001/*
002 * Copyright (C) 2008 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package com.google.common.collect;
018
019import static com.google.common.base.Preconditions.checkArgument;
020import static com.google.common.base.Preconditions.checkNotNull;
021
022import com.google.common.annotations.GwtCompatible;
023import com.google.common.base.Equivalence;
024import com.google.common.base.Predicate;
025import com.google.errorprone.annotations.Immutable;
026import com.google.errorprone.annotations.InlineMe;
027import java.io.Serializable;
028import java.util.Comparator;
029import java.util.Iterator;
030import java.util.NoSuchElementException;
031import java.util.SortedSet;
032import org.jspecify.annotations.Nullable;
033
034/**
035 * A range (or "interval") defines the <i>boundaries</i> around a contiguous span of values of some
036 * {@code Comparable} type; for example, "integers from 1 to 100 inclusive." Note that it is not
037 * possible to <i>iterate</i> over these contained values. To do so, pass this range instance and an
038 * appropriate {@link DiscreteDomain} to {@link ContiguousSet#create}.
039 *
040 * <h3>Types of ranges</h3>
041 *
042 * <p>Each end of the range may be bounded or unbounded. If bounded, there is an associated
043 * <i>endpoint</i> value, and the range is considered to be either <i>open</i> (does not include the
044 * endpoint) or <i>closed</i> (includes the endpoint) on that side. With three possibilities on each
045 * side, this yields nine basic types of ranges, enumerated below. (Notation: a square bracket
046 * ({@code [ ]}) indicates that the range is closed on that side; a parenthesis ({@code ( )}) means
047 * it is either open or unbounded. The construct {@code {x | statement}} is read "the set of all
048 * <i>x</i> such that <i>statement</i>.")
049 *
050 * <blockquote>
051 *
052 * <table>
053 * <caption>Range Types</caption>
054 * <tr><th>Notation        <th>Definition               <th>Factory method
055 * <tr><td>{@code (a..b)}  <td>{@code {x | a < x < b}}  <td>{@link Range#open open}
056 * <tr><td>{@code [a..b]}  <td>{@code {x | a <= x <= b}}<td>{@link Range#closed closed}
057 * <tr><td>{@code (a..b]}  <td>{@code {x | a < x <= b}} <td>{@link Range#openClosed openClosed}
058 * <tr><td>{@code [a..b)}  <td>{@code {x | a <= x < b}} <td>{@link Range#closedOpen closedOpen}
059 * <tr><td>{@code (a..+∞)} <td>{@code {x | x > a}}      <td>{@link Range#greaterThan greaterThan}
060 * <tr><td>{@code [a..+∞)} <td>{@code {x | x >= a}}     <td>{@link Range#atLeast atLeast}
061 * <tr><td>{@code (-∞..b)} <td>{@code {x | x < b}}      <td>{@link Range#lessThan lessThan}
062 * <tr><td>{@code (-∞..b]} <td>{@code {x | x <= b}}     <td>{@link Range#atMost atMost}
063 * <tr><td>{@code (-∞..+∞)}<td>{@code {x}}              <td>{@link Range#all all}
064 * </table>
065 *
066 * </blockquote>
067 *
068 * <p>When both endpoints exist, the upper endpoint may not be less than the lower. The endpoints
069 * may be equal only if at least one of the bounds is closed:
070 *
071 * <ul>
072 *   <li>{@code [a..a]} : a singleton range
073 *   <li>{@code [a..a); (a..a]} : {@linkplain #isEmpty empty} ranges; also valid
074 *   <li>{@code (a..a)} : <b>invalid</b>; an exception will be thrown
075 * </ul>
076 *
077 * <h3>Warnings</h3>
078 *
079 * <ul>
080 *   <li>Use immutable value types only, if at all possible. If you must use a mutable type, <b>do
081 *       not</b> allow the endpoint instances to mutate after the range is created!
082 *   <li>Your value type's comparison method should be {@linkplain Comparable consistent with
083 *       equals} if at all possible. Otherwise, be aware that concepts used throughout this
084 *       documentation such as "equal", "same", "unique" and so on actually refer to whether {@link
085 *       Comparable#compareTo compareTo} returns zero, not whether {@link Object#equals equals}
086 *       returns {@code true}.
087 *   <li>A class which implements {@code Comparable<UnrelatedType>} is very broken, and will cause
088 *       undefined horrible things to happen in {@code Range}. For now, the Range API does not
089 *       prevent its use, because this would also rule out all ungenerified (pre-JDK1.5) data types.
