Fix incorrect comment.

[bison.git] / src / gram.h

diff --git a/src/gram.h b/src/gram.h
index 080ce0d9fe4c701c6af9f2e8e9f3889020216965..b8f316a03945546fa2c6c63267bef98c7e08517d 100644 (file)
--- a/src/gram.h
+++ b/src/gram.h
@@ -1,125 +1,271 @@
-/* Data definitions for internal representation of bison's input,
-   Copyright (C) 1984, 1986, 1989, 1992 Free Software Foundation, Inc.
+/* Data definitions for internal representation of Bison's input.

 
 

-This file is part of Bison, the GNU Compiler Compiler.
+   Copyright (C) 1984, 1986, 1989, 1992, 2001, 2002, 2003, 2004, 2005
+   Free Software Foundation, Inc.

 
 

-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 file is part of Bison, the GNU Compiler Compiler.

 
 

-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.
+   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.

 
 

-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, 675 Mass Ave, Cambridge, MA 02139, USA.  */
+   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.

 
 

+   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.  */

 
 

-/* representation of the grammar rules:
+#ifndef GRAM_H_
+# define GRAM_H_

 
 

-ntokens is the number of tokens, and nvars is the number of variables
-(nonterminals).  nsyms is the total number, ntokens + nvars.
+/* Representation of the grammar rules:

 
 

-       (the true number of token values assigned is ntokens
-       reduced by one for each alias declaration)
+   NTOKENS is the number of tokens, and NVARS is the number of
+   variables (nonterminals).  NSYMS is the total number, ntokens +
+   nvars.

 
 

-Each symbol (either token or variable) receives a symbol number.
-Numbers 0 to ntokens-1 are for tokens, and ntokens to nsyms-1 are for
-variables.  Symbol number zero is the end-of-input token.  This token
-is counted in ntokens.
+   Each symbol (either token or variable) receives a symbol number.
+   Numbers 0 to NTOKENS - 1 are for tokens, and NTOKENS to NSYMS - 1
+   are for variables.  Symbol number zero is the end-of-input token.
+   This token is counted in ntokens.  The true number of token values
+   assigned is NTOKENS reduced by one for each alias declaration.

 
 

-The rules receive rule numbers 1 to nrules in the order they are written.
-Actions and guards are accessed via the rule number.
+   The rules receive rule numbers 1 to NRULES in the order they are
+   written.  More precisely Bison augments the grammar with the
+   initial rule, `$accept: START-SYMBOL $end', which is numbered 1,
+   all the user rules are 2, 3 etc.  Each time a rule number is
+   presented to the user, we subtract 1, so *displayed* rule numbers
+   are 0, 1, 2...

 
 

-The rules themselves are described by three arrays: rrhs, rlhs and
-ritem.  rlhs[R] is the symbol number of the left hand side of rule R.
-The right hand side is stored as symbol numbers in a portion of
-ritem.  rrhs[R] contains the index in ritem of the beginning of the
-portion for rule R.
+   Internally, we cannot use the number 0 for a rule because for
+   instance RITEM stores both symbol (the RHS) and rule numbers: the
+   symbols are shorts >= 0, and rule number are stored negative.
+   Therefore 0 cannot be used, since it would be both the rule number
+   0, and the token $end).

 
 

-If rlhs[R] is -1, the rule has been thrown out by reduce.c
-and should be ignored.
+   Actions are accessed via the rule number.

 
 

-The length of the portion is one greater
- than the number of symbols in the rule's right hand side.
-The last element in the portion contains minus R, which
-identifies it as the end of a portion and says which rule it is for.
+   The rules themselves are described by several arrays: amongst which
+   RITEM, and RULES.

 
 

-The portions of ritem come in order of increasing rule number and are
-followed by an element which is zero to mark the end.  nitems is the
-total length of ritem, not counting the final zero.  Each element of
-ritem is called an "item" and its index in ritem is an item number.
+   RULES is an array of rules, whose members are:

 
 

-Item numbers are used in the finite state machine to represent
-places that parsing can get to.
+   RULES[R].lhs -- the symbol of the left hand side of rule R.

