != NO_NODE; FORWARD (q)) {
 624        siga = A68_TRUE;
 625        while (siga) {
 626          siga = A68_FALSE;
 627          reduce (q, NO_NOTE, &siga, PARAMETER_LIST, PARAMETER, STOP);
 628          reduce (q, NO_NOTE, &siga, PARAMETER_LIST, PARAMETER_LIST, COMMA_SYMBOL, PARAMETER, STOP);
 629        }
 630      }
 631      q = p;
 632      reduce (q, NO_NOTE, NO_TICK, PARAMETER_PACK, OPEN_SYMBOL, PARAMETER_LIST, CLOSE_SYMBOL, STOP);
 633    } else if (expect == FORMAL_DECLARERS) {
 634      for (q = p; q != NO_NODE; FORWARD (q)) {
 635        siga = A68_TRUE;
 636        while (siga) {
 637          siga = A68_FALSE;
 638          reduce (q, NO_NOTE, &siga, FORMAL_DECLARERS_LIST, DECLARER, STOP);
 639          reduce (q, NO_NOTE, &siga, FORMAL_DECLARERS_LIST, FORMAL_DECLARERS_LIST, COMMA_SYMBOL, DECLARER, STOP);
 640          reduce (q, strange_separator, &siga, FORMAL_DECLARERS_LIST, FORMAL_DECLARERS_LIST, SEMI_SYMBOL, DECLARER, STOP);
 641          reduce (q, strange_separator, &siga, FORMAL_DECLARERS_LIST, FORMAL_DECLARERS_LIST, DECLARER, STOP);
 642        }
 643      }
 644      q = p;
 645      reduce (q, NO_NOTE, NO_TICK, FORMAL_DECLARERS, OPEN_SYMBOL, FORMAL_DECLARERS_LIST, CLOSE_SYMBOL, STOP);
 646    } else if (expect == UNION_PACK) {
 647      for (q = p; q != NO_NODE; FORWARD (q)) {
 648        siga = A68_TRUE;
 649        while (siga) {
 650          siga = A68_FALSE;
 651          reduce (q, NO_NOTE, &siga, UNION_DECLARER_LIST, DECLARER, STOP);
 652          reduce (q, NO_NOTE, &siga, UNION_DECLARER_LIST, VOID_SYMBOL, STOP);
 653          reduce (q, NO_NOTE, &siga, UNION_DECLARER_LIST, UNION_DECLARER_LIST, COMMA_SYMBOL, DECLARER, STOP);
 654          reduce (q, NO_NOTE, &siga, UNION_DECLARER_LIST, UNION_DECLARER_LIST, COMMA_SYMBOL, VOID_SYMBOL, STOP);
 655          reduce (q, strange_separator, &siga, UNION_DECLARER_LIST, UNION_DECLARER_LIST, SEMI_SYMBOL, DECLARER, STOP);
 656          reduce (q, strange_separator, &siga, UNION_DECLARER_LIST, UNION_DECLARER_LIST, SEMI_SYMBOL, VOID_SYMBOL, STOP);
 657          reduce (q, strange_separator, &siga, UNION_DECLARER_LIST, UNION_DECLARER_LIST, DECLARER, STOP);
 658          reduce (q, strange_separator, &siga, UNION_DECLARER_LIST, UNION_DECLARER_LIST, VOID_SYMBOL, STOP);
 659        }
 660      }
 661      q = p;
 662      reduce (q, NO_NOTE, NO_TICK, UNION_PACK, OPEN_SYMBOL, UNION_DECLARER_LIST, CLOSE_SYMBOL, STOP);
 663    } else if (expect == SPECIFIER) {
 664      reduce (p, NO_NOTE, NO_TICK, SPECIFIER, OPEN_SYMBOL, DECLARER, IDENTIFIER, CLOSE_SYMBOL, STOP);
 665      reduce (p, NO_NOTE, NO_TICK, SPECIFIER, OPEN_SYMBOL, DECLARER, CLOSE_SYMBOL, STOP);
 666      reduce (p, NO_NOTE, NO_TICK, SPECIFIER, OPEN_SYMBOL, VOID_SYMBOL, CLOSE_SYMBOL, STOP);
 667    } else {
 668      for (q = p; q != NO_NODE; FORWARD (q)) {
 669        if (whether (q, OPEN_SYMBOL, COLON_SYMBOL, STOP) && !(expect == GENERIC_ARGUMENT || expect == BOUNDS)) {
 670          if (is_one_of (p, IN_SYMBOL, THEN_BAR_SYMBOL, STOP)) {
 671            reduce_branch (q, SPECIFIER);
 672          }
 673        }
 674        if (whether (q, OPEN_SYMBOL, DECLARER, COLON_SYMBOL, STOP)) {
 675          reduce_branch (q, PARAMETER_PACK);
 676        }
 677        if (whether (q, OPEN_SYMBOL, VOID_SYMBOL, COLON_SYMBOL, STOP)) {
 678          reduce_branch (q, PARAMETER_PACK);
 679        }
 680      }
 681    }
 682  }
 683  
 684  //! @brief Handle cases that need reducing from right-to-left.
 685  
 686  void reduce_right_to_left_constructs (NODE_T * p)
 687  {
 688  // Here are cases that need reducing from right-to-left whereas many things
 689  // can be reduced left-to-right. Assignations are a notable example; one could
 690  // discuss whether it would not be more natural to write 1 =: k in stead of
 691  // k := 1. The latter is said to be more natural, or it could be just computing
 692  // history. Meanwhile we use this routine.
 693    if (p != NO_NODE) {
 694      reduce_right_to_left_constructs (NEXT (p));
 695  // Assignations.
 696      if (IS (p, TERTIARY)) {
 697        reduce (p, NO_NOTE, NO_TICK, ASSIGNATION, TERTIARY, ASSIGN_SYMBOL, TERTIARY, STOP);
 698        reduce (p, NO_NOTE, NO_TICK, ASSIGNATION, TERTIARY, ASSIGN_SYMBOL, IDENTITY_RELATION, STOP);
 699        reduce (p, NO_NOTE, NO_TICK, ASSIGNATION, TERTIARY, ASSIGN_SYMBOL, AND_FUNCTION, STOP);
 700        reduce (p, NO_NOTE, NO_TICK, ASSIGNATION, TERTIARY, ASSIGN_SYMBOL, OR_FUNCTION, STOP);
 701        reduce (p, NO_NOTE, NO_TICK, ASSIGNATION, TERTIARY, ASSIGN_SYMBOL, ROUTINE_TEXT, STOP);
 702        reduce (p, NO_NOTE, NO_TICK, ASSIGNATION, TERTIARY, ASSIGN_SYMBOL, JUMP, STOP);
 703        reduce (p, NO_NOTE, NO_TICK, ASSIGNATION, TERTIARY, ASSIGN_SYMBOL, SKIP, STOP);
 704        reduce (p, NO_NOTE, NO_TICK, ASSIGNATION, TERTIARY, ASSIGN_SYMBOL, ASSIGNATION, STOP);
 705        reduce (p, NO_NOTE, NO_TICK, ASSIGNATION, TERTIARY, ASSIGN_SYMBOL, CODE_CLAUSE, STOP);
 706      }
 707  // Routine texts with parameter pack.
 708      else if (IS (p, PARAMETER_PACK)) {
 709        reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, PARAMETER_PACK, DECLARER, COLON_SYMBOL, ASSIGNATION, STOP);
 710        reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, PARAMETER_PACK, DECLARER, COLON_SYMBOL, IDENTITY_RELATION, STOP);
 711        reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, PARAMETER_PACK, DECLARER, COLON_SYMBOL, AND_FUNCTION, STOP);
 712        reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, PARAMETER_PACK, DECLARER, COLON_SYMBOL, OR_FUNCTION, STOP);
 713        reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, PARAMETER_PACK, DECLARER, COLON_SYMBOL, JUMP, STOP);
 714        reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, PARAMETER_PACK, DECLARER, COLON_SYMBOL, SKIP, STOP);
 715        reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, PARAMETER_PACK, DECLARER, COLON_SYMBOL, TERTIARY, STOP);
 716        reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, PARAMETER_PACK, DECLARER, COLON_SYMBOL, ROUTINE_TEXT, STOP);
 717        reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, PARAMETER_PACK, DECLARER, COLON_SYMBOL, CODE_CLAUSE, STOP);
 718        reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, PARAMETER_PACK, VOID_SYMBOL, COLON_SYMBOL, ASSIGNATION, STOP);
 719        reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, PARAMETER_PACK, VOID_SYMBOL, COLON_SYMBOL, IDENTITY_RELATION, STOP);
 720        reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, PARAMETER_PACK, VOID_SYMBOL, COLON_SYMBOL, AND_FUNCTION, STOP);
 721        reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, PARAMETER_PACK, VOID_SYMBOL, COLON_SYMBOL, OR_FUNCTION, STOP);
 722        reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, PARAMETER_PACK, VOID_SYMBOL, COLON_SYMBOL, JUMP, STOP);
 723        reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, PARAMETER_PACK, VOID_SYMBOL, COLON_SYMBOL, SKIP, STOP);
 724        reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, PARAMETER_PACK, VOID_SYMBOL, COLON_SYMBOL, TERTIARY, STOP);
 725        reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, PARAMETER_PACK, VOID_SYMBOL, COLON_SYMBOL, ROUTINE_TEXT, STOP);
 726        reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, PARAMETER_PACK, VOID_SYMBOL, COLON_SYMBOL, CODE_CLAUSE, STOP);
 727      }
 728  // Routine texts without parameter pack.
 729      else if (IS (p, DECLARER)) {
 730        if (!(PREVIOUS (p) != NO_NODE && IS (PREVIOUS (p), PARAMETER_PACK))) {
 731          reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, DECLARER, COLON_SYMBOL, ASSIGNATION, STOP);
 732          reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, DECLARER, COLON_SYMBOL, IDENTITY_RELATION, STOP);
 733          reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, DECLARER, COLON_SYMBOL, AND_FUNCTION, STOP);
 734          reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, DECLARER, COLON_SYMBOL, OR_FUNCTION, STOP);
 735          reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, DECLARER, COLON_SYMBOL, JUMP, STOP);
 736          reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, DECLARER, COLON_SYMBOL, SKIP, STOP);
 737          reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, DECLARER, COLON_SYMBOL, TERTIARY, STOP);
 738          reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, DECLARER, COLON_SYMBOL, ROUTINE_TEXT, STOP);
 739          reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, DECLARER, COLON_SYMBOL, CODE_CLAUSE, STOP);
 740        }
 741      } else if (IS (p, VOID_SYMBOL)) {
 742        if (!(PREVIOUS (p) != NO_NODE && IS (PREVIOUS (p), PARAMETER_PACK))) {
 743          reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, VOID_SYMBOL, COLON_SYMBOL, ASSIGNATION, STOP);
 744          reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, VOID_SYMBOL, COLON_SYMBOL, IDENTITY_RELATION, STOP);
 745          reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, VOID_SYMBOL, COLON_SYMBOL, AND_FUNCTION, STOP);
 746          reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, VOID_SYMBOL, COLON_SYMBOL, OR_FUNCTION, STOP);
 747          reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, VOID_SYMBOL, COLON_SYMBOL, JUMP, STOP);
 748          reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, VOID_SYMBOL, COLON_SYMBOL, SKIP, STOP);
 749          reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, VOID_SYMBOL, COLON_SYMBOL, TERTIARY, STOP);
 750          reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, VOID_SYMBOL, COLON_SYMBOL, ROUTINE_TEXT, STOP);
 751          reduce (p, NO_NOTE, NO_TICK, ROUTINE_TEXT, VOID_SYMBOL, COLON_SYMBOL, CODE_CLAUSE, STOP);
 752        }
 753      }
 754    }
 755  }
 756  
 757  //! @brief Reduce primary elements.
 758  
 759  void reduce_primary_parts (NODE_T * p, int expect)
 760  {
 761    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
 762      if (whether (q, IDENTIFIER, OF_SYMBOL, STOP)) {
 763        ATTRIBUTE (q) = FIELD_IDENTIFIER;
 764      }
 765      reduce (q, NO_NOTE, NO_TICK, ENVIRON_NAME, ENVIRON_SYMBOL, ROW_CHAR_DENOTATION, STOP);
 766      reduce (q, NO_NOTE, NO_TICK, NIHIL, NIL_SYMBOL, STOP);
 767      reduce (q, NO_NOTE, NO_TICK, SKIP, SKIP_SYMBOL, STOP);
 768      reduce (q, NO_NOTE, NO_TICK, SELECTOR, FIELD_IDENTIFIER, OF_SYMBOL, STOP);
 769  // JUMPs without GOTO are resolved later.
 770      reduce (q, NO_NOTE, NO_TICK, JUMP, GOTO_SYMBOL, IDENTIFIER, STOP);
 771      reduce (q, NO_NOTE, NO_TICK, DENOTATION, LONGETY, INT_DENOTATION, STOP);
 772      reduce (q, NO_NOTE, NO_TICK, DENOTATION, LONGETY, REAL_DENOTATION, STOP);
 773      reduce (q, NO_NOTE, NO_TICK, DENOTATION, LONGETY, BITS_DENOTATION, STOP);
 774      reduce (q, NO_NOTE, NO_TICK, DENOTATION, SHORTETY, INT_DENOTATION, STOP);
 775      reduce (q, NO_NOTE, NO_TICK, DENOTATION, SHORTETY, REAL_DENOTATION, STOP);
 776      reduce (q, NO_NOTE, NO_TICK, DENOTATION, SHORTETY, BITS_DENOTATION, STOP);
 777      reduce (q, NO_NOTE, NO_TICK, DENOTATION, INT_DENOTATION, STOP);
 778      reduce (q, NO_NOTE, NO_TICK, DENOTATION, REAL_DENOTATION, STOP);
 779      reduce (q, NO_NOTE, NO_TICK, DENOTATION, BITS_DENOTATION, STOP);
 780      reduce (q, NO_NOTE, NO_TICK, DENOTATION, ROW_CHAR_DENOTATION, STOP);
 781      reduce (q, NO_NOTE, NO_TICK, DENOTATION, TRUE_SYMBOL, STOP);
 782      reduce (q, NO_NOTE, NO_TICK, DENOTATION, FALSE_SYMBOL, STOP);
 783      reduce (q, NO_NOTE, NO_TICK, DENOTATION, EMPTY_SYMBOL, STOP);
 784      if (expect == SERIAL_CLAUSE || expect == ENQUIRY_CLAUSE || expect == SOME_CLAUSE) {
 785        BOOL_T siga = A68_TRUE;
 786        while (siga) {
 787          siga = A68_FALSE;
 788          reduce (q, NO_NOTE, &siga, LABEL, DEFINING_IDENTIFIER, COLON_SYMBOL, STOP);
 789          reduce (q, NO_NOTE, &siga, LABEL, LABEL, DEFINING_IDENTIFIER, COLON_SYMBOL, STOP);
 790        }
 791      }
 792    }
 793    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
 794  #if defined (BUILD_PARALLEL_CLAUSE)
 795      reduce (q, NO_NOTE, NO_TICK, PARALLEL_CLAUSE, PAR_SYMBOL, COLLATERAL_CLAUSE, STOP);
 796  #else
 797      reduce (q, par_clause, NO_TICK, PARALLEL_CLAUSE, PAR_SYMBOL, COLLATERAL_CLAUSE, STOP);
 798  #endif
 799      reduce (q, NO_NOTE, NO_TICK, ENCLOSED_CLAUSE, PARALLEL_CLAUSE, STOP);
 800      reduce (q, NO_NOTE, NO_TICK, ENCLOSED_CLAUSE, CLOSED_CLAUSE, STOP);
 801      reduce (q, NO_NOTE, NO_TICK, ENCLOSED_CLAUSE, COLLATERAL_CLAUSE, STOP);
 802      reduce (q, NO_NOTE, NO_TICK, ENCLOSED_CLAUSE, CONDITIONAL_CLAUSE, STOP);
 803      reduce (q, NO_NOTE, NO_TICK, ENCLOSED_CLAUSE, CASE_CLAUSE, STOP);
 804      reduce (q, NO_NOTE, NO_TICK, ENCLOSED_CLAUSE, CONFORMITY_CLAUSE, STOP);
 805      reduce (q, NO_NOTE, NO_TICK, ENCLOSED_CLAUSE, LOOP_CLAUSE, STOP);
 806    }
 807  }
 808  
 809  //! @brief Reduce primaries completely.
