/* Data definitions for internal representation of bison's input,
- Copyright 1984, 1986, 1989, 1992, 2001 Free Software Foundation, Inc.
+ Copyright (C) 1984, 1986, 1989, 1992, 2001, 2002
+ Free Software Foundation, Inc.
This file is part of Bison, the GNU Compiler Compiler.
#ifndef GRAM_H_
# define GRAM_H_
-/* representation of the grammar rules:
+/* Representation of the grammar rules:
- ntokens is the number of tokens, and nvars is the number of
- variables (nonterminals). nsyms is the total number, ntokens +
+ NTOKENS is the number of tokens, and NVARS is the number of
+ variables (nonterminals). NSYMS is the total number, ntokens +
nvars.
- (the true number of token values assigned is ntokens reduced by one
- for each alias declaration)
-
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 rules receive rule numbers 1 to nrules in the order they are
- written. Actions and guards are accessed via the rule 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. More precisely Bison augments the grammar with the
+ initial rule, `$axiom: START-SYMBOL EOF', 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...
+
+ 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 EOF).
+
+ Actions and guards are accessed via the rule number.
The rules themselves are described by several arrays: amongst which
- RITEM, and RULE_TABLE.
+ RITEM, and RULES.
+
+ RULES is an array of struct rule_s, which members are:
- RULE_TABLE is an array of struct rule_s, which members are:
+ RULES[R].lhs -- the symbol of the left hand side of rule R.
- RULE_TABLE[R].lhs -- the symbol number of the left hand side of
- rule R. If -1, the rule has been thrown out by reduce.c and should
- be ignored.
+ RULES[R].rhs -- the index in RITEM of the beginning of the portion
+ for rule R.
- RULE_TABLE[R].rhs -- the index in RITEM of the beginning of the
- portion for rule R.
+ RULES[R].prec -- the symbol providing the precedence level of R.
- RULE_TABLE[R].prec -- the precedence level of R.
+ 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.
- RULE_TABLE[R].precsym -- the symbol-number of the symbol in %prec
- for R (if any).
+ RULES[R].assoc -- the associativity of R.
- RULE_TABLE[R].assoc -- the associativity of the rule.
+ 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.
says which rule it is for.
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
+ are followed by an element which is zero to mark the end. nritems
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
+ 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.
- SPREC records the precedence level of each symbol.
+ 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 rassoc and sassoc. */
+ Associativities are recorded similarly in SYMBOLS[I]->assoc. */
+#include "symtab.h"
#define ISTOKEN(s) ((s) < ntokens)
#define ISVAR(s) ((s) >= ntokens)
-extern int nitems;
extern int nrules;
extern int nsyms;
extern int ntokens;
extern int nvars;
extern short *ritem;
-
-extern short *sprec;
-extern short *sassoc;
-extern short *rline; /* Source line number of each rule */
+extern int nritems;
extern int start_symbol;
-/* associativity values in elements of rassoc, sassoc. */
-typedef enum
+typedef struct rule_s
{
- right_assoc,
- left_assoc,
- non_assoc
-} associativity;
+ /* The number of the rule in the source. It is usually the index in
+ RULES too, except if there are useless rules. */
+ short user_number;
+ /* The index in RULES. Usually the rule number in the source,
+ except if some rules are useless. */
+ short number;
-typedef struct rule_s
-{
- short lhs;
- short rhs;
- short prec;
- short precsym;
- short assoc;
+ symbol_t *lhs;
+ short *rhs;
+
+ /* This symbol provides both the associativity, and the precedence. */
+ symbol_t *prec;
+
+ /* This symbol was attached to the rule via %prec. */
+ symbol_t *precsym;
+
+ short line;
+ bool useful;
+
+ const char *action;
+ short action_line;
+
+ const char *guard;
+ short guard_line;
} rule_t;
-extern struct rule_s *rule_table;
+extern struct rule_s *rules;
+
+/* Table of the symbols, indexed by the symbol number. */
+extern symbol_t **symbols;
/* token translation table: indexed by a token number as returned by
the user's yylex routine, it yields the internal token number used
/* ERROR_TOKEN_NUMBER is the token number of the error token. */
extern int error_token_number;
+
+/* Report the length of the RHS. */
+int rule_rhs_length PARAMS ((rule_t *rule));
+
+/* Dump RITEM for traces. */
+void ritem_print PARAMS ((FILE *out));
+
+/* Return the size of the longest rule RHS. */
+size_t ritem_longest_rhs PARAMS ((void));
+
#endif /* !GRAM_H_ */
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