【C#】无中生有

时间：2010-09-30 来源：K#

In Lisp, car, cdr, and cons are fundamental functions.

The cons function is used to construct lists, and the car and cdr functions are used to take them apart.

(define (cons x y)
  (lambda (m) (m x y)))
(define (car z)
  (z (lambda (p q) p)))
(define (cdr z)
  (z (lambda (p q) q)))

using System;

namespace K_Lib
{
    class Program
    {
        static void Main()
        {
            var triple = cons("A", cons("B", "C"));
            var head = car(triple);
            var middle = car(cdr(triple));
            var tail = cdr(cdr(triple));
            print(head);
            print(middle);
            print(tail);
        }

        static Func<Func<dynamic, dynamic, dynamic>, dynamic> cons(dynamic hd, dynamic tl)
        {
            return x => x(hd, tl);
        }

        static dynamic car(Func<Func<dynamic, dynamic, dynamic>, dynamic> pair)
        {
            return pair((hd, tl) => hd);
        }

        static dynamic cdr(Func<Func<dynamic, dynamic, dynamic>, dynamic> pair)
        {
            return pair((hd, tl) => tl);
        }

        static void print(dynamic obj)
        {
            Console.WriteLine(obj);
        }
    }
}