/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
/// <summary>Procedure that attempts to fix a shift/reduce error by using
/// precedences. --frankf 6/26/96
///
/// if a production (also called rule) or the lookahead terminal
/// has a precedence, then the table can be fixed. if the rule
/// has greater precedence than the terminal, a reduce by that rule
/// in inserted in the table. If the terminal has a higher precedence,
/// it is shifted. if they have equal precedence, then the associativity
/// of the precedence is used to determine what to put in the table:
/// if the precedence is left associative, the action is to reduce.
/// if the precedence is right associative, the action is to shift.
/// if the precedence is non associative, then it is a syntax error.
/// *
/// </summary>
/// <param name="p"> the production
/// </param>
/// <param name="term_index"> the index of the lokahead terminal
/// </param>
/// <param name="parse_action_row"> a row of the action table
/// </param>
/// <param name="act"> the rule in conflict with the table entry
///
/// </param>
protected internal virtual bool fix_with_precedence(production p, int term_index, parse_action_row table_row, parse_action act)
{
terminal term = terminal.find(term_index);
/* if the production has a precedence number, it can be fixed */
if (p.precedence_num() > assoc.no_prec)
{
/* if production precedes terminal, put reduce in table */
if (p.precedence_num() > term.precedence_num())
{
table_row.under_term[term_index] = insert_reduce(table_row.under_term[term_index], act);
return(true);
}
else if (p.precedence_num() < term.precedence_num())
{
table_row.under_term[term_index] = insert_shift(table_row.under_term[term_index], act);
return(true);
}
else
{
/* they are == precedence */
/* equal precedences have equal sides, so only need to
* look at one: if it is right, put shift in table */
if (term.precedence_side() == assoc.right)
{
table_row.under_term[term_index] = insert_shift(table_row.under_term[term_index], act);
return(true);
}
else if (term.precedence_side() == assoc.left)
{
table_row.under_term[term_index] = insert_reduce(table_row.under_term[term_index], act);
return(true);
}
else if (term.precedence_side() == assoc.nonassoc)
{
table_row.under_term[term_index] = new nonassoc_action();
return(true);
}
else
{
/* something really went wrong */
throw new internal_error("Unable to resolve conflict correctly");
}
}
}
else if (term.precedence_num() > assoc.no_prec)
{
table_row.under_term[term_index] = insert_shift(table_row.under_term[term_index], act);
return(true);
}
/* otherwise, neither the rule nor the terminal has a precedence,
* so it can't be fixed. */
return(false);
}
/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
/// <summary>Add a single terminal to the set.
/// </summary>
/// <param name="sym">the terminal being added.
/// </param>
/// <returns>true if this changes the set.
///
/// </returns>
public virtual bool add(terminal sym)
{
bool result;
not_null(sym);
/* see if we already have this */
result = _elements.Get(sym.index());
/* if not we add it */
if (!result)
_elements.Set(sym.index(), true);
return result;
}
/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
/// <summary>Add a single terminal to the set.
/// </summary>
/// <param name="sym">the terminal being added.
/// </param>
/// <returns>true if this changes the set.
///
/// </returns>
public virtual bool add(terminal sym)
{
bool result;
not_null(sym);
/* see if we already have this */
result = _elements.Get(sym.index());
/* if not we add it */
if (!result)
{
_elements.Set(sym.index(), true);
}
return(result);
}
/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
/// <summary>Determine if the set contains a particular terminal.
/// </summary>
/// <param name="sym">the terminal symbol we are looking for.
///
/// </param>
public virtual bool contains(terminal sym)
{
not_null(sym);
return(_elements.Get(sym.index()));
}
/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
/// <summary>Remove a terminal if it is in the set.
/// </summary>
/// <param name="sym">the terminal being removed.
///
/// </param>
public virtual void remove(terminal sym)
{
not_null(sym);
_elements.Set(sym.index(), false);
}
/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
/// <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>Remove a terminal if it is in the set.
/// </summary>
/// <param name="sym">the terminal being removed.
///
/// </param>
public virtual void remove(terminal sym)
{
not_null(sym);
_elements.Set(sym.index(), false);
}
/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
/// <summary>Determine if the set contains a particular terminal.
/// </summary>
/// <param name="sym">the terminal symbol we are looking for.
///
/// </param>
public virtual bool contains(terminal sym)
{
not_null(sym);
return _elements.Get(sym.index());
}
