/// <summary>
/// Parses and extracts a numeric value at the current position.
/// </summary>
/// <param name="parser">Current parsing helper object.</param>
/// <returns>The extracted number token string.</returns>
private Variable ParseNumber(ParsingHelper parser)
{
Debug.Assert(IsNumberChar(parser.Peek()));
bool hasDecimal = false;
int start = parser.Index;
while (char.IsDigit(parser.Peek()) || parser.Peek() == '.')
{
if (parser.Peek() == '.')
{
if (hasDecimal)
{
throw new ExpressionException(ErrMultipleDecimalPoints, parser.Index);
}
hasDecimal = true;
}
parser++;
}
// Extract token
string token = parser.Extract(start, parser.Index);
if (token == ".")
{
throw new ExpressionException(ErrInvalidOperand, parser.Index - 1);
}
if (hasDecimal)
{
return(new Variable(double.Parse(token)));
}
return(new Variable(int.Parse(token)));
}
/// <summary>
/// Extracts and evaluates a function parameter and returns its value. If an
/// exception occurs, it is caught and the column is adjusted to reflect the
/// position in original string, and the exception is rethrown.
/// </summary>
/// <param name="parser">ParsingHelper object.</param>
/// <param name="start">Index where current parameter starts.</param>
/// <returns>The parameter value.</returns>
private Variable ParseParameter(ParsingHelper parser, int start)
{
try
{
// Recursively evaluate expression
string expression = parser.Extract(start, parser.Index);
return(Evaluate(expression));
}
catch (ExpressionException ex)
{
// Adjust column and rethrow exception
ex.Index += start;
throw ex;
}
}