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// Copyright (c) 2012, 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.
part of dart.core;
/**
* An indexable collection of objects with a length.
*
* Subclasses of this class implement different kinds of lists.
* The most common kinds of lists are:
*
* * Fixed-length list.
* An error occurs when attempting to use operations
* that can change the length of the list.
*
* * Growable list. Full implementation of the API defined in this class.
*
* The default growable list, as returned by `new List()` or `[]`, keeps
* an internal buffer, and grows that buffer when necessary. This guarantees
* that a sequence of [add] operations will each execute in amortized constant
* time. Setting the length directly may take time proportional to the new
* length, and may change the internal capacity so that a following add
* operation will need to immediately increase the buffer capacity.
* Other list implementations may have different performance behavior.
*
* The following code illustrates that some List implementations support
* only a subset of the API.
*
* List<int> fixedLengthList = new List(5);
* fixedLengthList.length = 0; // Error
* fixedLengthList.add(499); // Error
* fixedLengthList[0] = 87;
* List<int> growableList = [1, 2];
* growableList.length = 0;
* growableList.add(499);
* growableList[0] = 87;
*
* Lists are [Iterable]. Iteration occurs over values in index order. Changing
* the values does not affect iteration, but changing the valid
* indices&mdash;that is, changing the list's length&mdash;between iteration
* steps causes a [ConcurrentModificationError]. This means that only growable
* lists can throw ConcurrentModificationError. If the length changes
* temporarily and is restored before continuing the iteration, the iterator
* does not detect it.
*
* It is generally not allowed to modify the list's length (adding or removing
* elements) while an operation on the list is being performed,
* for example during a call to [forEach] or [sort].
* Changing the list's length while it is being iterated, either by iterating it
* directly or through iterating an [Iterable] that is backed by the list, will
* break the iteration.
*/
abstract class List<E> implements EfficientLengthIterable<E> {
/**
* Creates a list of the given length.
*
* The created list is fixed-length if [length] is provided.
*
* List fixedLengthList = new List(3);
* fixedLengthList.length; // 3
* fixedLengthList.length = 1; // Error
*
* The list has length 0 and is growable if [length] is omitted.
*
* List growableList = new List();
* growableList.length; // 0;
* growableList.length = 3;
*
* To create a growable list with a given length, just assign the length
* right after creation:
*
* List growableList = new List()..length = 500;
*
* The [length] must not be negative or null, if it is provided.
*/
factory List([int length]) = List<E>._internal;
/**
* Creates a fixed-length list of the given length, and initializes the
* value at each position with [fill]:
*
* new List<int>.filled(3, 0); // [0, 0, 0]
*
* The [length] must be a non-negative integer.
*
* If the list is growable, changing its length will not initialize new
* entries with [fill]. After being created and filled, the list is
* no different from any other growable or fixed-length list
* created using [List].
*
* All entries in the returned list point to the same provided [fill] value.
* That all items in the list are the same object is
* observable when the given value is a mutable object.
*
* ```
* var shared = new List.filled(3, []);
* shared[0].add(499);
* print(shared); // => [[499], [499], [499]]
* ```
*
* You may use [List.generate] to create a new object for each position in
* in the list.
* ```
* var unique = new List.generate(3, (_) => []);
* unique[0].add(499);
* print(unique); // => [[499], [], []]
* ```
*/
factory List.filled(int length, E fill, {bool growable: false}) {
// All error handling on the length parameter is done at the implementation
// of new _List.
var result = growable ? new _GrowableList<E>(length) : new _List<E>(length);
if (fill != null) {
for (int i = 0; i < length; i++) {
result[i] = fill;
}
}
return result;
}
/**
* Creates a list containing all [elements].
*
* The [Iterator] of [elements] provides the order of the elements.
*
* This constructor returns a growable list when [growable] is true;
* otherwise, it returns a fixed-length list.
*/
factory List.from(Iterable elements, {bool growable: true}) {
if (elements is EfficientLengthIterable) {
int length = elements.length;
var list = growable ? new _GrowableList<E>(length) : new _List<E>(length);
if (length > 0) {
// Avoid creating iterator unless necessary.
int i = 0;
for (var element in elements) {
list[i++] = element;
}
}
return list;
}
List<E> list = new _GrowableList<E>(0);
for (E e in elements) {
list.add(e);
}
if (growable) return list;
if (list.length == 0) {
// Avoid getting an immutable list from makeListFixedLength.
return new _List<E>(0);
}
return makeListFixedLength<E>(list);
}
/**
* Generates a list of values.
