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ixjava developed by David Karnok
There is a newer version: 1.0.0
/*
 * Copyright 2011-2016 David Karnok
 *
 * 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 ix;

import java.util.Iterator;

final class IxDistinctUntilChanged extends IxSource {

    final IxFunction keySelector;

    final IxPredicate2 comparer;

    IxDistinctUntilChanged(Iterable source, IxFunction keySelector,
            IxPredicate2 comparer) {
        super(source);
        this.keySelector = keySelector;
        this.comparer = comparer;
    }

    @Override
    public Iterator iterator() {
        return new DistinctUntilChangedIterator(source.iterator(), keySelector, comparer);
    }

    static final class DistinctUntilChangedIterator extends IxSourceIterator {

        final IxFunction keySelector;

        final IxPredicate2 comparer;

        K last;

        boolean once;

        DistinctUntilChangedIterator(Iterator it, IxFunction keySelector,
                IxPredicate2 comparer) {
            super(it);
            this.keySelector = keySelector;
            this.comparer = comparer;
        }

        @Override
        protected boolean moveNext() {
            Iterator it = this.it;

            K prev = last;
            K curr;

            while (it.hasNext()) {
                T v = it.next();
                curr = keySelector.apply(v);

                if (!once) {
                    once = true;

                    last = curr;

                    value = v;
                    hasValue = true;
                    return true;
                }

                if (!comparer.test(prev, curr)) {
                    last = curr;

                    value = v;
                    hasValue = true;
                    return true;
                }

                prev = curr;
            }


            done = true;
            return false;
        }


    }
}