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.primitives;
018
019import static com.google.common.base.Preconditions.checkArgument;
020import static com.google.common.base.Preconditions.checkElementIndex;
021import static com.google.common.base.Preconditions.checkNotNull;
022import static com.google.common.base.Preconditions.checkPositionIndexes;
023import static java.lang.Double.NEGATIVE_INFINITY;
024import static java.lang.Double.POSITIVE_INFINITY;
025
026import com.google.common.annotations.Beta;
027import com.google.common.annotations.GwtCompatible;
028import com.google.common.annotations.GwtIncompatible;
029import com.google.common.base.Converter;
030
031import java.io.Serializable;
032import java.util.AbstractList;
033import java.util.Arrays;
034import java.util.Collection;
035import java.util.Collections;
036import java.util.Comparator;
037import java.util.List;
038import java.util.RandomAccess;
039import java.util.regex.Pattern;
040
041import javax.annotation.Nullable;
042
043/**
044 * Static utility methods pertaining to {@code double} primitives, that are not
045 * already found in either {@link Double} or {@link Arrays}.
046 *
047 * <p>See the Guava User Guide article on <a href=
048 * "http://code.google.com/p/guava-libraries/wiki/PrimitivesExplained">
049 * primitive utilities</a>.
050 *
051 * @author Kevin Bourrillion
052 * @since 1.0
053 */
054@GwtCompatible(emulated = true)
055public final class Doubles {
056  private Doubles() {}
057
058  /**
059   * The number of bytes required to represent a primitive {@code double}
060   * value.
061   *
062   * @since 10.0
063   */
064  public static final int BYTES = Double.SIZE / Byte.SIZE;
065
066  /**
067   * Returns a hash code for {@code value}; equal to the result of invoking
068   * {@code ((Double) value).hashCode()}.
069   *
070   * @param value a primitive {@code double} value
071   * @return a hash code for the value
072   */
073  public static int hashCode(double value) {
074    return ((Double) value).hashCode();
075    // TODO(kevinb): do it this way when we can (GWT problem):
076    // long bits = Double.doubleToLongBits(value);
077    // return (int) (bits ^ (bits >>> 32));
078  }
079
080  /**
081   * Compares the two specified {@code double} values. The sign of the value
082   * returned is the same as that of <code>((Double) a).{@linkplain
083   * Double#compareTo compareTo}(b)</code>. As with that method, {@code NaN} is
084   * treated as greater than all other values, and {@code 0.0 > -0.0}.
085   *
086   * <p><b>Note:</b> this method simply delegates to the JDK method {@link
087   * Double#compare}. It is provided for consistency with the other primitive
088   * types, whose compare methods were not added to the JDK until JDK 7.
089   *
090   * @param a the first {@code double} to compare
091   * @param b the second {@code double} to compare
092   * @return a negative value if {@code a} is less than {@code b}; a positive
093   *     value if {@code a} is greater than {@code b}; or zero if they are equal
094   */
095  public static int compare(double a, double b) {
096    return Double.compare(a, b);
097  }
098
099  /**
100   * Returns {@code true} if {@code value} represents a real number. This is
101   * equivalent to, but not necessarily implemented as,
102   * {@code !(Double.isInfinite(value) || Double.isNaN(value))}.
103   *
104   * @since 10.0
105   */
106  public static boolean isFinite(double value) {
107    return NEGATIVE_INFINITY < value & value < POSITIVE_INFINITY;
108  }
109
110  /**
111   * Returns {@code true} if {@code target} is present as an element anywhere in
112   * {@code array}. Note that this always returns {@code false} when {@code
113   * target} is {@code NaN}.
114   *
115   * @param array an array of {@code double} values, possibly empty
116   * @param target a primitive {@code double} value
117   * @return {@code true} if {@code array[i] == target} for some value of {@code
118   *     i}
119   */
120  public static boolean contains(double[] array, double target) {
121    for (double value : array) {
122      if (value == target) {
123        return true;
124      }
125    }
126    return false;
127  }
128
129  /**
130   * Returns the index of the first appearance of the value {@code target} in
131   * {@code array}. Note that this always returns {@code -1} when {@code target}
132   * is {@code NaN}.
