Updated tech overview

src/site/docs/library-tour/index.markdown

Index: src/site/docs/library-tour/index.markdown
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----
-layout: default
-title: "A Tour of the Dart Libraries"
-description: "Learn how to use each major Dart library feature."
-has-permalinks: true
----
-
-# {{ page.title }}
-
-Welcome to the Dart library tour!
-We'll show you how to use the major features in each library
-that comes with Dart.
-
-This tour is just an overview of
-library functionality; it is by no means comprehensive.
-Consult the
-[Dart API reference](http://api.dartlang.org/)
-for the full details about a class or interface.
-
-<aside>
-  <div class="alert">
-    <strong>Warning:</strong>
-    Expect major changes to the Dart libraries before Dart's
-    first release.
-  </div>
-</aside>
-
-#### Contents {#toc}
-
-1. [dart:core - Strings, collections, and more](#dartcore---strings-collections-and-more)
-    1. [Collections](#collections)
-        1. [Lists](#lists)
-        1. [Sets](#sets)
-        1. [Common collection methods](#common-collection-methods)
-        1. [Maps (aka dictionaries or hashes)](#maps-aka-dictionaries-or-hashes)
-    1. [Dates and times](#dates-and-times)
-    1. [Utility interfaces](#utility-interfaces)
-    1. [Strings and regular expressions](#strings-and-regular-expressions)
-    1. [Asynchronous programming](#asynchronous-programming)
-    1. [Exceptions](#exceptions)
-1. [dart:math - Math](#dartmath---math)
-1. [dart:html - Using HTML5 APIs](#html)
-    1. [Manipulating the DOM](#html-dom)
-    1. [WebSockets](#html-websockets)
-1. [dart:isolate - Concurrency with isolates](#dartisolate---concurrency-with-isolates)
-    1. [Isolate concepts](#isolate-concepts)
-    1. [Using isolates](#using-isolates)
-        1. [Sending messages](#sending-messages)
-        1. [Receiving messages](#receiving-messages)
-        1. [Receiving replies](#receiving-replies)
-1. [dart:io - File and socket I/O for command-line apps](#dartio---file-and-socket-io-for-command-line-apps)
-    1. [Files and directories](#files-and-directories)
-    1. Sockets (coming soon)
-    1. HTTP Server (coming soon)
-    1. HTTP Client (coming soon)
-    1. Web socket server (coming soon)
-1. [dart:json - Encoding and decoding objects](#json)
-1. [dart:uri - Manipulating URLs](#uri)
-1. [dart:utf - Strings and Unicode](#utf)
-1. [dart:crypto - Hash codes and more](#crypto)
-{:.toc}
-
-## dart:core - Strings, collections, and more
-
-The Dart core library provides a small but critical set of built-in functionality.
-This library is automatically imported into every Dart program.
-
-### Collections
-
-Dart ships with a core collections API, which includes interfaces for Lists,
-Maps, and Sets.
-
-#### Lists
-
-A [list](http://api.dartlang.org/dart_core/List.html) in Dart is an ordered
-collection of items, analogous to an array in other languages.
-Lists are zero indexed, and they can contain duplicate items.
-
-The language tour has
-[more information about lists](/docs/language-tour/#lists).
-
-##### Creating, adding, and removing
-
-As the language tour shows, you can create and initialize lists using literals.
-Alternatively, use one of the [List
-constructors](http://api.dartlang.org/dart_core/List.html#List). The List class
-also provides several methods for adding items to and removing items from lists.
-
-{% highlight dart %}
-// Use a list constructor.
-var vegetables = new List();
-
-// Or simply use a list literal.
-var fruits = ['apples', 'oranges'];
-
-// Add to a list.
-fruits.add('kiwis');
-
-// Add multiple items to a list.
-fruits.addAll(['grapes', 'bananas']);
-
-// Get the list length.
-assert(fruits.length == 5);
-
-// Remove a single item.
-var appleIndex = fruits.indexOf('apples');
-fruits.removeRange(appleIndex, 1);
-assert(fruits.length == 4);
-
-// Remove all elements from a list.
-fruits.clear();
-assert(fruits.length == 0);
-{% endhighlight %}
-
-##### Getting and setting items
-
-Lists use zero-based indexing, where 0
-is the index of the first element, and
-`list.length-1` is the index of the last
-element. Use `indexOf()` to find
-the index of an object in a list.