 
 

-Precedence levels are recorded in the vectors sprec and rprec.
-sprec records the precedence level of each symbol,
-rprec the precedence level of each rule.
-rprecsym is the symbol-number of the symbol in %prec for this rule (if any).
+   RULES[R].rhs -- the index in RITEM of the beginning of the portion
+   for rule R.

 
 

-Precedence levels are assigned in increasing order starting with 1 so
-that numerically higher precedence values mean tighter binding as they
-ought to.  Zero as a symbol or rule's precedence means none is
-assigned.
+   RULES[R].prec -- the symbol providing the precedence level of R.

 
 

-Associativities are recorded similarly in rassoc and sassoc.  */
+   RULES[R].precsym -- the symbol attached (via %prec) to give its
+   precedence to R.  Of course, if set, it is equal to `prec', but we
+   need to distinguish one from the other when reducing: a symbol used
+   in a %prec is not useless.

 
 

+   RULES[R].assoc -- the associativity of R.

 
 

-#define        ISTOKEN(s)      ((s) < ntokens)
-#define        ISVAR(s)        ((s) >= ntokens)
+   RULES[R].dprec -- the dynamic precedence level of R (for GLR
+   parsing).

 
 

+   RULES[R].merger -- index of merging function for R (for GLR
+   parsing).
+
+   RULES[R].line -- the line where R was defined.
+
+   RULES[R].useful -- true iff the rule is used (i.e., false if thrown
+   away by reduce).
+
+   The right hand side is stored as symbol numbers in a portion of
+   RITEM.
+
+   The length of the portion is one greater than the number of symbols
+   in the rule's right hand side.  The last element in the portion
+   contains minus R, which identifies it as the end of a portion and
+   says which rule it is for.
+
+   The portions of RITEM come in order of increasing rule number.
+   NRITEMS is the total length of RITEM.  Each element of RITEM is
+   called an "item" and its index in RITEM is an item number.
+
+   Item numbers are used in the finite state machine to represent
+   places that parsing can get to.
+
+   SYMBOLS[I]->prec records the precedence level of each symbol.
+
+   Precedence levels are assigned in increasing order starting with 1
+   so that numerically higher precedence values mean tighter binding
+   as they ought to.  Zero as a symbol or rule's precedence means none
+   is assigned.
+
+   Associativities are recorded similarly in SYMBOLS[I]->assoc.  */
+
+# include "location.h"
+# include "symtab.h"
+
+# define ISTOKEN(i)    ((i) < ntokens)
+# define ISVAR(i)      ((i) >= ntokens)

 
 

-extern int nitems;
-extern int nrules;

 extern int nsyms;
 extern int ntokens;
 extern int nvars;
 
 extern int nsyms;
 extern int ntokens;
 extern int nvars;
 

-extern short *ritem;
-extern short *rlhs;
-extern short *rrhs;
-extern short *rprec;
-extern short *rprecsym;
-extern short *sprec;
-extern short *rassoc;
-extern short *sassoc;
-extern short *rline;           /* Source line number of each rule */
+typedef int item_number;
+extern item_number *ritem;
+extern unsigned int nritems;
+
+/* There is weird relationship between OT1H item_number and OTOH
+   symbol_number and rule_number: we store the latter in
+   item_number.  symbol_number values are stored as-is, while
+   the negation of (rule_number + 1) is stored.
+
+   Therefore, a symbol_number must be a valid item_number, and we
+   sometimes have to perform the converse transformation.  */
+
+static inline item_number
+symbol_number_as_item_number (symbol_number sym)
+{
+  return sym;
+}
+
+static inline symbol_number
+item_number_as_symbol_number (item_number i)
+{
+  return i;
+}
+
+static inline bool
+item_number_is_symbol_number (item_number i)
+{
+  return i >= 0;
+}
+
+/* Rule numbers.  */
+typedef int rule_number;
+extern rule_number nrules;
+
+static inline item_number
+rule_number_as_item_number (rule_number r)
+{
+  return -1 - r;
+}
+
+static inline rule_number
+item_number_as_rule_number (item_number i)
+{
+  return -1 - i;
+}
+
+static inline bool
+item_number_is_rule_number (item_number i)
+{
+  return i < 0;
+}
+
+/*--------.
+| Rules.  |
+`--------*/

