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Use $accept and $end, as BYacc and BTYacc do, instead of $axiom and $.

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* src/symtab.h, src/symtab.c (eoftoken, axiom): Rename as...
(endtoken, accept): these.
* src/reader.c (reader): Set endtoken's default tag to "$end".
Set undeftoken's tag to "$undefined" instead of "$undefined.".
* doc/bison.texinfo (Table of Symbols): Mention $accept and $end.
Adjust.
This commit is contained in:
Akim Demaille
2002-07-29 17:30:33 +00:00
parent 1bfb97dba5
commit 88bce5a2ef
15 changed files with 163 additions and 131 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
src/LR0.c
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@@ -63,7 +63,7 @@ state_list_append (symbol_number_t symbol,
fprintf (stderr, "state_list_append (state = %d, symbol = %d (%s))\n",
nstates, symbol, symbols[symbol]->tag);
/* If this is the eoftoken, and this is not the initial state, then
/* If this is the endtoken, and this is not the initial state, then
this is the final state. */
if (symbol == 0 && first_state)
final_state = state;
@@ -283,7 +283,7 @@ save_reductions (state_t *state)
int i;
/* If this is the final state, we want it to have no reductions at
all, although it has one for `START_SYMBOL EOF .'. */
all, although it has one for `START_SYMBOL $end .'. */
if (final_state && state->number == final_state->number)
return;

16
src/gram.h
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@@ -36,16 +36,16 @@
The rules receive rule numbers 1 to NRULES in the order they are
written. More precisely Bison augments the grammar with the
initial rule, `$axiom: START-SYMBOL EOF', which is numbered 1, all
the user rules are 2, 3 etc. Each time a rule number is presented
to the user, we subtract 1, so *displayed* rule numbers are 0, 1,
2...
initial rule, `$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...
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).
0, and the token $end).
Actions are accessed via the rule number.
@@ -68,9 +68,11 @@
RULES[R].assoc -- the associativity of R.
RULES[R].dprec -- the dynamic precedence level of R (for GLR parsing).
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].merger -- index of merging function for R (for GLR
parsing).
RULES[R].line -- the line where R was defined.

28
src/reader.c
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@@ -475,10 +475,10 @@ reader (void)
/* Initialize the symbol table. */
symbols_new ();
/* Construct the axiom symbol. */
axiom = symbol_get ("$axiom", empty_location);
axiom->class = nterm_sym;
axiom->number = nvars++;
/* Construct the accept symbol. */
accept = symbol_get ("$accept", empty_location);
accept->class = nterm_sym;
accept->number = nvars++;
/* Construct the error token */
errtoken = symbol_get ("error", empty_location);
@@ -487,7 +487,7 @@ reader (void)
/* Construct a token that represents all undefined literal tokens.
It is always token number 2. */
undeftoken = symbol_get ("$undefined.", empty_location);
undeftoken = symbol_get ("$undefined", empty_location);
undeftoken->class = token_sym;
undeftoken->number = ntokens++;
@@ -515,25 +515,25 @@ reader (void)
/* Report any undefined symbols and consider them nonterminals. */
symbols_check_defined ();
/* If the user did not define her EOFTOKEN, do it now. */
if (!eoftoken)
/* If the user did not define her ENDTOKEN, do it now. */
if (!endtoken)
{
eoftoken = symbol_get ("$", empty_location);
eoftoken->class = token_sym;
eoftoken->number = 0;
endtoken = symbol_get ("$end", empty_location);
endtoken->class = token_sym;
endtoken->number = 0;
/* Value specified by POSIX. */
eoftoken->user_token_number = 0;
endtoken->user_token_number = 0;
}
/* Insert the initial rule, which line is that of the first rule
(not that of the start symbol):
axiom: %start EOF. */
accept: %start EOF. */
{
symbol_list_t *p = symbol_list_new (axiom, empty_location);
symbol_list_t *p = symbol_list_new (accept, empty_location);
p->location = grammar->location;
p->next = symbol_list_new (startsymbol, empty_location);
p->next->next = symbol_list_new (eoftoken, empty_location);
p->next->next = symbol_list_new (endtoken, empty_location);
p->next->next->next = symbol_list_new (NULL, empty_location);
p->next->next->next->next = grammar;
nrules += 1;

