/// <summary>
/// Creates a new Grammar instance and sets it's GrammarDefiniton, LexerData and
/// GrammarCode properties to provided values. The ParserData structure will be
/// initialized and it's ProductionOutlines and SymbolNames properties will be set.
/// </summary>
/// <param name="grammarDefinition">The definition of the grammar.</param>
/// <param name="lexerData">A structure defining the lexer's runtime behaviour.</param>
/// <param name="grammarCode">The collection of user code describing the actions of the parser.</param>
public Grammar(GrammarDefinition grammarDefinition, LexerData lexerData, GrammarCode grammarCode)
{
this.grammarDefinition = grammarDefinition;
this.lexerData = lexerData;
this.grammarCode = grammarCode;
ProductionOutline[] productionOutlines = new ProductionOutline[grammarDefinition.Productions.Length];
for (int i = 0; i < productionOutlines.Length; i++)
{
productionOutlines[i] = new ProductionOutline(grammarDefinition.Productions[i].LHSSymbol, grammarDefinition.Productions[i].RHSSymbols.Count);
}
this.parserData = new ParserData(grammarDefinition.SymbolNames, productionOutlines);
}
/// <summary>
/// Parses input tokens supplied by the <i>lexer</i> and returns the result.
/// </summary>
/// <param name="lexer">The ILexer which will supply the Parser with tokens.</param>
/// <returns>An object containing the value returned for the root nonterminal.</returns>
/// <exception cref="ParsingException">when the lexer's output doesn't conform to the grammar's rules or
/// when the lexer throws a ParsingException.</exception>
public object Parse(ILexer lexer, object userObject)
{
Stack <PartialResult> resultStack = new Stack <PartialResult>();
Stack <int> stateStack = new Stack <int>();
//počáteční stav
stateStack.Push(0);
bool done = false;
Token nextToken = lexer.GetNextToken();
int state = stateStack.Peek();
while (!done && (lexer.HasTokens || ((state >= 0) && (parseTable[state, nextToken.SymbolCode].ActionType != ParserActionType.Fail))))
{
ParserAction nextAction = parseTable[state, nextToken.SymbolCode];
switch (nextAction.ActionType)
{
case ParserActionType.Shift:
resultStack.Push(new PartialResult(nextToken.Value, symbolNames[nextToken.SymbolCode],
nextToken.LineNumber, nextToken.ColumnNumber));
stateStack.Push(nextAction.Argument);
state = stateStack.Peek();
nextToken = lexer.GetNextToken();
break;
case ParserActionType.Reduce:
//podle informací o patřičném přepisovacím pravidle odebereme ze zásobníků
//příslušný počet prvků
ProductionOutline production = productions[nextAction.Argument];
Stack <PartialResult> constituents = new Stack <PartialResult>();
for (int i = 0; i < production.NumRHSSymbols; i++)
{
constituents.Push(resultStack.Pop());
stateStack.Pop();
}
state = stateStack.Peek();
// We take the values of the constituents and compute the value of the composite
// element using the relevant action. This new result replaces the old ones on the
// result stack; the accompanying state for the state stack is found in the goto
// table of the parser. The line and column number for the new result are taken from
// the first constituent. If the nonterminal has no constituents, we take the position
// of the upcoming token.
int numConstituents = constituents.Count;
object[] constituentValues = new object[numConstituents];
int[] constituentLines = new int[numConstituents];
int[] constituentColumns = new int[numConstituents];
for (int i = 0; i < numConstituents; i++)
{
PartialResult constituent = constituents.Pop();
constituentValues[i] = constituent.Value;
constituentLines[i] = constituent.LineNumber;
constituentColumns[i] = constituent.ColumnNumber;
}
object result = actions[nextAction.Argument](constituentValues, constituentLines, constituentColumns, userObject);
if (numConstituents > 0)
{
resultStack.Push(new PartialResult(result, symbolNames[production.LHSSymbol],
constituentLines[0], constituentColumns[0]));
}
else
{
resultStack.Push(new PartialResult(result, symbolNames[production.LHSSymbol],
nextToken.LineNumber, nextToken.ColumnNumber));
}
stateStack.Push(gotoTable[state, production.LHSSymbol - numTerminals]);
state = stateStack.Peek();
//přepisovací pravidlo 0 je vždy $start ::= <start-symbol> $end a provedení
//redukce podle tohoto pravidla znamená, že jsme načetli i $end a podařilo
//se nám vstup rozparsovat, tudíž končíme;
//pokud by se nám snažil lexer ještě nějaké tokeny vrazit, tak to ohlásíme
if (nextAction.Argument == 0)
{
done = true;
}
break;
case ParserActionType.Fail:
StringBuilder expectedTerminals = new StringBuilder();
for (int terminal = 0; terminal < numTerminals; terminal++)
{
if (parseTable[state, terminal].ActionType != ParserActionType.Fail)
{
expectedTerminals.Append(", ");
expectedTerminals.Append(symbolNames[terminal]);
}
}
throw new ParsingException(string.Format("Unexpected terminal {0}({1}) encountered by the parser, expected one of the following terminals: {2}.",
symbolNames[nextToken.SymbolCode], nextToken.Value, expectedTerminals.ToString(2, expectedTerminals.Length - 2)),
nextToken.LineNumber, nextToken.ColumnNumber);
}
}
if (lexer.HasTokens)
{
//lexer nám chce něco říct, ale my už jsme hotovi; tohle by se s naším lexerem nemělo nikdy
//stát, jelikož po tom, co vrátí $end, už další tokeny nenabízí
nextToken = lexer.GetNextToken();
throw new ParsingException(string.Format("There are additional symbols in the input string starting with terminal {0}({1}).",
symbolNames[nextToken.SymbolCode], nextToken.Value), nextToken.LineNumber, nextToken.ColumnNumber);
}
else if ((resultStack.Count == 1) && (resultStack.Peek().SymbolName == "$start"))
{
//vše je, jak má být
return(resultStack.Pop().Value);
}
else if (resultStack.Count == 0)
{
throw new ParsingException("There were no symbols in the input.",
nextToken.LineNumber, nextToken.ColumnNumber);
}
else
{
//tohle znamená, že parser nebyl ještě se vstupem spokojen a očekává další symboly
StringBuilder symbolsOnStack = new StringBuilder();
foreach (PartialResult stackItem in resultStack.Reverse())
{
symbolsOnStack.Append(", ");
symbolsOnStack.Append(stackItem.SymbolName);
}
throw new ParsingException("The entire input was reduced to more than one symbol: "
+ symbolsOnStack.ToString(2, symbolsOnStack.Length - 2) +
". Input text was probably incomplete.", nextToken.LineNumber, nextToken.ColumnNumber);
}
}