*
* Creates a list with [length] positions and fills it with values created by
* calling [generator] for each index in the range `0` .. `length - 1`
* in increasing order.
*
* new List<int>.generate(3, (int index) => index * index); // [0, 1, 4]
*
* The created list is fixed-length unless [growable] is true.
*/
factory List.generate(int length, E generator(int index),
{bool growable: true}) {
List<E> result;
if (growable) {
result = <E>[]..length = length;
} else {
result = new List<E>(length);
}
for (int i = 0; i < length; i++) {
result[i] = generator(i);
}
return result;
}
/**
* Creates an unmodifiable list containing all [elements].
*
* The [Iterator] of [elements] provides the order of the elements.
*
* An unmodifiable list cannot have its length or elements changed.
* If the elements are themselves immutable, then the resulting list
* is also immutable.
*/
factory List.unmodifiable(Iterable elements) {
List result = new List<E>.from(elements, growable: false);
return makeFixedListUnmodifiable(result);
}
/**
* Returns the object at the given [index] in the list
* or throws a [RangeError] if [index] is out of bounds.
*/
E operator [](int index);
/**
* Sets the value at the given [index] in the list to [value]
* or throws a [RangeError] if [index] is out of bounds.
*/
void operator []=(int index, E value);
/**
* Returns the number of objects in this list.
*
* The valid indices for a list are `0` through `length - 1`.
*/
int get length;
/**
* Changes the length of this list.
*
* If [newLength] is greater than
* the current length, entries are initialized to [:null:].
*
* Throws an [UnsupportedError] if the list is fixed-length.
*/
set length(int newLength);
/**
* Adds [value] to the end of this list,
* extending the length by one.
*
* Throws an [UnsupportedError] if the list is fixed-length.
*/
void add(E value);
/**
* Appends all objects of [iterable] to the end of this list.
*
* Extends the length of the list by the number of objects in [iterable].
* Throws an [UnsupportedError] if this list is fixed-length.
*/
void addAll(Iterable<E> iterable);
/**
* Returns an [Iterable] of the objects in this list in reverse order.
*/
Iterable<E> get reversed;
/**
* Sorts this list according to the order specified by the [compare] function.
*
* The [compare] function must act as a [Comparator].
*
* List<String> numbers = ['two', 'three', 'four'];
* // Sort from shortest to longest.
* numbers.sort((a, b) => a.length.compareTo(b.length));
* print(numbers); // [two, four, three]
*
* The default List implementations use [Comparable.compare] if
* [compare] is omitted.
*
* List<int> nums = [13, 2, -11];
* nums.sort();
* print(nums); // [-11, 2, 13]
*
* A [Comparator] may compare objects as equal (return zero), even if they
* are distinct objects.
* The sort function is not guaranteed to be stable, so distinct objects
* that compare as equal may occur in any order in the result:
*
* List<String> numbers = ['one', 'two', 'three', 'four'];
* numbers.sort((a, b) => a.length.compareTo(b.length));
* print(numbers); // [one, two, four, three] OR [two, one, four, three]
*/
void sort([int compare(E a, E b)]);
/**
* Shuffles the elements of this list randomly.
*/
void shuffle([Random random]);
/**
* Returns the first index of [element] in this list.
*
* Searches the list from index [start] to the end of the list.
* The first time an object [:o:] is encountered so that [:o == element:],
* the index of [:o:] is returned.
*
* List<String> notes = ['do', 're', 'mi', 're'];
* notes.indexOf('re'); // 1
* notes.indexOf('re', 2); // 3
*
* Returns -1 if [element] is not found.
*
* notes.indexOf('fa'); // -1
*/
int indexOf(E element, [int start = 0]);
/**
* Returns the last index of [element] in this list.
*
* Searches the list backwards from index [start] to 0.
*
* The first time an object [:o:] is encountered so that [:o == element:],
* the index of [:o:] is returned.
*
* List<String> notes = ['do', 're', 'mi', 're'];
* notes.lastIndexOf('re', 2); // 1
*
* If [start] is not provided, this method searches from the end of the
* list./Returns
*
* notes.lastIndexOf('re'); // 3
*
* Returns -1 if [element] is not found.