-
-{% highlight dart %}
-var fruits = ['apples', 'oranges'];
-
-// Access a list item by index.
-assert(fruits[0] == 'apples');
-
-// Find an item in a list.
-assert(fruits.indexOf('apples') == 0);
-{% endhighlight %}
-
-##### Sorting
-
-Sort a list using the `sort()` method, and you must provide
-a sorting function that compares two objects.
-The sorting function must
-return &lt; 0 for _smaller_,
-0 for the _same_, and &gt; 0 for _bigger_.
-
-{% highlight dart %}
-var fruits = ['bananas', 'apples', 'oranges'];
-
-// Sort a list.
-fruits.sort((a, b) => a.compareTo(b));
-assert(fruits[1] == 'bananas');
-{% endhighlight %}
-
-##### Generics
-
-Lists are parameterized types, so you can specify the type that a list
-should contain.
-
-{% highlight dart %}
-// This list should contain only strings.
-var fruits = new List<String>();
-
-fruits.add('apples');
-var fruit = fruits[0];
-assert(fruit is String);
-
-// Generates static analysis warning; num is not a string.
-fruits.add(5);  // BAD: Throws exception in checked mode.
-{% endhighlight %}
-
-##### More information
-
-Refer to the full
-[List API docs](http://api.dartlang.org/dart_core/List.html)
-for a full list of methods.
-
-[Back to contents.](#toc)
-{:.up-to-toc}
-
-#### Sets
-
-A [set](http://api.dartlang.org/dart_core/Set.html)
-in Dart
-is an unordered collection of unique items.
-Because a set is unordered,
-you can't get a set's items by index (position).
-
-##### Adding and removing
-
-{% highlight dart %}
-var ingredients = new Set();
-ingredients.addAll(['gold', 'titanium', 'xenon']);
-assert(ingredients.length == 3);
-
-// Adding a duplicate item has no effect.
-ingredients.add('gold');
-assert(ingredients.length == 3);
-
-// Remove an item from a set.
-ingredients.remove('gold');
-assert(ingredients.length == 2);
-{% endhighlight %}
-
-##### Checking membership
-
-Use `contains()` and `containsAll()` to check whether
-one or more objects are in a set.
-
-{% highlight dart %}
-var ingredients = new Set();
-ingredients.addAll(['gold', 'titanium', 'xenon']);
-
-// Check whether an item is in the set.
-assert(ingredients.contains('titanium') == true);
-
-// Check whether all the items are in the set.
-assert(ingredients.containsAll(['titanium', 'xenon']) == true);
-{% endhighlight %}
-
-##### Intersection and subset
-
-An intersection is a set whose items are in two other sets.
-A subset has all of its items included
-in another, potentially larger, collection.
-
-{% highlight dart %}
-var ingredients = new Set();
-ingredients.addAll(['gold', 'titanium', 'xenon']);
-
-// Create the intersection of two sets.
-var nobleGases = new Set.from(['xenon', 'argon']);
-var intersection = ingredients.intersection(nobleGases);
-assert(intersection.length == 1);
-assert(intersection.contains('xenon'));
-
-// Check whether this set is a subset of another collection.
-// That is, does another collection contains all the items of this set?
-var allElements = ['hydrogen', 'helium', 'lithium', 'beryllium',
-                   'gold', 'titanium', 'xenon' /* all the rest */];
-assert(ingredients.isSubsetOf(allElements) == true);
-{% endhighlight %}
-
-##### More information
-
-Refer to the full
-[Set API docs](http://api.dartlang.org/dart_core/Set.html)
-for a full list of methods.
-
-[Back to contents.](#toc)
-{:.up-to-toc}
-
-#### Common collection methods
-
-Both List and Set extend the
-[Collection](http://api.dartlang.org/dart_core/Collection.html) interface.
-As such, they share common functionality found in all collections.
-
-The following examples work with any object that implements Collection.
-
-##### Checking whether a collection has items
-
-{% highlight dart %}
-var teas = ['green', 'black', 'chamomile', 'earl grey'];
-
-// Use isEmpty() to check whether a collection has no items.
-assert(teas.isEmpty() == false);
-{% endhighlight %}
-
-##### Applying a function to each item
-
-{% highlight dart %}
-var teas = ['green', 'black', 'chamomile', 'earl grey'];
-
-// Use forEach() to apply a function to every item in a collection.
