1/* Data definitions for internal representation of Bison's input.
2
3   Copyright (C) 1984, 1986, 1989, 1992, 2001, 2002, 2003, 2004, 2005
4   Free Software Foundation, Inc.
5
6   This file is part of Bison, the GNU Compiler Compiler.
7
8   Bison is free software; you can redistribute it and/or modify
9   it under the terms of the GNU General Public License as published by
10   the Free Software Foundation; either version 2, or (at your option)
11   any later version.
12
13   Bison is distributed in the hope that it will be useful,
14   but WITHOUT ANY WARRANTY; without even the implied warranty of
15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16   GNU General Public License for more details.
17
18   You should have received a copy of the GNU General Public License
19   along with Bison; see the file COPYING.  If not, write to
20   the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
21   Boston, MA 02110-1301, USA.  */
22
23#ifndef GRAM_H_
24# define GRAM_H_
25
26/* Representation of the grammar rules:
27
28   NTOKENS is the number of tokens, and NVARS is the number of
29   variables (nonterminals).  NSYMS is the total number, ntokens +
30   nvars.
31
32   Each symbol (either token or variable) receives a symbol number.
33   Numbers 0 to NTOKENS - 1 are for tokens, and NTOKENS to NSYMS - 1
34   are for variables.  Symbol number zero is the end-of-input token.
35   This token is counted in ntokens.  The true number of token values
36   assigned is NTOKENS reduced by one for each alias declaration.
37
38   The rules receive rule numbers 1 to NRULES in the order they are
39   written.  More precisely Bison augments the grammar with the
40   initial rule, `$accept: START-SYMBOL $end', which is numbered 1,
41   all the user rules are 2, 3 etc.  Each time a rule number is
42   presented to the user, we subtract 1, so *displayed* rule numbers
43   are 0, 1, 2...
44
45   Internally, we cannot use the number 0 for a rule because for
46   instance RITEM stores both symbol (the RHS) and rule numbers: the
47   symbols are shorts >= 0, and rule number are stored negative.
48   Therefore 0 cannot be used, since it would be both the rule number
49   0, and the token $end).
50
51   Actions are accessed via the rule number.
52
53   The rules themselves are described by several arrays: amongst which
54   RITEM, and RULES.
55
56   RULES is an array of rules, whose members are:
57
58   RULES[R].lhs -- the symbol of the left hand side of rule R.
59
60   RULES[R].rhs -- the index in RITEM of the beginning of the portion
61   for rule R.
62
63   RULES[R].prec -- the symbol providing the precedence level of R.
64
65   RULES[R].precsym -- the symbol attached (via %prec) to give its
66   precedence to R.  Of course, if set, it is equal to `prec', but we
67   need to distinguish one from the other when reducing: a symbol used
68   in a %prec is not useless.
69
70   RULES[R].assoc -- the associativity of R.
71
72   RULES[R].dprec -- the dynamic precedence level of R (for GLR
73   parsing).
74
75   RULES[R].merger -- index of merging function for R (for GLR
76   parsing).
77
78   RULES[R].line -- the line where R was defined.
79
80   RULES[R].useful -- true iff the rule is used (i.e., false if thrown
81   away by reduce).
82
83   The right hand side is stored as symbol numbers in a portion of
84   RITEM.
85
86   The length of the portion is one greater than the number of symbols
87   in the rule's right hand side.  The last element in the portion
88   contains minus R, which identifies it as the end of a portion and
89   says which rule it is for.
90
91   The portions of RITEM come in order of increasing rule number.
92   NRITEMS is the total length of RITEM.  Each element of RITEM is
93   called an "item" and its index in RITEM is an item number.
94
95   Item numbers are used in the finite state machine to represent
96   places that parsing can get to.
97
98   SYMBOLS[I]->prec records the precedence level of each symbol.
99
100   Precedence levels are assigned in increasing order starting with 1
101   so that numerically higher precedence values mean tighter binding
102   as they ought to.  Zero as a symbol or rule's precedence means none
103   is assigned.
104
105   Associativities are recorded similarly in SYMBOLS[I]->assoc.  */
106
107# include "location.h"
108# include "symtab.h"
109
110# define ISTOKEN(i)	((i) < ntokens)
111# define ISVAR(i)	((i) >= ntokens)
112
113extern int nsyms;
114extern int ntokens;
115extern int nvars;
116
117typedef int item_number;
118extern item_number *ritem;
119extern unsigned int nritems;
120
121/* There is weird relationship between OT1H item_number and OTOH
122   symbol_number and rule_number: we store the latter in
123   item_number.  symbol_number values are stored as-is, while
124   the negation of (rule_number + 1) is stored.
