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Immutable Clojure collections and a Transformation abstraction for Java 8+, immutably, type-safely, and with good performance. Name will change to "Paguro" in November 2016.
/*
Copyright (c) Rich Hickey. All rights reserved. The use and distribution terms for this software
are covered by the Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
which can be found in the file epl-v10.html at the root of this distribution. By using this
software in any fashion, you are agreeing to be bound by the terms of this license. You must not
remove this notice, or any other, from this software.
*/
/* rich Mar 3, 2008 */
package org.organicdesign.fp.collections;
import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.Comparator;
import java.util.Map;
import java.util.SortedSet;
import org.organicdesign.fp.Option;
import static org.organicdesign.fp.collections.Equator.defaultComparator;
/**
A wrapper that turns a PersistentTreeMap into a set.
This file is a derivative work based on a Clojure collection licensed under the Eclipse Public
License 1.0 Copyright Rich Hickey. Errors by Glen Peterson.
*/
public class PersistentTreeSet implements ImSortedSet, Serializable {
/**
Be extremely careful with this because it uses the default comparator, which only works for
items that implement Comparable (have a "natural ordering"). An attempt to use it with other
items will blow up at runtime. Either a withComparator() method will be added, or this will
be removed.
*/
// TODO: Should really require a comparator.
@SuppressWarnings("unchecked")
static public final PersistentTreeSet EMPTY = new PersistentTreeSet(PersistentTreeMap.EMPTY);
/**
Be extremely careful with this because it uses the default comparator, which only works for
items that implement Comparable (have a "natural ordering"). An attempt to use it with other
items will blow up at runtime. Either a withComparator() method will be added, or this will
be removed.
*/
@SuppressWarnings("unchecked")
static public > PersistentTreeSet empty() { return EMPTY; }
/**
Returns a new PersistentTreeSet of the given comparator. Always use this instead of starting
with empty() because there is no way to assign a comparator to an existing set.
*/
public static PersistentTreeSet ofComp(Comparator comp) {
return new PersistentTreeSet<>(PersistentTreeMap.empty(comp));
}
/**
Returns a new PersistentTreeSet of the given comparator and items.
@param comp A comparator that defines the sort order of elements in the new set. This
becomes part of the set (it's not for pre-sorting).
@param elements items to go into the set. In the case of a duplicate element, later
values in the input list overwrite the earlier ones.
@return a new PersistentTreeSet of the specified comparator and the given elements
*/
public static PersistentTreeSet ofComp(Comparator comp,
Iterable elements) {
PersistentTreeSet ret = new PersistentTreeSet<>(PersistentTreeMap.empty(comp));
if (elements == null) { return ret; }
for (T element : elements) {
ret = ret.put(element);
}
return ret;
}
/** Returns a new PersistentTreeSet of the given comparable items. */
public static > PersistentTreeSet of(Iterable items) {
// empty() uses default comparator
if (items == null) { return empty(); }
PersistentTreeSet ret = empty();
for (T item : items) {
ret = ret.put(item);
}
return ret;
}
/**
Returns a new PersistentTreeSet of the keys and comparator in the given map. Since
PersistentTreeSet is just a wrapper for a PersistentTreeMap, this can be a very cheap
operation.
*/
public static PersistentTreeSet ofMap(ImSortedMap i) {
return new PersistentTreeSet<>(i);
}
// ==================================== Instance Variables ====================================
private transient final ImSortedMap impl;
// ======================================= Constructor =======================================
private PersistentTreeSet(ImSortedMap i) { impl = i; }
// ======================================= Serialization =======================================
// This class has a custom serialized form designed to be as small as possible. It does not
// have the same internal structure as an instance of this class.
// For serializable. Make sure to change whenever internal data format changes.
private static final long serialVersionUID = 20160904120000L;
// Check out Josh Bloch Item 78, p. 312 for an explanation of what's going on here.
private static class SerializationProxy implements Serializable {
// For serializable. Make sure to change whenever internal data format changes.
private static final long serialVersionUID = 20160904120000L;
private Comparator comparator;
private final int size;
private transient ImSortedMap theMap;
SerializationProxy(ImSortedMap phm) {
comparator = phm.comparator();
if ( (comparator != null) && !(comparator instanceof Serializable) ) {
throw new IllegalStateException("Comparator must implement serializable." +
" Instead it was " + comparator);
}
if (comparator instanceof PersistentTreeMap.KeyComparator) {
Comparator wc = ((PersistentTreeMap.KeyComparator) comparator).unwrap();
if ( !(wc instanceof Serializable) ) {
throw new IllegalStateException("Wrapped key comparator must implement" +
"serializable. Instead it was " + wc);
}
}
size = phm.size();
theMap = phm;
}
// Taken from Josh Bloch Item 75, p. 298
private void writeObject(ObjectOutputStream s) throws IOException {
s.defaultWriteObject();
// Write out all elements in the proper order
for (Map.Entry entry : theMap) {
s.writeObject(entry.getKey());
}
}
@SuppressWarnings("unchecked")
private void readObject(ObjectInputStream s) throws IOException, ClassNotFoundException {
s.defaultReadObject();
if (comparator == null) {
comparator = defaultComparator();
}
theMap = PersistentTreeMap.ofComp(comparator, null);
for (int i = 0; i < size; i++) {
theMap = theMap.assoc((K) s.readObject(), null);
}
}
private Object readResolve() { return new PersistentTreeSet<>(theMap); }
}
private Object writeReplace() { return new SerializationProxy<>(impl); }
private void readObject(java.io.ObjectInputStream in) throws IOException,
ClassNotFoundException {
throw new InvalidObjectException("Proxy required");
}
// ===================================== Instance Methods =====================================
/**
Returns the comparator used to order the items in this set, or null if it uses
Function2.DEFAULT_COMPARATOR (for compatibility with java.util.SortedSet).
