Each core contains a vector of NITEMS items which are the indices
in the RITEMS vector of the items that are selected in this state.
- The two types of transitions are shifts (push the lookahead token
- and read another) and reductions (combine the last n things on the
- stack via a rule, replace them with the symbol that the rule
- derives, and leave the lookahead token alone). When the states are
- generated, these transitions are represented in two other lists.
-
- Each shifts structure describes the possible shift transitions out
- of one state, the state whose number is in the number field. The
- shifts structures are linked through next and first_shift points to
- them. Each contains a vector of numbers of the states that shift
- transitions can go to. The accessing_symbol fields of those
- states' cores say what kind of input leads to them.
-
- A shift to state zero should be ignored. Conflict resolution
- deletes shifts by changing them to zero.
+ The two types of actions are shifts/gotos (push the lookahead token
+ and read another/goto to the state designated by a nterm) and
+ reductions (combine the last n things on the stack via a rule,
+ replace them with the symbol that the rule derives, and leave the
+ lookahead token alone). When the states are generated, these
+ actions are represented in two other lists.
+
+ Each transition_t structure describes the possible transitions out
+ of one state, the state whose number is in the number field. Each
+ contains a vector of numbers of the states that transitions can go
+ to. The accessing_symbol fields of those states' cores say what
+ kind of input leads to them.
+
+ A transition to state zero should be ignored: conflict resolution
+ deletes transitions by having them point to zero.
Each reductions structure describes the possible reductions at the
state whose number is in the number field. The data is a list of
Conflict resolution can decide that certain tokens in certain
states should explicitly be errors (for implementing %nonassoc).
For each state, the tokens that are errors for this reason are
- recorded in an errs structure, which has the state number in its
- number field. The rest of the errs structure is full of token
- numbers.
+ recorded in an errs structure, which holds the token numbers.
- There is at least one shift transition present in state zero. It
+ There is at least one goto transition present in state zero. It
leads to a next-to-final state whose accessing_symbol is the
grammar's start symbol. The next-to-final state has one shift to
the final state, whose accessing_symbol is zero (end of input).
- The final state has one shift, which goes to the termination state
- (whose number is nstates-1). The reason for the extra state at the
- end is to placate the parser's strategy of making all decisions one
- token ahead of its actions. */
+ The final state has one shift, which goes to the termination state.
+ The reason for the extra state at the end is to placate the
+ parser's strategy of making all decisions one token ahead of its
+ actions. */
#ifndef STATE_H_
# define STATE_H_
/* Be ready to map a state_number_t to an int. */
# define state_number_as_int(Tok) ((int) (Tok))
-/*---------.
-| Shifts. |
-`---------*/
+/*--------------.
+| Transitions. |
+`--------------*/
-typedef struct shifts
+typedef struct transtion_s
{
- short nshifts;
- state_number_t shifts[1];
-} shifts;
+ short num;
+ state_number_t states[1];
+} transitions_t;
-shifts *shifts_new PARAMS ((int n));
+/* What is the symbol labelling the transition to
+ TRANSITIONS->states[Num]? Can be a token (amongst which the error
+ token), or non terminals in case of gotos. */
-/* What is the symbol which is shifted by SHIFTS->shifts[Shift]? Can
- be a token (amongst which the error token), or non terminals in
- case of gotos. */
+#define TRANSITION_SYMBOL(Transitions, Num) \
