Task: Angles (geometric), normalization and conversion

C: #define PI 3.141592653589793
#define TWO_PI 6.283185307179586

double normalize2deg(double a) {
  while (a < 0) a += 360;
  while (a >= 360) a -= 360;
  return a;
}
double normalize2grad(double a) {
  while (a < 0) a += 400;
  while (a >= 400) a -= 400;
  return a;
}
double normalize2mil(double a) {
  while (a < 0) a += 6400;
  while (a >= 6400) a -= 6400;
  return a;
}
double normalize2rad(double a) {
  while (a < 0) a += TWO_PI;
  while (a >= TWO_PI) a -= TWO_PI;
  return a;
}

double deg2grad(double a) {return a * 10 / 9;}
double deg2mil(double a) {return a * 160 / 9;}
double deg2rad(double a) {return a * PI / 180;}

double grad2deg(double a) {return a * 9 / 10;}
double grad2mil(double a) {return a * 16;}
double grad2rad(double a) {return a * PI / 200;}

double mil2deg(double a) {return a * 9 / 160;}
double mil2grad(double a) {return a / 16;}
double mil2rad(double a) {return a * PI / 3200;}

double rad2deg(double a) {return a * 180 / PI;}
double rad2grad(double a) {return a * 200 / PI;}
double rad2mil(double a) {return a * 3200 / PI;}



C#: using System;

public static class Angles
{
    public static void Main() => Print(-2, -1, 0, 1, 2, 6.2831853, 16, 57.2957795, 359, 6399, 1_000_000);

    public static void Print(params double[] angles) {
        string[] names = { "Degrees", "Gradians", "Mils", "Radians" };
        Func<double, double> rnd = a => Math.Round(a, 4);
        Func<double, double>[] normal = { NormalizeDeg, NormalizeGrad, NormalizeMil, NormalizeRad };

        Func<double, double>[,] convert = {
            { a => a, DegToGrad, DegToMil, DegToRad },
            { GradToDeg, a => a, GradToMil, GradToRad },
            { MilToDeg, MilToGrad, a => a, MilToRad },
            { RadToDeg, RadToGrad, RadToMil, a => a }
        };

        Console.WriteLine($@"{"Angle",-12}{"Normalized",-12}{"Unit",-12}{
            "Degrees",-12}{"Gradians",-12}{"Mils",-12}{"Radians",-12}");

        foreach (double angle in angles) {
            for (int i = 0; i < 4; i++) {
                double nAngle = normal[i](angle);

                Console.WriteLine($@"{
                    rnd(angle),-12}{
                    rnd(nAngle),-12}{
                    names[i],-12}{
                    rnd(convert[i, 0](nAngle)),-12}{
                    rnd(convert[i, 1](nAngle)),-12}{
                    rnd(convert[i, 2](nAngle)),-12}{
                    rnd(convert[i, 3](nAngle)),-12}");
            }
        }
    }

    public static double NormalizeDeg(double angle) => Normalize(angle, 360);
    public static double NormalizeGrad(double angle) => Normalize(angle, 400);
    public static double NormalizeMil(double angle) => Normalize(angle, 6400);
    public static double NormalizeRad(double angle) => Normalize(angle, 2 * Math.PI);

    private static double Normalize(double angle, double N) {
        while (angle <= -N) angle += N;
        while (angle >= N) angle -= N;
        return angle;
    }

    public static double DegToGrad(double angle) => angle * 10 / 9;
    public static double DegToMil(double angle) => angle * 160 / 9;
    public static double DegToRad(double angle) => angle * Math.PI / 180;
    
    public static double GradToDeg(double angle) => angle * 9 / 10;
    public static double GradToMil(double angle) => angle * 16;
    public static double GradToRad(double angle) => angle * Math.PI / 200;
    
    public static double MilToDeg(double angle) => angle * 9 / 160;
    public static double MilToGrad(double angle) => angle / 16;
    public static double MilToRad(double angle) => angle * Math.PI / 3200;
    
    public static double RadToDeg(double angle) => angle * 180 / Math.PI;
    public static double RadToGrad(double angle) => angle * 200 / Math.PI;
    public static double RadToMil(double angle) => angle * 3200 / Math.PI;
}