-teas.forEach((tea) => print('I drink $tea'));
-
-// Use map() to create a new collection by applying a function to each
-// item and collecting the results.
-var loudTeas = teas.map((tea) => tea.toUpperCase());
-assert(loudTeas.some((tea) => tea == 'GREEN'));
-{% endhighlight %}
-
-##### Filtering and checking items
-
-Use `forEach()` and `map()` to apply a function to each
-element of the collection. Use `some()` and `every()`
-to check whether some or all items in a collection
-match a condition.
-
-{% highlight dart %}
-var teas = ['green', 'black', 'chamomile', 'earl grey'];
-
-// Chamomile is not caffeinated.
-isDecaffeinated(String teaName) => teaName == 'chamomile';
-
-// Use filter() to create a new collection with only the items
-// that return true from the provided function.
-var decaffeinatedTeas = teas.filter((tea) => isDecaffeinated(tea));
-// Or teas.filter(isDecaffeinated)
-
-// Use some() to check whether at least one item in the collection
-// satisfies a condition.
-assert(teas.some(isDecaffeinated) == true);
-
-// Use every() to check whether all the items in a collection
-// satisfy a condition.
-assert(teas.every(isDecaffeinated) == false);
-{% endhighlight %}
-
-##### More information
-
-Refer to the full
-[Collection API docs](http://api.dartlang.org/dart_core/Collection.html)
-for a full list of methods.
-
-[Back to contents.](#toc)
-{:.up-to-toc}
-
-#### Maps (aka dictionaries or hashes)
-
-The [Map](http://api.dartlang.org/dart_core/Map.html)
-interface, commonly known as a _dictionary_ or _hash_,
-is an unordered collection of key-value pairs.
-Maps associate a key to some value for easy retrieval.
-Unlike in JavaScript, Dart objects are not maps.
-
-The language tour has more
-[information about maps](/docs/language-tour/#maps).
-
-<aside>
-  <div class="alert alert-info">
-    <strong>Note:</strong>
-    The Map
-    interface does not extend Collection.
-  </div>
-</aside>
-
-##### Creating maps
-
-You can declare a map using a terse literal syntax,
-or you can use a traditional constructor.
-
-{% highlight dart %}
-// Map literals use strings as keys.
-var hawaiianBeaches = {
-  "oahu" : ['waikiki', 'kailua', 'waimanalo'],
-  "big island" : ['wailea bay', 'pololu beach'],
-  "kauai" : ['hanalei', 'poipu']
-};
-
-// Maps can be built from a constructor.
-var searchTerms = new Map();
-
-// Maps are parameterized types; you can specify what types
-// the key and value should be.
-var nobleGases = new Map<int, String>();
-{% endhighlight %}
-
-##### Adding, retrieving, and removing items
-
-You add, get, and set map items using the bracket syntax.
-Use `remove()` to remove a key and its value from a map.
-
-{% highlight dart %}
-var nobleGases = new Map<int, String>();
-
-// Maps from constructors can use any Hashable object as a key;
-// for example, int implements Hashable.
-nobleGases[54] = 'xenon';
-
-// Associate a key with a value.
-nobleGases[54] = 'xenon';
-
-// Retrieve a value with a key.
-assert(nobleGases[54] == 'xenon');
-
-// Check whether a map contains a key.
-assert(nobleGases.containsKey(54) == true);
-
-// Add a key-value pair only if the key doesn't yet exist in the map.
-var value = nobleGases.putIfAbsent(36, () => 'krypton');
-assert(value == 'krypton');
-
-// Remove a key and its value.
-nobleGases.remove(54);
-assert(nobleGases.containsKey(54) == false);
-{% endhighlight %}
-
-##### Iterating through a map
-
-You can retrieve all the values or all the keys from
-a map. You can also iterate through the key-value
-pairs.
-
-{% highlight dart %}
-var hawaiianBeaches = {
-  "oahu" : ['waikiki', 'kailua', 'waimanalo'],
-  "big island" : ['wailea bay', 'pololu beach'],
-  "kauai" : ['hanalei', 'poipu']
-};
-
-// Get all the keys as an unordered collection.
-var keys = hawaiianBeaches.getKeys();
-
-assert(keys.length == 3);
-assert(new Set.from(keys).contains('oahu') == true);
-
-// Get all the values as an unordered collection.
-var values = hawaiianBeaches.getValues();
-assert(values.length == 3);
-assert(values.some((v) => v.indexOf('waikiki') != -1) == true);
-
-// Iterate through the key-value pairs.