133   *
134   * @param array an array of {@code double} values, possibly empty
135   * @param target a primitive {@code double} value
136   * @return the least index {@code i} for which {@code array[i] == target}, or
137   *     {@code -1} if no such index exists.
138   */
139  public static int indexOf(double[] array, double target) {
140    return indexOf(array, target, 0, array.length);
141  }
142
143  // TODO(kevinb): consider making this public
144  private static int indexOf(
145      double[] array, double target, int start, int end) {
146    for (int i = start; i < end; i++) {
147      if (array[i] == target) {
148        return i;
149      }
150    }
151    return -1;
152  }
153
154  /**
155   * Returns the start position of the first occurrence of the specified {@code
156   * target} within {@code array}, or {@code -1} if there is no such occurrence.
157   *
158   * <p>More formally, returns the lowest index {@code i} such that {@code
159   * java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly
160   * the same elements as {@code target}.
161   *
162   * <p>Note that this always returns {@code -1} when {@code target} contains
163   * {@code NaN}.
164   *
165   * @param array the array to search for the sequence {@code target}
166   * @param target the array to search for as a sub-sequence of {@code array}
167   */
168  public static int indexOf(double[] array, double[] target) {
169    checkNotNull(array, "array");
170    checkNotNull(target, "target");
171    if (target.length == 0) {
172      return 0;
173    }
174
175    outer:
176    for (int i = 0; i < array.length - target.length + 1; i++) {
177      for (int j = 0; j < target.length; j++) {
178        if (array[i + j] != target[j]) {
179          continue outer;
180        }
181      }
182      return i;
183    }
184    return -1;
185  }
186
187  /**
188   * Returns the index of the last appearance of the value {@code target} in
189   * {@code array}. Note that this always returns {@code -1} when {@code target}
190   * is {@code NaN}.
191   *
192   * @param array an array of {@code double} values, possibly empty
193   * @param target a primitive {@code double} value
194   * @return the greatest index {@code i} for which {@code array[i] == target},
195   *     or {@code -1} if no such index exists.
196   */
197  public static int lastIndexOf(double[] array, double target) {
198    return lastIndexOf(array, target, 0, array.length);
199  }
200
201  // TODO(kevinb): consider making this public
202  private static int lastIndexOf(
203      double[] array, double target, int start, int end) {
204    for (int i = end - 1; i >= start; i--) {
205      if (array[i] == target) {
206        return i;
207      }
208    }
209    return -1;
210  }
211
212  /**
213   * Returns the least value present in {@code array}, using the same rules of
214   * comparison as {@link Math#min(double, double)}.
215   *
216   * @param array a <i>nonempty</i> array of {@code double} values
217   * @return the value present in {@code array} that is less than or equal to
218   *     every other value in the array
219   * @throws IllegalArgumentException if {@code array} is empty
220   */
221  public static double min(double... array) {
222    checkArgument(array.length > 0);
223    double min = array[0];
224    for (int i = 1; i < array.length; i++) {
225      min = Math.min(min, array[i]);
226    }
227    return min;
228  }
229
230  /**
231   * Returns the greatest value present in {@code array}, using the same rules
232   * of comparison as {@link Math#max(double, double)}.
233   *
234   * @param array a <i>nonempty</i> array of {@code double} values
235   * @return the value present in {@code array} that is greater than or equal to
236   *     every other value in the array
237   * @throws IllegalArgumentException if {@code array} is empty
238   */
239  public static double max(double... array) {
240    checkArgument(array.length > 0);
241    double max = array[0];
242    for (int i = 1; i < array.length; i++) {
243      max = Math.max(max, array[i]);
244    }
245    return max;
246  }
247
248  /**
249   * Returns the values from each provided array combined into a single array.
250   * For example, {@code concat(new double[] {a, b}, new double[] {}, new
251   * double[] {c}} returns the array {@code {a, b, c}}.
