Create associated packages for the dart:collection and dart:async libs.

pkg/collection_helpers/lib/algorithms.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/**
- * Operations on collections.
- */
+@deprecated
 library dart.collection_helpers.algorithms;
 
-import "dart:math" show Random;
-
-/** Version of [binarySearch] optimized for comparable keys */
-int _comparableBinarySearch(List<Comparable> list, Comparable key) {
-  int min = 0;
-  int max = list.length;
-  while (min < max) {
-    int mid = min + ((max - min) >> 1);
-    var element = list[mid];
-    int comp = element.compareTo(key);
-    if (comp == 0) return mid;
-    if (comp < 0) {
-      min = mid + 1;
-    } else {
-      max = mid;
-    }
-  }
-  return -1;
-}
-
-/**
- * Returns a position of the [key] in [sortedList], if it is there.
- *
- * If the list isn't sorted according to the [compare] function, the result
- * is unpredictable.
- *
- * If [compare] is omitted, it defaults to calling [Comparable.compareTo] on
- * the objects.
- *
- * Returns -1 if [key] is not in the list by default.
- */
-int binarySearch(List sortedList, var key,
-                 { int compare(var a, var b) }) {
-  if (compare == null) {
-    return _comparableBinarySearch(sortedList, key);
-  }
-  int min = 0;
-  int max = sortedList.length;
-  while (min < max) {
-    int mid = min + ((max - min) >> 1);
-    var element = sortedList[mid];
-    int comp = compare(element, key);
-    if (comp == 0) return mid;
-    if (comp < 0) {
-      min = mid + 1;
-    } else {
-      max = mid;
-    }
-  }
-  return -1;
-}
-
-
-/**
- * Shuffles a list randomly.
- *
- * A sub-range of a list can be shuffled by providing [start] and [end].
- */
-void shuffle(List list, [int start = 0, int end = null]) {
-  Random random = new Random();
-  if (end == null) end = list.length;
-  int length = end - start;
-  while (length > 1) {
-    int pos = random.nextInt(length);
-    length--;
-    var tmp1 = list[start + pos];
-    list[start + pos] = list[start + length];
-    list[start + length] = tmp1;
-  }
-}
-
-
-/**
- * Reverses a list, or a part of a list, in-place.
- */
-void reverse(List list, [int start = 0, int end = null]) {
-  if (end == null) end = list.length;
-  _reverse(list, start, end);
-}
-
-// Internal helper function that assumes valid arguments.
-void _reverse(List list, int start, int end) {
-  for (int i = start, j = end - 1; i < j; i++, j--) {
-    var tmp = list[i];
-    list[i] = list[j];
-    list[j] = tmp;
-  }
-}
-
-/**
- * Sort a list using insertion sort.
- *
- * Insertion sort is a simple sorting algorithm. For `n` elements it does on
- * the order of `n * log(n)` comparisons but up to `n` squared moves. The
- * sorting is performed in-place, without using extra memory.
- *
- * For short lists the many moves have less impact than the simple algorithm,
- * and it is often the favored sorting algorithm for short lists.
- *
- * This insertion sort is stable: Equal elements end up in the same order
- * as they started in.
- */
-void insertionSort(List list,
-                   { int compare(a, b),
-                     int start: 0,
-                     int end: null }) {
-  // If the same method could have both positional and named optional
-  // parameters, this should be (list, [start, end], {compare}).
-  if (end == null) end = list.length;
-  if (compare == null) compare = Comparable.compare;
-  _insertionSort(list, compare, start, end, start + 1);
-}
-
-/**
- * Internal helper function that assumes arguments correct.
- *
- * Assumes that the elements up to [sortedUntil] (not inclusive) are
- * already sorted. The [sortedUntil] values should always be at least
- * `start + 1`.
- */
-void _insertionSort(List list, int compare(a, b), int start, int end,
-                    int sortedUntil) {
-  for (int pos = sortedUntil; pos < end; pos++) {
-    int min = start;
-    int max = pos;
-    var element = list[pos];
-    while (min < max) {
-      int mid = min + ((max - min) >> 1);
-      int comparison = compare(element, list[mid]);
-      if (comparison < 0) {
-        max = mid;
-      } else {
-        min = mid + 1;
-      }
-    }
-    list.setRange(min + 1, pos + 1, list, min);
-    list[min] = element;
-  }
-}
-
-/** Limit below which merge sort defaults to insertion sort. */
-const int _MERGE_SORT_LIMIT = 32;
-
-/**
- * Sorts a list, or a range of a list, using the merge sort algorithm.
- *
- * Merge-sorting works by splitting the job into two parts, sorting each
- * recursively, and then merging the two sorted parts.
- *
- * This takes on the order of `n * log(n)` comparisons and moves to sort
- * `n` elements, but requires extra space of about the same size as the list
- * being sorted.
- *
- * This merge sort is stable: Equal elements end up in the same order
- * as they started in.