-// NOTE: Do not depend on iteration order.
-hawaiianBeaches.forEach((k,v) {
-  print("I want to visit $k and swim at $v");
-  // I want to visit oahu and swim at [waikiki, kailua, waimanalo]
-});
-{% endhighlight %}
-
-##### More information
-
-Refer to the full
-[Map API docs](http://api.dartlang.org/dart_core/Map.html)
-for a full list of methods.
-
-[Back to contents.](#toc)
-{:.up-to-toc}
-
-### Dates and times
-
-A [Date](http://api.dartlang.org/dart_core/Date.html) object is a point in time.
-The time is either UTC or the local time zone.
-
-#### Constructing dates
-
-{% highlight dart %}
-// Get the current date and time.
-var now = new Date.now();
-
-// Create a new Date with the local time zone.
-var y2k = new Date(2000, 1, 1, 0, 0, 0, 0);
-
-// You can also use named parameters.
-y2k = new Date(2000, month: 1, day: 1, hour: 0, minute: 0, second: 0,
-               millisecond: 0);
-
-// Specify all the parts of a date as a UTC time.
-y2k = new Date(2000, 1, 1, 0, 0, 0, 0, isUtc: true);
-
-// Specify a UTC date and time in milliseconds since the Unix epoch.
-y2k = new Date.fromMillisecondsSinceEpoch(1336017592000, isUtc: true);
-
-// Parse an ISO 8601 date.
-y2k = new Date.fromString('2000-01-01T00:00:00Z');
-{% endhighlight %}
-
-#### The epoch
-
-The `millisecondsSinceEpoch` getter on a date returns the number
-of milliseconds since the epoch.
-
-{% highlight dart %}
-var y2k = new Date.fromString('2000-01-01T00:00:00Z');
-assert(y2k.millisecondsSinceEpoch == 946684800000);
-{% endhighlight %}
-
-#### Calculations
-
-Use the [Duration](http://api.dartlang.org/dart_core/Duration.html) class to
-calculate the difference between two dates
-and to shift a date's time forward or backwards.
-
-{% highlight dart %}
-var y2k = new Date.fromString('2000-01-01T00:00:00Z');
-
-// Add one year.
-var y2001 = y2k.add(const Duration(366, 0, 0, 0, 0));
-assert(y2001.year == 2001);
-
-// Subtract 30 days.
-var december2000 = y2001.subtract(const Duration(30, 0 ,0, 0, 0));
-assert(december2000.year == 2000);
-assert(december2000.month == 12);
-
-// Calculate the difference between two dates.
-// Returns a Duration object.
-var duration = y2001.difference(y2k);
-assert(duration.inDays == 366); // y2k was a leap year.
-{% endhighlight %}
-
-#### More information
-
-Refer to the full
-[Date API docs](http://api.dartlang.org/dart_core/Date.html) and
-[Duration API docs](http://api.dartlang.org/dart_core/Duration.html)
-for a full list of methods.
-
-[Back to contents.](#toc)
-{:.up-to-toc}
-
-### Utility interfaces
-
-The core library contains various utility interfaces, useful for
-sorting, mapping values, and iterating.
-
-#### Comparing objects
-
-Use the [Comparable](http://api.dartlang.org/dart_core/Comparable.html)
-interface to indicate that an object can be compared
-to another object, usually for sorting. The `compareTo` method
-returns &lt; 0 for _smaller_,
-0 for the _same_, and &gt; 0 for _bigger_.
-
-{% highlight dart %}
-class Line implements Comparable {
-  final length;
-  const Line(this.length);
-  int compareTo(Line other) => length - other.length;
-}
-
-main() {
-  var short = const Line(1);
-  var long = const Line(100);
-  assert(short.compareTo(long) < 0);
-}
-{% endhighlight %}
-
-[Back to contents.](#toc)
-{:.up-to-toc}
-
-#### Implementing map keys
-
-The default implementation of Map requires map keys to implement Hashable.
-The [Hashable](http://api.dartlang.org/dart_core/Hashable.html) interface
-indicates that an object can provide an integer
-hash code.
-
-Objects that are equal (via ==) must have identical hash codes.
-A hash code doesn't have to be unique, but it should
-be well distributed.
