/// <summary>
/// validates whether $ variables are corresponding to valid symbols
/// errors are added to the tree Error object.
/// </summary>
/// <param name="nts">non terminal and its production rule</param>
/// <returns>a formated codeblock</returns>
private void ValidateCodeBlock(ParseTree tree, NonTerminalSymbol nts, ParseNode node)
{
if (nts == null)
{
return;
}
string codeblock = nts.CodeBlock;
Regex var = new Regex(@"\$(?<var>[a-zA-Z_0-9]+)(\[(?<index>[^]]+)\])?", RegexOptions.Compiled);
Symbols symbols = nts.DetermineProductionSymbols();
MatchCollection matches = var.Matches(codeblock);
foreach (Match match in matches)
{
Symbol s = symbols.Find(match.Groups["var"].Value);
if (s == null)
{
tree.Errors.Add(new ParseError("Variable $" + match.Groups["var"].Value + " cannot be matched.", 0x1016, node.Token.File, node.Token.StartPos + match.Groups["var"].Index, node.Token.StartPos + match.Groups["var"].Index, match.Groups["var"].Length));
break; // error situation
}
}
}
protected override object EvalProduction(ParseTree tree, params object[] paramlist)
{
Grammar g = (Grammar)paramlist[0];
if (Nodes[2].Nodes[0].Token.Type == TokenType.STRING)
{
TerminalSymbol term = g.Symbols.Find(Nodes[0].Token.Text) as TerminalSymbol;
if (term == null)
{
tree.Errors.Add(new ParseError("Symbol '" + Nodes[0].Token.Text + "' is not declared. ", 0x1040, Nodes[0]));
}
}
else
{
NonTerminalSymbol nts = g.Symbols.Find(Nodes[0].Token.Text) as NonTerminalSymbol;
if (nts == null)
{
tree.Errors.Add(new ParseError("Symbol '" + Nodes[0].Token.Text + "' is not declared. ", 0x1041, Nodes[0]));
}
Rule r = (Rule)Nodes[2].Eval(tree, g, nts);
if (nts != null)
{
nts.Rules.Add(r);
}
if (Nodes[3].Token.Type == TokenType.CODEBLOCK)
{
string codeblock = Nodes[3].Token.Text;
nts.CodeBlock = codeblock;
ValidateCodeBlock(tree, nts, Nodes[3]);
// beautify the codeblock format
codeblock = codeblock.Substring(1, codeblock.Length - 3).Trim();
nts.CodeBlock = codeblock;
}
}
return(g);
}
internal bool DetermineFirstTerminals(Symbols FirstTerminals, int index)
{
// indicates if Nonterminal can evaluate to an empty terminal (e.g. in case T -> a? or T -> a*)
// in which case the parent rule should continue scanning after this nonterminal for Firsts.
bool containsEmpty = false; // assume terminal is found
switch (Type)
{
case RuleType.Terminal:
if (Symbol == null)
{
return(true);
}
if (!FirstTerminals.Exists(Symbol))
{
FirstTerminals.Add(Symbol);
}
else
{
Console.WriteLine("throw new Exception(\"Terminal already exists\");");
}
break;
case RuleType.NonTerminal:
if (Symbol == null)
{
return(true);
}
NonTerminalSymbol nts = Symbol as NonTerminalSymbol;
containsEmpty = nts.DetermineFirstTerminals();
// add first symbols of the nonterminal if not already added
foreach (TerminalSymbol t in nts.FirstTerminals)
{
if (!FirstTerminals.Exists(t))
{
FirstTerminals.Add(t);
}
else
{
Console.WriteLine("throw new Exception(\"Terminal already exists\");");
}
}
break;
case RuleType.Choice:
{
// all subrules must be evaluated to determine if they contain first terminals
// if any subrule contains an empty, then this rule also contains an empty
foreach (Rule r in Rules)
{
containsEmpty |= r.DetermineFirstTerminals(FirstTerminals);
}
break;
}
case RuleType.OneOrMore:
{
// if a non-empty subrule was found, then stop further parsing.
foreach (Rule r in Rules)
{
containsEmpty = r.DetermineFirstTerminals(FirstTerminals);
if (!containsEmpty) // found the final set of first terminals
{
break;
}
}
break;
}
case RuleType.Concat:
{
// if a non-empty subrule was found, then stop further parsing.