125
126   Therefore, a symbol_number must be a valid item_number, and we
127   sometimes have to perform the converse transformation.  */
128
129static inline item_number
130symbol_number_as_item_number (symbol_number sym)
131{
132  return sym;
133}
134
135static inline symbol_number
136item_number_as_symbol_number (item_number i)
137{
138  return i;
139}
140
141static inline bool
142item_number_is_symbol_number (item_number i)
143{
144  return i >= 0;
145}
146
147/* Rule numbers.  */
148typedef int rule_number;
149extern rule_number nrules;
150
151static inline item_number
152rule_number_as_item_number (rule_number r)
153{
154  return -1 - r;
155}
156
157static inline rule_number
158item_number_as_rule_number (item_number i)
159{
160  return -1 - i;
161}
162
163static inline bool
164item_number_is_rule_number (item_number i)
165{
166  return i < 0;
167}
168
169/*--------.
170| Rules.  |
171`--------*/
172
173typedef struct
174{
175  /* The number of the rule in the source.  It is usually the index in
176     RULES too, except if there are useless rules.  */
177  rule_number user_number;
178
179  /* The index in RULES.  Usually the rule number in the source,
180     except if some rules are useless.  */
181  rule_number number;
182
183  symbol *lhs;
184  item_number *rhs;
185
186  /* This symbol provides both the associativity, and the precedence. */
187  symbol *prec;
188
189  int dprec;
190  int merger;
191
192  /* This symbol was attached to the rule via %prec. */
193  symbol *precsym;
194
195  location location;
196  bool useful;
197
198  const char *action;
199  location action_location;
200} rule;
201
202extern rule *rules;
203
204/* A function that selects a rule.  */
205typedef bool (*rule_filter) (rule *);
206
207/* Return true IFF the rule has a `number' smaller than NRULES.  */
208bool rule_useful_p (rule *r);
209
210/* Return true IFF the rule has a `number' higher than NRULES.  */
211bool rule_useless_p (rule *r);
212
213/* Return true IFF the rule is not flagged as useful *and* is useful.
214   In other words, it was discarded because of conflicts.  */
215bool rule_never_reduced_p (rule *r);
216
217/* Print this rule's number and lhs on OUT.  If a PREVIOUS_LHS was
218   already displayed (by a previous call for another rule), avoid
219   useless repetitions.  */
220void rule_lhs_print (rule *r, symbol *previous_lhs, FILE *out);
221
222/* Return the length of the RHS.  */
223int rule_rhs_length (rule *r);
224
225/* Print this rule's RHS on OUT.  */
226void rule_rhs_print (rule *r, FILE *out);
227
228/* Print this rule on OUT.  */
229void rule_print (rule *r, FILE *out);
230
231
232
233
234/* Table of the symbols, indexed by the symbol number. */
235extern symbol **symbols;
236
237/* TOKEN_TRANSLATION -- a table indexed by a token number as returned
238   by the user's yylex routine, it yields the internal token number
239   used by the parser and throughout bison.  */
240extern symbol_number *token_translations;
241extern int max_user_token_number;
242
243
244
245/* Dump RITEM for traces. */
246void ritem_print (FILE *out);
247
248/* Return the size of the longest rule RHS.  */
249size_t ritem_longest_rhs (void);
250
251/* Print the grammar's rules numbers from BEGIN (inclusive) to END
252   (exclusive) on OUT under TITLE.  */
253void grammar_rules_partial_print (FILE *out, const char *title,
254				  rule_filter filter);
255
256/* Print the grammar's rules on OUT.  */
257void grammar_rules_print (FILE *out);
258
259/* Dump the grammar. */
260void grammar_dump (FILE *out, const char *title);
261
262/* Report on STDERR the rules that are not flagged USEFUL, using the
263   MESSAGE (which can be `useless rule' when invoked after grammar
264   reduction, or `never reduced' after conflicts were taken into
265   account).  */
266void grammar_rules_never_reduced_report (const char *message);
267
268/* Free the packed grammar. */
269void grammar_free (void);
270
271#endif /* !GRAM_H_ */
272