// ****************************************************************************
// Method: Parser::Reduce
//
// Purpose:
// Reduces what is on the stack using the given rule.
//
// Programmer: Jeremy Meredith
// Creation: April 5, 2002
//
// Modifications:
// Jeremy Meredith, Wed Nov 24 09:02:32 PST 2004
// Added list of tokens. Also, significant refactoring.
//
// Hank Childs, Fri Jan 28 13:19:33 PST 2005
// Use exception macros.
//
// Jeremy Meredith, Mon Jun 13 15:53:51 PDT 2005
// I made other changes to enforce that no Token will be stored
// inside a parse tree node, leaving us free to delete them after
// applying the reduction. This fixes a number of memory leaks.
// I also ensured that pos was well populated in all cases.
//
// Jeremy Meredith, Wed Jul 23 13:26:26 EDT 2008
// Add the rule index to the debug info.
//
// Kathleen Bonnell, Thu Nov 6 11:57:28 PST 2008
// To prevent a crash on windows for referencing (from GetParseTree)
// elems[0] when elems is empty, don't pop elems if rule->index is 0.
//
// Jeremy Meredith, Mon Nov 17 17:07:04 EST 2008
// The windows bug (see previous comment) was truly a multi-platform
// bug. Now we store the result parse tree directly instead of
// trying to pretend it's still on the parse elem stack (which
// wasn't even happening anyway; it only worked due to a lot of luck!)...
//
// ****************************************************************************
void
Parser::Reduce(int r)
{
#ifdef MOREDEBUG
cerr << "Reducing using rule " << G->GetRule(r)->GetIndex() << ": "
<< *(G->GetRule(r)) << endl;
#endif
const Rule *rule = G->GetRule(r);
const Symbol *lhs = rule->GetLHS();
const Symbol &sym = *lhs;
int len = rule->GetRHS().Length();
vector<ParseTreeNode*> E;
vector<Token*> T;
Pos p;
int i;
for (i=0; i<len; i++)
{
int index = (int)elems.size() - len + i;
E.push_back(elems[index].node);
T.push_back(elems[index].token);
p.Join(elems[index].pos);
}
ParseTreeNode *node = ApplyRule(sym, rule, E, T, p);
// We're done with the tokens now that we've applied the rule
for (i=0; i<len; i++)
{
delete T[i];
}
if (!node)
{
EXCEPTION2(UnhandledReductionException, p, rule);
}
node->GetPos().Join(p);
for (i=0; i<len; i++)
{
states.pop_back();
elems.pop_back();
}
State &state = G->GetState(states.back());
if (G->GetStartSymbol() == lhs)
{
parseTree = node;
PrintState(cerr);
#ifdef MOREDEBUG
cerr << "Accepting!\n\n";
#endif
accept = true;
return;
}
// now do the goto
elems.push_back(ParseElem(lhs, node));
states.push_back(state.shift[lhs]);
PrintState(cerr);
}