090 *       <b>This may change in the future.</b>
091 * </ul>
092 *
093 * <h3>Other notes</h3>
094 *
095 * <ul>
096 *   <li>All ranges are shallow-immutable.
097 *   <li>Instances of this type are obtained using the static factory methods in this class.
098 *   <li>Ranges are <i>convex</i>: whenever two values are contained, all values in between them
099 *       must also be contained. More formally, for any {@code c1 <= c2 <= c3} of type {@code C},
100 *       {@code r.contains(c1) && r.contains(c3)} implies {@code r.contains(c2)}). This means that a
101 *       {@code Range<Integer>} can never be used to represent, say, "all <i>prime</i> numbers from
102 *       1 to 100."
103 *   <li>When evaluated as a {@link Predicate}, a range yields the same result as invoking {@link
104 *       #contains}.
105 *   <li>Terminology note: a range {@code a} is said to be the <i>maximal</i> range having property
106 *       <i>P</i> if, for all ranges {@code b} also having property <i>P</i>, {@code a.encloses(b)}.
107 *       Likewise, {@code a} is <i>minimal</i> when {@code b.encloses(a)} for all {@code b} having
108 *       property <i>P</i>. See, for example, the definition of {@link #intersection intersection}.
109 *   <li>A {@code Range} is serializable if it has no bounds, or if each bound is serializable.
110 * </ul>
111 *
112 * <h3>Further reading</h3>
113 *
114 * <p>See the Guava User Guide article on <a
115 * href="https://github.com/google/guava/wiki/RangesExplained">{@code Range}</a>.
116 *
117 * @author Kevin Bourrillion
118 * @author Gregory Kick
119 * @since 10.0
120 */
121@GwtCompatible
122@SuppressWarnings("rawtypes") // https://github.com/google/guava/issues/989
123@Immutable(containerOf = "C")
124public final class Range<C extends Comparable> extends RangeGwtSerializationDependencies
125    implements Predicate<C>, Serializable {
126  @SuppressWarnings("unchecked")
127  static <C extends Comparable<?>> Ordering<Range<C>> rangeLexOrdering() {
128    return (Ordering<Range<C>>) RangeLexOrdering.INSTANCE;
129  }
130
131  static <C extends Comparable<?>> Range<C> create(Cut<C> lowerBound, Cut<C> upperBound) {
132    return new Range<>(lowerBound, upperBound);
133  }
134
135  /**
136   * Returns a range that contains all values strictly greater than {@code lower} and strictly less
137   * than {@code upper}.
138   *
139   * @throws IllegalArgumentException if {@code lower} is greater than <i>or equal to</i> {@code
140   *     upper}
141   * @throws ClassCastException if {@code lower} and {@code upper} are not mutually comparable
142   * @since 14.0
143   */
144  public static <C extends Comparable<?>> Range<C> open(C lower, C upper) {
145    return create(Cut.aboveValue(lower), Cut.belowValue(upper));
146  }
147
148  /**
149   * Returns a range that contains all values greater than or equal to {@code lower} and less than
150   * or equal to {@code upper}.
151   *
152   * @throws IllegalArgumentException if {@code lower} is greater than {@code upper}
153   * @throws ClassCastException if {@code lower} and {@code upper} are not mutually comparable
154   * @since 14.0
155   */
156  public static <C extends Comparable<?>> Range<C> closed(C lower, C upper) {
157    return create(Cut.belowValue(lower), Cut.aboveValue(upper));
158  }
159
160  /**
161   * Returns a range that contains all values greater than or equal to {@code lower} and strictly
162   * less than {@code upper}.
163   *
164   * @throws IllegalArgumentException if {@code lower} is greater than {@code upper}
165   * @throws ClassCastException if {@code lower} and {@code upper} are not mutually comparable
166   * @since 14.0
167   */
168  public static <C extends Comparable<?>> Range<C> closedOpen(C lower, C upper) {
169    return create(Cut.belowValue(lower), Cut.belowValue(upper));
170  }
171
172  /**
173   * Returns a range that contains all values strictly greater than {@code lower} and less than or
174   * equal to {@code upper}.