 810  
 811  void reduce_primaries (NODE_T * p, int expect)
 812  {
 813    NODE_T *q = p;
 814    while (q != NO_NODE) {
 815      BOOL_T fwd = A68_TRUE, siga;
 816  // Primaries excepts call and slice.
 817      reduce (q, NO_NOTE, NO_TICK, PRIMARY, IDENTIFIER, STOP);
 818      reduce (q, NO_NOTE, NO_TICK, PRIMARY, DENOTATION, STOP);
 819      reduce (q, NO_NOTE, NO_TICK, CAST, DECLARER, ENCLOSED_CLAUSE, STOP);
 820      reduce (q, NO_NOTE, NO_TICK, CAST, VOID_SYMBOL, ENCLOSED_CLAUSE, STOP);
 821      reduce (q, NO_NOTE, NO_TICK, ASSERTION, ASSERT_SYMBOL, ENCLOSED_CLAUSE, STOP);
 822      reduce (q, NO_NOTE, NO_TICK, PRIMARY, CAST, STOP);
 823      reduce (q, NO_NOTE, NO_TICK, PRIMARY, ENCLOSED_CLAUSE, STOP);
 824      reduce (q, NO_NOTE, NO_TICK, PRIMARY, FORMAT_TEXT, STOP);
 825  // Call and slice.
 826      siga = A68_TRUE;
 827      while (siga) {
 828        NODE_T *x = NEXT (q);
 829        siga = A68_FALSE;
 830        if (IS (q, PRIMARY) && x != NO_NODE) {
 831          if (IS (x, OPEN_SYMBOL)) {
 832            reduce_branch (NEXT (q), GENERIC_ARGUMENT);
 833            reduce (q, NO_NOTE, &siga, SPECIFICATION, PRIMARY, GENERIC_ARGUMENT, STOP);
 834            reduce (q, NO_NOTE, &siga, PRIMARY, SPECIFICATION, STOP);
 835          } else if (IS (x, SUB_SYMBOL)) {
 836            reduce_branch (NEXT (q), GENERIC_ARGUMENT);
 837            reduce (q, NO_NOTE, &siga, SPECIFICATION, PRIMARY, GENERIC_ARGUMENT, STOP);
 838            reduce (q, NO_NOTE, &siga, PRIMARY, SPECIFICATION, STOP);
 839          }
 840        }
 841      }
 842  // Now that call and slice are known, reduce remaining ( .. ).
 843      if (IS (q, OPEN_SYMBOL) && SUB (q) != NO_NODE) {
 844        reduce_branch (q, SOME_CLAUSE);
 845        reduce (q, NO_NOTE, NO_TICK, ENCLOSED_CLAUSE, CLOSED_CLAUSE, STOP);
 846        reduce (q, NO_NOTE, NO_TICK, ENCLOSED_CLAUSE, COLLATERAL_CLAUSE, STOP);
 847        reduce (q, NO_NOTE, NO_TICK, ENCLOSED_CLAUSE, CONDITIONAL_CLAUSE, STOP);
 848        reduce (q, NO_NOTE, NO_TICK, ENCLOSED_CLAUSE, CASE_CLAUSE, STOP);
 849        reduce (q, NO_NOTE, NO_TICK, ENCLOSED_CLAUSE, CONFORMITY_CLAUSE, STOP);
 850        if (PREVIOUS (q) != NO_NODE) {
 851          BACKWARD (q);
 852          fwd = A68_FALSE;
 853        }
 854      }
 855  // Format text items.
 856      if (expect == FORMAT_TEXT) {
 857        NODE_T *r;
 858        for (r = p; r != NO_NODE; FORWARD (r)) {
 859          reduce (r, NO_NOTE, NO_TICK, DYNAMIC_REPLICATOR, FORMAT_ITEM_N, ENCLOSED_CLAUSE, STOP);
 860          reduce (r, NO_NOTE, NO_TICK, GENERAL_PATTERN, FORMAT_ITEM_G, ENCLOSED_CLAUSE, STOP);
 861          reduce (r, NO_NOTE, NO_TICK, GENERAL_PATTERN, FORMAT_ITEM_H, ENCLOSED_CLAUSE, STOP);
 862          reduce (r, NO_NOTE, NO_TICK, FORMAT_PATTERN, FORMAT_ITEM_F, ENCLOSED_CLAUSE, STOP);
 863        }
 864      }
 865      if (fwd) {
 866        FORWARD (q);
 867      }
 868    }
 869  }
 870  
 871  //! @brief Enforce that ambiguous patterns are separated by commas.
 872  
 873  void ambiguous_patterns (NODE_T * p)
 874  {
 875  // Example: printf (($+d.2d +d.2d$, 1, 2)) can produce either "+1.00 +2.00" or
 876  // "+1+002.00". A comma must be supplied to resolve the ambiguity.
 877  // 
 878  // The obvious thing would be to weave this into the syntax, letting the BU parser
 879  // sort it out. But the C-style patterns do not suffer from Algol 68 pattern
 880  // ambiguity, so by solving it this way we maximise freedom in writing the patterns
 881  // as we want without introducing two "kinds" of patterns, and so we have shorter
 882  // routines for implementing formatted transput. This is a pragmatic system.
 883    NODE_T *q, *last_pat = NO_NODE;
 884    for (q = p; q != NO_NODE; FORWARD (q)) {
 885      switch (ATTRIBUTE (q)) {
 886      case INTEGRAL_PATTERN:     // These are the potentially ambiguous patterns
 887      case REAL_PATTERN:
 888      case COMPLEX_PATTERN:
 889      case BITS_PATTERN: {
 890          if (last_pat != NO_NODE) {
 891            diagnostic (A68_SYNTAX_ERROR, q, ERROR_COMMA_MUST_SEPARATE, ATTRIBUTE (last_pat), ATTRIBUTE (q));
 892          }
 893          last_pat = q;
 894          break;
 895        }
 896      case COMMA_SYMBOL: {
 897          last_pat = NO_NODE;
 898          break;
 899        }
 900      }
 901    }
 902  }
 903  
 904  //! @brief Reduce format texts completely.
 905  
 906  void reduce_c_pattern (NODE_T * p, int pr, int let)
 907  {
 908    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
 909      reduce (q, NO_NOTE, NO_TICK, pr, FORMAT_ITEM_ESCAPE, let, STOP);
 910      reduce (q, NO_NOTE, NO_TICK, pr, FORMAT_ITEM_ESCAPE, FORMAT_ITEM_POINT, REPLICATOR, let, STOP);
 911      reduce (q, NO_NOTE, NO_TICK, pr, FORMAT_ITEM_ESCAPE, REPLICATOR, let, STOP);
 912      reduce (q, NO_NOTE, NO_TICK, pr, FORMAT_ITEM_ESCAPE, REPLICATOR, FORMAT_ITEM_POINT, REPLICATOR, let, STOP);
 913      reduce (q, NO_NOTE, NO_TICK, pr, FORMAT_ITEM_ESCAPE, FORMAT_ITEM_PLUS, let, STOP);
 914      reduce (q, NO_NOTE, NO_TICK, pr, FORMAT_ITEM_ESCAPE, FORMAT_ITEM_PLUS, FORMAT_ITEM_POINT, REPLICATOR, let, STOP);
 915      reduce (q, NO_NOTE, NO_TICK, pr, FORMAT_ITEM_ESCAPE, FORMAT_ITEM_PLUS, REPLICATOR, let, STOP);
 916      reduce (q, NO_NOTE, NO_TICK, pr, FORMAT_ITEM_ESCAPE, FORMAT_ITEM_PLUS, REPLICATOR, FORMAT_ITEM_POINT, REPLICATOR, let, STOP);
 917      reduce (q, NO_NOTE, NO_TICK, pr, FORMAT_ITEM_ESCAPE, FORMAT_ITEM_MINUS, let, STOP);
 918      reduce (q, NO_NOTE, NO_TICK, pr, FORMAT_ITEM_ESCAPE, FORMAT_ITEM_MINUS, FORMAT_ITEM_POINT, REPLICATOR, let, STOP);
 919      reduce (q, NO_NOTE, NO_TICK, pr, FORMAT_ITEM_ESCAPE, FORMAT_ITEM_MINUS, REPLICATOR, let, STOP);
 920      reduce (q, NO_NOTE, NO_TICK, pr, FORMAT_ITEM_ESCAPE, FORMAT_ITEM_MINUS, REPLICATOR, FORMAT_ITEM_POINT, REPLICATOR, let, STOP);
 921      reduce (q, NO_NOTE, NO_TICK, pr, FORMAT_ITEM_ESCAPE, FORMAT_ITEM_MINUS, FORMAT_ITEM_PLUS, let, STOP);
 922      reduce (q, NO_NOTE, NO_TICK, pr, FORMAT_ITEM_ESCAPE, FORMAT_ITEM_MINUS, FORMAT_ITEM_PLUS, FORMAT_ITEM_POINT, REPLICATOR, let, STOP);
 923      reduce (q, NO_NOTE, NO_TICK, pr, FORMAT_ITEM_ESCAPE, FORMAT_ITEM_MINUS, FORMAT_ITEM_PLUS, REPLICATOR, let, STOP);
 924      reduce (q, NO_NOTE, NO_TICK, pr, FORMAT_ITEM_ESCAPE, FORMAT_ITEM_MINUS, FORMAT_ITEM_PLUS, REPLICATOR, FORMAT_ITEM_POINT, REPLICATOR, let, STOP);
 925    }
 926  }
 927  
 928  //! @brief Reduce format texts completely.
 929  
 930  void reduce_format_texts (NODE_T * p)
 931  {
 932  // Replicators.
 933    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
 934      reduce (q, NO_NOTE, NO_TICK, REPLICATOR, STATIC_REPLICATOR, STOP);
 935      reduce (q, NO_NOTE, NO_TICK, REPLICATOR, DYNAMIC_REPLICATOR, STOP);
 936    }
 937  // "OTHER" patterns.
 938    reduce_c_pattern (p, BITS_C_PATTERN, FORMAT_ITEM_B);
 939    reduce_c_pattern (p, BITS_C_PATTERN, FORMAT_ITEM_O);
 940    reduce_c_pattern (p, BITS_C_PATTERN, FORMAT_ITEM_X);
 941    reduce_c_pattern (p, CHAR_C_PATTERN, FORMAT_ITEM_C);
 942    reduce_c_pattern (p, FIXED_C_PATTERN, FORMAT_ITEM_F);
 943    reduce_c_pattern (p, FLOAT_C_PATTERN, FORMAT_ITEM_E);
 944    reduce_c_pattern (p, GENERAL_C_PATTERN, FORMAT_ITEM_G);
 945    reduce_c_pattern (p, INTEGRAL_C_PATTERN, FORMAT_ITEM_D);
 946    reduce_c_pattern (p, INTEGRAL_C_PATTERN, FORMAT_ITEM_I);
 947    reduce_c_pattern (p, STRING_C_PATTERN, FORMAT_ITEM_S);
 948  // Radix frames.
 949    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
 950      reduce (q, NO_NOTE, NO_TICK, RADIX_FRAME, REPLICATOR, FORMAT_ITEM_R, STOP);
 951    }
 952  // Insertions.
 953    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
 954      reduce (q, NO_NOTE, NO_TICK, INSERTION, FORMAT_ITEM_X, STOP);
 955      reduce (q, NO_NOTE, NO_TICK, INSERTION, FORMAT_ITEM_Y, STOP);
 956      reduce (q, NO_NOTE, NO_TICK, INSERTION, FORMAT_ITEM_L, STOP);
 957      reduce (q, NO_NOTE, NO_TICK, INSERTION, FORMAT_ITEM_P, STOP);
 958      reduce (q, NO_NOTE, NO_TICK, INSERTION, FORMAT_ITEM_Q, STOP);
 959      reduce (q, NO_NOTE, NO_TICK, INSERTION, FORMAT_ITEM_K, STOP);
 960      reduce (q, NO_NOTE, NO_TICK, INSERTION, LITERAL, STOP);
 961    }
 962    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
 963      reduce (q, NO_NOTE, NO_TICK, INSERTION, REPLICATOR, INSERTION, STOP);
 964    }
 965    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
 966      BOOL_T siga = A68_TRUE;
 967      while (siga) {
 968        siga = A68_FALSE;
 969        reduce (q, NO_NOTE, &siga, INSERTION, INSERTION, INSERTION, STOP);
 970      }
 971    }
 972  // Replicated suppressible frames.
 973    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
 974      reduce (q, NO_NOTE, NO_TICK, FORMAT_A_FRAME, REPLICATOR, FORMAT_ITEM_S, FORMAT_ITEM_A, STOP);
 975      reduce (q, NO_NOTE, NO_TICK, FORMAT_Z_FRAME, REPLICATOR, FORMAT_ITEM_S, FORMAT_ITEM_Z, STOP);
 976      reduce (q, NO_NOTE, NO_TICK, FORMAT_D_FRAME, REPLICATOR, FORMAT_ITEM_S, FORMAT_ITEM_D, STOP);
 977    }
 978  // Suppressible frames.
