duke@1: /*
ohair@554:  * Copyright (c) 2002, 2003, Oracle and/or its affiliates. All rights reserved.
duke@1:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@1:  *
duke@1:  * This code is free software; you can redistribute it and/or modify it
duke@1:  * under the terms of the GNU General Public License version 2 only, as
duke@1:  * published by the Free Software Foundation.
duke@1:  *
duke@1:  * This code is distributed in the hope that it will be useful, but WITHOUT
duke@1:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@1:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
duke@1:  * version 2 for more details (a copy is included in the LICENSE file that
duke@1:  * accompanied this code).
duke@1:  *
duke@1:  * You should have received a copy of the GNU General Public License version
duke@1:  * 2 along with this work; if not, write to the Free Software Foundation,
duke@1:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@1:  *
ohair@554:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
ohair@554:  * or visit www.oracle.com if you need additional information or have any
ohair@554:  * questions.
duke@1:  */
duke@1: 
duke@1: class List<A> {
duke@1: 
duke@1:     /** The first element of the list, supposed to be immutable.
duke@1:      */
duke@1:     public A head;
duke@1: 
duke@1:     /** The remainder of the list except for its first element, supposed
duke@1:      *  to be immutable.
duke@1:      */
duke@1:     public List<A> tail;
duke@1: 
duke@1:     /** Construct a list given its head and tail.
duke@1:      */
duke@1:     public List(A head, List<A> tail) {
duke@1:         this.tail = tail;
duke@1:         this.head = head;
duke@1:     }
duke@1: 
duke@1:     /** Construct an empty list.
duke@1:      */
duke@1:     public List() {
duke@1:         this(null, null);
duke@1:     }
duke@1: 
duke@1:     /** Construct a list consisting of given element.
duke@1:      */
duke@1:     public static <A> List<A> make(A x1) {
duke@1:         return new List<A>(x1, new List<A>());
duke@1:     }
duke@1: 
duke@1:     /** Construct a list consisting of given elements.
duke@1:      */
duke@1:     public static <A> List<A> make(A x1, A x2) {
duke@1:         return new List<A>(x1, new List<A>(x2, new List<A>()));
duke@1:     }
duke@1: 
duke@1:     /** Construct a list consisting of given elements.
duke@1:      */
duke@1:     public static <A> List<A> make(A x1, A x2, A x3) {
duke@1:         return new List<A>(x1, new List<A>(x2, new List<A>(x3, new List<A>())));
duke@1:     }
duke@1: 
duke@1:     /** Construct a list consisting all elements of given array.
duke@1:      */
duke@1:     public static <A> List<A> make(A[] vec) {
duke@1:         List<A> xs = new List<A>();
duke@1:         for (int i = vec.length - 1; i >= 0; i--)
duke@1:             xs = new List<A>(vec[i], xs);
duke@1:         return xs;
duke@1:     }
duke@1: 
duke@1:     /** Construct a list consisting of a given number of identical elements.
duke@1:      *  @param len    The number of elements in the list.
duke@1:      *  @param init   The value of each element.
duke@1:      */
duke@1:     public static <A> List<A> make(int len, A init) {
duke@1:         List<A> l = new List<A>();
duke@1:         for (int i = 0; i < len; i++) l = new List<A>(init, l);
duke@1:         return l;
duke@1:     }
duke@1: 
duke@1:     /** Does list have no elements?
duke@1:      */
duke@1:     public boolean isEmpty() {
duke@1:         return tail == null;
duke@1:     }
duke@1: 
duke@1:     /** Does list have elements?
duke@1:      */
duke@1:     public boolean nonEmpty() {
duke@1:         return tail != null;
duke@1:     }
duke@1: 
duke@1:     /** Return the number of elements in this list.
duke@1:      */
duke@1:     public int length() {
duke@1:         List<A> l = this;
duke@1:         int len = 0;
duke@1:         while (l.tail != null) {
duke@1:             l = l.tail;
duke@1:             len++;
duke@1:         }
duke@1:         return len;
duke@1:     }
duke@1: 
duke@1:     /** Prepend given element to front of list, forming and returning
duke@1:      *  a new list.
duke@1:      */
duke@1:     public List<A> prepend(A x) {
duke@1:         return new List<A>(x, this);
duke@1:     }
duke@1: 
duke@1:     /** Prepend given list of elements to front of list, forming and returning
duke@1:      *  a new list.
