/// <summary>
/// Constructs a Parser for the given input stream.
/// In order to actually parse the data, call the
/// Perform method, which returns a SymMapBase containing
/// the parse tree.
/// </summary>
/// <param name="input">Input stream.</param>
/// <param name="fileName"></param>
public Parser(Stream input, string fileName)
{
m_result.TypeName = Vrml97Sym.Vrml97;
m_result[Vrml97Sym.filename] = fileName;
m_tokenizer = new Tokenizer(input);
}