lrn@google.com
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R=sgjesse@google.com Review URL: https://codereview.chromium.org//113883002 git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@31260 260f80e4-7a28-3924-810f-c04153c831b5
56 lines
1.8 KiB
Markdown
56 lines
1.8 KiB
Markdown
Helper libraries for working with collections.
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The `collection` package contains a number of separate libraries
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with utility functions and classes that makes working with collections easier.
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## Using
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The `collection` package can be imported as separate libraries, or
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in totality:
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import 'package:collection/equality.dart';
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import 'package:collection/algorithms.dart';
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import 'package:collection/wrappers.dart';
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or
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import 'package:collection/collection.dart';
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## Equality
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The equality library gives a way to specify equality of elements and
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collections.
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Collections in Dart have no inherent equality. Two sets are not equal, even
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if they contain exactly the same objects as elements.
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The equality library provides a way to say define such an equality. In this
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case, for example, `const SetEquality(const IdentityEquality())` is an equality
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that considers two sets equal exactly if they contain identical elements.
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The library provides ways to define equalities on `Iterable`s, `List`s, `Set`s, and
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`Map`s, as well as combinations of these, such as:
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const MapEquality(const IdentityEquality(), const ListEquality());
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This equality considers maps equal if they have identical keys, and the corresponding values are lists with equal (`operator==`) values.
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## Algorithms
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The algorithms library contains functions that operate on lists.
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It contains ways to shuffle a `List`, do binary search on a sorted `List`, and
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some different sorting algorithms.
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## Wrappers
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The wrappers library contains classes that "wrap" a collection.
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A wrapper class contains an object of the same type, and it forwards all
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methods to the wrapped object.
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Wrapper classes can be used in various ways, for example to restrict the type
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of an object to that of a supertype, or to change the behavior of selected
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functions on an existing object.
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