duke@1:      */
duke@1:     public List<A> prependList(List<A> xs) {
duke@1:         if (this.isEmpty()) return xs;
duke@1:         else if (xs.isEmpty()) return this;
duke@1:         else return this.prependList(xs.tail).prepend(xs.head);
duke@1:     }
duke@1: 
duke@1:     /** Reverse list, forming and returning a new list.
duke@1:      */
duke@1:     public List<A> reverse() {
duke@1:         List<A> rev = new List<A>();
duke@1:         for (List<A> l = this; l.nonEmpty(); l = l.tail)
duke@1:             rev = new List<A>(l.head, rev);
duke@1:         return rev;
duke@1:     }
duke@1: 
duke@1:     /** Append given element at length, forming and returning
duke@1:      *  a new list.
duke@1:      */
duke@1:     public List<A> append(A x) {
duke@1:         return make(x).prependList(this);
duke@1:     }
duke@1: 
duke@1:     /** Append given list at length, forming and returning
duke@1:      *  a new list.
duke@1:      */
duke@1:     public List<A> appendList(List<A> x) {
duke@1:         return x.prependList(this);
duke@1:     }
duke@1: 
duke@1:     /** Copy successive elements of this list into given vector until
duke@1:      *  list is exhausted or end of vector is reached.
duke@1:      */
duke@1:     public A[] toArray(A[] vec) {
duke@1:         int i = 0;
duke@1:         List<A> l = this;
duke@1:         while (l.nonEmpty() && i < vec.length) {
duke@1:             vec[i] = l.head;
duke@1:             l = l.tail;
duke@1:             i++;
duke@1:         }
duke@1:         return vec;
duke@1:     }
duke@1: 
duke@1:     /** Form a string listing all elements with given separator character.
duke@1:      */
duke@1:     public String toString(String sep) {
duke@1:         if (isEmpty()) {
duke@1:             return "";
duke@1:         } else {
duke@1:             StringBuffer buf = new StringBuffer();
duke@1:             buf.append(((Object)head).toString());
duke@1:             for (List<A> l = tail; l.nonEmpty(); l = l.tail) {
duke@1:                 buf.append(sep);
duke@1:                 buf.append(((Object)l.head).toString());
duke@1:             }
duke@1:             return buf.toString();
duke@1:         }
duke@1:     }
duke@1: 
duke@1:     /** Form a string listing all elements with comma as the separator character.
duke@1:      */
duke@1:     public String toString() {
duke@1:         return toString(",");
duke@1:     }
duke@1: 
duke@1:     /** Compute a hash code, overrides Object
duke@1:      */
duke@1:     public int hashCode() {
duke@1:         List<A> l = this;
duke@1:         int h = 0;
duke@1:         while (l.tail != null) {
duke@1:             h = h * 41 + (head != null ? head.hashCode() : 0);
duke@1:             l = l.tail;
duke@1:         }
duke@1:         return h;
duke@1:     }
duke@1: 
duke@1:     /** Is this list the same as other list?
duke@1:      */
duke@1:     public boolean equals(Object other) {
duke@1:         return other instanceof List && equals(this, (List)other);
duke@1:     }
duke@1: 
duke@1:     /** Are the two lists the same?
duke@1:      */
duke@1:     public static boolean equals(List xs, List ys) {
duke@1:         while (xs.tail != null && ys.tail != null) {
duke@1:             if (xs.head == null) {
duke@1:                 if (ys.head != null) return false;
duke@1:             } else {
duke@1:                 if (!xs.head.equals(ys.head)) return false;
duke@1:             }
duke@1:             xs = xs.tail;
duke@1:             ys = ys.tail;
duke@1:         }
duke@1:         return xs.tail == null && ys.tail == null;
duke@1:     }
duke@1: 
duke@1:     /** Does the list contain the specified element?
duke@1:      */
duke@1:     public boolean contains(A x) {
duke@1:         List<A> l = this;
duke@1:         while (l.tail != null) {
duke@1:             if (x == null) {
duke@1:                 if (l.head == null) return true;
duke@1:             } else {
duke@1:                 if (x.equals(l.head)) return true;
duke@1:             }
duke@1:             l = l.tail;
duke@1:         }
duke@1:         return false;
duke@1:     }
duke@1: 
duke@1: }