protected void pushOperator(Lexeme op)
{
if (!op.IsOperator())
{
throw new ParseException("Cannot push a non-operator token onto the operator stack!");
}
if (op.IsRightAssociative())
{
// pushing a right-associative operator
// pop the top of the stack into the output queue as long as it isn't
// an opening parenthesis or its precedence is lower or equal to that of
// the operator being pushed onto the stack
try
{
while (true)
{
Lexeme stackTop = operatorStack.Peek();
if (stackTop.Type == Lexeme.LexemeType.LEFT_PAREN)
{
break;
}
else if (stackTop.IsHigherPrecedenceThan(op))
{
output.Enqueue(stackTop);
operatorStack.Pop();
}
else
{
break;
}
}
}
catch (InvalidOperationException ex)
{
// operator stack is empty, continue with pushing operator
}
lastProcessedElement = op;
operatorStack.Push(op);
}
else
{
// pushing a left-associative operator
// pop the top of the stack into the output queue as long as it isn't
// an opening parenthesis or its precedence is lower to that of
// the operator being pushed onto the stack
try
{
while (true)
{
Lexeme stackTop = operatorStack.Peek();
if (stackTop.Type == Lexeme.LexemeType.LEFT_PAREN)
{
break;
}
else if (!stackTop.IsLowerPrecedenceThan(op))
{
output.Enqueue(stackTop);
operatorStack.Pop();
}
else
{
break;
}
}
}
catch (InvalidOperationException ex)
{
// operator stack is empty, continue with pushing operator
}
lastProcessedElement = op;
operatorStack.Push(op);
}
}