-
-{% highlight dart %}
-class Person implements Hashable {
-  String firstName, lastName;
-
-  Person(this.firstName, this.lastName);
-
-  // Strategy from Effective Java, Chapter 11.
-  int hashCode() {
-    int result = 17;
-    result = 37 * result + firstName.hashCode();
-    result = 37 * result + lastName.hashCode();
-    return result;
-  }
-
-  // Always implement operator== if class implements Hashable.
-  bool operator==(other) {
-    if (other == null) return false;
-    if (other === this) return true;
-    return (other.firstName == firstName && other.lastName == lastName);
-  }
-}
-
-main() {
-  var p1 = new Person('bob', 'smith');
-  var p2 = new Person('bob', 'smith');
-  assert(p1.hashCode() == p2.hashCode());
-}
-{% endhighlight %}
-
-##### More information
-
-Refer to the full
-[Hashable API docs](http://api.dartlang.org/dart_core/Hashable.html)
-for a full list of methods.
-
-[Back to contents.](#toc)
-{:.up-to-toc}
-
-#### Iteration
-
-Two interfaces contribute to iteration abilities in Dart, allowing objects
-to work in for-in loops. Implementing the
-[Iterable](http://api.dartlang.org/dart_core/Iterable.html)
-interface signals that an object can provide an Iterator.
-The [Iterator](http://api.dartlang.org/dart_core/Iterator.html) interface
-defines the actual iteration ability.
-
-{% highlight dart %}
-class Process {
-  // Represents a process...
-}
-
-class ProcessIterator implements Iterator<Process> {
-  Process next() {
-    // Return the next process if possible; but if not:
-    throw new NoMoreElementsException();
-  }
-  bool hasNext() {
-    // True if calling next() would return a process.
-    return false;
-  }
-}
-
-// A mythical class that lets you iterate through all processes.
-class Processes implements Iterable<Process> {
-  Iterator<Process> iterator() {
-    return new ProcessIterator();
-  }
-}
-
-main() {
-  // Objects that implement Iterable can be used with for-in.
-  for (var process in new Processes()) {
-    // Do something with the process.
-  }
-}
-{% endhighlight %}
-
-##### More information
-
-Refer to the full
-[Iterable API docs](http://api.dartlang.org/dart_core/Iterable.html)
-and
-[Iterator API docs](http://api.dartlang.org/dart_core/Iterator.html)
-for a full list of methods.
-
-[Back to contents.](#toc)
-{:.up-to-toc}
-
-### Strings and regular expressions
-
-A [String](http://api.dartlang.org/dart_core/String.html) is
-an immutable, ordered list of 32-bit Unicode character codes.
-You can use regular expressions to
-search within strings and to replace parts of strings.
-
-The [Pattern](http://api.dartlang.org/dart_core/Pattern.html)
-interface is implemented by both String and
-[RegExp](http://api.dartlang.org/dart_core/RegExp.html),
-and is used for methods like
-[split](http://api.dartlang.org/dart_core/String.html#split) and
-[contains](http://api.dartlang.org/dart_core/String.html#contains).
-
-The language tour has
-[more information about strings](/docs/language-tour/#strings).
-
-#### Searching inside a string
-
-You can find particular locations within a string, as well as check
-whether a string begins with or ends with a particular pattern.
-
-{% highlight dart %}
-// Check whether a string contains another string.
-assert("Never odd or even".contains("odd") == true);
-
-// Does a string start with another string?
-assert("Never odd or even".startsWith("Never") == true);
-
-// Does a string end with another string?
-assert("Never odd or even".endsWith("even") == true);
-
-// Find the location of a string inside a string.
-assert("Never odd or even".indexOf("odd") == 6);
-{% endhighlight %}
-
-#### Extracting data from a string
-
-You can get the individual characters (as Strings)
-or individual character codes (as ints) from a string.
-
-You can also extract a substring or split a string
-into a list of substrings.
-
-{% highlight dart %}
-// Grab a substring.
-assert("Never odd or even".substring(6, 9) == 'odd');
-
-// Split a string using a string pattern.
-var parts = "structured web apps".split(" ");
-assert(parts.length == 3);
-assert(parts[0] == 'structured');
-
-// Get the character (as a string) by index.
-assert("Never odd or even"[0] == "N");
-
-// Use splitChars() to get a list of all characters (as Strings);
-// good for iterating.
-for (var char in "hello".splitChars()) {
-  print(char);
-}
-
-// Get the char code at an index.