 979    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
 980      reduce (q, NO_NOTE, NO_TICK, FORMAT_A_FRAME, FORMAT_ITEM_S, FORMAT_ITEM_A, STOP);
 981      reduce (q, NO_NOTE, NO_TICK, FORMAT_Z_FRAME, FORMAT_ITEM_S, FORMAT_ITEM_Z, STOP);
 982      reduce (q, NO_NOTE, NO_TICK, FORMAT_D_FRAME, FORMAT_ITEM_S, FORMAT_ITEM_D, STOP);
 983      reduce (q, NO_NOTE, NO_TICK, FORMAT_E_FRAME, FORMAT_ITEM_S, FORMAT_ITEM_E, STOP);
 984      reduce (q, NO_NOTE, NO_TICK, FORMAT_POINT_FRAME, FORMAT_ITEM_S, FORMAT_ITEM_POINT, STOP);
 985      reduce (q, NO_NOTE, NO_TICK, FORMAT_I_FRAME, FORMAT_ITEM_S, FORMAT_ITEM_I, STOP);
 986    }
 987  // Replicated frames.
 988    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
 989      reduce (q, NO_NOTE, NO_TICK, FORMAT_A_FRAME, REPLICATOR, FORMAT_ITEM_A, STOP);
 990      reduce (q, NO_NOTE, NO_TICK, FORMAT_Z_FRAME, REPLICATOR, FORMAT_ITEM_Z, STOP);
 991      reduce (q, NO_NOTE, NO_TICK, FORMAT_D_FRAME, REPLICATOR, FORMAT_ITEM_D, STOP);
 992    }
 993  // Frames.
 994    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
 995      reduce (q, NO_NOTE, NO_TICK, FORMAT_A_FRAME, FORMAT_ITEM_A, STOP);
 996      reduce (q, NO_NOTE, NO_TICK, FORMAT_Z_FRAME, FORMAT_ITEM_Z, STOP);
 997      reduce (q, NO_NOTE, NO_TICK, FORMAT_D_FRAME, FORMAT_ITEM_D, STOP);
 998      reduce (q, NO_NOTE, NO_TICK, FORMAT_E_FRAME, FORMAT_ITEM_E, STOP);
 999      reduce (q, NO_NOTE, NO_TICK, FORMAT_POINT_FRAME, FORMAT_ITEM_POINT, STOP);
1000      reduce (q, NO_NOTE, NO_TICK, FORMAT_I_FRAME, FORMAT_ITEM_I, STOP);
1001    }
1002  // Frames with an insertion.
1003    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1004      reduce (q, NO_NOTE, NO_TICK, FORMAT_A_FRAME, INSERTION, FORMAT_A_FRAME, STOP);
1005      reduce (q, NO_NOTE, NO_TICK, FORMAT_Z_FRAME, INSERTION, FORMAT_Z_FRAME, STOP);
1006      reduce (q, NO_NOTE, NO_TICK, FORMAT_D_FRAME, INSERTION, FORMAT_D_FRAME, STOP);
1007      reduce (q, NO_NOTE, NO_TICK, FORMAT_E_FRAME, INSERTION, FORMAT_E_FRAME, STOP);
1008      reduce (q, NO_NOTE, NO_TICK, FORMAT_POINT_FRAME, INSERTION, FORMAT_POINT_FRAME, STOP);
1009      reduce (q, NO_NOTE, NO_TICK, FORMAT_I_FRAME, INSERTION, FORMAT_I_FRAME, STOP);
1010    }
1011  // String patterns.
1012    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1013      reduce (q, NO_NOTE, NO_TICK, STRING_PATTERN, REPLICATOR, FORMAT_A_FRAME, STOP);
1014    }
1015    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1016      reduce (q, NO_NOTE, NO_TICK, STRING_PATTERN, FORMAT_A_FRAME, STOP);
1017    }
1018    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1019      BOOL_T siga = A68_TRUE;
1020      while (siga) {
1021        siga = A68_FALSE;
1022        reduce (q, NO_NOTE, &siga, STRING_PATTERN, STRING_PATTERN, STRING_PATTERN, STOP);
1023        reduce (q, NO_NOTE, &siga, STRING_PATTERN, STRING_PATTERN, INSERTION, STRING_PATTERN, STOP);
1024      }
1025    }
1026  // Integral moulds.
1027    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1028      reduce (q, NO_NOTE, NO_TICK, INTEGRAL_MOULD, FORMAT_Z_FRAME, STOP);
1029      reduce (q, NO_NOTE, NO_TICK, INTEGRAL_MOULD, FORMAT_D_FRAME, STOP);
1030    }
1031    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1032      BOOL_T siga = A68_TRUE;
1033      while (siga) {
1034        siga = A68_FALSE;
1035        reduce (q, NO_NOTE, &siga, INTEGRAL_MOULD, INTEGRAL_MOULD, INTEGRAL_MOULD, STOP);
1036        reduce (q, NO_NOTE, &siga, INTEGRAL_MOULD, INTEGRAL_MOULD, INSERTION, STOP);
1037      }
1038    }
1039  // Sign moulds.
1040    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1041      reduce (q, NO_NOTE, NO_TICK, SIGN_MOULD, INTEGRAL_MOULD, FORMAT_ITEM_PLUS, STOP);
1042      reduce (q, NO_NOTE, NO_TICK, SIGN_MOULD, INTEGRAL_MOULD, FORMAT_ITEM_MINUS, STOP);
1043    }
1044    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1045      reduce (q, NO_NOTE, NO_TICK, SIGN_MOULD, FORMAT_ITEM_PLUS, STOP);
1046      reduce (q, NO_NOTE, NO_TICK, SIGN_MOULD, FORMAT_ITEM_MINUS, STOP);
1047    }
1048  // Exponent frames.
1049    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1050      reduce (q, NO_NOTE, NO_TICK, EXPONENT_FRAME, FORMAT_E_FRAME, SIGN_MOULD, INTEGRAL_MOULD, STOP);
1051      reduce (q, NO_NOTE, NO_TICK, EXPONENT_FRAME, FORMAT_E_FRAME, INTEGRAL_MOULD, STOP);
1052    }
1053  // Real patterns.
1054    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1055      reduce (q, NO_NOTE, NO_TICK, REAL_PATTERN, SIGN_MOULD, INTEGRAL_MOULD, FORMAT_POINT_FRAME, INTEGRAL_MOULD, EXPONENT_FRAME, STOP);
1056      reduce (q, NO_NOTE, NO_TICK, REAL_PATTERN, SIGN_MOULD, INTEGRAL_MOULD, FORMAT_POINT_FRAME, INTEGRAL_MOULD, STOP);
1057      reduce (q, NO_NOTE, NO_TICK, REAL_PATTERN, SIGN_MOULD, INTEGRAL_MOULD, FORMAT_POINT_FRAME, EXPONENT_FRAME, STOP);
1058      reduce (q, NO_NOTE, NO_TICK, REAL_PATTERN, SIGN_MOULD, INTEGRAL_MOULD, FORMAT_POINT_FRAME, STOP);
1059    }
1060    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1061      reduce (q, NO_NOTE, NO_TICK, REAL_PATTERN, SIGN_MOULD, FORMAT_POINT_FRAME, INTEGRAL_MOULD, EXPONENT_FRAME, STOP);
1062      reduce (q, NO_NOTE, NO_TICK, REAL_PATTERN, SIGN_MOULD, FORMAT_POINT_FRAME, INTEGRAL_MOULD, STOP);
1063      reduce (q, NO_NOTE, NO_TICK, REAL_PATTERN, SIGN_MOULD, FORMAT_POINT_FRAME, EXPONENT_FRAME, STOP);
1064      reduce (q, NO_NOTE, NO_TICK, REAL_PATTERN, SIGN_MOULD, FORMAT_POINT_FRAME, STOP);
1065    }
1066    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1067      reduce (q, NO_NOTE, NO_TICK, REAL_PATTERN, INTEGRAL_MOULD, FORMAT_POINT_FRAME, INTEGRAL_MOULD, EXPONENT_FRAME, STOP);
1068      reduce (q, NO_NOTE, NO_TICK, REAL_PATTERN, INTEGRAL_MOULD, FORMAT_POINT_FRAME, INTEGRAL_MOULD, STOP);
1069      reduce (q, NO_NOTE, NO_TICK, REAL_PATTERN, INTEGRAL_MOULD, FORMAT_POINT_FRAME, EXPONENT_FRAME, STOP);
1070      reduce (q, NO_NOTE, NO_TICK, REAL_PATTERN, INTEGRAL_MOULD, FORMAT_POINT_FRAME, STOP);
1071      reduce (q, NO_NOTE, NO_TICK, REAL_PATTERN, FORMAT_POINT_FRAME, INTEGRAL_MOULD, EXPONENT_FRAME, STOP);
1072      reduce (q, NO_NOTE, NO_TICK, REAL_PATTERN, FORMAT_POINT_FRAME, INTEGRAL_MOULD, STOP);
1073    }
1074    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1075      reduce (q, NO_NOTE, NO_TICK, REAL_PATTERN, SIGN_MOULD, INTEGRAL_MOULD, EXPONENT_FRAME, STOP);
1076      reduce (q, NO_NOTE, NO_TICK, REAL_PATTERN, INTEGRAL_MOULD, EXPONENT_FRAME, STOP);
1077    }
1078  // Complex patterns.
1079    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1080      reduce (q, NO_NOTE, NO_TICK, COMPLEX_PATTERN, REAL_PATTERN, FORMAT_I_FRAME, REAL_PATTERN, STOP);
1081    }
1082  // Bits patterns.
1083    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1084      reduce (q, NO_NOTE, NO_TICK, BITS_PATTERN, RADIX_FRAME, INTEGRAL_MOULD, STOP);
1085    }
1086  // Integral patterns.
1087    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1088      reduce (q, NO_NOTE, NO_TICK, INTEGRAL_PATTERN, SIGN_MOULD, INTEGRAL_MOULD, STOP);
1089      reduce (q, NO_NOTE, NO_TICK, INTEGRAL_PATTERN, INTEGRAL_MOULD, STOP);
1090    }
1091  // Patterns.
1092    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1093      reduce (q, NO_NOTE, NO_TICK, BOOLEAN_PATTERN, FORMAT_ITEM_B, COLLECTION, STOP);
1094      reduce (q, NO_NOTE, NO_TICK, CHOICE_PATTERN, FORMAT_ITEM_C, COLLECTION, STOP);
1095    }
1096    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1097      reduce (q, NO_NOTE, NO_TICK, BOOLEAN_PATTERN, FORMAT_ITEM_B, STOP);
1098      reduce (q, NO_NOTE, NO_TICK, GENERAL_PATTERN, FORMAT_ITEM_G, STOP);
1099      reduce (q, NO_NOTE, NO_TICK, GENERAL_PATTERN, FORMAT_ITEM_H, STOP);
1100    }
1101    ambiguous_patterns (p);
1102    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1103      reduce (q, a68_extension, NO_TICK, A68_PATTERN, BITS_C_PATTERN, STOP);
1104      reduce (q, a68_extension, NO_TICK, A68_PATTERN, CHAR_C_PATTERN, STOP);
1105      reduce (q, a68_extension, NO_TICK, A68_PATTERN, FIXED_C_PATTERN, STOP);
1106      reduce (q, a68_extension, NO_TICK, A68_PATTERN, FLOAT_C_PATTERN, STOP);
1107      reduce (q, a68_extension, NO_TICK, A68_PATTERN, GENERAL_C_PATTERN, STOP);
1108      reduce (q, a68_extension, NO_TICK, A68_PATTERN, INTEGRAL_C_PATTERN, STOP);
1109      reduce (q, a68_extension, NO_TICK, A68_PATTERN, STRING_C_PATTERN, STOP);
1110      reduce (q, NO_NOTE, NO_TICK, A68_PATTERN, BITS_PATTERN, STOP);
1111      reduce (q, NO_NOTE, NO_TICK, A68_PATTERN, BOOLEAN_PATTERN, STOP);
1112      reduce (q, NO_NOTE, NO_TICK, A68_PATTERN, CHOICE_PATTERN, STOP);
1113      reduce (q, NO_NOTE, NO_TICK, A68_PATTERN, COMPLEX_PATTERN, STOP);
1114      reduce (q, NO_NOTE, NO_TICK, A68_PATTERN, FORMAT_PATTERN, STOP);
1115      reduce (q, NO_NOTE, NO_TICK, A68_PATTERN, GENERAL_PATTERN, STOP);
1116      reduce (q, NO_NOTE, NO_TICK, A68_PATTERN, INTEGRAL_PATTERN, STOP);
1117      reduce (q, NO_NOTE, NO_TICK, A68_PATTERN, REAL_PATTERN, STOP);
1118      reduce (q, NO_NOTE, NO_TICK, A68_PATTERN, STRING_PATTERN, STOP);
1119    }
1120  // Pictures.
1121    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1122      reduce (q, NO_NOTE, NO_TICK, PICTURE, INSERTION, STOP);
1123      reduce (q, NO_NOTE, NO_TICK, PICTURE, A68_PATTERN, STOP);
1124      reduce (q, NO_NOTE, NO_TICK, PICTURE, COLLECTION, STOP);
1125      reduce (q, NO_NOTE, NO_TICK, PICTURE, REPLICATOR, COLLECTION, STOP);
1126    }
1127  // Picture lists.
1128    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1129      if (IS (q, PICTURE)) {
1130        BOOL_T siga = A68_TRUE;
1131        reduce (q, NO_NOTE, NO_TICK, PICTURE_LIST, PICTURE, STOP);
1132        while (siga) {
1133          siga = A68_FALSE;
1134          reduce (q, NO_NOTE, &siga, PICTURE_LIST, PICTURE_LIST, COMMA_SYMBOL, PICTURE, STOP);
1135  // We filtered ambiguous patterns, so commas may be omitted 
1136          reduce (q, NO_NOTE, &siga, PICTURE_LIST, PICTURE_LIST, PICTURE, STOP);
1137        }
1138      }
1139    }
1140  }
1141  
1142  //! @brief Reduce secondaries completely.