 
 

-extern int start_symbol;
+typedef struct
+{
+  /* The number of the rule in the source.  It is usually the index in
+     RULES too, except if there are useless rules.  */
+  rule_number user_number;

 
 

+  /* The index in RULES.  Usually the rule number in the source,
+     except if some rules are useless.  */
+  rule_number number;

 
 

-/* associativity values in elements of rassoc, sassoc.  */
+  symbol *lhs;
+  item_number *rhs;

 
 

-#define RIGHT_ASSOC 1
-#define LEFT_ASSOC 2
-#define NON_ASSOC 3
+  /* This symbol provides both the associativity, and the precedence. */
+  symbol *prec;

 
 

-/* token translation table:
-indexed by a token number as returned by the user's yylex routine,
-it yields the internal token number used by the parser and throughout bison.
-If translations is zero, the translation table is not used because
-the two kinds of token numbers are the same.  
-(It is noted in reader.c that "Nowadays translations is always set to 1...")
-*/
+  int dprec;
+  int merger;

 
 

-extern short *token_translations;
-extern int translations;
+  /* This symbol was attached to the rule via %prec. */
+  symbol *precsym;
+
+  location location;
+  bool useful;
+
+  const char *action;
+  location action_location;
+} rule;
+
+extern rule *rules;
+
+/* A function that selects a rule.  */
+typedef bool (*rule_filter) (rule *);
+
+/* Return true IFF the rule has a `number' smaller than NRULES.  */
+bool rule_useful_p (rule *r);
+
+/* Return true IFF the rule has a `number' higher than NRULES.  */
+bool rule_useless_p (rule *r);
+
+/* Return true IFF the rule is not flagged as useful *and* is useful.
+   In other words, it was discarded because of conflicts.  */
+bool rule_never_reduced_p (rule *r);
+
+/* Print this rule's number and lhs on OUT.  If a PREVIOUS_LHS was
+   already displayed (by a previous call for another rule), avoid
+   useless repetitions.  */
+void rule_lhs_print (rule *r, symbol *previous_lhs, FILE *out);
+
+/* Return the length of the RHS.  */
+int rule_rhs_length (rule *r);
+
+/* Print this rule's RHS on OUT.  */
+void rule_rhs_print (rule *r, FILE *out);
+
+/* Print this rule on OUT.  */
+void rule_print (rule *r, FILE *out);
+
+
+
+
+/* Table of the symbols, indexed by the symbol number. */
+extern symbol **symbols;
+
+/* TOKEN_TRANSLATION -- a table indexed by a token number as returned
+   by the user's yylex routine, it yields the internal token number
+   used by the parser and throughout bison.  */
+extern symbol_number *token_translations;

 extern int max_user_token_number;
 
 extern int max_user_token_number;
 

-/* semantic_parser is nonzero if the input file says to use the hairy parser
-that provides for semantic error recovery.  If it is zero, the yacc-compatible
-simplified parser is used.  */

 
 

-extern int semantic_parser;

 
 

-/* pure_parser is nonzero if should generate a parser that is all pure and reentrant. */
+/* Dump RITEM for traces. */
+void ritem_print (FILE *out);
+
+/* Return the size of the longest rule RHS.  */
+size_t ritem_longest_rhs (void);
+
+/* Print the grammar's rules numbers from BEGIN (inclusive) to END
+   (exclusive) on OUT under TITLE.  */
+void grammar_rules_partial_print (FILE *out, const char *title,
+                                 rule_filter filter);
+
+/* Print the grammar's rules on OUT.  */
+void grammar_rules_print (FILE *out);
+
+/* Dump the grammar. */
+void grammar_dump (FILE *out, const char *title);

 
 

-extern int pure_parser;
+/* Report on STDERR the rules that are not flagged USEFUL, using the
+   MESSAGE (which can be `useless rule' when invoked after grammar
+   reduction, or `never reduced' after conflicts were taken into
+   account).  */
+void grammar_rules_never_reduced_report (const char *message);

 
 

-/* error_token_number is the token number of the error token.  */
+/* Free the packed grammar. */
+void grammar_free (void);

 
 

-extern int error_token_number;
+#endif /* !GRAM_H_ */