/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
/// <summary>Calculate lookahead representing symbols that could appear after the
/// symbol that the dot is currently in front of. Note: this routine must
/// not be invoked before first sets and nullability has been calculated
/// for all non terminals.
/// </summary>
public virtual terminal_set calc_lookahead(terminal_set lookahead_after)
{
terminal_set result;
int pos;
production_part part;
symbol sym;
/* sanity check */
if (dot_at_end())
{
throw new internal_error("Attempt to calculate a lookahead set with a completed item");
}
/* start with an empty result */
result = new terminal_set();
/* consider all nullable symbols after the one to the right of the dot */
for (pos = dot_pos() + 1; pos < the_production().rhs_length(); pos++)
{
part = the_production().rhs(pos);
/* consider what kind of production part it is -- skip actions */
if (!part.is_action())
{
sym = ((symbol_part)part).the_symbol();
/* if its a terminal add it in and we are done */
if (!sym.is_non_term())
{
result.add((terminal)sym);
return(result);
}
else
{
/* otherwise add in first set of the non terminal */
result.add(((non_terminal)sym).first_set());
/* if its nullable we continue adding, if not, we are done */
if (!((non_terminal)sym).nullable())
{
return(result);
}
}
}
}
/* if we get here everything past the dot was nullable
* we add in the lookahead for after the production and we are done */
result.add(lookahead_after);
return(result);
}
/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
/// <summary>Update (and return) the first set based on current NT firsts.
/// This assumes that nullability has already been computed for all non
/// terminals and productions.
/// </summary>
public virtual terminal_set check_first_set()
{
int part;
symbol sym;
/* walk down the right hand side till we get past all nullables */
for (part = 0; part < rhs_length(); part++)
{
/* only look at non-actions */
if (!rhs(part).is_action())
{
sym = ((symbol_part)rhs(part)).the_symbol();
/* is it a non-terminal?*/
if (sym.is_non_term())
{
/* add in current firsts from that NT */
_first_set.add(((non_terminal)sym).first_set());
/* if its not nullable, we are done */
if (!((non_terminal)sym).nullable())
{
break;
}
}
else
{
/* its a terminal -- add that to the set */
_first_set.add((terminal)sym);
/* we are done */
break;
}
}
}
/* return our updated first set */
return(first_set());
}
/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
/// <summary>Calculate lookahead representing symbols that could appear after the
/// symbol that the dot is currently in front of. Note: this routine must
/// not be invoked before first sets and nullability has been calculated
/// for all non terminals.
/// </summary>
public virtual terminal_set calc_lookahead(terminal_set lookahead_after)
{
terminal_set result;
int pos;
production_part part;
symbol sym;
/* sanity check */
if (dot_at_end())
throw new internal_error("Attempt to calculate a lookahead set with a completed item");
/* start with an empty result */
result = new terminal_set();
/* consider all nullable symbols after the one to the right of the dot */
for (pos = dot_pos() + 1; pos < the_production().rhs_length(); pos++)
{
part = the_production().rhs(pos);
/* consider what kind of production part it is -- skip actions */
if (!part.is_action())
{
sym = ((symbol_part) part).the_symbol();
/* if its a terminal add it in and we are done */
if (!sym.is_non_term())
{
result.add((terminal) sym);
return result;
}
else
{
/* otherwise add in first set of the non terminal */
result.add(((non_terminal) sym).first_set());
/* if its nullable we continue adding, if not, we are done */
if (!((non_terminal) sym).nullable())
return result;
}
}
}
/* if we get here everything past the dot was nullable
we add in the lookahead for after the production and we are done */
result.add(lookahead_after);
return result;
}
/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
/// <summary>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.
/// *
/// </summary>
/// <param name="act_table"> the action table to put entries in.
/// </param>
/// <param name="reduce_table">the reduce-goto table to put entries in.
///
/// </param>
public virtual 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 */
//UPGRADE_TODO: method 'java.util.Enumeration.hasMoreElements' was converted to ' ' which has a different behavior. 'ms-help://MS.VSCC/commoner/redir/redirect.htm?keyword="jlca1073_javautilEnumerationhasMoreElements"'
for (System.Collections.IEnumerator i = items().all(); i.MoveNext(); )
{
//UPGRADE_TODO: method 'java.util.Enumeration.nextElement' was converted to ' ' which has a different behavior. 'ms-help://MS.VSCC/commoner/redir/redirect.htm?keyword="jlca1073_javautilEnumerationnextElement"'
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);
}
/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
/// <summary>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.
/// *
/// </summary>
/// <param name="act_table"> the action table to put entries in.
/// </param>
/// <param name="reduce_table">the reduce-goto table to put entries in.
///
/// </param>
public virtual 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 */
//UPGRADE_TODO: method 'java.util.Enumeration.hasMoreElements' was converted to ' ' which has a different behavior. 'ms-help://MS.VSCC/commoner/redir/redirect.htm?keyword="jlca1073_javautilEnumerationhasMoreElements"'
for (System.Collections.IEnumerator i = items().all(); i.MoveNext();)
{
//UPGRADE_TODO: method 'java.util.Enumeration.nextElement' was converted to ' ' which has a different behavior. 'ms-help://MS.VSCC/commoner/redir/redirect.htm?keyword="jlca1073_javautilEnumerationnextElement"'
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);
}
}
