001/*
002 * Copyright (C) 2008 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005 * in compliance with the License. You may obtain a copy of the License at
006 *
007 * http://www.apache.org/licenses/LICENSE-2.0
008 *
009 * Unless required by applicable law or agreed to in writing, software distributed under the License
010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
011 * or implied. See the License for the specific language governing permissions and limitations under
012 * the License.
013 */
014
015package com.google.common.primitives;
016
017import static com.google.common.base.Preconditions.checkArgument;
018import static com.google.common.base.Preconditions.checkElementIndex;
019import static com.google.common.base.Preconditions.checkNotNull;
020import static com.google.common.base.Preconditions.checkPositionIndexes;
021import static java.lang.Double.NEGATIVE_INFINITY;
022import static java.lang.Double.POSITIVE_INFINITY;
023
024import com.google.common.annotations.Beta;
025import com.google.common.annotations.GwtCompatible;
026import com.google.common.annotations.GwtIncompatible;
027import com.google.common.base.Converter;
028import java.io.Serializable;
029import java.util.AbstractList;
030import java.util.Arrays;
031import java.util.Collection;
032import java.util.Collections;
033import java.util.Comparator;
034import java.util.List;
035import java.util.RandomAccess;
036import java.util.Spliterator;
037import java.util.Spliterators;
038import org.checkerframework.checker.nullness.qual.Nullable;
039
040/**
041 * Static utility methods pertaining to {@code double} primitives, that are not already found in
042 * either {@link Double} or {@link Arrays}.
043 *
044 * <p>See the Guava User Guide article on <a
045 * href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities</a>.
046 *
047 * @author Kevin Bourrillion
048 * @since 1.0
049 */
050@GwtCompatible(emulated = true)
051public final class Doubles {
052  private Doubles() {}
053
054  /**
055   * The number of bytes required to represent a primitive {@code double} value.
056   *
057   * <p><b>Java 8 users:</b> use {@link Double#BYTES} instead.
058   *
059   * @since 10.0
060   */
061  public static final int BYTES = Double.SIZE / Byte.SIZE;
062
063  /**
064   * Returns a hash code for {@code value}; equal to the result of invoking {@code ((Double)
065   * value).hashCode()}.
066   *
067   * <p><b>Java 8 users:</b> use {@link Double#hashCode(double)} instead.
068   *
069   * @param value a primitive {@code double} value
070   * @return a hash code for the value
071   */
072  public static int hashCode(double value) {
073    return ((Double) value).hashCode();
074    // TODO(kevinb): do it this way when we can (GWT problem):
075    // long bits = Double.doubleToLongBits(value);
076    // return (int) (bits ^ (bits >>> 32));
077  }
078
079  /**
080   * Compares the two specified {@code double} values. The sign of the value returned is the same as
081   * that of <code>((Double) a).{@linkplain Double#compareTo compareTo}(b)</code>. As with that
082   * method, {@code NaN} is treated as greater than all other values, and {@code 0.0 > -0.0}.
083   *
084   * <p><b>Note:</b> this method simply delegates to the JDK method {@link Double#compare}. It is
085   * provided for consistency with the other primitive types, whose compare methods were not added
086   * to the JDK until JDK 7.
087   *
088   * @param a the first {@code double} to compare
089   * @param b the second {@code double} to compare
090   * @return a negative value if {@code a} is less than {@code b}; a positive value if {@code a} is
091   *     greater than {@code b}; or zero if they are equal
092   */
093  public static int compare(double a, double b) {
094    return Double.compare(a, b);
095  }
096
097  /**
098   * Returns {@code true} if {@code value} represents a real number. This is equivalent to, but not
099   * necessarily implemented as, {@code !(Double.isInfinite(value) || Double.isNaN(value))}.
100   *
101   * <p><b>Java 8 users:</b> use {@link Double#isFinite(double)} instead.
102   *
103   * @since 10.0
104   */
105  public static boolean isFinite(double value) {
106    return NEGATIVE_INFINITY < value && value < POSITIVE_INFINITY;
107  }
108
109  /**
110   * Returns {@code true} if {@code target} is present as an element anywhere in {@code array}. Note
111   * that this always returns {@code false} when {@code target} is {@code NaN}.
