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Pure Functional Programming Semantics For Java
/**
* 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.pure4j.collections;
import java.io.IOException;
import java.io.NotSerializableException;
import java.util.Enumeration;
public class EnumerationSeq extends ASeq {
final Enumeration iter;
final State state;
static class State {
volatile Object val;
volatile Object _rest;
}
private static EnumerationSeq create(Enumeration iter) {
if (iter.hasMoreElements())
return new EnumerationSeq(iter);
return null;
}
public EnumerationSeq(Enumeration iter) {
this.iter = iter;
state = new State();
this.state.val = state;
this.state._rest = state;
}
EnumerationSeq(Enumeration iter, State state) {
this.iter = iter;
this.state = state;
}
@SuppressWarnings("unchecked")
public K first() {
if (state.val == state)
synchronized (state) {
if (state.val == state)
state.val = iter.nextElement();
}
return (K) state.val;
}
@SuppressWarnings("unchecked")
public ISeq next() {
if (state._rest == state)
synchronized (state) {
if (state._rest == state) {
first();
state._rest = create(iter);
}
}
return (ISeq) state._rest;
}
private void writeObject(java.io.ObjectOutputStream out) throws IOException {
throw new NotSerializableException(getClass().getName());
}
}
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