175   *
176   * @throws IllegalArgumentException if {@code lower} is greater than {@code upper}
177   * @throws ClassCastException if {@code lower} and {@code upper} are not mutually comparable
178   * @since 14.0
179   */
180  public static <C extends Comparable<?>> Range<C> openClosed(C lower, C upper) {
181    return create(Cut.aboveValue(lower), Cut.aboveValue(upper));
182  }
183
184  /**
185   * Returns a range that contains any value from {@code lower} to {@code upper}, where each
186   * endpoint may be either inclusive (closed) or exclusive (open).
187   *
188   * @throws IllegalArgumentException if {@code lower} is greater than {@code upper}
189   * @throws ClassCastException if {@code lower} and {@code upper} are not mutually comparable
190   * @since 14.0
191   */
192  public static <C extends Comparable<?>> Range<C> range(
193      C lower, BoundType lowerType, C upper, BoundType upperType) {
194    checkNotNull(lowerType);
195    checkNotNull(upperType);
196
197    Cut<C> lowerBound =
198        (lowerType == BoundType.OPEN) ? Cut.aboveValue(lower) : Cut.belowValue(lower);
199    Cut<C> upperBound =
200        (upperType == BoundType.OPEN) ? Cut.belowValue(upper) : Cut.aboveValue(upper);
201    return create(lowerBound, upperBound);
202  }
203
204  /**
205   * Returns a range that contains all values strictly less than {@code endpoint}.
206   *
207   * @since 14.0
208   */
209  public static <C extends Comparable<?>> Range<C> lessThan(C endpoint) {
210    return create(Cut.<C>belowAll(), Cut.belowValue(endpoint));
211  }
212
213  /**
214   * Returns a range that contains all values less than or equal to {@code endpoint}.
215   *
216   * @since 14.0
217   */
218  public static <C extends Comparable<?>> Range<C> atMost(C endpoint) {
219    return create(Cut.<C>belowAll(), Cut.aboveValue(endpoint));
220  }
221
222  /**
223   * Returns a range with no lower bound up to the given endpoint, which may be either inclusive
224   * (closed) or exclusive (open).
225   *
226   * @since 14.0
227   */
228  public static <C extends Comparable<?>> Range<C> upTo(C endpoint, BoundType boundType) {
229    switch (boundType) {
230      case OPEN:
231        return lessThan(endpoint);
232      case CLOSED:
233        return atMost(endpoint);
234    }
235    throw new AssertionError();
236  }
237
238  /**
239   * Returns a range that contains all values strictly greater than {@code endpoint}.
240   *
241   * @since 14.0
242   */
243  public static <C extends Comparable<?>> Range<C> greaterThan(C endpoint) {
244    return create(Cut.aboveValue(endpoint), Cut.<C>aboveAll());
245  }
246
247  /**
248   * Returns a range that contains all values greater than or equal to {@code endpoint}.
249   *
250   * @since 14.0
251   */
252  public static <C extends Comparable<?>> Range<C> atLeast(C endpoint) {
253    return create(Cut.belowValue(endpoint), Cut.<C>aboveAll());
254  }
255
256  /**
257   * Returns a range from the given endpoint, which may be either inclusive (closed) or exclusive
258   * (open), with no upper bound.
259   *
260   * @since 14.0
261   */
262  public static <C extends Comparable<?>> Range<C> downTo(C endpoint, BoundType boundType) {
263    switch (boundType) {
264      case OPEN:
265        return greaterThan(endpoint);
266      case CLOSED:
267        return atLeast(endpoint);
268    }
269    throw new AssertionError();
270  }
271
272  private static final Range<Comparable> ALL = new Range<>(Cut.belowAll(), Cut.aboveAll());
273
274  /**
275   * Returns a range that contains every value of type {@code C}.
276   *
277   * @since 14.0
278   */
279  @SuppressWarnings("unchecked")
280  public static <C extends Comparable<?>> Range<C> all() {
281    return (Range) ALL;
282  }
283
284  /**
285   * Returns a range that {@linkplain Range#contains(Comparable) contains} only the given value. The
286   * returned range is {@linkplain BoundType#CLOSED closed} on both ends.
287   *
288   * @since 14.0
289   */
290  public static <C extends Comparable<?>> Range<C> singleton(C value) {
291    return closed(value, value);
292  }
293
294  /**
295   * Returns the minimal range that {@linkplain Range#contains(Comparable) contains} all of the
296   * given values. The returned range is {@linkplain BoundType#CLOSED closed} on both ends.