1143  
1144  void reduce_secondaries (NODE_T * p)
1145  {
1146    NODE_T *q; BOOL_T siga;
1147    for (q = p; q != NO_NODE; FORWARD (q)) {
1148      reduce (q, NO_NOTE, NO_TICK, SECONDARY, PRIMARY, STOP);
1149      reduce (q, NO_NOTE, NO_TICK, GENERATOR, LOC_SYMBOL, DECLARER, STOP);
1150      reduce (q, NO_NOTE, NO_TICK, GENERATOR, HEAP_SYMBOL, DECLARER, STOP);
1151      reduce (q, NO_NOTE, NO_TICK, GENERATOR, NEW_SYMBOL, DECLARER, STOP);
1152      reduce (q, NO_NOTE, NO_TICK, SECONDARY, GENERATOR, STOP);
1153    }
1154    siga = A68_TRUE;
1155    while (siga) {
1156      siga = A68_FALSE;
1157      for (q = p; NEXT (q) != NO_NODE; FORWARD (q)) {
1158        ;
1159      }
1160      for (; q != NO_NODE; BACKWARD (q)) {
1161        reduce (q, NO_NOTE, &siga, SELECTION, SELECTOR, SECONDARY, STOP);
1162        reduce (q, NO_NOTE, &siga, SECONDARY, SELECTION, STOP);
1163      }
1164    }
1165  }
1166  
1167  //! @brief Whether "q" is an operator with priority "k".
1168  
1169  int operator_with_priority (NODE_T * q, int k)
1170  {
1171    return NEXT (q) != NO_NODE && ATTRIBUTE (NEXT (q)) == OPERATOR && PRIO (INFO (NEXT (q))) == k;
1172  }
1173  
1174  //! @brief Reduce formulae.
1175  
1176  void reduce_formulae (NODE_T * p)
1177  {
1178    NODE_T *q = p;
1179    while (q != NO_NODE) {
1180      if (is_one_of (q, OPERATOR, SECONDARY, STOP)) {
1181        q = reduce_dyadic (q, STOP);
1182      } else {
1183        FORWARD (q);
1184      }
1185    }
1186  // Reduce the expression.
1187    for (int prio = MAX_PRIORITY; prio >= 0; prio--) {
1188      for (q = p; q != NO_NODE; FORWARD (q)) {
1189        if (operator_with_priority (q, prio)) {
1190          BOOL_T siga = A68_FALSE;
1191          NODE_T *op = NEXT (q);
1192          if (IS (q, SECONDARY)) {
1193            reduce (q, NO_NOTE, &siga, FORMULA, SECONDARY, OPERATOR, SECONDARY, STOP);
1194            reduce (q, NO_NOTE, &siga, FORMULA, SECONDARY, OPERATOR, MONADIC_FORMULA, STOP);
1195            reduce (q, NO_NOTE, &siga, FORMULA, SECONDARY, OPERATOR, FORMULA, STOP);
1196          } else if (IS (q, MONADIC_FORMULA)) {
1197            reduce (q, NO_NOTE, &siga, FORMULA, MONADIC_FORMULA, OPERATOR, SECONDARY, STOP);
1198            reduce (q, NO_NOTE, &siga, FORMULA, MONADIC_FORMULA, OPERATOR, MONADIC_FORMULA, STOP);
1199            reduce (q, NO_NOTE, &siga, FORMULA, MONADIC_FORMULA, OPERATOR, FORMULA, STOP);
1200          }
1201          if (prio == 0 && siga) {
1202            diagnostic (A68_SYNTAX_ERROR, op, ERROR_NO_PRIORITY);
1203          }
1204          siga = A68_TRUE;
1205          while (siga) {
1206            NODE_T *op2 = NEXT (q);
1207            siga = A68_FALSE;
1208            if (operator_with_priority (q, prio)) {
1209              reduce (q, NO_NOTE, &siga, FORMULA, FORMULA, OPERATOR, SECONDARY, STOP);
1210            }
1211            if (operator_with_priority (q, prio)) {
1212              reduce (q, NO_NOTE, &siga, FORMULA, FORMULA, OPERATOR, MONADIC_FORMULA, STOP);
1213            }
1214            if (operator_with_priority (q, prio)) {
1215              reduce (q, NO_NOTE, &siga, FORMULA, FORMULA, OPERATOR, FORMULA, STOP);
1216            }
1217            if (prio == 0 && siga) {
1218              diagnostic (A68_SYNTAX_ERROR, op2, ERROR_NO_PRIORITY);
1219            }
1220          }
1221        }
1222      }
1223    }
1224  }
1225  
1226  //! @brief Reduce dyadic expressions.
1227  
1228  NODE_T *reduce_dyadic (NODE_T * p, int u)
1229  {
1230  // We work inside out - higher priority expressions get reduced first.
1231    if (u > MAX_PRIORITY) {
1232      if (p == NO_NODE) {
1233        return NO_NODE;
1234      } else if (IS (p, OPERATOR)) {
1235  // Reduce monadic formulas.
1236        NODE_T *q = p;
1237        BOOL_T siga;
1238        do {
1239          PRIO (INFO (q)) = 10;
1240          siga = (BOOL_T) ((NEXT (q) != NO_NODE) && (IS (NEXT (q), OPERATOR)));
1241          if (siga) {
1242            FORWARD (q);
1243          }
1244        } while (siga);
1245        reduce (q, NO_NOTE, NO_TICK, MONADIC_FORMULA, OPERATOR, SECONDARY, STOP);
1246        while (q != p) {
1247          BACKWARD (q);
1248          reduce (q, NO_NOTE, NO_TICK, MONADIC_FORMULA, OPERATOR, MONADIC_FORMULA, STOP);
1249        }
1250      }
1251      FORWARD (p);
1252    } else {
1253      p = reduce_dyadic (p, u + 1);
1254      while (p != NO_NODE && IS (p, OPERATOR) && PRIO (INFO (p)) == u) {
1255        FORWARD (p);
1256        p = reduce_dyadic (p, u + 1);
1257      }
1258    }
1259    return p;
1260  }
1261  
1262  //! @brief Reduce tertiaries completely.
1263  
1264  void reduce_tertiaries (NODE_T * p)
1265  {
1266    BOOL_T siga;
1267    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1268      reduce (q, NO_NOTE, NO_TICK, TERTIARY, NIHIL, STOP);
1269      reduce (q, NO_NOTE, NO_TICK, FORMULA, MONADIC_FORMULA, STOP);
1270      reduce (q, NO_NOTE, NO_TICK, TERTIARY, FORMULA, STOP);
1271      reduce (q, NO_NOTE, NO_TICK, TERTIARY, SECONDARY, STOP);
1272    }
1273    siga = A68_TRUE;
1274    while (siga) {
1275      siga = A68_FALSE;
1276      for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1277        reduce (q, NO_NOTE, &siga, TRANSPOSE_FUNCTION, TRANSPOSE_SYMBOL, TERTIARY, STOP);
1278        reduce (q, NO_NOTE, &siga, DIAGONAL_FUNCTION, TERTIARY, DIAGONAL_SYMBOL, TERTIARY, STOP);
1279        reduce (q, NO_NOTE, &siga, DIAGONAL_FUNCTION, DIAGONAL_SYMBOL, TERTIARY, STOP);
1280        reduce (q, NO_NOTE, &siga, COLUMN_FUNCTION, TERTIARY, COLUMN_SYMBOL, TERTIARY, STOP);
1281        reduce (q, NO_NOTE, &siga, COLUMN_FUNCTION, COLUMN_SYMBOL, TERTIARY, STOP);
1282        reduce (q, NO_NOTE, &siga, ROW_FUNCTION, TERTIARY, ROW_SYMBOL, TERTIARY, STOP);
1283        reduce (q, NO_NOTE, &siga, ROW_FUNCTION, ROW_SYMBOL, TERTIARY, STOP);
1284      }
1285      for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1286        reduce (q, a68_extension, &siga, TERTIARY, TRANSPOSE_FUNCTION, STOP);
1287        reduce (q, a68_extension, &siga, TERTIARY, DIAGONAL_FUNCTION, STOP);
1288        reduce (q, a68_extension, &siga, TERTIARY, COLUMN_FUNCTION, STOP);
1289        reduce (q, a68_extension, &siga, TERTIARY, ROW_FUNCTION, STOP);
1290      }
1291    }
1292    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1293      reduce (q, NO_NOTE, NO_TICK, IDENTITY_RELATION, TERTIARY, IS_SYMBOL, TERTIARY, STOP);
1294      reduce (q, NO_NOTE, NO_TICK, IDENTITY_RELATION, TERTIARY, ISNT_SYMBOL, TERTIARY, STOP);
1295    }
1296    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1297      reduce (q, NO_NOTE, NO_TICK, AND_FUNCTION, TERTIARY, ANDF_SYMBOL, TERTIARY, STOP);
1298      reduce (q, NO_NOTE, NO_TICK, OR_FUNCTION, TERTIARY, ORF_SYMBOL, TERTIARY, STOP);
1299    }
1300  }
1301  
1302  //! @brief Reduce units.
1303  
1304  void reduce_units (NODE_T * p)
1305  {
1306  // Stray ~ is a SKIP.
1307    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1308      if (IS (q, OPERATOR) && IS_LITERALLY (q, "~")) {
1309        ATTRIBUTE (q) = SKIP;
1310      }
1311    }
1312  // Reduce units.
1313    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1314      reduce (q, NO_NOTE, NO_TICK, UNIT, ASSIGNATION, STOP);
1315      reduce (q, NO_NOTE, NO_TICK, UNIT, IDENTITY_RELATION, STOP);
1316      reduce (q, a68_extension, NO_TICK, UNIT, AND_FUNCTION, STOP);
1317      reduce (q, a68_extension, NO_TICK, UNIT, OR_FUNCTION, STOP);
1318      reduce (q, NO_NOTE, NO_TICK, UNIT, ROUTINE_TEXT, STOP);
1319      reduce (q, NO_NOTE, NO_TICK, UNIT, JUMP, STOP);
1320      reduce (q, NO_NOTE, NO_TICK, UNIT, SKIP, STOP);
1321      reduce (q, NO_NOTE, NO_TICK, UNIT, TERTIARY, STOP);
1322      reduce (q, NO_NOTE, NO_TICK, UNIT, ASSERTION, STOP);
1323      reduce (q, NO_NOTE, NO_TICK, UNIT, CODE_CLAUSE, STOP);
1324    }
1325  }
1326  
1327  //! @brief Reduce_generic arguments.
1328  
1329  void reduce_generic_arguments (NODE_T * p)
1330  {
1331    NODE_T *q; BOOL_T siga; // In this scope.
1332    for (q = p; q != NO_NODE; FORWARD (q)) {
1333      if (IS (q, UNIT)) {
1334        reduce (q, NO_NOTE, NO_TICK, TRIMMER, UNIT, COLON_SYMBOL, UNIT, AT_SYMBOL, UNIT, STOP);
1335        reduce (q, NO_NOTE, NO_TICK, TRIMMER, UNIT, COLON_SYMBOL, UNIT, STOP);
1336        reduce (q, NO_NOTE, NO_TICK, TRIMMER, UNIT, COLON_SYMBOL, AT_SYMBOL, UNIT, STOP);
1337        reduce (q, NO_NOTE, NO_TICK, TRIMMER, UNIT, COLON_SYMBOL, STOP);
1338        reduce (q, NO_NOTE, NO_TICK, TRIMMER, UNIT, DOTDOT_SYMBOL, UNIT, AT_SYMBOL, UNIT, STOP);
1339        reduce (q, NO_NOTE, NO_TICK, TRIMMER, UNIT, DOTDOT_SYMBOL, UNIT, STOP);
1340        reduce (q, NO_NOTE, NO_TICK, TRIMMER, UNIT, DOTDOT_SYMBOL, AT_SYMBOL, UNIT, STOP);
1341        reduce (q, NO_NOTE, NO_TICK, TRIMMER, UNIT, DOTDOT_SYMBOL, STOP);
1342      } else if (IS (q, COLON_SYMBOL)) {
1343        reduce (q, NO_NOTE, NO_TICK, TRIMMER, COLON_SYMBOL, UNIT, AT_SYMBOL, UNIT, STOP);
1344        reduce (q, NO_NOTE, NO_TICK, TRIMMER, COLON_SYMBOL, UNIT, STOP);
1345        reduce (q, NO_NOTE, NO_TICK, TRIMMER, COLON_SYMBOL, AT_SYMBOL, UNIT, STOP);
1346        reduce (q, NO_NOTE, NO_TICK, TRIMMER, COLON_SYMBOL, STOP);
1347      } else if (IS (q, DOTDOT_SYMBOL)) {
1348        reduce (q, NO_NOTE, NO_TICK, TRIMMER, DOTDOT_SYMBOL, UNIT, AT_SYMBOL, UNIT, STOP);
1349        reduce (q, NO_NOTE, NO_TICK, TRIMMER, DOTDOT_SYMBOL, UNIT, STOP);
1350        reduce (q, NO_NOTE, NO_TICK, TRIMMER, DOTDOT_SYMBOL, AT_SYMBOL, UNIT, STOP);
1351        reduce (q, NO_NOTE, NO_TICK, TRIMMER, DOTDOT_SYMBOL, STOP);
1352      }
1353    }
1354    for (q = p; q != NO_NODE; FORWARD (q)) {
1355      reduce (q, NO_NOTE, NO_TICK, TRIMMER, UNIT, AT_SYMBOL, UNIT, STOP);
1356    }
1357    for (q = p; q != NO_NODE; FORWARD (q)) {
1358      reduce (q, NO_NOTE, NO_TICK, TRIMMER, AT_SYMBOL, UNIT, STOP);
1359    }
1360    for (q = p; q && NEXT (q); FORWARD (q)) {
1361      if (IS (q, COMMA_SYMBOL)) {
1362        if (!(ATTRIBUTE (NEXT (q)) == UNIT || ATTRIBUTE (NEXT (q)) == TRIMMER)) {
1363          pad_node (q, TRIMMER);
1364        }
1365      } else {
1366        if (IS (NEXT (q), COMMA_SYMBOL)) {
1367          if (!IS (q, UNIT) && !IS (q, TRIMMER)) {
1368            pad_node (q, TRIMMER);
1369          }
1370        }
1371      }
1372    }
1373    q = NEXT (p);
1374    ABEND (q == NO_NODE, ERROR_INTERNAL_CONSISTENCY, __func__);
1375    reduce (q, NO_NOTE, NO_TICK, GENERIC_ARGUMENT_LIST, UNIT, STOP);
1376    reduce (q, NO_NOTE, NO_TICK, GENERIC_ARGUMENT_LIST, TRIMMER, STOP);
1377    do {
1378      siga = A68_FALSE;
1379      reduce (q, NO_NOTE, &siga, GENERIC_ARGUMENT_LIST, GENERIC_ARGUMENT_LIST, COMMA_SYMBOL, UNIT, STOP);
1380      reduce (q, NO_NOTE, &siga, GENERIC_ARGUMENT_LIST, GENERIC_ARGUMENT_LIST, COMMA_SYMBOL, TRIMMER, STOP);
1381      reduce (q, strange_separator, &siga, GENERIC_ARGUMENT_LIST, GENERIC_ARGUMENT_LIST, UNIT, STOP);
1382      reduce (q, strange_separator, &siga, GENERIC_ARGUMENT_LIST, GENERIC_ARGUMENT_LIST, TRIMMER, STOP);
1383    } while (siga);
1384  }
1385  
1386  //! @brief Reduce bounds.
