/*-----------------------------------------------------------*/
/*--- General Methods ---------------------------------------*/
/*-----------------------------------------------------------*/
/** Add a transition out of this state to another.
* @param on_sym the symbol the transition is under.
* @param to_st the state the transition goes to.
*/
public void add_transition(symbol on_sym, lalr_state to_st)
{
lalr_transition trans;
/* create a new transition object and put it in our list */
trans = new lalr_transition(on_sym, to_st, _transitions);
_transitions = trans;
}
/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
/** Fill in the parse table entries for this state. There are two
* parse tables that encode the viable prefix recognition machine, an
* action table and a reduce-goto table. The rows in each table
* correspond to states of the machine. The columns of the action table
* are indexed by terminal symbols and correspond to either transitions
* out of the state (shift entries) or reductions from the state to some
* previous state saved on the stack (reduce entries). All entries in the
* action table that are not shifts or reduces, represent errors. The
* reduce-goto table is indexed by non terminals and represents transitions
* out of a state on that non-terminal.<p>
* Conflicts occur if more than one action needs to go in one entry of the
* action table (this cannot happen with the reduce-goto table). Conflicts
* are resolved by always shifting for shift/reduce conflicts and choosing
* the lowest numbered production (hence the one that appeared first in
* the specification) in reduce/reduce conflicts. All conflicts are
* reported and if more conflicts are detected than were declared by the
* user, code generation is aborted.
*
* @param act_table the action table to put entries in.
* @param reduce_table the reduce-goto table to put entries in.
*/
public void build_table_entries(
parse_action_table act_table,
parse_reduce_table reduce_table)
{
parse_action_row our_act_row;
parse_reduce_row our_red_row;
lalr_item itm;
parse_action act, other_act;
symbol sym;
terminal_set conflict_set = new terminal_set();
/* pull out our rows from the tables */
our_act_row = act_table.under_state[index()];
our_red_row = reduce_table.under_state[index()];
/* consider each item in our state */
IEnumerator i = items().all();
while (i.MoveNext())
{
itm = (lalr_item)i.Current;
/* if its completed (dot at end) then reduce under the lookahead */
if (itm.dot_at_end())
{
act = new reduce_action(itm.the_production());
/* consider each lookahead symbol */
for (int t = 0; t < terminal.number(); t++)
{
/* skip over the ones not in the lookahead */
if (!itm.lookahead().contains(t))
{
continue;
}
/* if we don't already have an action put this one in */
if (our_act_row.under_term[t].kind() ==
parse_action.ERROR)
{
our_act_row.under_term[t] = act;
}
else
{
/* we now have at least one conflict */
terminal term = terminal.find(t);
other_act = our_act_row.under_term[t];
/* if the other act was not a shift */
if ((other_act.kind() != parse_action.SHIFT) &&
(other_act.kind() != parse_action.NONASSOC))
{
/* if we have lower index hence priority, replace it*/
if (itm.the_production().index() <
((reduce_action)other_act).reduce_with().index())
{
/* replace the action */
our_act_row.under_term[t] = act;
}
}
else
{
/* Check precedences,see if problem is correctable */
if (fix_with_precedence(itm.the_production(),
t, our_act_row, act))
{
term = null;
}
}
if (term != null)
{
conflict_set.add(term);
}
}
}
}
}
/* consider each outgoing transition */
for (lalr_transition trans = transitions(); trans != null; trans = trans.next())
{
/* if its on an terminal add a shift entry */
sym = trans.on_symbol();
if (!sym.is_non_term())
{
act = new shift_action(trans.to_state());
/* if we don't already have an action put this one in */
if (our_act_row.under_term[sym.index()].kind() ==
parse_action.ERROR)
{
our_act_row.under_term[sym.index()] = act;
}
else
{
/* we now have at least one conflict */
production p = ((reduce_action)our_act_row.under_term[sym.index()]).reduce_with();
/* shift always wins */
if (!fix_with_precedence(p, sym.index(), our_act_row, act))
{
our_act_row.under_term[sym.index()] = act;
conflict_set.add(terminal.find(sym.index()));
}
}
}
else
{
/* for non terminals add an entry to the reduce-goto table */
our_red_row.under_non_term[sym.index()] = trans.to_state();
}
}
/* if we end up with conflict(s), report them */
if (!conflict_set.empty())
{
report_conflicts(conflict_set);
}
}
/*-----------------------------------------------------------*/
/*--- General Methods ---------------------------------------*/
/*-----------------------------------------------------------*/
/** Add a transition out of this state to another.
* @param on_sym the symbol the transition is under.
* @param to_st the state the transition goes to.
*/
public void add_transition(symbol on_sym, lalr_state to_st)
{
lalr_transition trans;
/* create a new transition object and put it in our list */
trans = new lalr_transition(on_sym, to_st, _transitions);
_transitions = trans;
}