112   *
113   * @param array an array of {@code double} values, possibly empty
114   * @param target a primitive {@code double} value
115   * @return {@code true} if {@code array[i] == target} for some value of {@code i}
116   */
117  public static boolean contains(double[] array, double target) {
118    for (double value : array) {
119      if (value == target) {
120        return true;
121      }
122    }
123    return false;
124  }
125
126  /**
127   * Returns the index of the first appearance of the value {@code target} in {@code array}. Note
128   * that this always returns {@code -1} when {@code target} is {@code NaN}.
129   *
130   * @param array an array of {@code double} values, possibly empty
131   * @param target a primitive {@code double} value
132   * @return the least index {@code i} for which {@code array[i] == target}, or {@code -1} if no
133   *     such index exists.
134   */
135  public static int indexOf(double[] array, double target) {
136    return indexOf(array, target, 0, array.length);
137  }
138
139  // TODO(kevinb): consider making this public
140  private static int indexOf(double[] array, double target, int start, int end) {
141    for (int i = start; i < end; i++) {
142      if (array[i] == target) {
143        return i;
144      }
145    }
146    return -1;
147  }
148
149  /**
150   * Returns the start position of the first occurrence of the specified {@code target} within
151   * {@code array}, or {@code -1} if there is no such occurrence.
152   *
153   * <p>More formally, returns the lowest index {@code i} such that {@code Arrays.copyOfRange(array,
154   * i, i + target.length)} contains exactly the same elements as {@code target}.
155   *
156   * <p>Note that this always returns {@code -1} when {@code target} contains {@code NaN}.
157   *
158   * @param array the array to search for the sequence {@code target}
159   * @param target the array to search for as a sub-sequence of {@code array}
160   */
161  public static int indexOf(double[] array, double[] target) {
162    checkNotNull(array, "array");
163    checkNotNull(target, "target");
164    if (target.length == 0) {
165      return 0;
166    }
167
168    outer:
169    for (int i = 0; i < array.length - target.length + 1; i++) {
170      for (int j = 0; j < target.length; j++) {
171        if (array[i + j] != target[j]) {
172          continue outer;
173        }
174      }
175      return i;
176    }
177    return -1;
178  }
179
180  /**
181   * Returns the index of the last appearance of the value {@code target} in {@code array}. Note
182   * that this always returns {@code -1} when {@code target} is {@code NaN}.
183   *
184   * @param array an array of {@code double} values, possibly empty
185   * @param target a primitive {@code double} value
186   * @return the greatest index {@code i} for which {@code array[i] == target}, or {@code -1} if no
187   *     such index exists.
188   */
189  public static int lastIndexOf(double[] array, double target) {
190    return lastIndexOf(array, target, 0, array.length);
191  }
192
193  // TODO(kevinb): consider making this public
194  private static int lastIndexOf(double[] array, double target, int start, int end) {
195    for (int i = end - 1; i >= start; i--) {
196      if (array[i] == target) {
197        return i;
198      }
199    }
200    return -1;
201  }
202
203  /**
204   * Returns the least value present in {@code array}, using the same rules of comparison as {@link
205   * Math#min(double, double)}.
206   *
207   * @param array a <i>nonempty</i> array of {@code double} values
208   * @return the value present in {@code array} that is less than or equal to every other value in
209   *     the array
210   * @throws IllegalArgumentException if {@code array} is empty
211   */
212  public static double min(double... array) {
213    checkArgument(array.length > 0);
214    double min = array[0];
215    for (int i = 1; i < array.length; i++) {
216      min = Math.min(min, array[i]);
217    }
218    return min;
219  }
220
221  /**
222   * Returns the greatest value present in {@code array}, using the same rules of comparison as
223   * {@link Math#max(double, double)}.
224   *
225   * @param array a <i>nonempty</i> array of {@code double} values
226   * @return the value present in {@code array} that is greater than or equal to every other value
227   *     in the array
228   * @throws IllegalArgumentException if {@code array} is empty
229   */
230  public static double max(double... array) {
231    checkArgument(array.length > 0);
232    double max = array[0];
233    for (int i = 1; i < array.length; i++) {
234      max = Math.max(max, array[i]);
235    }
236    return max;
237  }
238
239  /**
240   * Returns the value nearest to {@code value} which is within the closed range {@code [min..max]}.