1387  
1388  void reduce_bounds (NODE_T * p)
1389  {
1390    NODE_T *q; BOOL_T siga;
1391    for (q = p; q != NO_NODE; FORWARD (q)) {
1392      reduce (q, NO_NOTE, NO_TICK, BOUND, UNIT, COLON_SYMBOL, UNIT, STOP);
1393      reduce (q, NO_NOTE, NO_TICK, BOUND, UNIT, DOTDOT_SYMBOL, UNIT, STOP);
1394      reduce (q, NO_NOTE, NO_TICK, BOUND, UNIT, STOP);
1395    }
1396    q = NEXT (p);
1397    reduce (q, NO_NOTE, NO_TICK, BOUNDS_LIST, BOUND, STOP);
1398    reduce (q, NO_NOTE, NO_TICK, FORMAL_BOUNDS_LIST, COMMA_SYMBOL, STOP);
1399    reduce (q, NO_NOTE, NO_TICK, ALT_FORMAL_BOUNDS_LIST, COLON_SYMBOL, STOP);
1400    reduce (q, NO_NOTE, NO_TICK, ALT_FORMAL_BOUNDS_LIST, DOTDOT_SYMBOL, STOP);
1401    do {
1402      siga = A68_FALSE;
1403      reduce (q, NO_NOTE, &siga, BOUNDS_LIST, BOUNDS_LIST, COMMA_SYMBOL, BOUND, STOP);
1404      reduce (q, NO_NOTE, &siga, FORMAL_BOUNDS_LIST, FORMAL_BOUNDS_LIST, COMMA_SYMBOL, STOP);
1405      reduce (q, NO_NOTE, &siga, ALT_FORMAL_BOUNDS_LIST, FORMAL_BOUNDS_LIST, COLON_SYMBOL, STOP);
1406      reduce (q, NO_NOTE, &siga, ALT_FORMAL_BOUNDS_LIST, FORMAL_BOUNDS_LIST, DOTDOT_SYMBOL, STOP);
1407      reduce (q, NO_NOTE, &siga, FORMAL_BOUNDS_LIST, ALT_FORMAL_BOUNDS_LIST, COMMA_SYMBOL, STOP);
1408      reduce (q, strange_separator, &siga, BOUNDS_LIST, BOUNDS_LIST, BOUND, STOP);
1409    } while (siga);
1410  }
1411  
1412  //! @brief Reduce argument packs.
1413  
1414  void reduce_arguments (NODE_T * p)
1415  {
1416    if (NEXT (p) != NO_NODE) {
1417      NODE_T *q = NEXT (p);
1418      BOOL_T siga;
1419      reduce (q, NO_NOTE, NO_TICK, ARGUMENT_LIST, UNIT, STOP);
1420      do {
1421        siga = A68_FALSE;
1422        reduce (q, NO_NOTE, &siga, ARGUMENT_LIST, ARGUMENT_LIST, COMMA_SYMBOL, UNIT, STOP);
1423        reduce (q, strange_separator, &siga, ARGUMENT_LIST, ARGUMENT_LIST, UNIT, STOP);
1424      } while (siga);
1425    }
1426  }
1427  
1428  //! @brief Reduce declarations.
1429  
1430  void reduce_basic_declarations (NODE_T * p)
1431  {
1432    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1433      reduce (q, NO_NOTE, NO_TICK, ENVIRON_NAME, ENVIRON_SYMBOL, ROW_CHAR_DENOTATION, STOP);
1434      reduce (q, NO_NOTE, NO_TICK, PRIORITY_DECLARATION, PRIO_SYMBOL, DEFINING_OPERATOR, EQUALS_SYMBOL, PRIORITY, STOP);
1435      reduce (q, NO_NOTE, NO_TICK, MODE_DECLARATION, MODE_SYMBOL, DEFINING_INDICANT, EQUALS_SYMBOL, DECLARER, STOP);
1436      reduce (q, NO_NOTE, NO_TICK, MODE_DECLARATION, MODE_SYMBOL, DEFINING_INDICANT, EQUALS_SYMBOL, VOID_SYMBOL, STOP);
1437      reduce (q, NO_NOTE, NO_TICK, PROCEDURE_DECLARATION, PROC_SYMBOL, DEFINING_IDENTIFIER, EQUALS_SYMBOL, ROUTINE_TEXT, STOP);
1438      reduce (q, NO_NOTE, NO_TICK, PROCEDURE_VARIABLE_DECLARATION, PROC_SYMBOL, DEFINING_IDENTIFIER, ASSIGN_SYMBOL, ROUTINE_TEXT, STOP);
1439      reduce (q, NO_NOTE, NO_TICK, PROCEDURE_VARIABLE_DECLARATION, QUALIFIER, PROC_SYMBOL, DEFINING_IDENTIFIER, ASSIGN_SYMBOL, ROUTINE_TEXT, STOP);
1440      reduce (q, NO_NOTE, NO_TICK, BRIEF_OPERATOR_DECLARATION, OP_SYMBOL, DEFINING_OPERATOR, EQUALS_SYMBOL, ROUTINE_TEXT, STOP);
1441  // Errors.
1442      reduce (q, strange_tokens, NO_TICK, PRIORITY_DECLARATION, PRIO_SYMBOL, -DEFINING_OPERATOR, -EQUALS_SYMBOL, -PRIORITY, STOP);
1443      reduce (q, strange_tokens, NO_TICK, MODE_DECLARATION, MODE_SYMBOL, DEFINING_INDICANT, EQUALS_SYMBOL, -DECLARER, STOP);
1444      reduce (q, strange_tokens, NO_TICK, PROCEDURE_DECLARATION, PROC_SYMBOL, DEFINING_IDENTIFIER, EQUALS_SYMBOL, -ROUTINE_TEXT, STOP);
1445      reduce (q, strange_tokens, NO_TICK, PROCEDURE_VARIABLE_DECLARATION, PROC_SYMBOL, DEFINING_IDENTIFIER, ASSIGN_SYMBOL, -ROUTINE_TEXT, STOP);
1446      reduce (q, strange_tokens, NO_TICK, PROCEDURE_VARIABLE_DECLARATION, QUALIFIER, PROC_SYMBOL, DEFINING_IDENTIFIER, ASSIGN_SYMBOL, -ROUTINE_TEXT, STOP);
1447      reduce (q, strange_tokens, NO_TICK, BRIEF_OPERATOR_DECLARATION, OP_SYMBOL, DEFINING_OPERATOR, EQUALS_SYMBOL, -ROUTINE_TEXT, STOP);
1448  // Errors. WILDCARD catches TERTIARY which catches IDENTIFIER.
1449      reduce (q, strange_tokens, NO_TICK, PROCEDURE_DECLARATION, PROC_SYMBOL, WILDCARD, ROUTINE_TEXT, STOP);
1450    }
1451    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1452      BOOL_T siga;
1453      do {
1454        siga = A68_FALSE;
1455        reduce (q, NO_NOTE, &siga, ENVIRON_NAME, ENVIRON_NAME, COMMA_SYMBOL, ROW_CHAR_DENOTATION, STOP);
1456        reduce (q, NO_NOTE, &siga, PRIORITY_DECLARATION, PRIORITY_DECLARATION, COMMA_SYMBOL, DEFINING_OPERATOR, EQUALS_SYMBOL, PRIORITY, STOP);
1457        reduce (q, NO_NOTE, &siga, MODE_DECLARATION, MODE_DECLARATION, COMMA_SYMBOL, DEFINING_INDICANT, EQUALS_SYMBOL, DECLARER, STOP);
1458        reduce (q, NO_NOTE, &siga, MODE_DECLARATION, MODE_DECLARATION, COMMA_SYMBOL, DEFINING_INDICANT, EQUALS_SYMBOL, VOID_SYMBOL, STOP);
1459        reduce (q, NO_NOTE, &siga, PROCEDURE_DECLARATION, PROCEDURE_DECLARATION, COMMA_SYMBOL, DEFINING_IDENTIFIER, EQUALS_SYMBOL, ROUTINE_TEXT, STOP);
1460        reduce (q, NO_NOTE, &siga, PROCEDURE_VARIABLE_DECLARATION, PROCEDURE_VARIABLE_DECLARATION, COMMA_SYMBOL, DEFINING_IDENTIFIER, ASSIGN_SYMBOL, ROUTINE_TEXT, STOP);
1461        reduce (q, NO_NOTE, &siga, BRIEF_OPERATOR_DECLARATION, BRIEF_OPERATOR_DECLARATION, COMMA_SYMBOL, DEFINING_OPERATOR, EQUALS_SYMBOL, ROUTINE_TEXT, STOP);
1462  // Errors. WILDCARD catches TERTIARY which catches IDENTIFIER.
1463        reduce (q, strange_tokens, &siga, PROCEDURE_DECLARATION, PROCEDURE_DECLARATION, COMMA_SYMBOL, WILDCARD, ROUTINE_TEXT, STOP);
1464      } while (siga);
1465    }
1466  }
1467  
1468  //! @brief Reduce declaration lists.
1469  
1470  void reduce_declaration_lists (NODE_T * p)
1471  {
1472    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1473      reduce (q, NO_NOTE, NO_TICK, IDENTITY_DECLARATION, DECLARER, DEFINING_IDENTIFIER, EQUALS_SYMBOL, UNIT, STOP);
1474      reduce (q, NO_NOTE, NO_TICK, VARIABLE_DECLARATION, QUALIFIER, DECLARER, DEFINING_IDENTIFIER, ASSIGN_SYMBOL, UNIT, STOP);
1475      reduce (q, NO_NOTE, NO_TICK, VARIABLE_DECLARATION, QUALIFIER, DECLARER, DEFINING_IDENTIFIER, STOP);
1476      reduce (q, NO_NOTE, NO_TICK, VARIABLE_DECLARATION, DECLARER, DEFINING_IDENTIFIER, ASSIGN_SYMBOL, UNIT, STOP);
1477      reduce (q, NO_NOTE, NO_TICK, VARIABLE_DECLARATION, DECLARER, DEFINING_IDENTIFIER, STOP);
1478    }
1479    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1480      BOOL_T siga;
1481      do {
1482        siga = A68_FALSE;
1483        reduce (q, NO_NOTE, &siga, IDENTITY_DECLARATION, IDENTITY_DECLARATION, COMMA_SYMBOL, DEFINING_IDENTIFIER, EQUALS_SYMBOL, UNIT, STOP);
1484        reduce (q, NO_NOTE, &siga, VARIABLE_DECLARATION, VARIABLE_DECLARATION, COMMA_SYMBOL, DEFINING_IDENTIFIER, ASSIGN_SYMBOL, UNIT, STOP);
1485        if (!whether (q, VARIABLE_DECLARATION, COMMA_SYMBOL, DEFINING_IDENTIFIER, ASSIGN_SYMBOL, UNIT, STOP)) {
1486          reduce (q, NO_NOTE, &siga, VARIABLE_DECLARATION, VARIABLE_DECLARATION, COMMA_SYMBOL, DEFINING_IDENTIFIER, STOP);
1487        }
1488      } while (siga);
1489    }
1490    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1491      reduce (q, NO_NOTE, NO_TICK, OPERATOR_DECLARATION, OPERATOR_PLAN, DEFINING_OPERATOR, EQUALS_SYMBOL, UNIT, STOP);
1492    }
1493    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1494      BOOL_T siga;
1495      do {
1496        siga = A68_FALSE;
1497        reduce (q, NO_NOTE, &siga, OPERATOR_DECLARATION, OPERATOR_DECLARATION, COMMA_SYMBOL, DEFINING_OPERATOR, EQUALS_SYMBOL, UNIT, STOP);
1498      } while (siga);
1499    }
1500    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1501      reduce (q, NO_NOTE, NO_TICK, DECLARATION_LIST, MODE_DECLARATION, STOP);
1502      reduce (q, NO_NOTE, NO_TICK, DECLARATION_LIST, PRIORITY_DECLARATION, STOP);
1503      reduce (q, NO_NOTE, NO_TICK, DECLARATION_LIST, BRIEF_OPERATOR_DECLARATION, STOP);
1504      reduce (q, NO_NOTE, NO_TICK, DECLARATION_LIST, OPERATOR_DECLARATION, STOP);
1505      reduce (q, NO_NOTE, NO_TICK, DECLARATION_LIST, IDENTITY_DECLARATION, STOP);
1506      reduce (q, NO_NOTE, NO_TICK, DECLARATION_LIST, PROCEDURE_DECLARATION, STOP);
1507      reduce (q, NO_NOTE, NO_TICK, DECLARATION_LIST, PROCEDURE_VARIABLE_DECLARATION, STOP);
1508      reduce (q, NO_NOTE, NO_TICK, DECLARATION_LIST, VARIABLE_DECLARATION, STOP);
1509      reduce (q, NO_NOTE, NO_TICK, DECLARATION_LIST, ENVIRON_NAME, STOP);
1510    }
1511    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1512      BOOL_T siga;
1513      do {
1514        siga = A68_FALSE;
1515        reduce (q, NO_NOTE, &siga, DECLARATION_LIST, DECLARATION_LIST, COMMA_SYMBOL, DECLARATION_LIST, STOP);
1516      } while (siga);
1517    }
1518  }
1519  
1520  //! @brief Reduce serial clauses.
1521  
1522  void reduce_serial_clauses (NODE_T * p)
1523  {
1524    if (NEXT (p) != NO_NODE) {
1525      NODE_T *q = NEXT (p), *u;
1526      BOOL_T siga, label_seen;
1527  // Check wrong exits.
1528      for (u = q; u != NO_NODE; FORWARD (u)) {
1529        if (IS (u, EXIT_SYMBOL)) {
1530          if (NEXT (u) == NO_NODE || !IS (NEXT (u), LABELED_UNIT)) {
1531            diagnostic (A68_SYNTAX_ERROR, u, ERROR_LABELED_UNIT_MUST_FOLLOW);
1532          }
1533        }
1534      }
1535  // Check wrong jumps and declarations.
1536      for (u = q, label_seen = A68_FALSE; u != NO_NODE; FORWARD (u)) {
1537        if (IS (u, LABELED_UNIT)) {
1538          label_seen = A68_TRUE;
1539        } else if (IS (u, DECLARATION_LIST)) {
1540          if (label_seen) {
1541            diagnostic (A68_SYNTAX_ERROR, u, ERROR_LABEL_BEFORE_DECLARATION);
1542          }
1543        }
1544      }
1545  // Reduce serial clauses.
