src/gram.h

   1 /* Data definitions for internal representation of bison's input,
   2    Copyright 1984, 1986, 1989, 1992, 2001  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 GRAM_H_
  22 # define GRAM_H_
  23
  24 /* representation of the grammar rules:
  25
  26    ntokens is the number of tokens, and nvars is the number of
  27    variables (nonterminals).  nsyms is the total number, ntokens +
  28    nvars.
  29
  30    (the true number of token values assigned is ntokens reduced by one
  31    for each alias declaration)
  32
  33    Each symbol (either token or variable) receives a symbol number.
  34    Numbers 0 to ntokens-1 are for tokens, and ntokens to nsyms-1 are
  35    for variables.  Symbol number zero is the end-of-input token.  This
  36    token is counted in ntokens.
  37
  38    The rules receive rule numbers 1 to nrules in the order they are
  39    written.  Actions and guards are accessed via the rule number.
  40
  41    The rules themselves are described by several arrays: amongst which
  42    RITEM, and RULE_TABLE.
  43
  44    RULE_TABLE is an array of struct rule_s, which members are:
  45
  46    RULE_TABLE[R].lhs -- the symbol number of the left hand side of
  47    rule R.  If -1, the rule has been thrown out by reduce.c and should
  48    be ignored.
  49
  50    RULE_TABLE[R].rhs -- the index in RITEM of the beginning of the
  51    portion for rule R.
  52
  53    RULE_TABLE[R].prec -- the precedence level of R.
  54
  55    RULE_TABLE[R].precsym -- the symbol-number of the symbol in %prec
  56    for R (if any).
  57
  58    RULE_TABLE[R].assoc -- the associativity of R.
  59
  60    RULE_TABLE[R].line -- the line where R was defined.
  61
  62    The right hand side is stored as symbol numbers in a portion of
  63    RITEM.
  64
  65    The length of the portion is one greater than the number of symbols
  66    in the rule's right hand side.  The last element in the portion
  67    contains minus R, which identifies it as the end of a portion and
  68    says which rule it is for.
  69
  70    The portions of RITEM come in order of increasing rule number and
  71    are followed by an element which is zero to mark the end.  nitems
  72    is the total length of ritem, not counting the final zero.  Each
  73    element of ritem is called an "item" and its index in ritem is an
  74    item number.
  75
  76    Item numbers are used in the finite state machine to represent
  77    places that parsing can get to.
  78
  79    SPREC records the precedence level of each symbol.
  80
  81    Precedence levels are assigned in increasing order starting with 1
  82    so that numerically higher precedence values mean tighter binding
  83    as they ought to.  Zero as a symbol or rule's precedence means none
  84    is assigned.
  85
  86    Associativities are recorded similarly in rassoc and sassoc.  */
  87
  88
  89 #define ISTOKEN(s)      ((s) < ntokens)
  90 #define ISVAR(s)        ((s) >= ntokens)
  91
  92 extern int nitems;
  93 extern int nrules;
  94 extern int nsyms;
  95 extern int ntokens;
  96 extern int nvars;
  97
  98 extern short *ritem;
  99
 100 extern short *sprec;
 101 extern short *sassoc;
 102
 103 extern int start_symbol;
 104
 105 /* associativity values in elements of rassoc, sassoc.  */
 106 typedef enum
 107 {
 108   right_assoc,
 109   left_assoc,
 110   non_assoc
 111 } associativity;
 112
 113
 114 typedef struct rule_s
 115 {
 116   short lhs;
 117   short rhs;
 118   short prec;
 119   short precsym;
 120   short assoc;
 121   short line;
 122 } rule_t;
 123
 124 extern struct rule_s *rule_table;
 125
 126 /* token translation table: indexed by a token number as returned by
 127    the user's yylex routine, it yields the internal token number used
 128    by the parser and throughout bison.  */
 129
 130 extern short *token_translations;
 131 extern int max_user_token_number;
 132
 133 /* SEMANTIC_PARSER is nonzero if the input file says to use the hairy
 134    parser that provides for semantic error recovery.  If it is zero,
 135    the yacc-compatible simplified parser is used.  */
 136
 137 extern int semantic_parser;
 138
 139 /* PURE_PARSER is nonzero if should generate a parser that is all pure
 140    and reentrant.  */
 141
 142 extern int pure_parser;
 143
 144 /* ERROR_TOKEN_NUMBER is the token number of the error token.  */
 145
 146 extern int error_token_number;
 147 #endif /* !GRAM_H_ */