297   *
298   * @throws ClassCastException if the values are not mutually comparable
299   * @throws NoSuchElementException if {@code values} is empty
300   * @throws NullPointerException if any of {@code values} is null
301   * @since 14.0
302   */
303  public static <C extends Comparable<?>> Range<C> encloseAll(Iterable<C> values) {
304    checkNotNull(values);
305    if (values instanceof SortedSet) {
306      SortedSet<C> set = (SortedSet<C>) values;
307      Comparator<?> comparator = set.comparator();
308      if (Ordering.<C>natural().equals(comparator) || comparator == null) {
309        return closed(set.first(), set.last());
310      }
311    }
312    Iterator<C> valueIterator = values.iterator();
313    C min = checkNotNull(valueIterator.next());
314    C max = min;
315    while (valueIterator.hasNext()) {
316      C value = checkNotNull(valueIterator.next());
317      min = Ordering.<C>natural().min(min, value);
318      max = Ordering.<C>natural().max(max, value);
319    }
320    return closed(min, max);
321  }
322
323  final Cut<C> lowerBound;
324  final Cut<C> upperBound;
325
326  private Range(Cut<C> lowerBound, Cut<C> upperBound) {
327    this.lowerBound = checkNotNull(lowerBound);
328    this.upperBound = checkNotNull(upperBound);
329    if (lowerBound.compareTo(upperBound) > 0
330        || lowerBound == Cut.<C>aboveAll()
331        || upperBound == Cut.<C>belowAll()) {
332      throw new IllegalArgumentException("Invalid range: " + toString(lowerBound, upperBound));
333    }
334  }
335
336  /** Returns {@code true} if this range has a lower endpoint. */
337  public boolean hasLowerBound() {
338    return lowerBound != Cut.belowAll();
339  }
340
341  /**
342   * Returns the lower endpoint of this range.
343   *
344   * @throws IllegalStateException if this range is unbounded below (that is, {@link
345   *     #hasLowerBound()} returns {@code false})
346   */
347  public C lowerEndpoint() {
348    return lowerBound.endpoint();
349  }
350
351  /**
352   * Returns the type of this range's lower bound: {@link BoundType#CLOSED} if the range includes
353   * its lower endpoint, {@link BoundType#OPEN} if it does not.
354   *
355   * @throws IllegalStateException if this range is unbounded below (that is, {@link
356   *     #hasLowerBound()} returns {@code false})
357   */
358  public BoundType lowerBoundType() {
359    return lowerBound.typeAsLowerBound();
360  }
361
362  /** Returns {@code true} if this range has an upper endpoint. */
363  public boolean hasUpperBound() {
364    return upperBound != Cut.aboveAll();
365  }
366
367  /**
368   * Returns the upper endpoint of this range.
369   *
370   * @throws IllegalStateException if this range is unbounded above (that is, {@link
371   *     #hasUpperBound()} returns {@code false})
372   */
373  public C upperEndpoint() {
374    return upperBound.endpoint();
375  }
376
377  /**
378   * Returns the type of this range's upper bound: {@link BoundType#CLOSED} if the range includes
379   * its upper endpoint, {@link BoundType#OPEN} if it does not.
380   *
381   * @throws IllegalStateException if this range is unbounded above (that is, {@link
382   *     #hasUpperBound()} returns {@code false})
383   */
384  public BoundType upperBoundType() {
385    return upperBound.typeAsUpperBound();
386  }
387
388  /**
389   * Returns {@code true} if this range is of the form {@code [v..v)} or {@code (v..v]}. (This does
390   * not encompass ranges of the form {@code (v..v)}, because such ranges are <i>invalid</i> and
391   * can't be constructed at all.)
392   *
393   * <p>Note that certain discrete ranges such as the integer range {@code (3..4)} are <b>not</b>
394   * considered empty, even though they contain no actual values. In these cases, it may be helpful
395   * to preprocess ranges with {@link #canonical(DiscreteDomain)}.
396   */
397  public boolean isEmpty() {
398    return lowerBound.equals(upperBound);
399  }
400
401  /**
402   * Returns {@code true} if {@code value} is within the bounds of this range. For example, on the
403   * range {@code [0..2)}, {@code contains(1)} returns {@code true}, while {@code contains(2)}
404   * returns {@code false}.
405   */
406  public boolean contains(C value) {
407    checkNotNull(value);
408    // let this throw CCE if there is some trickery going on
409    return lowerBound.isLessThan(value) && !upperBound.isLessThan(value);
410  }
411
412  /**
413   * @deprecated Provided only to satisfy the {@link Predicate} interface; use {@link #contains}
414   *     instead.