241   *
242   * <p>If {@code value} is within the range {@code [min..max]}, {@code value} is returned
243   * unchanged. If {@code value} is less than {@code min}, {@code min} is returned, and if {@code
244   * value} is greater than {@code max}, {@code max} is returned.
245   *
246   * @param value the {@code double} value to constrain
247   * @param min the lower bound (inclusive) of the range to constrain {@code value} to
248   * @param max the upper bound (inclusive) of the range to constrain {@code value} to
249   * @throws IllegalArgumentException if {@code min > max}
250   * @since 21.0
251   */
252  @Beta
253  public static double constrainToRange(double value, double min, double max) {
254    checkArgument(min <= max, "min (%s) must be less than or equal to max (%s)", min, max);
255    return Math.min(Math.max(value, min), max);
256  }
257
258  /**
259   * Returns the values from each provided array combined into a single array. For example, {@code
260   * concat(new double[] {a, b}, new double[] {}, new double[] {c}} returns the array {@code {a, b,
261   * c}}.
262   *
263   * @param arrays zero or more {@code double} arrays
264   * @return a single array containing all the values from the source arrays, in order
265   */
266  public static double[] concat(double[]... arrays) {
267    int length = 0;
268    for (double[] array : arrays) {
269      length += array.length;
270    }
271    double[] result = new double[length];
272    int pos = 0;
273    for (double[] array : arrays) {
274      System.arraycopy(array, 0, result, pos, array.length);
275      pos += array.length;
276    }
277    return result;
278  }
279
280  private static final class DoubleConverter extends Converter<String, Double>
281      implements Serializable {
282    static final DoubleConverter INSTANCE = new DoubleConverter();
283
284    @Override
285    protected Double doForward(String value) {
286      return Double.valueOf(value);
287    }
288
289    @Override
290    protected String doBackward(Double value) {
291      return value.toString();
292    }
293
294    @Override
295    public String toString() {
296      return "Doubles.stringConverter()";
297    }
298
299    private Object readResolve() {
300      return INSTANCE;
301    }
302
303    private static final long serialVersionUID = 1;
304  }
305
306  /**
307   * Returns a serializable converter object that converts between strings and doubles using {@link
308   * Double#valueOf} and {@link Double#toString()}.
309   *
310   * @since 16.0
311   */
312  @Beta
313  public static Converter<String, Double> stringConverter() {
314    return DoubleConverter.INSTANCE;
315  }
316
317  /**
318   * Returns an array containing the same values as {@code array}, but guaranteed to be of a
319   * specified minimum length. If {@code array} already has a length of at least {@code minLength},
320   * it is returned directly. Otherwise, a new array of size {@code minLength + padding} is
321   * returned, containing the values of {@code array}, and zeroes in the remaining places.
322   *
323   * @param array the source array
324   * @param minLength the minimum length the returned array must guarantee
325   * @param padding an extra amount to "grow" the array by if growth is necessary
326   * @throws IllegalArgumentException if {@code minLength} or {@code padding} is negative
327   * @return an array containing the values of {@code array}, with guaranteed minimum length {@code
328   *     minLength}
329   */
330  public static double[] ensureCapacity(double[] array, int minLength, int padding) {
331    checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
332    checkArgument(padding >= 0, "Invalid padding: %s", padding);
333    return (array.length < minLength) ? Arrays.copyOf(array, minLength + padding) : array;
334  }
335
336  /**
337   * Returns a string containing the supplied {@code double} values, converted to strings as
338   * specified by {@link Double#toString(double)}, and separated by {@code separator}. For example,
339   * {@code join("-", 1.0, 2.0, 3.0)} returns the string {@code "1.0-2.0-3.0"}.
340   *
341   * <p>Note that {@link Double#toString(double)} formats {@code double} differently in GWT
342   * sometimes. In the previous example, it returns the string {@code "1-2-3"}.