1546      reduce (q, NO_NOTE, NO_TICK, SERIAL_CLAUSE, LABELED_UNIT, STOP);
1547      reduce (q, NO_NOTE, NO_TICK, SERIAL_CLAUSE, UNIT, STOP);
1548      reduce (q, NO_NOTE, NO_TICK, INITIALISER_SERIES, DECLARATION_LIST, STOP);
1549      do {
1550        siga = A68_FALSE;
1551        if (IS (q, SERIAL_CLAUSE)) {
1552          reduce (q, NO_NOTE, &siga, SERIAL_CLAUSE, SERIAL_CLAUSE, SEMI_SYMBOL, UNIT, STOP);
1553          reduce (q, NO_NOTE, &siga, SERIAL_CLAUSE, SERIAL_CLAUSE, EXIT_SYMBOL, LABELED_UNIT, STOP);
1554          reduce (q, NO_NOTE, &siga, SERIAL_CLAUSE, SERIAL_CLAUSE, SEMI_SYMBOL, LABELED_UNIT, STOP);
1555          reduce (q, NO_NOTE, &siga, INITIALISER_SERIES, SERIAL_CLAUSE, SEMI_SYMBOL, DECLARATION_LIST, STOP);
1556  // Errors 
1557          reduce (q, strange_separator, &siga, SERIAL_CLAUSE, SERIAL_CLAUSE, COMMA_SYMBOL, UNIT, STOP);
1558          reduce (q, strange_separator, &siga, SERIAL_CLAUSE, SERIAL_CLAUSE, COMMA_SYMBOL, LABELED_UNIT, STOP);
1559          reduce (q, strange_separator, &siga, INITIALISER_SERIES, SERIAL_CLAUSE, COMMA_SYMBOL, DECLARATION_LIST, STOP);
1560          reduce (q, strange_separator, &siga, SERIAL_CLAUSE, SERIAL_CLAUSE, COLON_SYMBOL, UNIT, STOP);
1561          reduce (q, strange_separator, &siga, SERIAL_CLAUSE, SERIAL_CLAUSE, COLON_SYMBOL, LABELED_UNIT, STOP);
1562          reduce (q, strange_separator, &siga, INITIALISER_SERIES, SERIAL_CLAUSE, COLON_SYMBOL, DECLARATION_LIST, STOP);
1563          reduce (q, strange_separator, &siga, SERIAL_CLAUSE, SERIAL_CLAUSE, UNIT, STOP);
1564          reduce (q, strange_separator, &siga, SERIAL_CLAUSE, SERIAL_CLAUSE, LABELED_UNIT, STOP);
1565          reduce (q, strange_separator, &siga, INITIALISER_SERIES, SERIAL_CLAUSE, DECLARATION_LIST, STOP);
1566        } else if (IS (q, INITIALISER_SERIES)) {
1567          reduce (q, NO_NOTE, &siga, SERIAL_CLAUSE, INITIALISER_SERIES, SEMI_SYMBOL, UNIT, STOP);
1568          reduce (q, NO_NOTE, &siga, SERIAL_CLAUSE, INITIALISER_SERIES, SEMI_SYMBOL, LABELED_UNIT, STOP);
1569          reduce (q, NO_NOTE, &siga, INITIALISER_SERIES, INITIALISER_SERIES, SEMI_SYMBOL, DECLARATION_LIST, STOP);
1570  // Errors 
1571          reduce (q, strange_separator, &siga, SERIAL_CLAUSE, INITIALISER_SERIES, COMMA_SYMBOL, UNIT, STOP);
1572          reduce (q, strange_separator, &siga, SERIAL_CLAUSE, INITIALISER_SERIES, COMMA_SYMBOL, LABELED_UNIT, STOP);
1573          reduce (q, strange_separator, &siga, INITIALISER_SERIES, INITIALISER_SERIES, COMMA_SYMBOL, DECLARATION_LIST, STOP);
1574          reduce (q, strange_separator, &siga, SERIAL_CLAUSE, INITIALISER_SERIES, COLON_SYMBOL, UNIT, STOP);
1575          reduce (q, strange_separator, &siga, SERIAL_CLAUSE, INITIALISER_SERIES, COLON_SYMBOL, LABELED_UNIT, STOP);
1576          reduce (q, strange_separator, &siga, INITIALISER_SERIES, INITIALISER_SERIES, COLON_SYMBOL, DECLARATION_LIST, STOP);
1577          reduce (q, strange_separator, &siga, SERIAL_CLAUSE, INITIALISER_SERIES, UNIT, STOP);
1578          reduce (q, strange_separator, &siga, SERIAL_CLAUSE, INITIALISER_SERIES, LABELED_UNIT, STOP);
1579          reduce (q, strange_separator, &siga, INITIALISER_SERIES, INITIALISER_SERIES, DECLARATION_LIST, STOP);
1580        }
1581      }
1582      while (siga);
1583    }
1584  }
1585  
1586  //! @brief Reduce enquiry clauses.
1587  
1588  void reduce_enquiry_clauses (NODE_T * p)
1589  {
1590    if (NEXT (p) != NO_NODE) {
1591      NODE_T *q = NEXT (p);
1592      BOOL_T siga;
1593      reduce (q, NO_NOTE, NO_TICK, ENQUIRY_CLAUSE, UNIT, STOP);
1594      reduce (q, NO_NOTE, NO_TICK, INITIALISER_SERIES, DECLARATION_LIST, STOP);
1595      do {
1596        siga = A68_FALSE;
1597        if (IS (q, ENQUIRY_CLAUSE)) {
1598          reduce (q, NO_NOTE, &siga, ENQUIRY_CLAUSE, ENQUIRY_CLAUSE, SEMI_SYMBOL, UNIT, STOP);
1599          reduce (q, NO_NOTE, &siga, INITIALISER_SERIES, ENQUIRY_CLAUSE, SEMI_SYMBOL, DECLARATION_LIST, STOP);
1600          reduce (q, strange_separator, &siga, ENQUIRY_CLAUSE, ENQUIRY_CLAUSE, COMMA_SYMBOL, UNIT, STOP);
1601          reduce (q, strange_separator, &siga, INITIALISER_SERIES, ENQUIRY_CLAUSE, COMMA_SYMBOL, DECLARATION_LIST, STOP);
1602          reduce (q, strange_separator, &siga, ENQUIRY_CLAUSE, ENQUIRY_CLAUSE, COLON_SYMBOL, UNIT, STOP);
1603          reduce (q, strange_separator, &siga, INITIALISER_SERIES, ENQUIRY_CLAUSE, COLON_SYMBOL, DECLARATION_LIST, STOP);
1604          reduce (q, strange_separator, &siga, ENQUIRY_CLAUSE, ENQUIRY_CLAUSE, UNIT, STOP);
1605          reduce (q, strange_separator, &siga, INITIALISER_SERIES, ENQUIRY_CLAUSE, DECLARATION_LIST, STOP);
1606        } else if (IS (q, INITIALISER_SERIES)) {
1607          reduce (q, NO_NOTE, &siga, ENQUIRY_CLAUSE, INITIALISER_SERIES, SEMI_SYMBOL, UNIT, STOP);
1608          reduce (q, NO_NOTE, &siga, INITIALISER_SERIES, INITIALISER_SERIES, SEMI_SYMBOL, DECLARATION_LIST, STOP);
1609          reduce (q, strange_separator, &siga, ENQUIRY_CLAUSE, INITIALISER_SERIES, COMMA_SYMBOL, UNIT, STOP);
1610          reduce (q, strange_separator, &siga, INITIALISER_SERIES, INITIALISER_SERIES, COMMA_SYMBOL, DECLARATION_LIST, STOP);
1611          reduce (q, strange_separator, &siga, ENQUIRY_CLAUSE, INITIALISER_SERIES, COLON_SYMBOL, UNIT, STOP);
1612          reduce (q, strange_separator, &siga, INITIALISER_SERIES, INITIALISER_SERIES, COLON_SYMBOL, DECLARATION_LIST, STOP);
1613          reduce (q, strange_separator, &siga, ENQUIRY_CLAUSE, INITIALISER_SERIES, UNIT, STOP);
1614          reduce (q, strange_separator, &siga, INITIALISER_SERIES, INITIALISER_SERIES, DECLARATION_LIST, STOP);
1615        }
1616      }
1617      while (siga);
1618    }
1619  }
1620  
1621  //! @brief Reduce collateral clauses.
1622  
1623  void reduce_collateral_clauses (NODE_T * p)
1624  {
1625    if (NEXT (p) != NO_NODE) {
1626      NODE_T *q = NEXT (p);
1627      if (IS (q, UNIT)) {
1628        BOOL_T siga;
1629        reduce (q, NO_NOTE, NO_TICK, UNIT_LIST, UNIT, STOP);
1630        do {
1631          siga = A68_FALSE;
1632          reduce (q, NO_NOTE, &siga, UNIT_LIST, UNIT_LIST, COMMA_SYMBOL, UNIT, STOP);
1633          reduce (q, strange_separator, &siga, UNIT_LIST, UNIT_LIST, UNIT, STOP);
1634        } while (siga);
1635      } else if (IS (q, SPECIFIED_UNIT)) {
1636        BOOL_T siga;
1637        reduce (q, NO_NOTE, NO_TICK, SPECIFIED_UNIT_LIST, SPECIFIED_UNIT, STOP);
1638        do {
1639          siga = A68_FALSE;
1640          reduce (q, NO_NOTE, &siga, SPECIFIED_UNIT_LIST, SPECIFIED_UNIT_LIST, COMMA_SYMBOL, SPECIFIED_UNIT, STOP);
1641          reduce (q, strange_separator, &siga, SPECIFIED_UNIT_LIST, SPECIFIED_UNIT_LIST, SPECIFIED_UNIT, STOP);
1642        } while (siga);
1643      }
1644    }
1645  }
1646  
1647  //! @brief Reduces enclosed clauses.
1648  
1649  void reduce_enclosed_clauses (NODE_T * q, int expect)
1650  {
1651    NODE_T *p = q;
1652    if (SUB (p) == NO_NODE) {
1653      if (IS (p, FOR_SYMBOL)) {
1654        reduce (p, NO_NOTE, NO_TICK, FOR_PART, FOR_SYMBOL, DEFINING_IDENTIFIER, STOP);
1655      } else if (IS (p, OPEN_SYMBOL)) {
1656        if (expect == ENQUIRY_CLAUSE) {
1657          reduce (p, NO_NOTE, NO_TICK, OPEN_PART, OPEN_SYMBOL, ENQUIRY_CLAUSE, STOP);
1658        } else if (expect == ARGUMENT) {
1659          reduce (p, NO_NOTE, NO_TICK, ARGUMENT, OPEN_SYMBOL, CLOSE_SYMBOL, STOP);
1660          reduce (p, NO_NOTE, NO_TICK, ARGUMENT, OPEN_SYMBOL, ARGUMENT_LIST, CLOSE_SYMBOL, STOP);
1661          reduce (p, empty_clause, NO_TICK, ARGUMENT, OPEN_SYMBOL, INITIALISER_SERIES, CLOSE_SYMBOL, STOP);
1662        } else if (expect == GENERIC_ARGUMENT) {
1663          if (whether (p, OPEN_SYMBOL, CLOSE_SYMBOL, STOP)) {
1664            pad_node (p, TRIMMER);
1665            reduce (p, NO_NOTE, NO_TICK, GENERIC_ARGUMENT, OPEN_SYMBOL, TRIMMER, CLOSE_SYMBOL, STOP);
1666          }
1667          reduce (p, NO_NOTE, NO_TICK, GENERIC_ARGUMENT, OPEN_SYMBOL, GENERIC_ARGUMENT_LIST, CLOSE_SYMBOL, STOP);
1668        } else if (expect == BOUNDS) {
1669          reduce (p, NO_NOTE, NO_TICK, FORMAL_BOUNDS, OPEN_SYMBOL, CLOSE_SYMBOL, STOP);
1670          reduce (p, NO_NOTE, NO_TICK, BOUNDS, OPEN_SYMBOL, BOUNDS_LIST, CLOSE_SYMBOL, STOP);
1671          reduce (p, NO_NOTE, NO_TICK, FORMAL_BOUNDS, OPEN_SYMBOL, FORMAL_BOUNDS_LIST, CLOSE_SYMBOL, STOP);
1672          reduce (p, NO_NOTE, NO_TICK, FORMAL_BOUNDS, OPEN_SYMBOL, ALT_FORMAL_BOUNDS_LIST, CLOSE_SYMBOL, STOP);
1673        } else {
1674          reduce (p, NO_NOTE, NO_TICK, CLOSED_CLAUSE, OPEN_SYMBOL, SERIAL_CLAUSE, CLOSE_SYMBOL, STOP);
1675          reduce (p, NO_NOTE, NO_TICK, COLLATERAL_CLAUSE, OPEN_SYMBOL, UNIT_LIST, CLOSE_SYMBOL, STOP);
1676          reduce (p, NO_NOTE, NO_TICK, COLLATERAL_CLAUSE, OPEN_SYMBOL, CLOSE_SYMBOL, STOP);
1677          reduce (p, empty_clause, NO_TICK, CLOSED_CLAUSE, OPEN_SYMBOL, INITIALISER_SERIES, CLOSE_SYMBOL, STOP);
1678        }
1679      } else if (IS (p, SUB_SYMBOL)) {
1680        if (expect == GENERIC_ARGUMENT) {
1681          if (whether (p, SUB_SYMBOL, BUS_SYMBOL, STOP)) {
1682            pad_node (p, TRIMMER);
1683            reduce (p, NO_NOTE, NO_TICK, GENERIC_ARGUMENT, SUB_SYMBOL, TRIMMER, BUS_SYMBOL, STOP);
1684          }
1685          reduce (p, NO_NOTE, NO_TICK, GENERIC_ARGUMENT, SUB_SYMBOL, GENERIC_ARGUMENT_LIST, BUS_SYMBOL, STOP);
1686        } else if (expect == BOUNDS) {
1687          reduce (p, NO_NOTE, NO_TICK, FORMAL_BOUNDS, SUB_SYMBOL, BUS_SYMBOL, STOP);
1688          reduce (p, NO_NOTE, NO_TICK, BOUNDS, SUB_SYMBOL, BOUNDS_LIST, BUS_SYMBOL, STOP);
1689          reduce (p, NO_NOTE, NO_TICK, FORMAL_BOUNDS, SUB_SYMBOL, FORMAL_BOUNDS_LIST, BUS_SYMBOL, STOP);
1690          reduce (p, NO_NOTE, NO_TICK, FORMAL_BOUNDS, SUB_SYMBOL, ALT_FORMAL_BOUNDS_LIST, BUS_SYMBOL, STOP);
1691        }
1692      } else if (IS (p, BEGIN_SYMBOL)) {
1693        reduce (p, NO_NOTE, NO_TICK, COLLATERAL_CLAUSE, BEGIN_SYMBOL, UNIT_LIST, END_SYMBOL, STOP);
1694        reduce (p, NO_NOTE, NO_TICK, COLLATERAL_CLAUSE, BEGIN_SYMBOL, END_SYMBOL, STOP);
1695        reduce (p, NO_NOTE, NO_TICK, CLOSED_CLAUSE, BEGIN_SYMBOL, SERIAL_CLAUSE, END_SYMBOL, STOP);
1696        reduce (p, empty_clause, NO_TICK, CLOSED_CLAUSE, BEGIN_SYMBOL, INITIALISER_SERIES, END_SYMBOL, STOP);
1697      } else if (IS (p, FORMAT_DELIMITER_SYMBOL)) {
1698        reduce (p, NO_NOTE, NO_TICK, FORMAT_TEXT, FORMAT_DELIMITER_SYMBOL, PICTURE_LIST, FORMAT_DELIMITER_SYMBOL, STOP);
1699        reduce (p, NO_NOTE, NO_TICK, FORMAT_TEXT, FORMAT_DELIMITER_SYMBOL, FORMAT_DELIMITER_SYMBOL, STOP);
1700      } else if (IS (p, FORMAT_OPEN_SYMBOL)) {
1701        reduce (p, NO_NOTE, NO_TICK, COLLECTION, FORMAT_OPEN_SYMBOL, PICTURE_LIST, FORMAT_CLOSE_SYMBOL, STOP);
1702      } else if (IS (p, IF_SYMBOL)) {
1703        reduce (p, NO_NOTE, NO_TICK, IF_PART, IF_SYMBOL, ENQUIRY_CLAUSE, STOP);
1704        reduce (p, empty_clause, NO_TICK, IF_PART, IF_SYMBOL, INITIALISER_SERIES, STOP);
1705      } else if (IS (p, THEN_SYMBOL)) {
1706        reduce (p, NO_NOTE, NO_TICK, THEN_PART, THEN_SYMBOL, SERIAL_CLAUSE, STOP);
1707        reduce (p, empty_clause, NO_TICK, THEN_PART, THEN_SYMBOL, INITIALISER_SERIES, STOP);
1708      } else if (IS (p, ELSE_SYMBOL)) {
1709        reduce (p, NO_NOTE, NO_TICK, ELSE_PART, ELSE_SYMBOL, SERIAL_CLAUSE, STOP);
1710        reduce (p, empty_clause, NO_TICK, ELSE_PART, ELSE_SYMBOL, INITIALISER_SERIES, STOP);
1711      } else if (IS (p, ELIF_SYMBOL)) {
1712        reduce (p, NO_NOTE, NO_TICK, ELIF_IF_PART, ELIF_SYMBOL, ENQUIRY_CLAUSE, STOP);