415   */
416  @InlineMe(replacement = "this.contains(input)")
417  @Deprecated
418  @Override
419  public boolean apply(C input) {
420    return contains(input);
421  }
422
423  /**
424   * Returns {@code true} if every element in {@code values} is {@linkplain #contains contained} in
425   * this range.
426   */
427  public boolean containsAll(Iterable<? extends C> values) {
428    if (Iterables.isEmpty(values)) {
429      return true;
430    }
431
432    // this optimizes testing equality of two range-backed sets
433    if (values instanceof SortedSet) {
434      SortedSet<? extends C> set = (SortedSet<? extends C>) values;
435      Comparator<?> comparator = set.comparator();
436      if (Ordering.natural().equals(comparator) || comparator == null) {
437        return contains(set.first()) && contains(set.last());
438      }
439    }
440
441    for (C value : values) {
442      if (!contains(value)) {
443        return false;
444      }
445    }
446    return true;
447  }
448
449  /**
450   * Returns {@code true} if the bounds of {@code other} do not extend outside the bounds of this
451   * range. Examples:
452   *
453   * <ul>
454   *   <li>{@code [3..6]} encloses {@code [4..5]}
455   *   <li>{@code (3..6)} encloses {@code (3..6)}
456   *   <li>{@code [3..6]} encloses {@code [4..4)} (even though the latter is empty)
457   *   <li>{@code (3..6]} does not enclose {@code [3..6]}
458   *   <li>{@code [4..5]} does not enclose {@code (3..6)} (even though it contains every value
459   *       contained by the latter range)
460   *   <li>{@code [3..6]} does not enclose {@code (1..1]} (even though it contains every value
461   *       contained by the latter range)
462   * </ul>
463   *
464   * <p>Note that if {@code a.encloses(b)}, then {@code b.contains(v)} implies {@code
465   * a.contains(v)}, but as the last two examples illustrate, the converse is not always true.
466   *
467   * <p>Being reflexive, antisymmetric and transitive, the {@code encloses} relation defines a
468   * <i>partial order</i> over ranges. There exists a unique {@linkplain Range#all maximal} range
469   * according to this relation, and also numerous {@linkplain #isEmpty minimal} ranges. Enclosure
470   * also implies {@linkplain #isConnected connectedness}.
471   */
472  public boolean encloses(Range<C> other) {
473    return lowerBound.compareTo(other.lowerBound) <= 0
474        && upperBound.compareTo(other.upperBound) >= 0;
475  }
476
477  /**
478   * Returns {@code true} if there exists a (possibly empty) range which is {@linkplain #encloses
479   * enclosed} by both this range and {@code other}.
480   *
481   * <p>For example,
482   *
483   * <ul>
484   *   <li>{@code [2, 4)} and {@code [5, 7)} are not connected
485   *   <li>{@code [2, 4)} and {@code [3, 5)} are connected, because both enclose {@code [3, 4)}
486   *   <li>{@code [2, 4)} and {@code [4, 6)} are connected, because both enclose the empty range
487   *       {@code [4, 4)}
488   * </ul>
489   *
490   * <p>Note that this range and {@code other} have a well-defined {@linkplain #span union} and
491   * {@linkplain #intersection intersection} (as a single, possibly-empty range) if and only if this
492   * method returns {@code true}.
493   *
494   * <p>The connectedness relation is both reflexive and symmetric, but does not form an {@linkplain
495   * Equivalence equivalence relation} as it is not transitive.
496   *
497   * <p>Note that certain discrete ranges are not considered connected, even though there are no
498   * elements "between them." For example, {@code [3, 5]} is not considered connected to {@code [6,
499   * 10]}. In these cases, it may be desirable for both input ranges to be preprocessed with {@link
500   * #canonical(DiscreteDomain)} before testing for connectedness.
501   */
502  public boolean isConnected(Range<C> other) {
503    return lowerBound.compareTo(other.upperBound) <= 0
504        && other.lowerBound.compareTo(upperBound) <= 0;
505  }
506
507  /**
508   * Returns the maximal range {@linkplain #encloses enclosed} by both this range and {@code
509   * connectedRange}, if such a range exists.
510   *
511   * <p>For example, the intersection of {@code [1..5]} and {@code (3..7)} is {@code (3..5]}. The
512   * resulting range may be empty; for example, {@code [1..5)} intersected with {@code [5..7)}
513   * yields the empty range {@code [5..5)}.