*
* notes.lastIndexOf('fa'); // -1
*/
int lastIndexOf(E element, [int start]);
/**
* Removes all objects from this list;
* the length of the list becomes zero.
*
* Throws an [UnsupportedError], and retains all objects, if this
* is a fixed-length list.
*/
void clear();
/**
* Inserts the object at position [index] in this list.
*
* This increases the length of the list by one and shifts all objects
* at or after the index towards the end of the list.
*
* An error occurs if the [index] is less than 0 or greater than length.
* An [UnsupportedError] occurs if the list is fixed-length.
*/
void insert(int index, E element);
/**
* Inserts all objects of [iterable] at position [index] in this list.
*
* This increases the length of the list by the length of [iterable] and
* shifts all later objects towards the end of the list.
*
* An error occurs if the [index] is less than 0 or greater than length.
* An [UnsupportedError] occurs if the list is fixed-length.
*/
void insertAll(int index, Iterable<E> iterable);
/**
* Overwrites objects of `this` with the objects of [iterable], starting
* at position [index] in this list.
*
* List<String> list = ['a', 'b', 'c'];
* list.setAll(1, ['bee', 'sea']);
* list.join(', '); // 'a, bee, sea'
*
* This operation does not increase the length of `this`.
*
* The [index] must be non-negative and no greater than [length].
*
* The [iterable] must not have more elements than what can fit from [index]
* to [length].
*
* If `iterable` is based on this list, its values may change /during/ the
* `setAll` operation.
*/
void setAll(int index, Iterable<E> iterable);
/**
* Removes the first occurrence of [value] from this list.
*
* Returns true if [value] was in the list, false otherwise.
*
* List<String> parts = ['head', 'shoulders', 'knees', 'toes'];
* parts.remove('head'); // true
* parts.join(', '); // 'shoulders, knees, toes'
*
* The method has no effect if [value] was not in the list.
*
* // Note: 'head' has already been removed.
* parts.remove('head'); // false
* parts.join(', '); // 'shoulders, knees, toes'
*
* An [UnsupportedError] occurs if the list is fixed-length.
*/
bool remove(Object value);
/**
* Removes the object at position [index] from this list.
*
* This method reduces the length of `this` by one and moves all later objects
* down by one position.
*
* Returns the removed object.
*
* The [index] must be in the range `0 ≤ index < length`.
*
* Throws an [UnsupportedError] if this is a fixed-length list. In that case
* the list is not modified.
*/
E removeAt(int index);
/**
* Pops and returns the last object in this list.
*
* Throws an [UnsupportedError] if this is a fixed-length list.
*/
E removeLast();
/**
* Removes all objects from this list that satisfy [test].
*
* An object [:o:] satisfies [test] if [:test(o):] is true.
*
* List<String> numbers = ['one', 'two', 'three', 'four'];
* numbers.removeWhere((item) => item.length == 3);
* numbers.join(', '); // 'three, four'
*
* Throws an [UnsupportedError] if this is a fixed-length list.
*/
void removeWhere(bool test(E element));
/**
* Removes all objects from this list that fail to satisfy [test].
*
* An object [:o:] satisfies [test] if [:test(o):] is true.
*
* List<String> numbers = ['one', 'two', 'three', 'four'];
* numbers.retainWhere((item) => item.length == 3);
* numbers.join(', '); // 'one, two'
*
* Throws an [UnsupportedError] if this is a fixed-length list.
*/
void retainWhere(bool test(E element));
/**
* Returns a new list containing the objects from [start] inclusive to [end]
* exclusive.
*
* List<String> colors = ['red', 'green', 'blue', 'orange', 'pink'];
* colors.sublist(1, 3); // ['green', 'blue']
*
* If [end] is omitted, the [length] of `this` is used.
*
* colors.sublist(1); // ['green', 'blue', 'orange', 'pink']
*
* An error occurs if [start] is outside the range `0` .. `length` or if
* [end] is outside the range `start` .. `length`.
*/
List<E> sublist(int start, [int end]);
/**
* Returns an [Iterable] that iterates over the objects in the range
* [start] inclusive to [end] exclusive.
*
* The provide range, given by [start] and [end], must be valid at the time
* of the call.
*
* A range from [start] to [end] is valid if `0 <= start <= end <= len`, where
* `len` is this list's `length`. The range starts at `start` and has length
* `end - start`. An empty range (with `end == start`) is valid.
