using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data;

namespace FancyCalc
{
    public class FancyCalcEnguine
    {

        public double Add(double a, double b)
        {
            return a + b;
        }


        public double Subtract(double a, double b)
        {
            return a - b;
        }

        public double Multiply(double a, double b)
        {
            return a * b;
        }
        public double Divide(double a, double b)
        {
            if (b == 0) return a;
            return a / b;
        }
        //generic calc method. usage: "10 + 20"  => result 30
        public double Culculate(string expression)
        {
            if (expression == null) throw new ArgumentNullException();
            int myInt;
            DataTable dt = new DataTable();
            var v = dt.Compute(expression, "");
            bool IsNumerical = int.TryParse(v.ToString(), out myInt);
            if (IsNumerical == false)
            {
                return 0;
            }
            double c = Convert.ToDouble(v.ToString());
            return c;
        }
    }
}