Need a formula interpreter for .Net [closed]

Question

I'm looking for a formula interpreter that I can use in a C# application. It needs to be able to interpret a string like this:

max(1+2, 4) * x

I found Writing a fast formula interpreter (codeproject.com) which almost does what I need but it doesn't allow for functions with multiple parameters. I could probably add that functionality to it but I was just wondering if something like this already exists.

Thanks

Answer 1

A couple I've used in the past with no problems:

• NCalc
• Fast Lightweight Expression Evaluator

Answer 2

You can actually build a very effective interpreter by parsing and replacing certain functional keywords such as max with Math.Max and then dynamically building and executing the formula as a C# class and method. So actually you would be parsing and wrapping the formula and allowing the C# compiler to interpret and execute it.

So, taking your sample formula of max(1+2, 4) * x would turn into:

public class MyFormula
{
    public double calc(double x)
    {
        return Math.Max(1+2, 4) * x;
    }
}

Which you would compile on the fly and then execute per the linked article. You still have to parse for and pass the x value of course.

Answer 3

A long time ago in one project i had to create some booking with formulas, and i used VsaEngine. To use this engine you need to add reference to Microsoft.JScript. Here is example:

Code for usage is very simple, just replace formula parameters like:

string formula = "x+y";
formula=  formula.Replace("x","100").Replace("y","200");
string result = CalculateFormula(formula);

And here is core method, CalculateFormula:

public string CalculateFormula(string evaluationString)
{ 
      VsaEngine en = VsaEngine.CreateEngine();
      Object result = Eval.JScriptEvaluate(evaluationString, en);
      return result.ToString();
}

With this you can create your custom formula interpreter engine.