343   *
344   * @param separator the text that should appear between consecutive values in the resulting string
345   *     (but not at the start or end)
346   * @param array an array of {@code double} values, possibly empty
347   */
348  public static String join(String separator, double... array) {
349    checkNotNull(separator);
350    if (array.length == 0) {
351      return "";
352    }
353
354    // For pre-sizing a builder, just get the right order of magnitude
355    StringBuilder builder = new StringBuilder(array.length * 12);
356    builder.append(array[0]);
357    for (int i = 1; i < array.length; i++) {
358      builder.append(separator).append(array[i]);
359    }
360    return builder.toString();
361  }
362
363  /**
364   * Returns a comparator that compares two {@code double} arrays <a
365   * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it
366   * compares, using {@link #compare(double, double)}), the first pair of values that follow any
367   * common prefix, or when one array is a prefix of the other, treats the shorter array as the
368   * lesser. For example, {@code [] < [1.0] < [1.0, 2.0] < [2.0]}.
369   *
370   * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays
371   * support only identity equality), but it is consistent with {@link Arrays#equals(double[],
372   * double[])}.
373   *
374   * @since 2.0
375   */
376  public static Comparator<double[]> lexicographicalComparator() {
377    return LexicographicalComparator.INSTANCE;
378  }
379
380  private enum LexicographicalComparator implements Comparator<double[]> {
381    INSTANCE;
382
383    @Override
384    public int compare(double[] left, double[] right) {
385      int minLength = Math.min(left.length, right.length);
386      for (int i = 0; i < minLength; i++) {
387        int result = Double.compare(left[i], right[i]);
388        if (result != 0) {
389          return result;
390        }
391      }
392      return left.length - right.length;
393    }
394
395    @Override
396    public String toString() {
397      return "Doubles.lexicographicalComparator()";
398    }
399  }
400
401  /**
402   * Sorts the elements of {@code array} in descending order.
403   *
404   * <p>Note that this method uses the total order imposed by {@link Double#compare}, which treats
405   * all NaN values as equal and 0.0 as greater than -0.0.
406   *
407   * @since 23.1
408   */
409  public static void sortDescending(double[] array) {
410    checkNotNull(array);
411    sortDescending(array, 0, array.length);
412  }
413
414  /**
415   * Sorts the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex}
416   * exclusive in descending order.
417   *
418   * <p>Note that this method uses the total order imposed by {@link Double#compare}, which treats
419   * all NaN values as equal and 0.0 as greater than -0.0.
420   *
421   * @since 23.1
422   */
423  public static void sortDescending(double[] array, int fromIndex, int toIndex) {
424    checkNotNull(array);
425    checkPositionIndexes(fromIndex, toIndex, array.length);
426    Arrays.sort(array, fromIndex, toIndex);
427    reverse(array, fromIndex, toIndex);
428  }
429
430  /**
431   * Reverses the elements of {@code array}. This is equivalent to {@code
432   * Collections.reverse(Doubles.asList(array))}, but is likely to be more efficient.
433   *
434   * @since 23.1
435   */
436  public static void reverse(double[] array) {
437    checkNotNull(array);
438    reverse(array, 0, array.length);
439  }
440
441  /**
442   * Reverses the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex}
443   * exclusive. This is equivalent to {@code
444   * Collections.reverse(Doubles.asList(array).subList(fromIndex, toIndex))}, but is likely to be
445   * more efficient.
446   *
447   * @throws IndexOutOfBoundsException if {@code fromIndex < 0}, {@code toIndex > array.length}, or
448   *     {@code toIndex > fromIndex}
449   * @since 23.1
450   */
451  public static void reverse(double[] array, int fromIndex, int toIndex) {
452    checkNotNull(array);
453    checkPositionIndexes(fromIndex, toIndex, array.length);
454    for (int i = fromIndex, j = toIndex - 1; i < j; i++, j--) {
455      double tmp = array[i];
456      array[i] = array[j];
457      array[j] = tmp;
458    }
459  }
460
461  /**
462   * Returns an array containing each value of {@code collection}, converted to a {@code double}
463   * value in the manner of {@link Number#doubleValue}.
464   *
465   * <p>Elements are copied from the argument collection as if by {@code collection.toArray()}.
466   * Calling this method is as thread-safe as calling that method.
