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    The right hand side is stored as symbol numbers in a portion of
  54    RITEM.
  55
  56    The length of the portion is one greater than the number of symbols
  57    in the rule's right hand side.  The last element in the portion
  58    contains minus R, which identifies it as the end of a portion and
  59    says which rule it is for.
  60
  61    The portions of RITEM come in order of increasing rule number and
  62    are followed by an element which is zero to mark the end.  nitems
  63    is the total length of ritem, not counting the final zero.  Each
  64    element of ritem is called an "item" and its index in ritem is an
  65    item number.
  66
  67    Item numbers are used in the finite state machine to represent
  68    places that parsing can get to.
  69
  70    Precedence levels are recorded in the vectors sprec and rprec.
  71    sprec records the precedence level of each symbol, rprec the
  72    precedence level of each rule.  rprecsym is the symbol-number of
  73    the symbol in %prec for this rule (if any).
  74
  75    Precedence levels are assigned in increasing order starting with 1
  76    so that numerically higher precedence values mean tighter binding
  77    as they ought to.  Zero as a symbol or rule's precedence means none
  78    is assigned.
  79
  80    Associativities are recorded similarly in rassoc and sassoc.  */
  81
  82
  83 #define ISTOKEN(s)      ((s) < ntokens)
  84 #define ISVAR(s)        ((s) >= ntokens)
  85
  86 extern int nitems;
  87 extern int nrules;
  88 extern int nsyms;
  89 extern int ntokens;
  90 extern int nvars;
  91
  92 extern short *ritem;
  93
  94 extern short *rprec;
  95 extern short *rprecsym;
  96 extern short *sprec;
  97 extern short *rassoc;
  98 extern short *sassoc;
  99 extern short *rline;            /* Source line number of each rule */
 100
 101 extern int start_symbol;
 102
 103 typedef struct rule_s
 104 {
 105   short lhs;
 106   short rhs;
 107 } rule_t;
 108
 109 extern struct rule_s *rule_table;
 110
 111 /* associativity values in elements of rassoc, sassoc.  */
 112 typedef enum
 113 {
 114   right_assoc,
 115   left_assoc,
 116   non_assoc
 117 } associativity;
 118
 119
 120 /* token translation table: indexed by a token number as returned by
 121    the user's yylex routine, it yields the internal token number used
 122    by the parser and throughout bison.  */
 123
 124 extern short *token_translations;
 125 extern int max_user_token_number;
 126
 127 /* SEMANTIC_PARSER is nonzero if the input file says to use the hairy
 128    parser that provides for semantic error recovery.  If it is zero,
 129    the yacc-compatible simplified parser is used.  */
 130
 131 extern int semantic_parser;
 132
 133 /* PURE_PARSER is nonzero if should generate a parser that is all pure
 134    and reentrant.  */
 135
 136 extern int pure_parser;
 137
 138 /* ERROR_TOKEN_NUMBER is the token number of the error token.  */
 139
 140 extern int error_token_number;
 141 #endif /* !GRAM_H_ */