using System;

using org.mariuszgromada.math.mxparser;

public class Program

{

    public static void Main()

    {

        var a = 702152;

        var b = 1;

        var c = 643078491;

        var expected = 643780644;

        var parsedExpression = new Expression("702152+1+643078491");

        var calc = parsedExpression.calculate();

        var calc2 = Double.Parse(Math.Round(calc, 15).ToString("G15"));

        var calc3 = Double.Parse(Math.Round(calc, 15).ToString("G17"));

        //var result = a + b + c;

        var equals = calc == expected;

        var equals15 = calc2 == expected;

        var equals17 = calc3 == expected;

        Console.WriteLine(calc.GetType());

        Console.WriteLine();

        Console.WriteLine(calc);

        Console.WriteLine(calc2);

        Console.WriteLine(calc3);

        Console.WriteLine();        

        Console.WriteLine(equals);

        Console.WriteLine(equals15);

        Console.WriteLine(equals17);

        //Console.WriteLine(calc.ToString("G15"));

        //Console.WriteLine(calc.ToString("G17"));

        //Console.WriteLine(expected);

        //Console.WriteLine(equals);

        //Console.WriteLine();

    }

}

​