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* src/LR0.c (insert_start_shift): Rename as...

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(insert_start_shifting_state): this.
(insert_eof_shifting_state, insert_accepting_state): New.
(augment_automaton): Adjust.
Better locality of the variables.
When looking if the start_symbol is shifted from the initial
state, using `while (... symbol != start_symbol ...)' sounds
better than `while (... symbol < start_symbol ...)': If fail
to see how the order between symbols could be relevant!
This commit is contained in:
Akim Demaille
2001-12-10 09:07:55 +00:00
parent 78af9bbcd3
commit 0ab3728b12
2 changed files with 92 additions and 43 deletions
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12
ChangeLog
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@@ -1,3 +1,15 @@
2001-12-10 Akim Demaille <akim@epita.fr>
* src/LR0.c (insert_start_shift): Rename as...
(insert_start_shifting_state): this.
(insert_eof_shifting_state, insert_accepting_state): New.
(augment_automaton): Adjust.
Better locality of the variables.
When looking if the start_symbol is shifted from the initial
state, using `while (... symbol != start_symbol ...)' sounds
better than `while (... symbol < start_symbol ...)': If fail
to see how the order between symbols could be relevant!
2001-12-10 Akim Demaille <akim@epita.fr>
* src/getargs.h: Don't declare `spec_name_prefix' and

123
src/LR0.c
View File

@@ -334,16 +334,26 @@ save_shifts (void)
/*------------------------------------------------------------------.
| Subroutine of augment_automaton. Create the next-to-final state, |
| to which a shift has already been made in the initial state. |
| |
| The task of this state consists in shifting (actually, it's a |
| goto, but shifts and gotos are both stored in SHIFTS) the start |
| symbols, hence the name. |
`------------------------------------------------------------------*/
static void
insert_start_shift (void)
insert_start_shifting_state (void)
{
state_t *statep;
shifts *sp;
statep = STATE_ALLOC (0);
statep->number = nstates;
/* The distinctive feature of this state from the
eof_shifting_state, is that it is labeled as post-start-symbol
shifting. I fail to understand why this state, and the
post-start-start can't be merged into one. But it does fail if
you try. --akim */
statep->accessing_symbol = start_symbol;
last_state->next = statep;
@@ -359,6 +369,61 @@ insert_start_shift (void)
}
/*-----------------------------------------------------------------.
| Subroutine of augment_automaton. Create the final state, which |
| shifts `0', the end of file. The initial state shifts the start |
| symbol, and goes to here. |
`-----------------------------------------------------------------*/
static void
insert_eof_shifting_state (void)
{
state_t *statep;
shifts *sp;
/* Make the final state--the one that follows a shift from the
next-to-final state.
The symbol for that shift is 0 (end-of-file). */
statep = STATE_ALLOC (0);
statep->number = nstates;
last_state->next = statep;
last_state = statep;
/* Make the shift from the final state to the termination state. */
sp = shifts_new (1);
sp->number = nstates++;
sp->shifts[0] = nstates;
last_shift->next = sp;
last_shift = sp;
}
/*---------------------------------------------------------------.
| Subroutine of augment_automaton. Create the accepting state. |
`---------------------------------------------------------------*/
static void
insert_accepting_state (void)
{
state_t *statep;
/* Note that the variable `final_state' refers to what we sometimes
call the termination state. */
final_state = nstates;
/* Make the termination state. */
statep = STATE_ALLOC (0);
statep->number = nstates++;
last_state->next = statep;
last_state = statep;
}
/*------------------------------------------------------------------.
| Make sure that the initial state has a shift that accepts the |
| grammar's start symbol and goes to the next-to-final state, which |
@@ -370,18 +435,12 @@ insert_start_shift (void)
static void
augment_automaton (void)
{
state_t *statep;
shifts *sp;
shifts *sp1 = NULL;
sp = first_shift;
if (!sp->nshifts)
if (!first_shift->nshifts)
{
/* There are no shifts for any state. Make one shift, from the
initial state to the next-to-final state. */
sp = shifts_new (1);
shifts *sp = shifts_new (1);
sp->shifts[0] = nstates;
/* Initialize the chain of shifts with sp. */
@@ -390,15 +449,16 @@ augment_automaton (void)
/* Create the next-to-final state, with shift to
what will be the final state. */
insert_start_shift ();
insert_start_shifting_state ();
}
else if (sp->number == 0)
else if (first_shift->number == 0)
{
statep = first_state->next;
state_t *statep = first_state->next;
shifts *sp = first_shift;
shifts *sp1 = NULL;
/* The states reached by shifts from FIRST_STATE are numbered
1..(SP->NSHIFTS). Look for one reached by START_SYMBOL. */
while (statep->accessing_symbol < start_symbol
while (statep->accessing_symbol != start_symbol
&& statep->number < sp->nshifts)
statep = statep->next;
@@ -446,12 +506,11 @@ augment_automaton (void)
{
int i, k;
shifts *sp2;
sp = first_shift;
/* There is no next-to-final state as yet. */
/* Add one more shift in first_shift,
going to the next-to-final state (yet to be made). */
sp = first_shift;
sp2 = shifts_new (sp->nshifts + 1);
/* Stick this shift into the vector at the proper place. */
@@ -477,14 +536,14 @@ augment_automaton (void)
/* Create the next-to-final state, with shift to
what will be the final state. */
insert_start_shift ();
insert_start_shifting_state ();
}
}
else
{
/* The initial state didn't even have any shifts.
Give it one shift, to the next-to-final state. */
sp = shifts_new (1);
shifts *sp = shifts_new (1);
sp->shifts[0] = nstates;
/* Patch sp into the chain of shifts at the beginning. */
@@ -493,33 +552,11 @@ augment_automaton (void)
/* Create the next-to-final state, with shift to
what will be the final state. */
insert_start_shift ();
insert_start_shifting_state ();
}
/* Make the final state--the one that follows a shift from the
next-to-final state.
The symbol for that shift is 0 (end-of-file). */
statep = STATE_ALLOC (0);
statep->number = nstates;
last_state->next = statep;
last_state = statep;
/* Make the shift from the final state to the termination state. */
sp = shifts_new (1);
sp->number = nstates++;
sp->shifts[0] = nstates;
last_shift->next = sp;
last_shift = sp;
/* Note that the variable `final_state' refers to what we sometimes call
the termination state. */
final_state = nstates;
/* Make the termination state. */
statep = STATE_ALLOC (0);
statep->number = nstates++;
last_state->next = statep;
last_state = statep;
insert_eof_shifting_state ();
insert_accepting_state ();
}