252   *
253   * @param arrays zero or more {@code double} arrays
254   * @return a single array containing all the values from the source arrays, in
255   *     order
256   */
257  public static double[] concat(double[]... arrays) {
258    int length = 0;
259    for (double[] array : arrays) {
260      length += array.length;
261    }
262    double[] result = new double[length];
263    int pos = 0;
264    for (double[] array : arrays) {
265      System.arraycopy(array, 0, result, pos, array.length);
266      pos += array.length;
267    }
268    return result;
269  }
270
271  private static final class DoubleConverter
272      extends Converter<String, Double> implements Serializable {
273    static final DoubleConverter INSTANCE = new DoubleConverter();
274
275    @Override
276    protected Double doForward(String value) {
277      return Double.valueOf(value);
278    }
279
280    @Override
281    protected String doBackward(Double value) {
282      return value.toString();
283    }
284
285    @Override
286    public String toString() {
287      return "Doubles.stringConverter()";
288    }
289
290    private Object readResolve() {
291      return INSTANCE;
292    }
293    private static final long serialVersionUID = 1;
294  }
295
296  /**
297   * Returns a serializable converter object that converts between strings and
298   * doubles using {@link Double#valueOf} and {@link Double#toString()}.
299   *
300   * @since 16.0
301   */
302  @Beta
303  public static Converter<String, Double> stringConverter() {
304    return DoubleConverter.INSTANCE;
305  }
306
307  /**
308   * Returns an array containing the same values as {@code array}, but
309   * guaranteed to be of a specified minimum length. If {@code array} already
310   * has a length of at least {@code minLength}, it is returned directly.
311   * Otherwise, a new array of size {@code minLength + padding} is returned,
312   * containing the values of {@code array}, and zeroes in the remaining places.
313   *
314   * @param array the source array
315   * @param minLength the minimum length the returned array must guarantee
316   * @param padding an extra amount to "grow" the array by if growth is
317   *     necessary
318   * @throws IllegalArgumentException if {@code minLength} or {@code padding} is
319   *     negative
320   * @return an array containing the values of {@code array}, with guaranteed
321   *     minimum length {@code minLength}
322   */
323  public static double[] ensureCapacity(
324      double[] array, int minLength, int padding) {
325    checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
326    checkArgument(padding >= 0, "Invalid padding: %s", padding);
327    return (array.length < minLength)
328        ? copyOf(array, minLength + padding)
329        : array;
330  }
331
332  // Arrays.copyOf() requires Java 6
333  private static double[] copyOf(double[] original, int length) {
334    double[] copy = new double[length];
335    System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
336    return copy;
337  }
338
339  /**
340   * Returns a string containing the supplied {@code double} values, converted
341   * to strings as specified by {@link Double#toString(double)}, and separated
342   * by {@code separator}. For example, {@code join("-", 1.0, 2.0, 3.0)} returns
343   * the string {@code "1.0-2.0-3.0"}.
344   *
345   * <p>Note that {@link Double#toString(double)} formats {@code double}
346   * differently in GWT sometimes.  In the previous example, it returns the
347   * string {@code "1-2-3"}.
348   *
349   * @param separator the text that should appear between consecutive values in
350   *     the resulting string (but not at the start or end)
351   * @param array an array of {@code double} values, possibly empty
352   */
353  public static String join(String separator, double... array) {
354    checkNotNull(separator);
355    if (array.length == 0) {
356      return "";
357    }
358
359    // For pre-sizing a builder, just get the right order of magnitude
360    StringBuilder builder = new StringBuilder(array.length * 12);
361    builder.append(array[0]);
362    for (int i = 1; i < array.length; i++) {
363      builder.append(separator).append(array[i]);
364    }
365    return builder.toString();
366  }
367
368  /**
369   * Returns a comparator that compares two {@code double} arrays
370   * lexicographically. That is, it compares, using {@link
371   * #compare(double, double)}), the first pair of values that follow any
372   * common prefix, or when one array is a prefix of the other, treats the
373   * shorter array as the lesser. For example,
374   * {@code [] < [1.0] < [1.0, 2.0] < [2.0]}.
375   *
376   * <p>The returned comparator is inconsistent with {@link
377   * Object#equals(Object)} (since arrays support only identity equality), but
378   * it is consistent with {@link Arrays#equals(double[], double[])}.
