src/gram.h

   1 /* Data definitions for internal representation of bison's input,
   2    Copyright 1984, 1986, 1989, 1992 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 three arrays: rrhs, rlhs and
  42    ritem.  rlhs[R] is the symbol number of the left hand side of rule
  43    R.  The right hand side is stored as symbol numbers in a portion of
  44    ritem.  rrhs[R] contains the index in ritem of the beginning of the
  45    portion for rule R.
  46
  47    If rlhs[R] is -1, the rule has been thrown out by reduce.c and
  48    should be ignored.
  49
  50    The length of the portion is one greater than the number of symbols
  51    in the rule's right hand side.  The last element in the portion
  52    contains minus R, which identifies it as the end of a portion and
  53    says which rule it is for.
  54
  55    The portions of ritem come in order of increasing rule number and
  56    are followed by an element which is zero to mark the end.  nitems
  57    is the total length of ritem, not counting the final zero.  Each
  58    element of ritem is called an "item" and its index in ritem is an
  59    item number.
  60
  61    Item numbers are used in the finite state machine to represent
  62    places that parsing can get to.
  63
  64    Precedence levels are recorded in the vectors sprec and rprec.
  65    sprec records the precedence level of each symbol, rprec the
  66    precedence level of each rule.  rprecsym is the symbol-number of
  67    the symbol in %prec for this rule (if any).
  68
  69    Precedence levels are assigned in increasing order starting with 1
  70    so that numerically higher precedence values mean tighter binding
  71    as they ought to.  Zero as a symbol or rule's precedence means none
  72    is assigned.
  73
  74    Associativities are recorded similarly in rassoc and sassoc.  */
  75
  76
  77 #define ISTOKEN(s)      ((s) < ntokens)
  78 #define ISVAR(s)        ((s) >= ntokens)
  79
  80 extern int nitems;
  81 extern int nrules;
  82 extern int nsyms;
  83 extern int ntokens;
  84 extern int nvars;
  85
  86 extern short *ritem;
  87 extern short *rlhs;
  88 extern short *rrhs;
  89 extern short *rprec;
  90 extern short *rprecsym;
  91 extern short *sprec;
  92 extern short *rassoc;
  93 extern short *sassoc;
  94 extern short *rline;            /* Source line number of each rule */
  95
  96 extern int start_symbol;
  97
  98
  99 /* associativity values in elements of rassoc, sassoc.  */
 100 typedef enum
 101 {
 102   right_assoc,
 103   left_assoc,
 104   non_assoc
 105 } associativity;
 106
 107
 108 /* token translation table: indexed by a token number as returned by
 109    the user's yylex routine, it yields the internal token number used
 110    by the parser and throughout bison.  If translations is zero, the
 111    translation table is not used because the two kinds of token
 112    numbers are the same.  (It is noted in reader.c that "Nowadays
 113    translations is always set to 1...") */
 114
 115 extern short *token_translations;
 116 extern int translations;
 117 extern int max_user_token_number;
 118
 119 /* SEMANTIC_PARSER is nonzero if the input file says to use the hairy
 120    parser that provides for semantic error recovery.  If it is zero,
 121    the yacc-compatible simplified parser is used.  */
 122
 123 extern int semantic_parser;
 124
 125 /* PURE_PARSER is nonzero if should generate a parser that is all pure
 126    and reentrant.  */
 127
 128 extern int pure_parser;
 129
 130 /* ERROR_TOKEN_NUMBER is the token number of the error token.  */
 131
 132 extern int error_token_number;
 133 #endif /* !GRAM_H_ */