-assert("Never odd or even".charCodeAt(0) == 78);
-
-// Get all the char codes as a list of integers.
-var charCodes = "Never odd or even".charCodes();
-assert(charCodes.length == 17);
-assert(charCodes[0] == 78);
-{% endhighlight %}
-
-#### Converting to uppercase or lowercase
-
-Easily convert strings to their uppercase and lowercase variants.
-
-{% highlight dart %}
-// Convert to uppercase.
-assert("structured web apps".toUpperCase() == 'STRUCTURED WEB APPS');
-
-// Convert to lowercase.
-assert("STRUCTURED WEB APPS".toLowerCase() == 'structured web apps');
-{% endhighlight %}
-
-#### Trimming and empty strings
-
-Remove all leading and trailing white space with trim().
-To check whether a string is empty (length is zero), use isEmpty().
-
-{% highlight dart %}
-// Trim a string.
-assert('  hello  '.trim() == 'hello');
-
-// Check whether a string is empty.
-assert(''.isEmpty() == true);
-
-// Strings with only white space are not empty.
-assert('  '.isEmpty() == false);
-{% endhighlight %}
-
-#### Regular expressions
-
-The [RegExp](http://api.dartlang.org/dart_core/RegExp.html)
-interface provides the same capabilities as JavaScript
-regular expressions. Use regular expressions for efficient searching
-and pattern matching of strings.
-
-{% highlight dart %}
-// A regular expression for one or more digits.
-var numbers = const RegExp(r'\d+');
-
-var allCharacters = "llamas live fifteen to twenty years";
-var someDigits = "llamas live 15 to 20 years";
-
-// contains() can use a regular expression.
-assert(allCharacters.contains(numbers) == false);
-assert(someDigits.contains(numbers) == true);
-
-// Replace every match with another string.
-var exedOut = someDigits.replaceAll(numbers, "XX");
-assert(exedOut == 'llamas live XX to XX years');
-{% endhighlight %}
-
-You can work directly with the RegExp class, too.
-The [Match](http://api.dartlang.org/dart_core/Match.html) interface
-provides access to a regular expression match.
-
-{% highlight dart %}
-var numbers = const RegExp(r'\d+');
-var someDigits = "llamas live 15 to 20 years";
-
-// Check whether the reg exp has a match in a string.
-assert(numbers.hasMatch(someDigits) == true);
-
-// Loop through all matches.
-for (var match in numbers.allMatches(someDigits)) {
-  print(match.group(0)); // 15, then 20.
-}
-{% endhighlight %}
-
-#### More information
-
-Refer to the full
-[String API docs](http://api.dartlang.org/dart_core/String.html)
-for a full list of methods.
-Also see the API docs for
-[RegExp](http://api.dartlang.org/dart_core/RegExp.html) and
-[Match](http://api.dartlang.org/dart_core/Match.html).
-
-[Back to contents.](#toc)
-{:.up-to-toc}
-
-### Asynchronous programming
-
-Async programming often uses callback functions,
-but Dart provides an alternative:
-the [Future](http://api.dartlang.org/dart_core/Future.html) interface.
-A Future is
-like a promise for a result to be provided "sometime in the future."
-
-You have the option of using a
-[Completer](http://api.dartlang.org/dart_core/Completer.html)
-to produce a Future
-and, later, to supply a value to the Future.
-
-{% highlight dart %}
-Future<bool> longExpensiveSearch() {
-  var completer = new Completer();
-  // Perform exhaustive search.
-  // ...
-  // Sometime later,
-  // found it!!
-  completer.complete(true);
-  return completer.future;
-}
-
-void main() {
-  var result = longExpensiveSearch(); //returns immediately
-
-  // result.then() returns immediately.
-  result.then((success) {
-    // The following code executes when the operation is complete.
-    print("The item was found: $success");
-  });
-}
-{% endhighlight %}
-
-#### Chaining multiple asynchronous methods
-
-The Future interface specifies a chain() method, which is a useful way
-to specify that multiple async methods run in a certain order.
-The chain() method takes a single function as a parameter, which
-receives the value from the previous Future in the chain.
-The function passed to chain() must itself return a Future.
-
-{% highlight dart %}
-Future expensiveWork() {
-  // ...
-}
-
-Future lengthyComputation() {
-  // ...
-}
-
-Future costlyQuery() {
-  // ...
