src/lalr.h

   1 /* Compute look-ahead criteria for bison,
   2    Copyright 1984, 1986, 1989, 2000 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
  25 /* Import the definition of CORE, SHIFTS and REDUCTIONS. */
  26 # include "state.h"
  27
  28
  29 /* Compute how to make the finite state machine deterministic; find
  30    which rules need lookahead in each state, and which lookahead
  31    tokens they accept.  */
  32
  33 void lalr PARAMS ((void));
  34
  35
  36 /* lalr() builds these data structures. */
  37
  38 /* GOTO_MAP, FROM_STATE and TO_STATE -- record each shift transition
  39    which accepts a variable (a nonterminal).
  40
  41    FROM_STATE[T] -- state number which a transition leads from.
  42    TO_STATE[T] -- state number it leads to.
  43
  44    All the transitions that accept a particular variable are grouped
  45    together and GOTO_MAP[I - NTOKENS] is the index in FROM_STATE and
  46    TO_STATE of the first of them.  */
  47
  48 extern short *goto_map;
  49 extern short *from_state;
  50 extern short *to_state;
  51
  52 /* LARULENO is a vector which records the rules that need lookahead in
  53    various states.  The elements of LARULENO that apply to state S are
  54    those from LOOKAHEADS[S] through LOOKAHEADS[S+1]-1.  Each element
  55    of LARULENO is a rule number.
  56
  57    If LR is the length of LAruleno, then a number from 0 to LR-1 can
  58    specify both a rule and a state where the rule might be applied.
  59    */
  60
  61 extern short *LAruleno;
  62
  63 /* LA is a lr by ntokens matrix of bits.  LA[l, i] is 1 if the rule
  64    LAruleno[l] is applicable in the appropriate state when the next
  65    token is symbol i.  If LA[l, i] and LA[l, j] are both 1 for i != j,
  66    it is a conflict.  */
  67
  68 extern unsigned *LA;
  69 #define LA(Rule) (LA + (Rule) * tokensetsize)
  70
  71
  72 /* A structure decorating a state, with additional information. */
  73 typedef struct state_s
  74 {
  75   /* A state.  */
  76   core *state;
  77
  78   /* Its accessing symbol. */
  79   short accessing_symbol;
  80
  81   shifts *shift_table;
  82   reductions *reduction_table;
  83
  84   /* Nonzero if no lookahead is needed to decide what to do in state
  85      S.  */
  86   char consistent;
  87
  88   short lookaheads;
  89 } state_t;
  90
  91 /* All the decorated states, indexed by the state number.  Warning:
  92    there is a state_TABLE in LR0.c, but it is different and static.
  93    */
  94 extern state_t *state_table;
  95
  96 extern int tokensetsize;
  97
  98 /* The number of lookaheads. */
  99 extern size_t nlookaheads;
 100 #endif /* !LALR_H_ */