514   *
515   * <p>The intersection exists if and only if the two ranges are {@linkplain #isConnected
516   * connected}.
517   *
518   * <p>The intersection operation is commutative, associative and idempotent, and its identity
519   * element is {@link Range#all}).
520   *
521   * @throws IllegalArgumentException if {@code isConnected(connectedRange)} is {@code false}
522   */
523  public Range<C> intersection(Range<C> connectedRange) {
524    int lowerCmp = lowerBound.compareTo(connectedRange.lowerBound);
525    int upperCmp = upperBound.compareTo(connectedRange.upperBound);
526    if (lowerCmp >= 0 && upperCmp <= 0) {
527      return this;
528    } else if (lowerCmp <= 0 && upperCmp >= 0) {
529      return connectedRange;
530    } else {
531      Cut<C> newLower = (lowerCmp >= 0) ? lowerBound : connectedRange.lowerBound;
532      Cut<C> newUpper = (upperCmp <= 0) ? upperBound : connectedRange.upperBound;
533
534      // create() would catch this, but give a confusing error message
535      checkArgument(
536          newLower.compareTo(newUpper) <= 0,
537          "intersection is undefined for disconnected ranges %s and %s",
538          this,
539          connectedRange);
540
541      // TODO(kevinb): all the precondition checks in the constructor are redundant...
542      return create(newLower, newUpper);
543    }
544  }
545
546  /**
547   * Returns the maximal range lying between this range and {@code otherRange}, if such a range
548   * exists. The resulting range may be empty if the two ranges are adjacent but non-overlapping.
549   *
550   * <p>For example, the gap of {@code [1..5]} and {@code (7..10)} is {@code (5..7]}. The resulting
551   * range may be empty; for example, the gap between {@code [1..5)} {@code [5..7)} yields the empty
552   * range {@code [5..5)}.
553   *
554   * <p>The gap exists if and only if the two ranges are either disconnected or immediately adjacent
555   * (any intersection must be an empty range).
556   *
557   * <p>The gap operation is commutative.
558   *
559   * @throws IllegalArgumentException if this range and {@code otherRange} have a nonempty
560   *     intersection
561   * @since 27.0
562   */
563  public Range<C> gap(Range<C> otherRange) {
564    /*
565     * For an explanation of the basic principle behind this check, see
566     * https://stackoverflow.com/a/35754308/28465
567     *
568     * In that explanation's notation, our `overlap` check would be `x1 < y2 && y1 < x2`. We've
569     * flipped one part of the check so that we're using "less than" in both cases (rather than a
570     * mix of "less than" and "greater than"). We've also switched to "strictly less than" rather
571     * than "less than or equal to" because of *handwave* the difference between "endpoints of
572     * inclusive ranges" and "Cuts."
573     */
574    if (lowerBound.compareTo(otherRange.upperBound) < 0
575        && otherRange.lowerBound.compareTo(upperBound) < 0) {
576      throw new IllegalArgumentException(
577          "Ranges have a nonempty intersection: " + this + ", " + otherRange);
578    }
579
580    boolean isThisFirst = this.lowerBound.compareTo(otherRange.lowerBound) < 0;
581    Range<C> firstRange = isThisFirst ? this : otherRange;
582    Range<C> secondRange = isThisFirst ? otherRange : this;
583    return create(firstRange.upperBound, secondRange.lowerBound);
584  }
585
586  /**
587   * Returns the minimal range that {@linkplain #encloses encloses} both this range and {@code
588   * other}. For example, the span of {@code [1..3]} and {@code (5..7)} is {@code [1..7)}.
589   *
590   * <p><i>If</i> the input ranges are {@linkplain #isConnected connected}, the returned range can
591   * also be called their <i>union</i>. If they are not, note that the span might contain values
592   * that are not contained in either input range.
593   *
594   * <p>Like {@link #intersection(Range) intersection}, this operation is commutative, associative
595   * and idempotent. Unlike it, it is always well-defined for any two input ranges.