+ (states[Transitions->states[Num]]->accessing_symbol)
-#define SHIFT_SYMBOL(Shifts, Shift) \
- (states[Shifts->shifts[Shift]]->accessing_symbol)
+/* Is the TRANSITIONS->states[Num] a shift? (as opposed to gotos). */
-/* Is the SHIFTS->shifts[Shift] a real shift? (as opposed to gotos.) */
+#define TRANSITION_IS_SHIFT(Transitions, Num) \
+ (ISTOKEN (TRANSITION_SYMBOL (Transitions, Num)))
-#define SHIFT_IS_SHIFT(Shifts, Shift) \
- (ISTOKEN (SHIFT_SYMBOL (Shifts, Shift)))
+/* Is the TRANSITIONS->states[Num] a goto?. */
-/* Is the SHIFTS->shifts[Shift] a goto?. */
+#define TRANSITION_IS_GOTO(Transitions, Num) \
+ (!TRANSITION_IS_SHIFT (Transitions, Num))
-#define SHIFT_IS_GOTO(Shifts, Shift) \
- (!SHIFT_IS_SHIFT (Shifts, Shift))
+/* Is the TRANSITIONS->states[Num] labelled by the error token? */
-/* Is the SHIFTS->shifts[Shift] then handling of the error token?. */
-
-#define SHIFT_IS_ERROR(Shifts, Shift) \
- (SHIFT_SYMBOL (Shifts, Shift) == errtoken->number)
+#define TRANSITION_IS_ERROR(Transitions, Num) \
+ (TRANSITION_SYMBOL (Transitions, Num) == errtoken->number)
/* When resolving a SR conflicts, if the reduction wins, the shift is
disabled. */
-#define SHIFT_DISABLE(Shifts, Shift) \
- (Shifts->shifts[Shift] = 0)
+#define TRANSITION_DISABLE(Transitions, Num) \
+ (Transitions->states[Num] = 0)
+
+#define TRANSITION_IS_DISABLED(Transitions, Num) \
+ (Transitions->states[Num] == 0)
-#define SHIFT_IS_DISABLED(Shifts, Shift) \
- (Shifts->shifts[Shift] == 0)
+/* Return the state such these TRANSITIONS contain a shift/goto to it on
+ SYMBOL. Aborts if none found. */
+struct state_s;
+struct state_s *transitions_to PARAMS ((transitions_t *state,
+ symbol_number_t s));
/*-------.
| Errs. |
`-------*/
-typedef struct errs
+typedef struct errs_s
{
- short nerrs;
- short errs[1];
-} errs;
+ short num;
+ symbol_number_t symbols[1];
+} errs_t;
-errs *errs_new PARAMS ((int n));
-errs *errs_dup PARAMS ((errs *src));
+errs_t *errs_new PARAMS ((int num, symbol_number_t *tokens));
/*-------------.
| Reductions. |
`-------------*/
-typedef struct reductions
+typedef struct reductions_s
{
- short nreds;
- short rules[1];
-} reductions;
+ short num;
+ rule_number_t rules[1];
+} reductions_t;
-reductions *reductions_new PARAMS ((int n));
/*----------.
typedef struct state_s
{
- struct state_s *next;
-
state_number_t number;
symbol_number_t accessing_symbol;
- shifts *shifts;
- reductions *reductions;
- errs *errs;
+ transitions_t *transitions;
+ reductions_t *reductions;
+ errs_t *errs;
/* Nonzero if no lookahead is needed to decide what to do in state S. */
char consistent;
- /* Used in LALR, not LR(0). */
+ /* Used in LALR, not LR(0).
+
+ When a state is not consistent (there is an S/R or R/R conflict),
+ lookaheads are needed to enable the reductions. NLOOKAHEADS is
+ the number of lookahead guarded reductions of the
+ LOOKAHEADS_RULE. For each rule LOOKAHEADS_RULE[R], LOOKAHEADS[R]
+ is the bitset of the lookaheads enabling this reduction. */
int nlookaheads;
bitsetv lookaheads;
rule_t **lookaheads_rule;
extern state_t *final_state;
/* Create a new state with ACCESSING_SYMBOL for those items. */
-
state_t *state_new PARAMS ((symbol_number_t accessing_symbol,
size_t core_size, item_number_t *core));
+/* Set the transitions of STATE. */
+void state_transitions_set PARAMS ((state_t *state,
+ int num, state_number_t *transitions));
+
+/* Set the reductions of STATE. */
+void state_reductions_set PARAMS ((state_t *state,
+ int num, rule_number_t *reductions));
+
+/* Set the errs of STATE. */
+void state_errs_set PARAMS ((state_t *state,
+ int num, symbol_number_t *errs));
+
/* Print on OUT all the lookaheads such that this STATE wants to
reduce this RULE. */
-
void state_rule_lookaheads_print PARAMS ((state_t *state, rule_t *rule,
FILE *out));
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