Program.cs

using System.Text;

namespace Methods;

class Program
{
    static void Main()
    {
        int q = Divide(10, 3, out int r);

        Console.WriteLine(q);

        string text = "42";
        int value = int.TryParse(text, out int x) ? x : -1;
        Console.WriteLine(value);

        UseOutParam();
        DiscardOutParam();
        UseRefParam();
        UseInParam();

        string? rose = null;
        ref string? rosaIndica = ref rose;
        rosaIndica = "smell as sweet";
        Console.WriteLine($"A rose by any other name would {rose}");

        Blame("mischievous gnomes");
        Blame(problem: "everything");

        StringInterpolation();
        StringFormatting();

        GetAverageDistanceFrom((0, 0), new[] { (1.0, 0.0), (0.0, 3.0) });
        GetAverageDistanceFromWithExpressionBodiedMethod((0, 0), new[] { (1.0, 0.0), (0.0, 3.0) });
    }

    public static int Divide(int x, int y, out int remainder)
    {
        remainder = x % y;
        return x / y;
    }

    private static void UseOutParam()
    {
        int r, q;
        q = Divide(10, 3, out r);
        Console.WriteLine($"3: {q}, {r}");
        q = Divide(10, 4, out r);
        Console.WriteLine($"4: {q}, {r}");
    }

    private static void DiscardOutParam()
    {
        int q = Divide(10, 3, out _);

        Console.WriteLine(q);
    }

    private static void UseRefParam()
    {
        long x = 41;
        Interlocked.Increment(ref x);
        Console.WriteLine(x);
    }

    public static double GetArea(in Rect r) => r.Width * r.Height;

    private static void UseInParam()
    {
        var r = new Rect(10, 20, 100, 100);
        double area = GetArea(in r);
        double area2 = GetArea(r);
    }

    public static void Blame(string perpetrator = "the youth of today",
        string problem = "the downfall of society")
    {
        Console.WriteLine($"I blame {perpetrator} for {problem}.");
    }

    public static void UnclearArguments(string filepath)
    {
        using Stream stream = new MemoryStream(Encoding.UTF8.GetBytes("Test"));
        using var r = new StreamReader(stream, Encoding.UTF8, true, 8192, false);
        using var w = new StreamWriter(filepath, true, Encoding.UTF8);
    }

    public static void ClearArguments(string filepath)
    {
        using Stream stream = new MemoryStream(Encoding.UTF8.GetBytes("Test"));
        using var r = new StreamReader(stream, Encoding.UTF8,
          detectEncodingFromByteOrderMarks: true, bufferSize: 8192, leaveOpen: false);
        using var w = new StreamWriter(filepath, append: true, Encoding.UTF8);
    }

    public static void StringInterpolation()
    {
        Console.WriteLine($"PI: {Math.PI}. Square root of 2: {Math.Sqrt(2)}");
        Console.WriteLine($"It is currently {DateTime.Now}");
        var r = new Random();
        Console.WriteLine(
            $"{r.Next(10)}, {r.Next(10)}, {r.Next(10)}, {r.Next(10)}");
    }

    public static void StringFormatting()
    {
        Console.WriteLine(string.Format(
            "PI: {0}. Square root of 2: {1}", Math.PI, Math.Sqrt(2)));
        Console.WriteLine(string.Format("It is currently {0}", DateTime.Now));
        var r = new Random();
        Console.WriteLine(
            "{0}, {1}, {2}, {3}",
            r.Next(10), r.Next(10), r.Next(10), r.Next(10));

        Console.WriteLine(
            "{0}, {1}, {2}, {3}",
            new object[] { r.Next(10), r.Next(10), r.Next(10), r.Next(10) });
    }

    /* This is for illustration only
    public static void WriteLine([StringSyntax("CompositeFormat")] string format, params object?[]? arg);
    */

    static double GetAverageDistanceFrom(
        (double X, double Y) referencePoint,
        (double X, double Y)[] points)
    {
        double total = 0;
        for (int i = 0; i < points.Length; ++i)
        {
            total += GetDistanceFromReference(points[i]);
        }
        return total / points.Length;

        double GetDistanceFromReference((double X, double Y) p)
        {
            return GetDistance(p, referencePoint);
        }

        static double GetDistance((double X, double Y) p1, (double X, double Y) p2)
        {
            double dx = p1.X - p2.X;
            double dy = p1.Y - p2.Y;
            return Math.Sqrt(dx * dx + dy * dy);
        }
    }

    static double GetAverageDistanceFromWithExpressionBodiedMethod(
        (double X, double Y) referencePoint,
        (double X, double Y)[] points)
    {
        double total = 0;
        for (int i = 0; i < points.Length; ++i)
        {
            total += GetDistanceFromReference(points[i]);
        }
        return total / points.Length;

        double GetDistanceFromReference((double X, double Y) p)
            => GetDistance(p, referencePoint);


        static double GetDistance((double X, double Y) p1, (double X, double Y) p2)
        {
            double dx = p1.X - p2.X;
            double dy = p1.Y - p2.Y;
            return Math.Sqrt(dx * dx + dy * dy);
        }
    }
}