/*
* Copyright 2002-2003 Sun Microsystems, Inc. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
* CA 95054 USA or visit www.sun.com if you need additional information or
* have any questions.
*/
class List<A> {
/** The first element of the list, supposed to be immutable.
*/
public A head;
/** The remainder of the list except for its first element, supposed
* to be immutable.
*/
public List<A> tail;
/** Construct a list given its head and tail.
*/
public List(A head, List<A> tail) {
this.tail = tail;
this.head = head;
}
/** Construct an empty list.
*/
public List() {
this(null, null);
}
/** Construct a list consisting of given element.
*/
public static <A> List<A> make(A x1) {
return new List<A>(x1, new List<A>());
}
/** Construct a list consisting of given elements.
*/
public static <A> List<A> make(A x1, A x2) {
return new List<A>(x1, new List<A>(x2, new List<A>()));
}
/** Construct a list consisting of given elements.
*/
public static <A> List<A> make(A x1, A x2, A x3) {
return new List<A>(x1, new List<A>(x2, new List<A>(x3, new List<A>())));
}
/** Construct a list consisting all elements of given array.
*/
public static <A> List<A> make(A[] vec) {
List<A> xs = new List<A>();
for (int i = vec.length - 1; i >= 0; i--)
xs = new List<A>(vec[i], xs);
return xs;
}
/** Construct a list consisting of a given number of identical elements.
* @param len The number of elements in the list.
* @param init The value of each element.
*/
public static <A> List<A> make(int len, A init) {
List<A> l = new List<A>();
for (int i = 0; i < len; i++) l = new List<A>(init, l);
return l;
}
/** Does list have no elements?
*/
public boolean isEmpty() {
return tail == null;
}
/** Does list have elements?
*/
public boolean nonEmpty() {
return tail != null;
}
/** Return the number of elements in this list.
*/
public int length() {
List<A> l = this;
int len = 0;
while (l.tail != null) {
l = l.tail;
len++;
}
return len;
}
/** Prepend given element to front of list, forming and returning
* a new list.
*/
public List<A> prepend(A x) {
return new List<A>(x, this);
}
/** Prepend given list of elements to front of list, forming and returning
* a new list.
*/
public List<A> prependList(List<A> xs) {
if (this.isEmpty()) return xs;
else if (xs.isEmpty()) return this;
else return this.prependList(xs.tail).prepend(xs.head);
}
/** Reverse list, forming and returning a new list.
*/
public List<A> reverse() {
List<A> rev = new List<A>();
for (List<A> l = this; l.nonEmpty(); l = l.tail)
rev = new List<A>(l.head, rev);
return rev;
}
/** Append given element at length, forming and returning
* a new list.
*/
public List<A> append(A x) {
return make(x).prependList(this);
}
/** Append given list at length, forming and returning
* a new list.
*/
public List<A> appendList(List<A> x) {
return x.prependList(this);
}
/** Copy successive elements of this list into given vector until
* list is exhausted or end of vector is reached.
*/
public A[] toArray(A[] vec) {
int i = 0;
List<A> l = this;
while (l.nonEmpty() && i < vec.length) {
vec[i] = l.head;
l = l.tail;
i++;
}
return vec;
}
/** Form a string listing all elements with given separator character.
*/
public String toString(String sep) {
if (isEmpty()) {
return "";
} else {
StringBuffer buf = new StringBuffer();
buf.append(((Object)head).toString());
for (List<A> l = tail; l.nonEmpty(); l = l.tail) {
buf.append(sep);
buf.append(((Object)l.head).toString());
}
return buf.toString();
}
}
/** Form a string listing all elements with comma as the separator character.
*/
public String toString() {
return toString(",");
}
/** Compute a hash code, overrides Object
*/
public int hashCode() {
List<A> l = this;
int h = 0;
while (l.tail != null) {
h = h * 41 + (head != null ? head.hashCode() : 0);
l = l.tail;
}
return h;
}
/** Is this list the same as other list?
*/
public boolean equals(Object other) {
return other instanceof List && equals(this, (List)other);
}
/** Are the two lists the same?
*/
public static boolean equals(List xs, List ys) {
while (xs.tail != null && ys.tail != null) {
if (xs.head == null) {
if (ys.head != null) return false;
} else {
if (!xs.head.equals(ys.head)) return false;
}
xs = xs.tail;
ys = ys.tail;
}
return xs.tail == null && ys.tail == null;
}
/** Does the list contain the specified element?
*/
public boolean contains(A x) {
List<A> l = this;
while (l.tail != null) {
if (x == null) {
if (l.head == null) return true;
} else {
if (x.equals(l.head)) return true;
}
l = l.tail;
}
return false;
}
}