| Clover coverage report - PLT Utilities Test Coverage (plt-20120304-r5436) |
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| DiagonalCartesianIterator.java | 0% | 0% | 0% | 0% |
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| 1 | /*BEGIN_COPYRIGHT_BLOCK* | |
| 2 | ||
| 3 | PLT Utilities BSD License | |
| 4 | ||
| 5 | Copyright (c) 2007-2010 JavaPLT group at Rice University | |
| 6 | All rights reserved. | |
| 7 | ||
| 8 | Developed by: Java Programming Languages Team | |
| 9 | Rice University | |
| 10 | http://www.cs.rice.edu/~javaplt/ | |
| 11 | ||
| 12 | Redistribution and use in source and binary forms, with or without modification, are permitted | |
| 13 | provided that the following conditions are met: | |
| 14 | ||
| 15 | - Redistributions of source code must retain the above copyright notice, this list of conditions | |
| 16 | and the following disclaimer. | |
| 17 | - Redistributions in binary form must reproduce the above copyright notice, this list of | |
| 18 | conditions and the following disclaimer in the documentation and/or other materials provided | |
| 19 | with the distribution. | |
| 20 | - Neither the name of the JavaPLT group, Rice University, nor the names of the library's | |
| 21 | contributors may be used to endorse or promote products derived from this software without | |
| 22 | specific prior written permission. | |
| 23 | ||
| 24 | THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR | |
| 25 | IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND | |
| 26 | FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS AND | |
| 27 | CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
| 28 | DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
| 29 | DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER | |
| 30 | IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT | |
| 31 | OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
| 32 | ||
| 33 | *END_COPYRIGHT_BLOCK*/ | |
| 34 | ||
| 35 | package edu.rice.cs.plt.iter; | |
| 36 | ||
| 37 | import java.util.Iterator; | |
| 38 | import java.util.LinkedList; | |
| 39 | import edu.rice.cs.plt.lambda.Lambda2; | |
| 40 | import edu.rice.cs.plt.object.Composite; | |
| 41 | import edu.rice.cs.plt.object.ObjectUtil; | |
| 42 | ||
| 43 | /** | |
| 44 | * <p>Enumerates the elements of a cartesian (or cross) product in diagonal order. Where the | |
| 45 | * "index" of the ith item in an iterator is i, this class produces all pairs of values with | |
| 46 | * indices that sum to n before proceding to those with indices that sum to n+1. This allows | |
| 47 | * the cartesian product of two infinite iterators to be methodically traversed. Within the | |
| 48 | * set of pairs with indices summing to n, the order is lexographical in terms of the respective | |
| 49 | * indices. For example, {@code [0, 1, 2]} crossed with itself will produce (under string concatenation) | |
| 50 | * {@code [00, 01, 10, 02, 11, 20, 12, 21, 22]}. The {@code combiner} function is used, rather than simply | |
| 51 | * producing {@code Pair}s, in order to provide a greater degree of flexibility. {@link Iterator#remove} | |
| 52 | * is not supported.</p> | |
| 53 | * <p>In order to support this traversal, the set of previously-seen values must be cached. The amount | |
| 54 | * of space required by this iterator after n invocations of {@code next()} is in O(sqrt(n)).</p> | |
| 55 | */ | |
| 56 | public class DiagonalCartesianIterator<T1, T2, R> extends ReadOnlyIterator<R> implements Composite { | |
| 57 | ||
| 58 | private final Lambda2<? super T1, ? super T2, ? extends R> _combiner; | |
| 59 | private final Iterator<? extends T1> _left; | |
| 60 | private final Iterator<? extends T2> _right; | |
| 61 | private LinkedList<T1> _leftCache; | |
| 62 | private Iterator<T1> _leftCacheIter; | |
| 63 | private LinkedList<T2> _rightCache; | |
| 64 | private Iterator<T2> _rightCacheIter; | |
| 65 | ||
| 66 | 0 | public DiagonalCartesianIterator(Iterator<? extends T1> left, Iterator<? extends T2> right, |
| 67 | Lambda2<? super T1, ? super T2, ? extends R> combiner) { | |
| 68 | 0 | _combiner = combiner; |
| 69 | 0 | _left = left; |
| 70 | 0 | _right = right; |
| 71 | 0 | _leftCache = new LinkedList<T1>(); |
| 72 | 0 | _rightCache = new LinkedList<T2>(); |
| 73 | 0 | _leftCacheIter = _leftCache.iterator(); |
| 74 | 0 | _rightCacheIter = _rightCache.iterator(); |
| 75 | } | |
| 76 | ||
| 77 | 0 | public int compositeHeight() { return ObjectUtil.compositeHeight(_left, _right) + 1; } |
| 78 | 0 | public int compositeSize() { return ObjectUtil.compositeSize(_left, _right) + 1; } |
| 79 | ||
| 80 | 0 | public boolean hasNext() { |
| 81 | 0 | if (_left.hasNext()) { return _right.hasNext() || !_rightCache.isEmpty(); } |
| 82 | 0 | else if (_right.hasNext()) { return !_leftCache.isEmpty(); } |
| 83 | else { | |
| 84 | 0 | return _leftCacheIter.hasNext() && _rightCacheIter.hasNext() || // there's more in the current traversal |
| 85 | _leftCache.size() > 1 && _rightCache.size() > 1; // there are leftovers to create a new traversal | |
| 86 | } | |
| 87 | // return (_left.hasNext() || !_leftCache.isEmpty()) && (_right.hasNext() || !_rightCache.isEmpty()) || | |
| 88 | // ; | |
| 89 | // return _leftCacheIter.hasNext() && _rightCacheIter.hasNext() || | |
| 90 | // _left.hasNext() && (_right.hasNext() || !_rightCache.isEmpty()) || | |
| 91 | // _right.hasNext() && !_leftCache.isEmpty(); | |
| 92 | } | |
| 93 | ||
| 94 | 0 | public R next() { |
| 95 | 0 | if (!_leftCacheIter.hasNext() || !_rightCacheIter.hasNext()) { |
| 96 | 0 | if (_left.hasNext()) { _leftCache.addLast(_left.next()); } |
| 97 | 0 | else if (!_rightCache.isEmpty()) { _rightCache.removeLast(); } |
| 98 | 0 | if (_right.hasNext()) { _rightCache.addFirst(_right.next()); } |
| 99 | 0 | else if (!_leftCache.isEmpty()) { _leftCache.removeFirst(); } |
| 100 | 0 | _leftCacheIter = _leftCache.iterator(); |
| 101 | 0 | _rightCacheIter = _rightCache.iterator(); |
| 102 | } | |
| 103 | // This may cause an exception, which is OK. | |
| 104 | 0 | return _combiner.value(_leftCacheIter.next(), _rightCacheIter.next()); |
| 105 | } | |
| 106 | ||
| 107 | /** Call the constructor (allows the type arguments to be inferred) */ | |
| 108 | 0 | public static <T1, T2, R> |
| 109 | DiagonalCartesianIterator<T1, T2, R> make(Iterator<? extends T1> left, Iterator<? extends T2> right, | |
| 110 | Lambda2<? super T1, ? super T2, ? extends R> combiner) { | |
| 111 | 0 | return new DiagonalCartesianIterator<T1, T2, R>(left, right, combiner); |
| 112 | } | |
| 113 | ||
| 114 | } |
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