public BottomUpParser(LexicalAnalyzer lexicalAnalyzer)
{
LexicalAnalyzer = lexicalAnalyzer;
GenerateAutomaton();
ParsingTable = new ParsingTable(CanonicalSets, GrammarSymbols, Shift, Accept, Reduce);
}
private ActionParsingTableEntry GetEntry()
{
List <ActionParsingTableEntry> entries = ParsingTable.GetSegment(Stack.Last()).Entries
.Where(x => x is ActionParsingTableEntry a &&
a.ExpressionDefinition.TokenType == Current.Type).Cast <ActionParsingTableEntry>().ToList();
if (entries.Count == 1)
{
return(entries.First());
}
else if (entries.Count > 1)
{
// reduce/reduce of shift/reduce conflict
List <ActionParsingTableEntry> entriesForLookahead = entries.Where(x => x.Items.Any(y => y.Lookahead.Any(z => z.TokenType == Current.Type))).ToList();;
if (entriesForLookahead.Count == 1)
{
return(entriesForLookahead.First());
}
if (entries.Count == 1)
{
return(entries.First());
}
else if (entries.Count > 1)
{
return(ResolveShiftReduceConflicts(entries));
}
else
{
Error();
}
}
else
{
Error();
}
return(null);
}
private bool Reduce(ActionParsingTableEntry entry)
{
SubProduction subProduction = null;
if (entry.Items.Count > 1)
{
Item match = entry.Items.First(x => x.Lookahead.Any(x => x.TokenType == Current.Type));
subProduction = match.SubProduction;
}
else
{
subProduction = entry.Items.First().SubProduction;
}
NonTerminalExpressionDefinition target = new NonTerminalExpressionDefinition {
Identifier = subProduction.Production.Identifier
};
ParsingNode parsingNode = new ParsingNode()
{
Expression = new NonTerminalExpression
{
Identifier = subProduction.Production.Identifier,
},
Parser = this,
SubProduction = subProduction
};
for (int y = subProduction.Count - 1; y >= 0; y--)
{
for (int i = ParsingNodes.Count - 1; i >= 0; i--)
{
if (ParsingNodes[i].Parent != null)
{
continue;
}
if (ParsingNodes[i].Expression is NonTerminalExpression ne &&
subProduction[y] is NonTerminalExpressionDefinition ned)
{
if (ne.Identifier == ned.Identifier)
{
ParsingNodes[i].Expression.Key = ned.Key;
ParsingNodes[i].Parent = parsingNode;
break;
}
}
if (ParsingNodes[i].Expression is TerminalExpression te &&
subProduction[y] is TerminalExpressionDefinition ted)
{
if (te.TokenType == ted.TokenType)
{
ParsingNodes[i].Parent = parsingNode;
break;
}
}
}
}
ParsingNodes.Add(parsingNode);
List <ExpressionDefinition> expressionDefinitionsToRemove = subProduction.Where(x => !(x is SemanticActionDefinition) && !(x is TerminalExpressionDefinition ted && ted.TokenType == TokenType.EmptyString)).ToList();
for (int i = 0; i < expressionDefinitionsToRemove.Count(); i++)
{
Stack.RemoveAt(Stack.Count - 1);
}
ItemSet tos = Stack.Last();
List <ParsingTableEntry> entries = ParsingTable.GetSegment(tos).Entries
.Where(x => x is GotoParsingTableEntry g &&
g.ItemSet == tos &&
g.ExpressionDefinition.IsEqualTo(target)).ToList();
if (entries.Count > 1)
{
throw new Exception();
}
GotoParsingTableEntry gotoEntry = (GotoParsingTableEntry)entries.First();
if (DebugModeEnabled)
{
Console.WriteLine("REDUCE DEST " + gotoEntry.Destination.Id + ", TARGET " + target.ToString());
}
Stack.Add(gotoEntry.Destination);
return(true);
}