379   *
380   * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
381   *     Lexicographical order article at Wikipedia</a>
382   * @since 2.0
383   */
384  public static Comparator<double[]> lexicographicalComparator() {
385    return LexicographicalComparator.INSTANCE;
386  }
387
388  private enum LexicographicalComparator implements Comparator<double[]> {
389    INSTANCE;
390
391    @Override
392    public int compare(double[] left, double[] right) {
393      int minLength = Math.min(left.length, right.length);
394      for (int i = 0; i < minLength; i++) {
395        int result = Double.compare(left[i], right[i]);
396        if (result != 0) {
397          return result;
398        }
399      }
400      return left.length - right.length;
401    }
402  }
403
404  /**
405   * Returns an array containing each value of {@code collection}, converted to
406   * a {@code double} value in the manner of {@link Number#doubleValue}.
407   *
408   * <p>Elements are copied from the argument collection as if by {@code
409   * collection.toArray()}.  Calling this method is as thread-safe as calling
410   * that method.
411   *
412   * @param collection a collection of {@code Number} instances
413   * @return an array containing the same values as {@code collection}, in the
414   *     same order, converted to primitives
415   * @throws NullPointerException if {@code collection} or any of its elements
416   *     is null
417   * @since 1.0 (parameter was {@code Collection<Double>} before 12.0)
418   */
419  public static double[] toArray(Collection<? extends Number> collection) {
420    if (collection instanceof DoubleArrayAsList) {
421      return ((DoubleArrayAsList) collection).toDoubleArray();
422    }
423
424    Object[] boxedArray = collection.toArray();
425    int len = boxedArray.length;
426    double[] array = new double[len];
427    for (int i = 0; i < len; i++) {
428      // checkNotNull for GWT (do not optimize)
429      array[i] = ((Number) checkNotNull(boxedArray[i])).doubleValue();
430    }
431    return array;
432  }
433
434  /**
435   * Returns a fixed-size list backed by the specified array, similar to {@link
436   * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)},
437   * but any attempt to set a value to {@code null} will result in a {@link
438   * NullPointerException}.
439   *
440   * <p>The returned list maintains the values, but not the identities, of
441   * {@code Double} objects written to or read from it.  For example, whether
442   * {@code list.get(0) == list.get(0)} is true for the returned list is
443   * unspecified.
444   *
445   * <p>The returned list may have unexpected behavior if it contains {@code
446   * NaN}, or if {@code NaN} is used as a parameter to any of its methods.
447   *
448   * @param backingArray the array to back the list
449   * @return a list view of the array
450   */
451  public static List<Double> asList(double... backingArray) {
452    if (backingArray.length == 0) {
453      return Collections.emptyList();
454    }
455    return new DoubleArrayAsList(backingArray);
456  }
457
458  @GwtCompatible
459  private static class DoubleArrayAsList extends AbstractList<Double>
460      implements RandomAccess, Serializable {
461    final double[] array;
462    final int start;
463    final int end;
464
465    DoubleArrayAsList(double[] array) {
466      this(array, 0, array.length);
467    }
468
469    DoubleArrayAsList(double[] array, int start, int end) {
470      this.array = array;
471      this.start = start;
472      this.end = end;
473    }
474
475    @Override public int size() {
476      return end - start;
477    }
478
479    @Override public boolean isEmpty() {
480      return false;
481    }
482
483    @Override public Double get(int index) {
484      checkElementIndex(index, size());
485      return array[start + index];
486    }
487
488    @Override public boolean contains(Object target) {
489      // Overridden to prevent a ton of boxing
490      return (target instanceof Double)
491          && Doubles.indexOf(array, (Double) target, start, end) != -1;
492    }
493
494    @Override public int indexOf(Object target) {
495      // Overridden to prevent a ton of boxing
496      if (target instanceof Double) {
497        int i = Doubles.indexOf(array, (Double) target, start, end);
498        if (i >= 0) {
499          return i - start;
500        }
501      }
502      return -1;
503    }
504
505    @Override public int lastIndexOf(Object target) {
506      // Overridden to prevent a ton of boxing
507      if (target instanceof Double) {
508        int i = Doubles.lastIndexOf(array, (Double) target, start, end);