// start scanning from Index
for (int i = index; i < Rules.Count; i++)
{
containsEmpty = Rules[i].DetermineFirstTerminals(FirstTerminals);
if (!containsEmpty) // found the final set of first terminals
{
break;
}
}
// assign this concat rule to each terminal
foreach (TerminalSymbol t in FirstTerminals)
{
t.Rule = this;
}
break;
}
case RuleType.Option:
case RuleType.ZeroOrMore:
{
// empty due to the nature of this rule (A? or A* can always be empty)
containsEmpty = true;
// if a non-empty subrule was found, then stop further parsing.
foreach (Rule r in Rules)
{
containsEmpty |= r.DetermineFirstTerminals(FirstTerminals);
if (!containsEmpty) // found the final set of first terminals
{
break;
}
}
break;
}
default:
throw new NotImplementedException();
}
return(containsEmpty);
}
/// <summary>
/// EvalStart will first do a semantic check to see if symbols are declared correctly
/// then it will also check for attributes and parse the directives
/// after that it will complete the transformation to the grammar tree.
/// </summary>
/// <param name="tree"></param>
/// <param name="paramlist"></param>
/// <returns></returns>
protected override object EvalStart(ParseTree tree, params object[] paramlist)
{
TerminalSymbol terminal = null;
bool StartFound = false;
Grammar g = new Grammar();
foreach (ParseNode n in Nodes)
{
if (n.Token.Type == TokenType.Directive)
{
EvalDirective(tree, new object[] { g, n });
}
if (n.Token.Type == TokenType.ExtProduction)
{
if (n.Nodes[n.Nodes.Count - 1].Nodes[2].Nodes[0].Token.Type == TokenType.STRING)
{
try
{
terminal = new TerminalSymbol(n.Nodes[n.Nodes.Count - 1].Nodes[0].Token.Text, (string)n.Nodes[n.Nodes.Count - 1].Nodes[2].Nodes[0].Token.Text);
for (int i = 0; i < n.Nodes.Count - 1; i++)
{
if (n.Nodes[i].Token.Type == TokenType.Attribute)
{
EvalAttribute(tree, new object[] { g, terminal, n.Nodes[i] });
}
}
}
catch (Exception ex)
{
tree.Errors.Add(new ParseError("regular expression for '" + n.Nodes[n.Nodes.Count - 1].Nodes[0].Token.Text + "' results in error: " + ex.Message, 0x1020, n.Nodes[0]));
continue;
}
if (terminal.Name == "Start")
{
tree.Errors.Add(new ParseError("'Start' symbol cannot be a regular expression.", 0x1021, n.Nodes[0]));
}
if (g.Symbols.Find(terminal.Name) == null)
{
g.Symbols.Add(terminal);
}
else
{
tree.Errors.Add(new ParseError("Terminal already declared: " + terminal.Name, 0x1022, n.Nodes[0]));
}
}
else
{
NonTerminalSymbol nts = new NonTerminalSymbol(n.Nodes[n.Nodes.Count - 1].Nodes[0].Token.Text);
if (g.Symbols.Find(nts.Name) == null)
{
g.Symbols.Add(nts);
}
else
{
tree.Errors.Add(new ParseError("Non terminal already declared: " + nts.Name, 0x1023, n.Nodes[0]));
}
for (int i = 0; i < n.Nodes.Count - 1; i++)
{
if (n.Nodes[i].Token.Type == TokenType.Attribute)
{
EvalAttribute(tree, new object[] { g, nts, n.Nodes[i] });
}
}
if (nts.Name == "Start")
{
StartFound = true;
}
}
}
}
if (!StartFound)
{
tree.Errors.Add(new ParseError("The grammar requires 'Start' to be a production rule.", 0x0024));
return(g);
}
foreach (ParseNode n in Nodes)
{
if (n.Token.Type == TokenType.ExtProduction)
{
n.Eval(tree, g);
}
}
return(g);
}