-}
-
-Future result = costlyQuery();
-result.handleException((exception) => print("DOH!"));
-
-result.chain((value) => expensiveWork())
-      .chain((value) => lengthyComputation())
-      .then((value)  => print("done!"));
-{% endhighlight %}
-
-In the above example, the methods run in the following order:
-
-1. costlyQuery()
-1. expensiveWork()
-1. lengthyComputation()
-
-In addition to the chain() method, the Future interface also defines a
-transform() method. Use transform() when you only need to manipulate the
-returned value, returning a new value immediately.
-Use chain() when you need to start
-another asynchronous operation, returning a Future.
-
-#### Waiting for multiple futures
-
-Sometimes your algorithm needs to initiate many asynchronous methods
-and wait for each one to complete before continuing. Use the Futures class
-to manage multiple Futures and wait for them all to complete.
-
-{% highlight dart %}
-Future deleteDone = deleteLotsOfFiles();
-Future copyDone = copyLotsOfFiles();
-Future checksumDone = checksumLotsOfOtherFiles();
-
-Futures.wait([deleteDone, copyDone, checksumDone]).then((List values) {
-  print('Done with all the long steps');
-});
-{% endhighlight %}
-
-#### More information
-
-Refer to the API docs for
-[Future](http://api.dartlang.org/dart_core/Future.html),
-[Futures](http://api.dartlang.org/dart_core/Futures.html), and
-[Completer](http://api.dartlang.org/dart_core/Completer.html)
-for a full list of methods.
-
-[Back to contents.](#toc)
-{:.up-to-toc}
-
-### Exceptions
-
-The Dart core library defines many common exceptions,
-all extending the base
-[Exception](http://api.dartlang.org/dart_core/Exception.html)
-interface.
-
-Learn more about throwing and catching exceptions
-in the [Exceptions section](/docs/language-tour/#exceptions)
-of the language tour.
-
-#### Common exceptions
-
-Some of the most common exceptions include:
-
-[NoSuchMethodException](http://api.dartlang.org/dart_core/NoSuchMethodException.html)
-: Thrown when a receiving object does not implement a method.
-
-[NullPointerException](http://api.dartlang.org/dart_core/NullPointerException.html)
-: Thrown when the program tries to call a method or access a field of a
-null object.
-
-[IllegalArgumentException](http://api.dartlang.org/dart_core/IllegalArgumentException.html)
-: Can be thrown by a method that encounters an unexpected argument.
-
-
-#### Defining your own exception
-
-Throwing an application-specific exception is a common way to indicate
-that an error has occurred. You can define a custom exception
-by implementing the Exception interface.
-
-{% highlight dart %}
-class FooException implements Exception {
-  final String msg;
-  const FooException([this.msg]);
-  String toString() => msg == null ? 'FooException' : msg;
-}
-{% endhighlight %}
-
-### More information
-
-See the
-[Exception API docs](http://api.dartlang.org/dart_core/Exception.html).
-
-[Back to contents.](#toc)
-{:.up-to-toc}
-
-## dart:math - Math
-
-The [Math](http://api.dartlang.org/dart_math/index.html) library
-provides common functionality such as sine and cosine,
-maximum and minimum,
-string-to-number conversion,
-and constants such as _pi_ and _e_.
-
-### Importing the Math library
-
-Math functionality is in the `dart:math` library.
-
-{% highlight dart %}
-#import('dart:math');
-
-main() {
-  // Do fun math stuff.
-}
-{% endhighlight %}
-
-### Converting strings to numbers
-
-You can convert a string into either an integer or double with the Math class.
-
-{% highlight dart %}
-#import('dart:math');
-
-main() {
-  assert(parseInt('42') == 42);
-  assert(parseDouble("0.50") == 0.5);
-}
-{% endhighlight %}
-
-### Converting numbers to strings
-
-Use the toString() method (defined by
-[Object](http://api.dartlang.org/dart_core/Object.html))
-to convert an int or double to a string.
-
-To specify the number of digits to the right of the decimal,
-use toStringAsFixed()
-(defined by [num](http://api.dartlang.org/dart_core/num.html)).
-To specify the number of significant digits in the string,
-use toStringAsPrecision().
-
-{% highlight dart %}
-// Convert an int to a string.
-assert(42.toString() == '42');
-
-// Convert a double to a string.
-assert(123.456.toString() == '123.456');
-
-// Specify the number of digits after the decimal.