1713      } else if (IS (p, CASE_SYMBOL)) {
1714        reduce (p, NO_NOTE, NO_TICK, CASE_PART, CASE_SYMBOL, ENQUIRY_CLAUSE, STOP);
1715        reduce (p, empty_clause, NO_TICK, CASE_PART, CASE_SYMBOL, INITIALISER_SERIES, STOP);
1716      } else if (IS (p, IN_SYMBOL)) {
1717        reduce (p, NO_NOTE, NO_TICK, CASE_IN_PART, IN_SYMBOL, UNIT_LIST, STOP);
1718        reduce (p, NO_NOTE, NO_TICK, CONFORMITY_IN_PART, IN_SYMBOL, SPECIFIED_UNIT_LIST, STOP);
1719      } else if (IS (p, OUT_SYMBOL)) {
1720        reduce (p, NO_NOTE, NO_TICK, OUT_PART, OUT_SYMBOL, SERIAL_CLAUSE, STOP);
1721        reduce (p, empty_clause, NO_TICK, OUT_PART, OUT_SYMBOL, INITIALISER_SERIES, STOP);
1722      } else if (IS (p, OUSE_SYMBOL)) {
1723        reduce (p, NO_NOTE, NO_TICK, OUSE_PART, OUSE_SYMBOL, ENQUIRY_CLAUSE, STOP);
1724      } else if (IS (p, THEN_BAR_SYMBOL)) {
1725        reduce (p, NO_NOTE, NO_TICK, CHOICE, THEN_BAR_SYMBOL, SERIAL_CLAUSE, STOP);
1726        reduce (p, NO_NOTE, NO_TICK, CASE_CHOICE_CLAUSE, THEN_BAR_SYMBOL, UNIT_LIST, STOP);
1727        reduce (p, NO_NOTE, NO_TICK, CONFORMITY_CHOICE, THEN_BAR_SYMBOL, SPECIFIED_UNIT_LIST, STOP);
1728        reduce (p, NO_NOTE, NO_TICK, CONFORMITY_CHOICE, THEN_BAR_SYMBOL, SPECIFIED_UNIT, STOP);
1729        reduce (p, empty_clause, NO_TICK, CHOICE, THEN_BAR_SYMBOL, INITIALISER_SERIES, STOP);
1730      } else if (IS (p, ELSE_BAR_SYMBOL)) {
1731        reduce (p, NO_NOTE, NO_TICK, ELSE_OPEN_PART, ELSE_BAR_SYMBOL, ENQUIRY_CLAUSE, STOP);
1732        reduce (p, empty_clause, NO_TICK, ELSE_OPEN_PART, ELSE_BAR_SYMBOL, INITIALISER_SERIES, STOP);
1733      } else if (IS (p, FROM_SYMBOL)) {
1734        reduce (p, NO_NOTE, NO_TICK, FROM_PART, FROM_SYMBOL, UNIT, STOP);
1735      } else if (IS (p, BY_SYMBOL)) {
1736        reduce (p, NO_NOTE, NO_TICK, BY_PART, BY_SYMBOL, UNIT, STOP);
1737      } else if (IS (p, TO_SYMBOL)) {
1738        reduce (p, NO_NOTE, NO_TICK, TO_PART, TO_SYMBOL, UNIT, STOP);
1739      } else if (IS (p, DOWNTO_SYMBOL)) {
1740        reduce (p, NO_NOTE, NO_TICK, TO_PART, DOWNTO_SYMBOL, UNIT, STOP);
1741      } else if (IS (p, WHILE_SYMBOL)) {
1742        reduce (p, NO_NOTE, NO_TICK, WHILE_PART, WHILE_SYMBOL, ENQUIRY_CLAUSE, STOP);
1743        reduce (p, empty_clause, NO_TICK, WHILE_PART, WHILE_SYMBOL, INITIALISER_SERIES, STOP);
1744      } else if (IS (p, UNTIL_SYMBOL)) {
1745        reduce (p, NO_NOTE, NO_TICK, UNTIL_PART, UNTIL_SYMBOL, ENQUIRY_CLAUSE, STOP);
1746        reduce (p, empty_clause, NO_TICK, UNTIL_PART, UNTIL_SYMBOL, INITIALISER_SERIES, STOP);
1747      } else if (IS (p, DO_SYMBOL)) {
1748        reduce (p, NO_NOTE, NO_TICK, DO_PART, DO_SYMBOL, SERIAL_CLAUSE, UNTIL_PART, OD_SYMBOL, STOP);
1749        reduce (p, NO_NOTE, NO_TICK, DO_PART, DO_SYMBOL, SERIAL_CLAUSE, OD_SYMBOL, STOP);
1750        reduce (p, NO_NOTE, NO_TICK, DO_PART, DO_SYMBOL, UNTIL_PART, OD_SYMBOL, STOP);
1751      } else if (IS (p, ALT_DO_SYMBOL)) {
1752        reduce (p, NO_NOTE, NO_TICK, ALT_DO_PART, ALT_DO_SYMBOL, SERIAL_CLAUSE, UNTIL_PART, OD_SYMBOL, STOP);
1753        reduce (p, NO_NOTE, NO_TICK, ALT_DO_PART, ALT_DO_SYMBOL, SERIAL_CLAUSE, OD_SYMBOL, STOP);
1754        reduce (p, NO_NOTE, NO_TICK, ALT_DO_PART, ALT_DO_SYMBOL, UNTIL_PART, OD_SYMBOL, STOP);
1755      }
1756    }
1757    p = q;
1758    if (SUB (p) != NO_NODE) {
1759      if (IS (p, OPEN_PART)) {
1760        reduce (p, NO_NOTE, NO_TICK, CONDITIONAL_CLAUSE, OPEN_PART, CHOICE, CHOICE, CLOSE_SYMBOL, STOP);
1761        reduce (p, NO_NOTE, NO_TICK, CONDITIONAL_CLAUSE, OPEN_PART, CHOICE, CLOSE_SYMBOL, STOP);
1762        reduce (p, NO_NOTE, NO_TICK, CONDITIONAL_CLAUSE, OPEN_PART, CHOICE, BRIEF_ELIF_PART, STOP);
1763        reduce (p, NO_NOTE, NO_TICK, CASE_CLAUSE, OPEN_PART, CASE_CHOICE_CLAUSE, CHOICE, CLOSE_SYMBOL, STOP);
1764        reduce (p, NO_NOTE, NO_TICK, CASE_CLAUSE, OPEN_PART, CASE_CHOICE_CLAUSE, CLOSE_SYMBOL, STOP);
1765        reduce (p, NO_NOTE, NO_TICK, CASE_CLAUSE, OPEN_PART, CASE_CHOICE_CLAUSE, BRIEF_OUSE_PART, STOP);
1766        reduce (p, NO_NOTE, NO_TICK, CONFORMITY_CLAUSE, OPEN_PART, CONFORMITY_CHOICE, CHOICE, CLOSE_SYMBOL, STOP);
1767        reduce (p, NO_NOTE, NO_TICK, CONFORMITY_CLAUSE, OPEN_PART, CONFORMITY_CHOICE, CLOSE_SYMBOL, STOP);
1768        reduce (p, NO_NOTE, NO_TICK, CONFORMITY_CLAUSE, OPEN_PART, CONFORMITY_CHOICE, BRIEF_CONFORMITY_OUSE_PART, STOP);
1769      } else if (IS (p, ELSE_OPEN_PART)) {
1770        reduce (p, NO_NOTE, NO_TICK, BRIEF_ELIF_PART, ELSE_OPEN_PART, CHOICE, CHOICE, CLOSE_SYMBOL, STOP);
1771        reduce (p, NO_NOTE, NO_TICK, BRIEF_ELIF_PART, ELSE_OPEN_PART, CHOICE, CLOSE_SYMBOL, STOP);
1772        reduce (p, NO_NOTE, NO_TICK, BRIEF_ELIF_PART, ELSE_OPEN_PART, CHOICE, BRIEF_ELIF_PART, STOP);
1773        reduce (p, NO_NOTE, NO_TICK, BRIEF_OUSE_PART, ELSE_OPEN_PART, CASE_CHOICE_CLAUSE, CHOICE, CLOSE_SYMBOL, STOP);
1774        reduce (p, NO_NOTE, NO_TICK, BRIEF_OUSE_PART, ELSE_OPEN_PART, CASE_CHOICE_CLAUSE, CLOSE_SYMBOL, STOP);
1775        reduce (p, NO_NOTE, NO_TICK, BRIEF_OUSE_PART, ELSE_OPEN_PART, CASE_CHOICE_CLAUSE, BRIEF_OUSE_PART, STOP);
1776        reduce (p, NO_NOTE, NO_TICK, BRIEF_CONFORMITY_OUSE_PART, ELSE_OPEN_PART, CONFORMITY_CHOICE, CHOICE, CLOSE_SYMBOL, STOP);
1777        reduce (p, NO_NOTE, NO_TICK, BRIEF_CONFORMITY_OUSE_PART, ELSE_OPEN_PART, CONFORMITY_CHOICE, CLOSE_SYMBOL, STOP);
1778        reduce (p, NO_NOTE, NO_TICK, BRIEF_CONFORMITY_OUSE_PART, ELSE_OPEN_PART, CONFORMITY_CHOICE, BRIEF_CONFORMITY_OUSE_PART, STOP);
1779      } else if (IS (p, IF_PART)) {
1780        reduce (p, NO_NOTE, NO_TICK, CONDITIONAL_CLAUSE, IF_PART, THEN_PART, ELSE_PART, FI_SYMBOL, STOP);
1781        reduce (p, NO_NOTE, NO_TICK, CONDITIONAL_CLAUSE, IF_PART, THEN_PART, ELIF_PART, STOP);
1782        reduce (p, NO_NOTE, NO_TICK, CONDITIONAL_CLAUSE, IF_PART, THEN_PART, FI_SYMBOL, STOP);
1783      } else if (IS (p, ELIF_IF_PART)) {
1784        reduce (p, NO_NOTE, NO_TICK, ELIF_PART, ELIF_IF_PART, THEN_PART, ELSE_PART, FI_SYMBOL, STOP);
1785        reduce (p, NO_NOTE, NO_TICK, ELIF_PART, ELIF_IF_PART, THEN_PART, FI_SYMBOL, STOP);
1786        reduce (p, NO_NOTE, NO_TICK, ELIF_PART, ELIF_IF_PART, THEN_PART, ELIF_PART, STOP);
1787      } else if (IS (p, CASE_PART)) {
1788        reduce (p, NO_NOTE, NO_TICK, CASE_CLAUSE, CASE_PART, CASE_IN_PART, OUT_PART, ESAC_SYMBOL, STOP);
1789        reduce (p, NO_NOTE, NO_TICK, CASE_CLAUSE, CASE_PART, CASE_IN_PART, ESAC_SYMBOL, STOP);
1790        reduce (p, NO_NOTE, NO_TICK, CASE_CLAUSE, CASE_PART, CASE_IN_PART, CASE_OUSE_PART, STOP);
1791        reduce (p, NO_NOTE, NO_TICK, CONFORMITY_CLAUSE, CASE_PART, CONFORMITY_IN_PART, OUT_PART, ESAC_SYMBOL, STOP);
1792        reduce (p, NO_NOTE, NO_TICK, CONFORMITY_CLAUSE, CASE_PART, CONFORMITY_IN_PART, ESAC_SYMBOL, STOP);
1793        reduce (p, NO_NOTE, NO_TICK, CONFORMITY_CLAUSE, CASE_PART, CONFORMITY_IN_PART, CONFORMITY_OUSE_PART, STOP);
1794      } else if (IS (p, OUSE_PART)) {
1795        reduce (p, NO_NOTE, NO_TICK, CASE_OUSE_PART, OUSE_PART, CASE_IN_PART, OUT_PART, ESAC_SYMBOL, STOP);
1796        reduce (p, NO_NOTE, NO_TICK, CASE_OUSE_PART, OUSE_PART, CASE_IN_PART, ESAC_SYMBOL, STOP);
1797        reduce (p, NO_NOTE, NO_TICK, CASE_OUSE_PART, OUSE_PART, CASE_IN_PART, CASE_OUSE_PART, STOP);
1798        reduce (p, NO_NOTE, NO_TICK, CONFORMITY_OUSE_PART, OUSE_PART, CONFORMITY_IN_PART, OUT_PART, ESAC_SYMBOL, STOP);
1799        reduce (p, NO_NOTE, NO_TICK, CONFORMITY_OUSE_PART, OUSE_PART, CONFORMITY_IN_PART, ESAC_SYMBOL, STOP);
1800        reduce (p, NO_NOTE, NO_TICK, CONFORMITY_OUSE_PART, OUSE_PART, CONFORMITY_IN_PART, CONFORMITY_OUSE_PART, STOP);
1801      } else if (IS (p, FOR_PART)) {
1802        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, FOR_PART, FROM_PART, BY_PART, TO_PART, WHILE_PART, ALT_DO_PART, STOP);
1803        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, FOR_PART, FROM_PART, BY_PART, WHILE_PART, ALT_DO_PART, STOP);
1804        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, FOR_PART, FROM_PART, TO_PART, WHILE_PART, ALT_DO_PART, STOP);
1805        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, FOR_PART, FROM_PART, WHILE_PART, ALT_DO_PART, STOP);
1806        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, FOR_PART, BY_PART, TO_PART, WHILE_PART, ALT_DO_PART, STOP);
1807        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, FOR_PART, BY_PART, WHILE_PART, ALT_DO_PART, STOP);
1808        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, FOR_PART, TO_PART, WHILE_PART, ALT_DO_PART, STOP);
1809        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, FOR_PART, WHILE_PART, ALT_DO_PART, STOP);
1810        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, FOR_PART, FROM_PART, BY_PART, TO_PART, ALT_DO_PART, STOP);
1811        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, FOR_PART, FROM_PART, BY_PART, ALT_DO_PART, STOP);
1812        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, FOR_PART, FROM_PART, TO_PART, ALT_DO_PART, STOP);
1813        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, FOR_PART, FROM_PART, ALT_DO_PART, STOP);
1814        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, FOR_PART, BY_PART, TO_PART, ALT_DO_PART, STOP);
1815        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, FOR_PART, BY_PART, ALT_DO_PART, STOP);
1816        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, FOR_PART, TO_PART, ALT_DO_PART, STOP);
1817        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, FOR_PART, ALT_DO_PART, STOP);
1818      } else if (IS (p, FROM_PART)) {
1819        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, FROM_PART, BY_PART, TO_PART, WHILE_PART, ALT_DO_PART, STOP);
1820        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, FROM_PART, BY_PART, WHILE_PART, ALT_DO_PART, STOP);
1821        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, FROM_PART, TO_PART, WHILE_PART, ALT_DO_PART, STOP);
1822        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, FROM_PART, WHILE_PART, ALT_DO_PART, STOP);
1823        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, FROM_PART, BY_PART, TO_PART, ALT_DO_PART, STOP);
1824        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, FROM_PART, BY_PART, ALT_DO_PART, STOP);
1825        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, FROM_PART, TO_PART, ALT_DO_PART, STOP);
1826        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, FROM_PART, ALT_DO_PART, STOP);
1827      } else if (IS (p, BY_PART)) {
1828        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, BY_PART, TO_PART, WHILE_PART, ALT_DO_PART, STOP);
1829        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, BY_PART, WHILE_PART, ALT_DO_PART, STOP);
1830        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, BY_PART, TO_PART, ALT_DO_PART, STOP);
1831        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, BY_PART, ALT_DO_PART, STOP);
1832      } else if (IS (p, TO_PART)) {
1833        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, TO_PART, WHILE_PART, ALT_DO_PART, STOP);
1834        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, TO_PART, ALT_DO_PART, STOP);
1835      } else if (IS (p, WHILE_PART)) {
1836        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, WHILE_PART, ALT_DO_PART, STOP);
1837      } else if (IS (p, DO_PART)) {
1838        reduce (p, NO_NOTE, NO_TICK, LOOP_CLAUSE, DO_PART, STOP);
1839      }
1840    }
1841  }
1842  
1843  //! @brief Substitute reduction when a phrase could not be parsed.