*
* The returned [Iterable] behaves like `skip(start).take(end - start)`.
* That is, it does *not* throw if this list changes size.
*
* List<String> colors = ['red', 'green', 'blue', 'orange', 'pink'];
* Iterable<String> range = colors.getRange(1, 4);
* range.join(', '); // 'green, blue, orange'
* colors.length = 3;
* range.join(', '); // 'green, blue'
*/
Iterable<E> getRange(int start, int end);
/**
* Copies the objects of [iterable], skipping [skipCount] objects first,
* into the range [start], inclusive, to [end], exclusive, of the list.
*
* List<int> list1 = [1, 2, 3, 4];
* List<int> list2 = [5, 6, 7, 8, 9];
* // Copies the 4th and 5th items in list2 as the 2nd and 3rd items
* // of list1.
* list1.setRange(1, 3, list2, 3);
* list1.join(', '); // '1, 8, 9, 4'
*
* The provide range, given by [start] and [end], must be valid.
* A range from [start] to [end] is valid if `0 <= start <= end <= len`, where
* `len` is this list's `length`. The range starts at `start` and has length
* `end - start`. An empty range (with `end == start`) is valid.
*
* The [iterable] must have enough objects to fill the range from `start`
* to `end` after skipping [skipCount] objects.
*
* If `iterable` is this list, the operation copies the elements
* originally in the range from `skipCount` to `skipCount + (end - start)` to
* the range `start` to `end`, even if the two ranges overlap.
*
* If `iterable` depends on this list in some other way, no guarantees are
* made.
*/
void setRange(int start, int end, Iterable<E> iterable, [int skipCount = 0]);
/**
* Removes the objects in the range [start] inclusive to [end] exclusive.
*
* The provide range, given by [start] and [end], must be valid.
* A range from [start] to [end] is valid if `0 <= start <= end <= len`, where
* `len` is this list's `length`. The range starts at `start` and has length
* `end - start`. An empty range (with `end == start`) is valid.
*
* Throws an [UnsupportedError] if this is a fixed-length list. In that case
* the list is not modified.
*/
void removeRange(int start, int end);
/**
* Sets the objects in the range [start] inclusive to [end] exclusive
* to the given [fillValue].
*
* The provide range, given by [start] and [end], must be valid.
* A range from [start] to [end] is valid if `0 <= start <= end <= len`, where
* `len` is this list's `length`. The range starts at `start` and has length
* `end - start`. An empty range (with `end == start`) is valid.
*/
void fillRange(int start, int end, [E fillValue]);
/**
* Removes the objects in the range [start] inclusive to [end] exclusive
* and inserts the contents of [replacement] in its place.
*
* List<int> list = [1, 2, 3, 4, 5];
* list.replaceRange(1, 4, [6, 7]);
* list.join(', '); // '1, 6, 7, 5'
*
* The provide range, given by [start] and [end], must be valid.
* A range from [start] to [end] is valid if `0 <= start <= end <= len`, where
* `len` is this list's `length`. The range starts at `start` and has length
* `end - start`. An empty range (with `end == start`) is valid.
*
* This method does not work on fixed-length lists, even when [replacement]
* has the same number of elements as the replaced range. In that case use
* [setRange] instead.
*/
void replaceRange(int start, int end, Iterable<E> replacement);
/**
* Returns an unmodifiable [Map] view of `this`.
*
* The map uses the indices of this list as keys and the corresponding objects
* as values. The `Map.keys` [Iterable] iterates the indices of this list
* in numerical order.
*
* List<String> words = ['fee', 'fi', 'fo', 'fum'];
* Map<int, String> map = words.asMap();
* map[0] + map[1]; // 'feefi';
* map.keys.toList(); // [0, 1, 2, 3]
*/
Map<int, E> asMap();
factory List._internal([int length = _GROWABLE_ARRAY_MARKER]) {
if (length == _GROWABLE_ARRAY_MARKER) {
return new _GrowableList<E>(0);
}
// All error handling on the length parameter is done at the implementation
// of new _List.
return new _List<E>(length);
}
factory List._fromLiteral(List elements) {
if (elements.isEmpty) {
return new _GrowableList<E>(0);
}
var result = new _GrowableList<E>.withData(elements);
result._setLength(elements.length);
return result;
}
}