private bool TryString(char c)
{
if (!char.IsLetter(c))
{
return(false);
}
_buffer.Length = 0;
_buffer.Append(c);
char p = (char)_expressionReader.Peek();
while (char.IsLetterOrDigit(p) || p.Equals('_') || p.Equals('@'))
{
_buffer.Append((char)_expressionReader.Read());
p = (char)_expressionReader.Peek();
}
if (_variables.Contains(_buffer.ToString()))
{
object value = GetVariableValue(_buffer.ToString());
NumberExpression expression = new NumberExpression(value);
_expressionQueue.Enqueue(expression);
return(true);
}
if (FunctionExpression.IsFunction(_buffer.ToString()))
{
_symbolStack.Push(_buffer.ToString());
return(true);
}
throw new ParseException("Invalid variable: " + _buffer);
}
//public void Parse(string expr)
//{
// expr = expr.Trim();
// _expressionReader = new StringReader(expr);
// while (_expressionReader.Peek() >= 0)
// {
// char c = (char)_expressionReader.Read();
// if (Char.IsWhiteSpace(c))
// continue;
// if (TryNumber(c))
// continue;
// if (TryString(c))
// continue;
// if (TryStartGroup(c))
// continue;
// if (TryOperator(c))
// continue;
// if (TryEndGroup(c))
// continue;
// throw new ParseException("Invalid character encountered: " + c);
// }
//}
private bool TryNumber(char c)
{
bool isNumber = NumberExpression.IsNumber(c);
bool isNegative = false;
if (NumberExpression.IsNegativeSign(c))
{
if (_expressionQueue.Count == 0)
{
isNegative = true;
}
else if (_expressionQueue.Count > 0 && _symbolStack.Count > 0)
{
if ((string)_symbolStack.Peek() == "(")
{
isNegative = true;
}
}
}
if (!isNumber && !isNegative)
{
return(false);
}
_buffer.Length = 0;
_buffer.Append(c);
char p = (char)_expressionReader.Peek();
while (NumberExpression.IsNumber(p))
{
_buffer.Append((char)_expressionReader.Read());
p = (char)_expressionReader.Peek();
}
double value;
if (!(double.TryParse(_buffer.ToString(), out value)))
{
throw new ParseException("Invalid number format: " + _buffer);
}
NumberExpression expression = new NumberExpression(value);
_expressionQueue.Enqueue(expression);
return(true);
}