596   */
597  public Range<C> span(Range<C> other) {
598    int lowerCmp = lowerBound.compareTo(other.lowerBound);
599    int upperCmp = upperBound.compareTo(other.upperBound);
600    if (lowerCmp <= 0 && upperCmp >= 0) {
601      return this;
602    } else if (lowerCmp >= 0 && upperCmp <= 0) {
603      return other;
604    } else {
605      Cut<C> newLower = (lowerCmp <= 0) ? lowerBound : other.lowerBound;
606      Cut<C> newUpper = (upperCmp >= 0) ? upperBound : other.upperBound;
607      return create(newLower, newUpper);
608    }
609  }
610
611  /**
612   * Returns the canonical form of this range in the given domain. The canonical form has the
613   * following properties:
614   *
615   * <ul>
616   *   <li>equivalence: {@code a.canonical().contains(v) == a.contains(v)} for all {@code v} (in
617   *       other words, {@code ContiguousSet.create(a.canonical(domain), domain).equals(
618   *       ContiguousSet.create(a, domain))}
619   *   <li>uniqueness: unless {@code a.isEmpty()}, {@code ContiguousSet.create(a,
620   *       domain).equals(ContiguousSet.create(b, domain))} implies {@code
621   *       a.canonical(domain).equals(b.canonical(domain))}
622   *   <li>idempotence: {@code a.canonical(domain).canonical(domain).equals(a.canonical(domain))}
623   * </ul>
624   *
625   * <p>Furthermore, this method guarantees that the range returned will be one of the following
626   * canonical forms:
627   *
628   * <ul>
629   *   <li>[start..end)
630   *   <li>[start..+∞)
631   *   <li>(-∞..end) (only if type {@code C} is unbounded below)
632   *   <li>(-∞..+∞) (only if type {@code C} is unbounded below)
633   * </ul>
634   */
635  public Range<C> canonical(DiscreteDomain<C> domain) {
636    checkNotNull(domain);
637    Cut<C> lower = lowerBound.canonical(domain);
638    Cut<C> upper = upperBound.canonical(domain);
639    return (lower == lowerBound && upper == upperBound) ? this : create(lower, upper);
640  }
641
642  /**
643   * Returns {@code true} if {@code object} is a range having the same endpoints and bound types as
644   * this range. Note that discrete ranges such as {@code (1..4)} and {@code [2..3]} are <b>not</b>
645   * equal to one another, despite the fact that they each contain precisely the same set of values.
646   * Similarly, empty ranges are not equal unless they have exactly the same representation, so
647   * {@code [3..3)}, {@code (3..3]}, {@code (4..4]} are all unequal.
648   */
649  @Override
650  public boolean equals(@Nullable Object object) {
651    if (object instanceof Range) {
652      Range<?> other = (Range<?>) object;
653      return lowerBound.equals(other.lowerBound) && upperBound.equals(other.upperBound);
654    }
655    return false;
656  }
657
658  /** Returns a hash code for this range. */
659  @Override
660  public int hashCode() {
661    return lowerBound.hashCode() * 31 + upperBound.hashCode();
662  }
663
664  /**
665   * Returns a string representation of this range, such as {@code "[3..5)"} (other examples are
666   * listed in the class documentation).
667   */
668  @Override
669  public String toString() {
670    return toString(lowerBound, upperBound);
671  }
672
673  private static String toString(Cut<?> lowerBound, Cut<?> upperBound) {
674    StringBuilder sb = new StringBuilder(16);
675    lowerBound.describeAsLowerBound(sb);
676    sb.append("..");
677    upperBound.describeAsUpperBound(sb);
678    return sb.toString();
679  }
680
681  // We declare accessors so that we can use method references like `Range::lowerBound`.
682
683  Cut<C> lowerBound() {
684    return lowerBound;
685  }
686
687  Cut<C> upperBound() {
688    return upperBound;
689  }
690
691  Object readResolve() {
692    if (this.equals(ALL)) {
693      return all();
694    } else {
695      return this;
696    }
697  }
698
699  @SuppressWarnings("unchecked") // this method may throw CCE
700  static int compareOrThrow(Comparable left, Comparable right) {
701    return left.compareTo(right);
702  }
703
704  /** Needed to serialize sorted collections of Ranges. */
705  private static class RangeLexOrdering extends Ordering<Range<?>> implements Serializable {
706    static final Ordering<?> INSTANCE = new RangeLexOrdering();
707
708    @Override
709    public int compare(Range<?> left, Range<?> right) {
710      return ComparisonChain.start()
711          .compare(left.lowerBound, right.lowerBound)
712          .compare(left.upperBound, right.upperBound)
713          .result();
714    }
715
716    private static final long serialVersionUID = 0;
717  }
718
719  private static final long serialVersionUID = 0;
720}