src/lalr.h

   1 /* Compute look-ahead criteria for bison,
   2    Copyright (C) 1984, 1986, 1989, 2000, 2002 Free Software Foundation, Inc.
   3
   4    This file is part of Bison, the GNU Compiler Compiler.
   5
   6    Bison is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2, or (at your option)
   9    any later version.
  10
  11    Bison is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with Bison; see the file COPYING.  If not, write to
  18    the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21 #ifndef LALR_H_
  22 # define LALR_H_
  23
  24 #include "bitset.h"
  25
  26 /* Import the definition of CORE, SHIFTS and REDUCTIONS. */
  27 # include "state.h"
  28
  29 /* Import the definition of RULE_T. */
  30 # include "gram.h"
  31
  32 /* Compute how to make the finite state machine deterministic; find
  33    which rules need lookahead in each state, and which lookahead
  34    tokens they accept.  */
  35
  36 void lalr PARAMS ((void));
  37
  38
  39 /* lalr() builds these data structures. */
  40
  41 /* GOTO_MAP, FROM_STATE and TO_STATE -- record each shift transition
  42    which accepts a variable (a nonterminal).
  43
  44    FROM_STATE[T] -- state number which a transition leads from.
  45    TO_STATE[T] -- state number it leads to.
  46
  47    All the transitions that accept a particular variable are grouped
  48    together and GOTO_MAP[I - NTOKENS] is the index in FROM_STATE and
  49    TO_STATE of the first of them.  */
  50
  51 extern short *goto_map;
  52 extern short *from_state;
  53 extern short *to_state;
  54
  55 /* LARULE is a vector which records the rules that need lookahead in
  56    various states.  The elements of LARULE that apply to state S are
  57    those from LOOKAHEADS[S] through LOOKAHEADS[S+1]-1.
  58
  59    If LR is the length of LArule, then a number from 0 to LR-1 can
  60    specify both a rule and a state where the rule might be applied.
  61    */
  62
  63 extern rule_t **LArule;
  64
  65 /* LA is a lr by ntokens matrix of bits.  LA[l, i] is 1 if the rule
  66    LAruleno[l] is applicable in the appropriate state when the next
  67    token is symbol i.  If LA[l, i] and LA[l, j] are both 1 for i != j,
  68    it is a conflict.  */
  69
  70 extern bitset *LA;
  71
  72
  73 /* All the states, indexed by the state number.  */
  74 extern state_t **states;
  75
  76 #endif /* !LALR_H_ */