private bool TryNumber(char lastChar)
{
bool isNumber = NumberExpression.IsNumber(_currentChar);
// only negative when last char is group start or symbol
bool isNegative = NumberExpression.IsNegativeSign(_currentChar) &&
(lastChar == '\0' || OperatorExpression.IsSymbol(lastChar));
if (!isNumber && !isNegative)
{
return(false);
}
_buffer.Length = 0;
_buffer.Append(_currentChar);
char p = (char)_expressionReader.Peek();
while (NumberExpression.IsNumber(p))
{
_currentChar = (char)_expressionReader.Read();
_buffer.Append(_currentChar);
p = (char)_expressionReader.Peek();
}
if (!(double.TryParse(_buffer.ToString(), out double value)))
{
throw new ParseException(Resources.InvalidNumberFormat + _buffer);
}
NumberExpression expression = new NumberExpression(value);
_expressionQueue.Enqueue(expression);
return(true);
}
private IExpression GetExpressionFromSymbol(string p)
{
IExpression e;
if (_expressionCache.ContainsKey(p))
{
e = _expressionCache[p];
}
else if (OperatorExpression.IsSymbol(Convert.ToChar(p)))
{
e = new OperatorExpression(p);
_expressionCache.Add(p, e);
}
else
{
throw new ParseException(Resources.InvalidSymbolOnStack + p);
}
return(e);
}
private bool TryOperator()
{
if (!OperatorExpression.IsSymbol(_currentChar))
{
return(false);
}
bool repeat;
string s = _currentChar.ToString();
do
{
string p = _symbolStack.Count == 0 ? string.Empty : _symbolStack.Peek();
repeat = false;
if (_symbolStack.Count == 0)
{
_symbolStack.Push(s);
}
else if (p == "(")
{
_symbolStack.Push(s);
}
else if (Precedence(s) > Precedence(p))
{
_symbolStack.Push(s);
}
else
{
IExpression e = GetExpressionFromSymbol(_symbolStack.Pop());
_expressionQueue.Enqueue(e);
repeat = true;
}
} while (repeat);
return(true);
}