467   *
468   * @param collection a collection of {@code Number} instances
469   * @return an array containing the same values as {@code collection}, in the same order, converted
470   *     to primitives
471   * @throws NullPointerException if {@code collection} or any of its elements is null
472   * @since 1.0 (parameter was {@code Collection<Double>} before 12.0)
473   */
474  public static double[] toArray(Collection<? extends Number> collection) {
475    if (collection instanceof DoubleArrayAsList) {
476      return ((DoubleArrayAsList) collection).toDoubleArray();
477    }
478
479    Object[] boxedArray = collection.toArray();
480    int len = boxedArray.length;
481    double[] array = new double[len];
482    for (int i = 0; i < len; i++) {
483      // checkNotNull for GWT (do not optimize)
484      array[i] = ((Number) checkNotNull(boxedArray[i])).doubleValue();
485    }
486    return array;
487  }
488
489  /**
490   * Returns a fixed-size list backed by the specified array, similar to {@link
491   * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)}, but any attempt to
492   * set a value to {@code null} will result in a {@link NullPointerException}.
493   *
494   * <p>The returned list maintains the values, but not the identities, of {@code Double} objects
495   * written to or read from it. For example, whether {@code list.get(0) == list.get(0)} is true for
496   * the returned list is unspecified.
497   *
498   * <p>The returned list may have unexpected behavior if it contains {@code NaN}, or if {@code NaN}
499   * is used as a parameter to any of its methods.
500   *
501   * <p><b>Note:</b> when possible, you should represent your data as an {@link
502   * ImmutableDoubleArray} instead, which has an {@link ImmutableDoubleArray#asList asList} view.
503   *
504   * @param backingArray the array to back the list
505   * @return a list view of the array
506   */
507  public static List<Double> asList(double... backingArray) {
508    if (backingArray.length == 0) {
509      return Collections.emptyList();
510    }
511    return new DoubleArrayAsList(backingArray);
512  }
513
514  @GwtCompatible
515  private static class DoubleArrayAsList extends AbstractList<Double>
516      implements RandomAccess, Serializable {
517    final double[] array;
518    final int start;
519    final int end;
520
521    DoubleArrayAsList(double[] array) {
522      this(array, 0, array.length);
523    }
524
525    DoubleArrayAsList(double[] array, int start, int end) {
526      this.array = array;
527      this.start = start;
528      this.end = end;
529    }
530
531    @Override
532    public int size() {
533      return end - start;
534    }
535
536    @Override
537    public boolean isEmpty() {
538      return false;
539    }
540
541    @Override
542    public Double get(int index) {
543      checkElementIndex(index, size());
544      return array[start + index];
545    }
546
547    @Override
548    public Spliterator.OfDouble spliterator() {
549      return Spliterators.spliterator(array, start, end, 0);
550    }
551
552    @Override
553    public boolean contains(Object target) {
554      // Overridden to prevent a ton of boxing
555      return (target instanceof Double)
556          && Doubles.indexOf(array, (Double) target, start, end) != -1;
557    }
558
559    @Override
560    public int indexOf(Object target) {
561      // Overridden to prevent a ton of boxing
562      if (target instanceof Double) {
563        int i = Doubles.indexOf(array, (Double) target, start, end);
564        if (i >= 0) {
565          return i - start;
566        }
567      }
568      return -1;
569    }
570
571    @Override
572    public int lastIndexOf(Object target) {
573      // Overridden to prevent a ton of boxing
574      if (target instanceof Double) {
575        int i = Doubles.lastIndexOf(array, (Double) target, start, end);
576        if (i >= 0) {
577          return i - start;
578        }
579      }
580      return -1;
581    }
582
583    @Override
584    public Double set(int index, Double element) {
585      checkElementIndex(index, size());
586      double oldValue = array[start + index];
587      // checkNotNull for GWT (do not optimize)
588      array[start + index] = checkNotNull(element);
589      return oldValue;
590    }
591
592    @Override
593    public List<Double> subList(int fromIndex, int toIndex) {
594      int size = size();
595      checkPositionIndexes(fromIndex, toIndex, size);
