/* Prepare the LALR and GLR parser tables.
- Copyright (C) 2002 Free Software Foundation, Inc.
+ Copyright (C) 2002, 2004, 2009 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.
+ This program 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 3 of the License, 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.
+ This program 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., 59 Temple Place - Suite 330, Boston, MA
- 02111-1307, USA. */
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
#ifndef TABLES_H_
# define TABLES_H_
YYSTOS[S] = the symbol number of the symbol that leads to state S.
- YYDEFACT[S] = default rule to reduce with in state s, when YYTABLE
- doesn't specify something else to do. Zero means the default is an
- error.
+ YYFINAL = the state number of the termination state.
+
+ YYTABLE = a vector filled with portions for different uses, found
+ via YYPACT and YYPGOTO, described below.
+
+ YYLAST ( = high) the number of the last element of YYTABLE, i.e.,
+ sizeof (YYTABLE) - 1.
+
+ YYCHECK = a vector indexed in parallel with YYTABLE. It indicates,
+ in a roundabout way, the bounds of the portion you are trying to
+ examine.
+
+ Suppose that the portion of YYTABLE starts at index P and the index
+ to be examined within the portion is I. Then if YYCHECK[P+I] != I,
+ I is outside the bounds of what is actually allocated, and the
+ default (from YYDEFACT or YYDEFGOTO) should be used. Otherwise,
+ YYTABLE[P+I] should be used.
+
+ YYDEFACT[S] = default reduction number in state s. Performed when
+ YYTABLE doesn't specify something else to do. Zero means the default
+ is an error.
YYDEFGOTO[I] = default state to go to after a reduction of a rule
that generates variable NTOKENS + I, except when YYTABLE specifies
something else to do.
YYPACT[S] = index in YYTABLE of the portion describing state S.
- The lookahead token's type is used to index that portion to find
- out what to do.
+ The lookahead token's number, I, is used to index that portion of
+ YYTABLE to find out what action to perform.
+
+ If YYPACT[S] == YYPACT_NINF, if YYPACT[S] + I is outside the bounds
+ of YYTABLE (from 0 to YYLAST), or I is outside the bounds for portion
+ S (that is, YYCHECK[YYPACT[S] + I] != I), then the default action
+ (that is, YYDEFACT[S]) should be used instead of YYTABLE. Otherwise,
+ the value YYTABLE[YYPACT[S] + I] should be used even if
+ YYPACT[S] < 0.
If the value in YYTABLE is positive, we shift the token and go to
that state.
If the value is negative, it is minus a rule number to reduce by.
- If the value is zero, the default action from YYDEFACT[S] is used.
+ If the value is YYTABLE_NINF, it's a syntax error.
YYPGOTO[I] = the index in YYTABLE of the portion describing what to
do after reducing a rule that derives variable I + NTOKENS. This
portion is indexed by the parser state number, S, as of before the
- text for this nonterminal was read. The value from YYTABLE is the
- state to go to if the corresponding value in YYCHECK is S.
-
- YYTABLE = a vector filled with portions for different uses, found
- via YYPACT and YYPGOTO.
-
- YYCHECK = a vector indexed in parallel with YYTABLE. It indicates,
- in a roundabout way, the bounds of the portion you are trying to
- examine.
-
- Suppose that the portion of YYTABLE starts at index P and the index
- to be examined within the portion is I. Then if YYCHECK[P+I] != I,
- I is outside the bounds of what is actually allocated, and the
- default (from YYDEFACT or YYDEFGOTO) should be used. Otherwise,
- YYTABLE[P+I] should be used.
-
- YYFINAL = the state number of the termination state.
-
- YYLAST ( = high) the number of the last element of YYTABLE, i.e.,
- sizeof (YYTABLE) - 1. */
+ text for this nonterminal was read.
+
+ If YYPGOTO[I] + S is outside the bounds of YYTABLE (from 0 to YYLAST)
+ or if S is outside the bounds of the portion for I (that is,
+ YYCHECK[YYPGOTO[I] + S] != S), then the default state (that is,
+ YYDEFGOTO[I]) should be used instead of YYTABLE. Otherwise,
+ YYTABLE[YYPGOTO[I] + S] is the state to go to even if YYPGOTO[I] < 0.
+
+ When the above YYPACT, YYPGOTO, and YYCHECK tests determine that a
+ value from YYTABLE should be used, that value is never zero, so it is
+ useless to check for zero. When those tests indicate that the value
+ from YYDEFACT or YYDEFGOTO should be used instead, the value from
+ YYTABLE *might* be zero, which, as a consequence of the way in which
+ the tables are constructed, also happens to indicate that YYDEFACT or
+ YYDEFGOTO should be used. However, the YYTABLE value cannot be
+ trusted when the YYDEFACT or YYDEFGOTO value should be used. In
+ summary, forget about zero values in YYTABLE.
+*/
extern int nvectors;
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