.Net 5 在函数中使用Lambda

using System;
                    
public class Program
{
    public static string CardinalToOrdinal(int number)
    {
        switch(number)
        {
            case 11:
            case 12:
            case 13:
                return $"{number}th";
            default:
                int lastDight = number %10;
                string suffix = lastDight switch
                {
                    1 => "st",
                    2 => "nd",
                    3 => "rd",
                    _ => "th"
                };
                return $"{number}{suffix}";
        }
    }
    
    public static int FibFunctional( int term) =>
        term switch
        {
            1 => 0,
            2 => 1,
            _ => FibFunctional(term-1) + FibFunctional(term-2)
        };
    
    public static void RunFibfunctional()
    {
        for(int i = 1;i <= 30;i++)
        {
            Console.WriteLine("The {0} term of the Fibonacci sequence is {1:N0}.",
                arg0:CardinalToOrdinal(i),
                arg1:FibFunctional(term:i));
        }
    }
    
    
    public static void Main()
    {
        RunFibfunctional();
    }
}