Constructing a Linked List

A linked list is usually made by linking new elements onto the front of the list.

In Lisp, the system function (cons item list ) makes a new list element containing item and adds it to the front of list:


(cons 'a nil)           ->   (a)

(cons 'a '())           ->   (a)

(cons 'a '(b c))        ->   (a b c)

We can easily do the same thing in Java:


public class Cons  {
    private Object car;
    private Cons cdr;

    private Cons(Object first, Cons rest)
       { car = first;
         cdr = rest; }
    public static Cons
                  cons(Object first, Cons rest)
      { return new Cons(first, rest); }

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