1844  
1845  void recover_from_error (NODE_T * p, int expect, BOOL_T suppress)
1846  {
1847  // This routine does not do fancy things as that might introduce more errors.
1848    NODE_T *q = p;
1849    if (p == NO_NODE) {
1850      return;
1851    }
1852    if (expect == SOME_CLAUSE) {
1853      expect = serial_or_collateral (p);
1854    }
1855    if (!suppress) {
1856  // Give an error message.
1857      NODE_T *w = p;
1858      char *seq = phrase_to_text (p, &w);
1859      if (strlen (seq) == 0) {
1860        if (ERROR_COUNT (&A68_JOB) == 0) {
1861          diagnostic (A68_SYNTAX_ERROR, w, ERROR_SYNTAX_EXPECTED, expect);
1862        }
1863      } else {
1864        diagnostic (A68_SYNTAX_ERROR, w, ERROR_INVALID_SEQUENCE, seq, expect);
1865      }
1866      if (ERROR_COUNT (&A68_JOB) >= MAX_ERRORS) {
1867        longjmp (A68_PARSER (bottom_up_crash_exit), 1);
1868      }
1869    }
1870  // Try to prevent spurious diagnostics by guessing what was expected.
1871    while (NEXT (q) != NO_NODE) {
1872      FORWARD (q);
1873    }
1874    if (is_one_of (p, BEGIN_SYMBOL, OPEN_SYMBOL, STOP)) {
1875      if (expect == ARGUMENT || expect == COLLATERAL_CLAUSE || expect == PARAMETER_PACK || expect == STRUCTURE_PACK || expect == UNION_PACK) {
1876        make_sub (p, q, expect);
1877      } else if (expect == ENQUIRY_CLAUSE) {
1878        make_sub (p, q, OPEN_PART);
1879      } else if (expect == FORMAL_DECLARERS) {
1880        make_sub (p, q, FORMAL_DECLARERS);
1881      } else {
1882        make_sub (p, q, CLOSED_CLAUSE);
1883      }
1884    } else if (IS (p, FORMAT_DELIMITER_SYMBOL) && expect == FORMAT_TEXT) {
1885      make_sub (p, q, FORMAT_TEXT);
1886    } else if (IS (p, CODE_SYMBOL)) {
1887      make_sub (p, q, CODE_CLAUSE);
1888    } else if (is_one_of (p, THEN_BAR_SYMBOL, CHOICE, STOP)) {
1889      make_sub (p, q, CHOICE);
1890    } else if (is_one_of (p, IF_SYMBOL, IF_PART, STOP)) {
1891      make_sub (p, q, IF_PART);
1892    } else if (is_one_of (p, THEN_SYMBOL, THEN_PART, STOP)) {
1893      make_sub (p, q, THEN_PART);
1894    } else if (is_one_of (p, ELSE_SYMBOL, ELSE_PART, STOP)) {
1895      make_sub (p, q, ELSE_PART);
1896    } else if (is_one_of (p, ELIF_SYMBOL, ELIF_IF_PART, STOP)) {
1897      make_sub (p, q, ELIF_IF_PART);
1898    } else if (is_one_of (p, CASE_SYMBOL, CASE_PART, STOP)) {
1899      make_sub (p, q, CASE_PART);
1900    } else if (is_one_of (p, OUT_SYMBOL, OUT_PART, STOP)) {
1901      make_sub (p, q, OUT_PART);
1902    } else if (is_one_of (p, OUSE_SYMBOL, OUSE_PART, STOP)) {
1903      make_sub (p, q, OUSE_PART);
1904    } else if (is_one_of (p, FOR_SYMBOL, FOR_PART, STOP)) {
1905      make_sub (p, q, FOR_PART);
1906    } else if (is_one_of (p, FROM_SYMBOL, FROM_PART, STOP)) {
1907      make_sub (p, q, FROM_PART);
1908    } else if (is_one_of (p, BY_SYMBOL, BY_PART, STOP)) {
1909      make_sub (p, q, BY_PART);
1910    } else if (is_one_of (p, TO_SYMBOL, DOWNTO_SYMBOL, TO_PART, STOP)) {
1911      make_sub (p, q, TO_PART);
1912    } else if (is_one_of (p, WHILE_SYMBOL, WHILE_PART, STOP)) {
1913      make_sub (p, q, WHILE_PART);
1914    } else if (is_one_of (p, UNTIL_SYMBOL, UNTIL_PART, STOP)) {
1915      make_sub (p, q, UNTIL_PART);
1916    } else if (is_one_of (p, DO_SYMBOL, DO_PART, STOP)) {
1917      make_sub (p, q, DO_PART);
1918    } else if (is_one_of (p, ALT_DO_SYMBOL, ALT_DO_PART, STOP)) {
1919      make_sub (p, q, ALT_DO_PART);
1920    } else if (non_terminal_string (A68 (edit_line), expect) != NO_TEXT) {
1921      make_sub (p, q, expect);
1922    }
1923  }
1924  
1925  //! @brief Heuristic aid in pinpointing errors.
1926  
1927  void reduce_erroneous_units (NODE_T * p)
1928  {
1929  // Constructs are reduced to units in an attempt to limit spurious diagnostics.
1930    for (NODE_T *q = p; q != NO_NODE; FORWARD (q)) {
1931  // Some implementations allow selection from a tertiary, when there is no risk
1932  // of ambiguity. Algol68G follows RR, so some extra attention here to guide an
1933  // unsuspecting user.
1934      if (whether (q, SELECTOR, -SECONDARY, STOP)) {
1935        diagnostic (A68_SYNTAX_ERROR, NEXT (q), ERROR_SYNTAX_EXPECTED, SECONDARY);
1936        reduce (q, NO_NOTE, NO_TICK, UNIT, SELECTOR, WILDCARD, STOP);
1937      }
1938  // Attention for identity relations that require tertiaries.
1939      if (whether (q, -TERTIARY, IS_SYMBOL, TERTIARY, STOP) || whether (q, TERTIARY, IS_SYMBOL, -TERTIARY, STOP) || whether (q, -TERTIARY, IS_SYMBOL, -TERTIARY, STOP)) {
1940        diagnostic (A68_SYNTAX_ERROR, NEXT (q), ERROR_SYNTAX_EXPECTED, TERTIARY);
1941        reduce (q, NO_NOTE, NO_TICK, UNIT, WILDCARD, IS_SYMBOL, WILDCARD, STOP);
1942      } else if (whether (q, -TERTIARY, ISNT_SYMBOL, TERTIARY, STOP) || whether (q, TERTIARY, ISNT_SYMBOL, -TERTIARY, STOP) || whether (q, -TERTIARY, ISNT_SYMBOL, -TERTIARY, STOP)) {
1943        diagnostic (A68_SYNTAX_ERROR, NEXT (q), ERROR_SYNTAX_EXPECTED, TERTIARY);
1944        reduce (q, NO_NOTE, NO_TICK, UNIT, WILDCARD, ISNT_SYMBOL, WILDCARD, STOP);
1945      }
1946    }
1947  }
1948  
1949  // A posteriori checks of the syntax tree built by the BU parser.
1950  
1951  //! @brief Driver for a posteriori error checking.
1952  
1953  void bottom_up_error_check (NODE_T * p)
1954  {
1955    for (; p != NO_NODE; FORWARD (p)) {
1956      if (IS (p, BOOLEAN_PATTERN)) {
1957        int k = 0;
1958        count_pictures (SUB (p), &k);
1959        if (!(k == 0 || k == 2)) {
1960          diagnostic (A68_SYNTAX_ERROR, p, ERROR_FORMAT_PICTURE_NUMBER, ATTRIBUTE (p));
1961        }
1962      } else {
1963        bottom_up_error_check (SUB (p));
1964      }
1965    }
1966  }
1967  
1968  // Next part rearranges and checks the tree after the symbol tables are finished.
1969  
1970  //! @brief Transfer IDENTIFIER to JUMP where appropriate.
1971  
1972  void rearrange_goto_less_jumps (NODE_T * p)
1973  {
1974    for (; p != NO_NODE; FORWARD (p)) {
1975      if (IS (p, UNIT)) {
1976        NODE_T *q = SUB (p);
1977        if (IS (q, TERTIARY)) {
1978          NODE_T *tertiary = q;
1979          q = SUB (q);
1980          if (q != NO_NODE && IS (q, SECONDARY)) {
1981            q = SUB (q);
1982            if (q != NO_NODE && IS (q, PRIMARY)) {
1983              q = SUB (q);
1984              if (q != NO_NODE && IS (q, IDENTIFIER)) {
1985                if (is_identifier_or_label_global (TABLE (q), NSYMBOL (q)) == LABEL) {
1986                  ATTRIBUTE (tertiary) = JUMP;
1987                  SUB (tertiary) = q;
1988                }
1989              }
1990            }
1991          }
1992        }
1993      } else if (IS (p, TERTIARY)) {
1994        NODE_T *q = SUB (p);
1995        if (q != NO_NODE && IS (q, SECONDARY)) {
1996          NODE_T *secondary = q;
1997          q = SUB (q);
1998          if (q != NO_NODE && IS (q, PRIMARY)) {
1999            q = SUB (q);
2000            if (q != NO_NODE && IS (q, IDENTIFIER)) {
2001              if (is_identifier_or_label_global (TABLE (q), NSYMBOL (q)) == LABEL) {
2002                ATTRIBUTE (secondary) = JUMP;
2003                SUB (secondary) = q;
2004              }
2005            }
2006          }
2007        }
2008      } else if (IS (p, SECONDARY)) {
2009        NODE_T *q = SUB (p);
2010        if (q != NO_NODE && IS (q, PRIMARY)) {
2011          NODE_T *primary = q;
2012          q = SUB (q);
2013          if (q != NO_NODE && IS (q, IDENTIFIER)) {
2014            if (is_identifier_or_label_global (TABLE (q), NSYMBOL (q)) == LABEL) {
2015              ATTRIBUTE (primary) = JUMP;
2016              SUB (primary) = q;
2017            }
2018          }
2019        }
2020      } else if (IS (p, PRIMARY)) {
2021        NODE_T *q = SUB (p);
2022        if (q != NO_NODE && IS (q, IDENTIFIER)) {
2023          if (is_identifier_or_label_global (TABLE (q), NSYMBOL (q)) == LABEL) {
2024            make_sub (q, q, JUMP);
2025          }
2026        }
2027      }
2028      rearrange_goto_less_jumps (SUB (p));
2029    }
2030  }