/// <name>Parser</name>
/// <type>Constructor</type>
/// <summary>
/// Creates a parser object.
/// </summary>
public Parser()
: base()
{
// Initalize class variables
currentOperator = new Token(TokenType.NO_TOKEN, String.Empty);
nextOperator = new Token(TokenType.NO_TOKEN, String.Empty);
operand = null;
literal = null;
symbol = null;
inExpression = false;
nextLocation = 1;
symbolTable = new Dictionary<string, Symbol>();
literalTable = new Dictionary<string, Literal>();
operatorStack = new Stack<Token>();
structureStack = new Stack<Structure>();
forwardRefStack = new Stack<ForwardReference>();
}
/// <name>Advance</name>
/// <type>Method</type>
/// <summary>
/// Advances the current and next operators from the input file and
/// populates the operand token between the operators if one exists.
/// </summary>
private void Advance()
{
// Advance one token
currentOperator = (Token)nextOperator.Clone();
Token peekToken = source.GetNextToken();
// Make sure operand, symbol and literal are null
operand = null;
symbol = null;
literal = null;
if (peekToken.Type == TokenType.SYMBOL)
{
// If the new token is a symbol then set operand to that token
operand = (Token)peekToken.Clone();
// Now check to see if the symbol is already defined - if
// it is then assign to symbol, otherwise add it to the table
if (symbolTable.ContainsKey(peekToken.Lexeme))
{
symbol = symbolTable[peekToken.Lexeme];
}
else
{
symbolTable.Add(peekToken.Lexeme, new Symbol(peekToken.Lexeme));
symbol = symbolTable[peekToken.Lexeme];
}
// Finally get the next token
nextOperator = source.GetNextToken();
}
else if (peekToken.Type == TokenType.LITERAL)
{
// If the new token is a literal then set operand to that token
operand = (Token)peekToken.Clone();
// Now check to see if the literal is already defined - if
// it is then assign to literal, otherwise add it to the table
if (literalTable.ContainsKey(peekToken.Lexeme))
{
literal = literalTable[peekToken.Lexeme];
}
else
{
literalTable.Add(peekToken.Lexeme, new Literal(peekToken.Lexeme));
literal = literalTable[peekToken.Lexeme];
}
// Finally get the next token
nextOperator = source.GetNextToken();
}
else
{
// Set the next operator to the token we just retrieved
nextOperator = (Token)peekToken.Clone();
}
// Output debug information
Compiler.WriteToDebug("Parser - Advance called (line " + Compiler.LineNumber + ")");
Compiler.WriteToDebug(" current operator:\t" + currentOperator.Lexeme);
if (operand != null)
{
Compiler.WriteToDebug(" operand:\t\t" + operand.Lexeme);
}
Compiler.WriteToDebug(" next operator:\t" + nextOperator.Lexeme);
Compiler.WriteToDebug(String.Empty);
}