* NEWS (2.3a+): Mention yesterday's state-removal change.

[bison.git] / src / lalr.h

/* Compute lookahead criteria for bison,

   Copyright (C) 1984, 1986, 1989, 2000, 2002, 2004, 2006, 2007 Free Software
   Foundation, Inc.

   This file is part of Bison, the GNU Compiler Compiler.

   Bison is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   Bison is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with Bison; see the file COPYING.  If not, write to
   the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
   Boston, MA 02110-1301, USA.  */

#ifndef LALR_H_
# define LALR_H_

# include <bitset.h>
# include <bitsetv.h>

/* Import the definition of RULE_T. */
# include "gram.h"

/* Import the definition of CORE, TRANSITIONS and REDUCTIONS. */
# include "state.h"


/** Build the LALR(1) automaton.

   Compute how to make the finite state machine deterministic; find
   which rules need lookahead in each state, and which lookahead
   tokens they accept.

   Builds:
   - #goto_map
   - #from_state
   - #to_state
*/
void lalr (void);

/**
 * Update state numbers recorded in #goto_map, #from_state, and #to_state such
 * that:
 *   - \c nstates_old is the old number of states.
 *   - Where \c i is the old state number, <tt>old_to_new[i]</tt> is either:
 *     - \c nstates_old if state \c i is removed because it is unreachable.
 *       Thus, remove all goto entries involving this state.
 *     - The new state number.
 */
void lalr_update_state_numbers (state_number old_to_new[],
                                state_number nstates_old);


/** Release the information related to lookahead tokens.

   Can be performed once the action tables are computed.  */
void lalr_free (void);


typedef size_t goto_number;
# define GOTO_NUMBER_MAXIMUM ((goto_number) -1)

/** Index into #from_state and #to_state.

   All the transitions that accept a particular variable are grouped
   together and GOTO_MAP[I - NTOKENS] is the index in FROM_STATE and
   TO_STATE of the first of them.  */
extern goto_number *goto_map;

/** State number which a transition leads from. */
extern state_number *from_state;

/** State number it leads to.  */
extern state_number *to_state;


#endif /* !LALR_H_ */