X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/0fb669f9d648dfdd7a39478a6b658511455ae966..2b45240d6c1b9177533aa5d83ac1c879198111c5:/src/tables.h diff --git a/src/tables.h b/src/tables.h index 911917fd..8b5c1fa4 100644 --- a/src/tables.h +++ b/src/tables.h @@ -1,22 +1,21 @@ /* Prepare the LALR and GLR parser tables. - Copyright (C) 2002, 2004 Free Software Foundation, Inc. + + Copyright (C) 2002, 2004, 2009-2012 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., 51 Franklin Street, Fifth Floor, Boston, MA - 02110-1301, USA. */ + along with this program. If not, see . */ #ifndef TABLES_H_ # define TABLES_H_ @@ -47,48 +46,71 @@ 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 look-ahead 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;