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Distinct.java
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53 lines (46 loc) · 1.53 KB
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/*
* Copyright (c) 2020, Fernando Miguel Carvalho, mcarvalho@cc.isel.ipl.pt
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.jayield.ops;
import org.jayield.Advancer;
import org.jayield.Query;
import org.jayield.Traverser;
import org.jayield.Yield;
import org.jayield.boxes.BoolBox;
import java.util.HashSet;
public class Distinct<T> implements Advancer<T>, Traverser<T> {
private final Query<T> upstream;
final HashSet<T> mem = new HashSet<>();
public Distinct(Query<T> adv) {
this.upstream = adv;
}
@Override
public void traverse(Yield<? super T> yield) {
upstream.traverse(item -> {
if(mem.add(item)) yield.ret(item);
});
}
@Override
public boolean tryAdvance(Yield<? super T> yield) {
final BoolBox found = new BoolBox();
while(found.isFalse() && upstream.tryAdvance(item -> {
if(mem.add(item)) {
yield.ret(item);
found.set();
}
}));
return found.isTrue();
}
}