509        if (i >= 0) {
510          return i - start;
511        }
512      }
513      return -1;
514    }
515
516    @Override public Double set(int index, Double element) {
517      checkElementIndex(index, size());
518      double oldValue = array[start + index];
519      // checkNotNull for GWT (do not optimize)
520      array[start + index] = checkNotNull(element);
521      return oldValue;
522    }
523
524    @Override public List<Double> subList(int fromIndex, int toIndex) {
525      int size = size();
526      checkPositionIndexes(fromIndex, toIndex, size);
527      if (fromIndex == toIndex) {
528        return Collections.emptyList();
529      }
530      return new DoubleArrayAsList(array, start + fromIndex, start + toIndex);
531    }
532
533    @Override public boolean equals(Object object) {
534      if (object == this) {
535        return true;
536      }
537      if (object instanceof DoubleArrayAsList) {
538        DoubleArrayAsList that = (DoubleArrayAsList) object;
539        int size = size();
540        if (that.size() != size) {
541          return false;
542        }
543        for (int i = 0; i < size; i++) {
544          if (array[start + i] != that.array[that.start + i]) {
545            return false;
546          }
547        }
548        return true;
549      }
550      return super.equals(object);
551    }
552
553    @Override public int hashCode() {
554      int result = 1;
555      for (int i = start; i < end; i++) {
556        result = 31 * result + Doubles.hashCode(array[i]);
557      }
558      return result;
559    }
560
561    @Override public String toString() {
562      StringBuilder builder = new StringBuilder(size() * 12);
563      builder.append('[').append(array[start]);
564      for (int i = start + 1; i < end; i++) {
565        builder.append(", ").append(array[i]);
566      }
567      return builder.append(']').toString();
568    }
569
570    double[] toDoubleArray() {
571      // Arrays.copyOfRange() is not available under GWT
572      int size = size();
573      double[] result = new double[size];
574      System.arraycopy(array, start, result, 0, size);
575      return result;
576    }
577
578    private static final long serialVersionUID = 0;
579  }
580
581  /**
582   * This is adapted from the regex suggested by {@link Double#valueOf(String)}
583   * for prevalidating inputs.  All valid inputs must pass this regex, but it's
584   * semantically fine if not all inputs that pass this regex are valid --
585   * only a performance hit is incurred, not a semantics bug.
586   */
587  @GwtIncompatible("regular expressions")
588  static final Pattern FLOATING_POINT_PATTERN = fpPattern();
589
590  @GwtIncompatible("regular expressions")
591  private static Pattern fpPattern() {
592    String decimal = "(?:\\d++(?:\\.\\d*+)?|\\.\\d++)";
593    String completeDec = decimal + "(?:[eE][+-]?\\d++)?[fFdD]?";
594    String hex = "(?:\\p{XDigit}++(?:\\.\\p{XDigit}*+)?|\\.\\p{XDigit}++)";
595    String completeHex = "0[xX]" + hex + "[pP][+-]?\\d++[fFdD]?";
596    String fpPattern = "[+-]?(?:NaN|Infinity|" + completeDec + "|" + completeHex + ")";
597    return Pattern.compile(fpPattern);
598  }
599
600  /**
601   * Parses the specified string as a double-precision floating point value.
602   * The ASCII character {@code '-'} (<code>'&#92;u002D'</code>) is recognized
603   * as the minus sign.
604   *
605   * <p>Unlike {@link Double#parseDouble(String)}, this method returns
606   * {@code null} instead of throwing an exception if parsing fails.
607   * Valid inputs are exactly those accepted by {@link Double#valueOf(String)},
608   * except that leading and trailing whitespace is not permitted.
609   *
610   * <p>This implementation is likely to be faster than {@code
611   * Double.parseDouble} if many failures are expected.
612   *
613   * @param string the string representation of a {@code double} value
614   * @return the floating point value represented by {@code string}, or
615   *     {@code null} if {@code string} has a length of zero or cannot be
616   *     parsed as a {@code double} value
617   * @since 14.0
618   */
619  @GwtIncompatible("regular expressions")
620  @Nullable
621  @Beta
622  public static Double tryParse(String string) {
623    if (FLOATING_POINT_PATTERN.matcher(string).matches()) {
624      // TODO(user): could be potentially optimized, but only with
625      // extensive testing
626      try {
627        return Double.parseDouble(string);
628      } catch (NumberFormatException e) {
629        // Double.parseDouble has changed specs several times, so fall through
630        // gracefully
631      }
632    }
633    return null;
634  }
635}