using System;

public class Utilities {

    public static double Theta(double x, double a, double buf_max = 80, int k_max = 500) {

        double sum, buf, xx, buf2;

        int k;

        if (a < 1 / Math.PI) {

            sum = 1;

            k = 0;

            do {

                k++;

                buf = (k * k) / a;

                sum += 2 * Math.Exp(-buf) * Math.Cos(2 * k * x);

            } while ((buf < buf_max) && (k < k_max));

            return sum;

        } else {

            k = (int)Math.Round(x / (Math.PI));

            xx = x - 2 * k * Math.PI;

            sum = Math.Exp(-(a * xx * xx));

            k = 0;

            do

            {

                k++;

                buf = (a * Math.Pow(xx + Math.PI * k, 2));

                buf2 = (a * Math.Pow(xx - Math.PI * k, 2));

                sum += Math.Exp(-buf) + Math.Exp(-buf2);

            } while (((buf < buf_max) || (buf2 < buf_max)) && (k < k_max));

​

            return Math.Sqrt(Math.PI * a) * sum;

        }

    }

​

    private static double mz_ini(double a, int maxBuff = 80) {

        double mul;

        if (a < 1 / Math.PI)

            mul = 1 / a;

        else

            mul = Math.Pow(Math.PI, 2) * a;

        double sum = Math.Exp(-mul / 4);

        int r = 0;

        double buff;

        do

        {

            r++;

            buff = mul * Math.Pow(-2 * r + 0.5, 2);

            sum += (-4 * r + 1) * Math.Exp(-buff);

            buff = mul * Math.Pow(2 * r + 0.5, 2);

            sum += (4 * r + 1) * Math.Exp(-buff);

        } while (buff < maxBuff);

        if (a < 1 / Math.PI)

            return sum;

        else

            return sum * Math.PI * a * Math.Sqrt(Math.PI * a);

    }

​

​

    public static double[] CalcCoeffs(int n_cnt, int n_DCT, double a, int maxBuff = 80)

        {

            int maxk_cnt = 1000;

            double h, sum;

            double[] work = new double[maxk_cnt];

            double[] c = new double[maxk_cnt];

​

            h = Math.PI / n_DCT;

​

            for (int m = 0; m <= n_DCT; m++)

            {

                work[m] = 1 / Math.Sqrt(Theta(m * h / 2, a));

            }

​

            for (int k = 0; k <= n_cnt; k++)

            {

                if (k % 2 != 0)

                    sum = (work[0] - work[n_DCT]) / 2;

                else

                    sum = (work[0] + work[n_DCT]) / 2;

                for (int m = 1; m < n_DCT; m++)

                    sum += work[m] * Math.Cos(k * h * m);

                c[k] = sum / n_DCT;

                Console.WriteLine(c[k]);

            }

            return c;

   }

​

}

​

public class Program

{

    public static void Main()

    {

        Console.Clear();

        double[] c_k = Utilities.CalcCoeffs(4, 499, 1, 80);

    }

}