596      if (fromIndex == toIndex) {
597        return Collections.emptyList();
598      }
599      return new DoubleArrayAsList(array, start + fromIndex, start + toIndex);
600    }
601
602    @Override
603    public boolean equals(@Nullable Object object) {
604      if (object == this) {
605        return true;
606      }
607      if (object instanceof DoubleArrayAsList) {
608        DoubleArrayAsList that = (DoubleArrayAsList) object;
609        int size = size();
610        if (that.size() != size) {
611          return false;
612        }
613        for (int i = 0; i < size; i++) {
614          if (array[start + i] != that.array[that.start + i]) {
615            return false;
616          }
617        }
618        return true;
619      }
620      return super.equals(object);
621    }
622
623    @Override
624    public int hashCode() {
625      int result = 1;
626      for (int i = start; i < end; i++) {
627        result = 31 * result + Doubles.hashCode(array[i]);
628      }
629      return result;
630    }
631
632    @Override
633    public String toString() {
634      StringBuilder builder = new StringBuilder(size() * 12);
635      builder.append('[').append(array[start]);
636      for (int i = start + 1; i < end; i++) {
637        builder.append(", ").append(array[i]);
638      }
639      return builder.append(']').toString();
640    }
641
642    double[] toDoubleArray() {
643      return Arrays.copyOfRange(array, start, end);
644    }
645
646    private static final long serialVersionUID = 0;
647  }
648
649  /**
650   * This is adapted from the regex suggested by {@link Double#valueOf(String)} for prevalidating
651   * inputs. All valid inputs must pass this regex, but it's semantically fine if not all inputs
652   * that pass this regex are valid -- only a performance hit is incurred, not a semantics bug.
653   */
654  @GwtIncompatible // regular expressions
655  static final
656  java.util.regex.Pattern
657      FLOATING_POINT_PATTERN = fpPattern();
658
659  @GwtIncompatible // regular expressions
660  private static
661  java.util.regex.Pattern
662      fpPattern() {
663    /*
664     * We use # instead of * for possessive quantifiers. This lets us strip them out when building
665     * the regex for RE2 (which doesn't support them) but leave them in when building it for
666     * java.util.regex (where we want them in order to avoid catastrophic backtracking).
667     */
668    String decimal = "(?:\\d+#(?:\\.\\d*#)?|\\.\\d+#)";
669    String completeDec = decimal + "(?:[eE][+-]?\\d+#)?[fFdD]?";
670    String hex = "(?:[0-9a-fA-F]+#(?:\\.[0-9a-fA-F]*#)?|\\.[0-9a-fA-F]+#)";
671    String completeHex = "0[xX]" + hex + "[pP][+-]?\\d+#[fFdD]?";
672    String fpPattern = "[+-]?(?:NaN|Infinity|" + completeDec + "|" + completeHex + ")";
673    fpPattern =
674        fpPattern.replace(
675            "#",
676            "+"
677            );
678    return
679    java.util.regex.Pattern
680        .compile(fpPattern);
681  }
682
683  /**
684   * Parses the specified string as a double-precision floating point value. The ASCII character
685   * {@code '-'} (<code>'&#92;u002D'</code>) is recognized as the minus sign.
686   *
687   * <p>Unlike {@link Double#parseDouble(String)}, this method returns {@code null} instead of
688   * throwing an exception if parsing fails. Valid inputs are exactly those accepted by {@link
689   * Double#valueOf(String)}, except that leading and trailing whitespace is not permitted.
690   *
691   * <p>This implementation is likely to be faster than {@code Double.parseDouble} if many failures
692   * are expected.
693   *
694   * @param string the string representation of a {@code double} value
695   * @return the floating point value represented by {@code string}, or {@code null} if {@code
696   *     string} has a length of zero or cannot be parsed as a {@code double} value
697   * @since 14.0
698   */
699  @Beta
700  @GwtIncompatible // regular expressions
701  public static @Nullable Double tryParse(String string) {
702    if (FLOATING_POINT_PATTERN.matcher(string).matches()) {
703      // TODO(lowasser): could be potentially optimized, but only with
704      // extensive testing
705      try {
706        return Double.parseDouble(string);
707      } catch (NumberFormatException e) {
708        // Double.parseDouble has changed specs several times, so fall through
709        // gracefully
710      }
711    }
712    return null;
713  }
714}