Is there a string math evaluator in .NET?

Question

If I have a string with a valid math expression such as:

String s = \"1 + 2 * 7\";

Is there a built in library/function in .NET that will p

Answer 1

A simple math parser is quite easy to build, and requires only a few lines of code:

Take this flexible example:

class RPN
{
    public static double Parse( Stack strStk )
    {
        if (strStk == null || strStk.Count == 0 )
        {
            return 0;
        }
        Stack numStk = new Stack();
        double result = 0;

        Func op = null;
        while (strStk.Count > 0)
        {
            var s = strStk.Pop();
            switch (s)
            {
                case "+":
                    op = ( b ) => { return numStk.Pop() + b; };
                    break;
                case "-":
                    op = ( b ) => { return numStk.Pop() - b; };
                    break;
                case "*":
                    op = ( b ) => { return numStk.Pop() * b; };
                    break;
                case "/":
                    op = ( b ) => { return numStk.Pop() / b; };
                    break;

                default:
                    double.TryParse(s, NumberStyles.Any, out result);
                    if (numStk.Count > 0)
                    {
                        result = op(result);
                    }
                    numStk.Push(result);
                    break;
            }
        }
        return result;
    }
}

....
var str = " 100.5 + 300.5 - 100 * 10 / 100";    
str = Regex.Replace(str, @"\s", "", RegexOptions.Multiline);
Stack strStk = new Stack(
     Regex.Split(str, @"([()*+\/-])", RegexOptions.Multiline).Reverse()
);
RPN.Parse(strStk);

To enable precedence by bracketing a stack of stacks will suffice, such as archived by recursion. Anything between brackets is put on a new stack. Finally you can support math operations in a clean readable fashion by lambdas.