*/
@Override public Comparator comparator() { return impl.comparator(); }
/**
Returns true if the set contains the given item in O(log n) time. This is the defining method
of a set.
*/
@SuppressWarnings("SuspiciousMethodCalls")
@Override public boolean contains(Object o) { return impl.containsKey(o); }
/** {@inheritDoc} */
@Override public PersistentTreeSet without(E key) {
return (impl.containsKey(key)) ? new PersistentTreeSet<>(impl.without(key))
: this;
}
/** {@inheritDoc} */
@Override
public UnmodSortedIterator iterator() {
return new UnmodSortedIterator() {
UnmodSortedIterator> iter = impl.iterator();
@Override public boolean hasNext() { return iter.hasNext(); }
@Override public E next() {
UnmodMap.UnEntry e = iter.next();
return e == null ? null : e.getKey();
}
};
}
/**
This is designed to be correct, rather than fully compatible with TreeSet.equals().
TreeSet.equals() does not take ordering into account and this does.
You want better equality? Define an Equator. This is for Java@trade; interop.
*/
@Override public boolean equals(Object other) {
if (this == other) { return true; }
if ( !(other instanceof SortedSet) ) { return false; }
SortedSet that = (SortedSet) other;
if (size() != that.size()) { return false; }
return UnmodSortedIterable.equal(this, UnmodSortedIterable.castFromSortedSet(that));
}
/**
Use head() inherited from Sequence instead of this method which is inherited from SortedSet.
This method returns the first element if it exists, or throws a NoSuchElementException if the
set is empty.
head() returns an Option of the first element where as this method throws an exception if this
set is empty. I had to rename the method on Sequence from first() to head() to work around
this. Also returning an Option is thread-safe for building a lazy sequence. The alternative,
examining the rest() of a sequence to see if it's == Sequence.empty() gets ugly very quickly
and makes many transformations eager (especially flatMap).
*/
@Override public E first() { return impl.firstKey(); }
/** {@inheritDoc} */
@Override public int hashCode() { return (size() == 0) ? 0 : UnmodIterable.hashCode(this); }
/** {@inheritDoc} */
@Override public Option head() {
return size() > 0 ? Option.of(impl.firstKey()) : Option.none();
}
/** {@inheritDoc} */
@Override public boolean isEmpty() { return impl.isEmpty(); }
/**
Inherited from SortedSet, returns the last item in this set, or throw an exception if this set
is empty. Good luck with that.
*/
@Override public E last() { return impl.lastKey(); }
/** {@inheritDoc} */
@Override public PersistentTreeSet put(E e) {
return (impl.containsKey(e)) ? this
: new PersistentTreeSet<>(impl.assoc(e, null));
}
/** The size of this set. */
@Override public int size() { return impl.size(); }
/** {@inheritDoc} */
@Override public ImSortedSet subSet(E fromElement, E toElement) {
return PersistentTreeSet.ofMap(impl.subMap(fromElement, toElement));
}
/** {@inheritDoc} */
@Override public ImSortedSet tailSet(E fromElement) {
return PersistentTreeSet.ofMap(impl.tailMap(fromElement));
}
// /** {@inheritDoc} */
// @Override public Sequence tail() { return impl.without(first()).keySet().seq(); }
/** Returns a string representation of this set. */
@Override public String toString() {
return UnmodIterable.toString("PersistentTreeSet", this);
}
// @Override
// public ISeq rseq() {
// return APersistentMap.KeySeq.create(((Reversible) impl).rseq());
// }
//
// @Override
// public Comparator comparator() {
// return ((Sorted) impl).comparator();
// }
// @Override
// public Object entryKey(E entry) {
// return entry;
// }
// @SuppressWarnings("unchecked")
// @Override
// public ISeq seq(boolean ascending) {
// PersistentTreeMap m = (PersistentTreeMap) impl;
// return RT.keys(m.seq(ascending));
// }
//
// @SuppressWarnings("unchecked")
// @Override
// public ISeq seqFrom(Object key, boolean ascending) {
// PersistentTreeMap m = (PersistentTreeMap) impl;
// return RT.keys(m.seqFrom(key, ascending));
// }
}