10
src/reduce.c
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@@ -161,9 +161,9 @@ inaccessable_symbols (void)
Pp = bitset_create (nrules, BITSET_FIXED);
/* If the start symbol isn't useful, then nothing will be useful. */
if (bitset_test (N, axiom->number - ntokens))
if (bitset_test (N, accept->number - ntokens))
{
bitset_set (V, axiom->number);
bitset_set (V, accept->number);
while (1)
{
@@ -194,7 +194,7 @@ inaccessable_symbols (void)
V = Vp;
/* Tokens 0, 1, and 2 are internal to Bison. Consider them useful. */
bitset_set (V, eoftoken->number); /* end-of-input token */
bitset_set (V, endtoken->number); /* end-of-input token */
bitset_set (V, errtoken->number); /* error token */
bitset_set (V, undeftoken->number); /* some undefined token */
@@ -333,7 +333,7 @@ nonterminals_reduce (void)
if (ISVAR (*rhsp))
*rhsp = symbol_number_as_item_number (nontermmap[*rhsp]);
}
axiom->number = nontermmap[axiom->number];
accept->number = nontermmap[accept->number];
}
nsyms -= nuseless_nonterminals;
@@ -438,7 +438,7 @@ reduce_grammar (void)
reduce_print ();
if (!bitset_test (N, axiom->number - ntokens))
if (!bitset_test (N, accept->number - ntokens))
fatal_at (startsymbol_location,
_("start symbol %s does not derive any sentence"),
startsymbol->tag);

2
src/state.c
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@@ -122,7 +122,7 @@ reductions_new (int num, rule_number_t *reductions)
state_number_t nstates = 0;
/* FINAL_STATE is properly set by new_state when it recognizes its
accessing symbol: EOF. */
accessing symbol: $end. */
state_t *final_state = NULL;
#define STATE_ALLOC(Nitems) \

16
src/symtab.c
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@@ -32,8 +32,8 @@
symbol_t *errtoken = NULL;
symbol_t *undeftoken = NULL;
symbol_t *eoftoken = NULL;
symbol_t *axiom = NULL;
symbol_t *endtoken = NULL;
symbol_t *accept = NULL;
symbol_t *startsymbol = NULL;
location_t startsymbol_location;
@@ -181,11 +181,11 @@ symbol_user_token_number_set (symbol_t *symbol,
symbol->tag);
symbol->user_token_number = user_token_number;
/* User defined EOF token? */
/* User defined $end token? */
if (user_token_number == 0)
{
eoftoken = symbol;
eoftoken->number = 0;
endtoken = symbol;
endtoken->number = 0;
/* It is always mapped to 0, so it was already counted in
NTOKENS. */
--ntokens;
@@ -322,7 +322,7 @@ symbol_pack (symbol_t *this)
prec and assoc fields and make both the same */
if (this->number == NUMBER_UNDEFINED)
{
if (this == eoftoken || this->alias == eoftoken)
if (this == endtoken || this->alias == endtoken)
this->number = this->alias->number = 0;
else
{
@@ -540,8 +540,8 @@ symbols_token_translations_init (void)
token_translations = XCALLOC (symbol_number_t, max_user_token_number + 1);
/* Initialize all entries for literal tokens to 2, the internal
token number for $undefined., which represents all invalid
inputs. */
token number for $undefined, which represents all invalid inputs.
*/
for (i = 0; i < max_user_token_number + 1; i++)
token_translations[i] = undeftoken->number;
symbols_do (symbol_translation, NULL);

4
src/symtab.h
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@@ -127,8 +127,8 @@ void symbol_user_token_number_set PARAMS ((symbol_t *symbol,
*/
extern symbol_t *errtoken;
extern symbol_t *undeftoken;
extern symbol_t *eoftoken;
extern symbol_t *axiom;
extern symbol_t *endtoken;
extern symbol_t *accept;
extern symbol_t *startsymbol;
extern location_t startsymbol_location;