C# function error (object reference)

Question

pretty straight-forward question, I get an error I don't know how to solve, in Visual C# Express, when I call the Romberg function in my main (I provided the error message at the appropriate line). I tried using this.Romberg too but it didn't help. What should I do differently?

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Romberg2
{
    class test
    {
        // the function
        double f(double x)
        {
            double f;
            f=8*(Math.Sqrt(1-x*x)-x);
            return f;
        }

        // The Integration function
        void Romberg(double a, double b, int n, double[,] R)
        {
            int i, j, k;
            double h, sum;

            h = b - a;
            R[0,0]=(h/2)*(f(a)+f(b));

            for (i=1; i<=n; i++)
            {
                h=h/2;
                sum=0;

                for (k=1; k <= (Math.Pow(2.0,i)-1); k +=2)
                    sum +=f(a+k*h);

                R[i,0]=R[i-1,0]/2+sum*h;

                for(j=1; j<=i; j++)
                    R[i,j]=R[i,j-1]+(R[i,j-1]-R[i-1,j-1])/(Math.Pow(4.0,j)-1);
            }
        }

        static void main(int argc, char [] argv)
        {
            double[,] R = new double [10,10];
            int n=5, digits=13;
            double a=0, b=1/Math.Sqrt(2.0);

            // Call the integrating function
            Romberg(a, b, n, R);//ERROR: An object reference is required for the non-static field, method, or property

            // Printout the diagram
            for(int i=0; i<n; i++)
            {
                for(int j=0; j<=i; j++)
                {
                    Console.WriteLine(R[i,j] + " ");
                }
                Console.WriteLine("\n");
            }

        }
    }
}

add static to void Romberg -> static void Romberg

feco
– feco

2012-05-07 21:32:03 +00:00
Commented May 7, 2012 at 21:32 — feco
– feco, Commented May 7, 2012 at 21:32
@Marc Finally something I knew the answer too :(

asawyer
– asawyer

2012-05-07 21:40:57 +00:00
Commented May 7, 2012 at 21:40 — asawyer
– asawyer, Commented May 7, 2012 at 21:40

Sleiman Jneidi · Accepted Answer · 2012-05-07 21:32:19Z

2

Romberg is not a static method ,so you should call it via an instance using the new keyword

new test().Romberg(a, b, n, R);

or simply make it a static function

static void Romberg(double a, double b, int n, double[,] R)

answered May 7, 2012 at 21:32

Sleiman Jneidi

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Comments

Jacob Krall · Accepted Answer · 2012-05-07 21:32:21Z

2

main is static, so it can't call instance methods. Declare Romberg as static, or create an instance of test and use that instance:

var inst = new test();
inst.Romberg(a, b, n, R);

For more information, please check out the MSDN article on Static Classes and Static Class Members.

answered May 7, 2012 at 21:32

Jacob Krall

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Comments

asawyer · Accepted Answer · 2012-05-07 21:32:22Z

2

Main is a static method, Roomberg is an instance method. Either create a new instance of the class inside Main and call it through the instance, or make Roomberg static also.

answered May 7, 2012 at 21:32

asawyer

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Comments

Mike · Accepted Answer · 2012-05-07 21:41:26Z

1

Three problems:

1) Main is not the correct format. It needs to be in one of these formats:

static void Main() {...} 
static void Main(string[] args) {... } 
static int Main() {...} 
static int Main(string [] args) {...}

Just change it to 'static void Main()'

2) Make Romberg method static

static void Romberg(double a, double b, int n, double[,] R)

3) Make f method static:

static double f(double x)

answered May 7, 2012 at 21:41

Mike

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Comments

scottm · Accepted Answer · 2012-05-07 21:32:16Z

1

You need to make your Romberg function static, or you could wrap it in it's own class, instantiate that and execute it.

answered May 7, 2012 at 21:32

scottm

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Comments

DarthVader · Accepted Answer · 2012-05-07 21:32:26Z

1

You need to call that method on an instance. That method belongs to instance of the class.

var inst = new test();
inst.Romberg(q, w, e, R);

answered May 7, 2012 at 21:32

DarthVader

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Comments

Amit · Accepted Answer · 2012-05-07 21:38:32Z

1

Try this. To call Romberg(a, b, n, R); you have to create test class object first. Romberg is a instance method.

test obj=new test();
obj.Romberg(a, b, n, R);

edited May 7, 2012 at 21:38

answered May 7, 2012 at 21:33

Amit

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Comments

unarity · Accepted Answer · 2012-05-07 21:33:37Z

0

you are tryin to call method from class that is not initializedt.

 static void Romberg(double a, double b, int n, double[,] R)

answered May 7, 2012 at 21:33

unarity

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