- */
-void mergeSort(List list, {int start: 0, int end: null, int compare(a, b)}) {
-  if (end == null) end = list.length;
-  if (compare == null) compare = Comparable.compare;
-  int length = end - start;
-  if (length < 2) return;
-  if (length < _MERGE_SORT_LIMIT) {
-    _insertionSort(list, compare, start, end, start + 1);
-    return;
-  }
-  // Special case the first split instead of directly calling
-  // _mergeSort, because the _mergeSort requires its target to
-  // be different from its source, and it requires extra space
-  // of the same size as the list to sort.
-  // This split allows us to have only half as much extra space,
-  // and it ends up in the original place.
-  int middle = start + ((end - start) >> 1);
-  int firstLength = middle - start;
-  int secondLength = end - middle;
-  // secondLength is always the same as firstLength, or one greater.
-  List scratchSpace = new List(secondLength);
-  _mergeSort(list, compare, middle, end, scratchSpace, 0);
-  int firstTarget = end - firstLength;
-  _mergeSort(list, compare, start, middle, list, firstTarget);
-  _merge(compare,
-         list, firstTarget, end,
-         scratchSpace, 0, secondLength,
-         list, start);
-}
-
-/**
- * Performs an insertion sort into a potentially different list than the
- * one containing the original values.
- *
- * It will work in-place as well.
- */
-void _movingInsertionSort(List list, int compare(a, b), int start, int end,
-                          List target, int targetOffset) {
-  int length = end - start;
-  if (length == 0) return;
-  target[targetOffset] = list[start];
-  for (int i = 1; i < length; i++) {
-    var element = list[start + i];
-    int min = targetOffset;
-    int max = targetOffset + i;
-    while (min < max) {
-      int mid = min + ((max - min) >> 1);
-      if (compare(element, target[mid]) < 0) {
-        max = mid;
-      } else {
-        min = mid + 1;
-      }
-    }
-    target.setRange(min + 1, targetOffset + i + 1,
-                    target, min);
-    target[min] = element;
-  }
-}
-
-/**
- * Sorts [list] from [start] to [end] into [target] at [targetOffset].
- *
- * The `target` list must be able to contain the range from `start` to `end`
- * after `targetOffset`.
- *
- * Allows target to be the same list as [list], as long as it's not
- * overlapping the `start..end` range.
- */
-void _mergeSort(List list, int compare(a, b), int start, int end,
-                List target, int targetOffset) {
-  int length = end - start;
-  if (length < _MERGE_SORT_LIMIT) {
-    _movingInsertionSort(list, compare, start, end, target, targetOffset);
-    return;
-  }
-  int middle = start + (length >> 1);
-  int firstLength = middle - start;
-  int secondLength = end - middle;
-  // Here secondLength >= firstLength (differs by at most one).
-  int targetMiddle = targetOffset + firstLength;
-  // Sort the second half into the end of the target area.
-  _mergeSort(list, compare, middle, end,
-             target, targetMiddle);
-  // Sort the first half into the end of the source area.
-  _mergeSort(list, compare, start, middle,
-             list, middle);
-  // Merge the two parts into the target area.
-  _merge(compare,
-         list, middle, middle + firstLength,
-         target, targetMiddle, targetMiddle + secondLength,
-         target, targetOffset);
-}
-
-/**
- * Merges two lists into a target list.
- *
- * One of the input lists may be positioned at the end of the target
- * list.
- *
- * For equal object, elements from [firstList] are always preferred.
- * This allows the merge to be stable if the first list contains elements
- * that started out earlier than the ones in [secondList]
- */
-void _merge(int compare(a, b),
-            List firstList, int firstStart, int firstEnd,
-            List secondList, int secondStart, int secondEnd,
-            List target, int targetOffset) {
-  // No empty lists reaches here.
-  assert(firstStart < firstEnd);
-  assert(secondStart < secondEnd);
-  int cursor1 = firstStart;
-  int cursor2 = secondStart;
-  var firstElement = firstList[cursor1++];
-  var secondElement = secondList[cursor2++];
-  while (true) {
-    if (compare(firstElement, secondElement) <= 0) {
-      target[targetOffset++] = firstElement;
-      if (cursor1 == firstEnd) break;  // Flushing second list after loop.
-      firstElement = firstList[cursor1++];
-    } else {
-      target[targetOffset++] = secondElement;
-      if (cursor2 != secondEnd) {
-        secondElement = secondList[cursor2++];
-        continue;
-      }
-      // Second list empties first. Flushing first list here.
-      target[targetOffset++] = firstElement;
-      target.setRange(targetOffset, targetOffset + (firstEnd - cursor1),
-          firstList, cursor1);
-      return;
-    }
-  }
-  // First list empties first. Reached by break above.
-  target[targetOffset++] = secondElement;
-  target.setRange(targetOffset, targetOffset + (secondEnd - cursor2),
-      secondList, cursor2);
-}
+export "package:collection/algorithms.dart";