-assert(123.456.toStringAsFixed(2) == '123.46');
-
-// Specify the number of significant figures.
-assert(123.456.toStringAsPrecision(2) == '1.2e+2');
-{% endhighlight %}
-
-### Trigonometry
-
-Use the Math library for the basic trigonometric functions.
-
-<aside>
-  <div class="alert alert-info">
-    <strong>Tip:</strong>
-    These methods use radians, not degrees!
-  </div>
-</aside>
-
-{% highlight dart %}
-#import('dart:math');
-
-main() {
-  // Cosine
-  assert(cos(PI) == -1.0);
-
-  // Sine
-  var degrees = 30;
-  var radians = degrees * (PI / 180);
-  // radians is now 0.52359.
-  var sinOf30degrees = sin(radians);
-
-  // Truncate the decimal places to 2.
-  assert(parseDouble(sinOf30degrees.toStringAsPrecision(2)) == 0.5);
-}
-{% endhighlight %}
-
-### Maximum and mininum
-
-The Math library provides optimized max and min methods.
-
-{% highlight dart %}
-#import('dart:math');
-
-main() {
-  assert(max(1, 1000) == 1000);
-  assert(min(1, -1000) == -1000);
-}
-{% endhighlight %}
-
-### Math constants
-
-Find your favorite constants&mdash;_pi_, _e_, and more&mdash;in
-the Math library.
-
-{% highlight dart %}
-// See the Math class for additional constants.
-
-#import('dart:math');
-
-main() {
-  print(E);     // 2.718281828459045
-  print(PI);    // 3.141592653589793
-  print(SQRT2); // 1.4142135623730951
-}
-{% endhighlight %}
-
-### Random numbers
-
-Generate random numbers with the Random class.
-You can optionally provide a seed to the Random
-constructor.
-
-{% highlight dart %}
-#import('dart:math');
-
-main() {
-  var random = new Random();
-  random.nextDouble(); // Between 0.0 and 0.1.
-  random.nextInt(10);  // Between 0 and 9.
-}
-{% endhighlight %}
-
-You can even generate random booleans.
-
-{% highlight dart %}
-#import('dart:math');
-
-main() {
-  var random = new Random();
-  random.nextBoolean();  // true or false
-}
-{% endhighlight %}
-
-### More information
-
-Refer to the full
-[Math API docs](http://api.dartlang.org/dart_math/index.html)
-for a full list of methods.
-Also see the API docs for
-[num](http://api.dartlang.org/dart_core/num.html),
-[int](http://api.dartlang.org/dart_core/int.html),
-and
-[double](http://api.dartlang.org/dart_core/double.html).
-
-[Back to contents.](#toc)
-{:.up-to-toc}
-
-## dart:html - Using HTML5 APIs {#html}
-
-{% render library-tour/html.markdown %}
-{% render library-tour/html-dom.markdown %}
-{% render library-tour/html-websockets.markdown %}
-
-### More information
-
-Refer to the API docs for
-[dart:html](http://api.dartlang.org/html.html).
-
-[Back to contents.](#toc)
-{:.up-to-toc}
-
-
-## dart:isolate - Concurrency with isolates
-
-{% render library-tour/isolates.markdown %}
-
-### More information
-
-Refer to the API docs for
-[isolates](http://api.dartlang.org/dart_isolate.html).
-
-[Back to contents.](#toc)
-{:.up-to-toc}
-
-## dart:io - File and socket I/O for command-line apps
-
-The [dart:io library](http://api.dartlang.org/io.html) provides
-file and socket capabilities
-for the Dart VM when running from the command line. These libraries
-are not yet available to Dart programs that target the web browser.
-
-In general, the dart:io library implements and promotes an
-asynchronous API. Synchronous
-methods can easily block the main loop, making
-it difficult to scale server applications. Therefore, most operations
-return results via callbacks or Future objects, a pattern common
-with modern server platforms such as Node.js.
-
-The few synchronous methods
-in the dart:io library
-are clearly marked with a Sync suffix on the method name.
-We don't cover them here.
-
-### Importing the I/O library
-
-I/O functionality is in the `dart:io` library.
-
-{% highlight dart %}
-#import('dart:io');
-
-main() {
-  // The app
-}
-{% endhighlight %}
-
-### Files and directories
-
-Command-line Dart applications can read and write files and browse directories.
-You have two choices for reading the contents of a file:
-all at once, or streaming.
-Reading a file all at once requires enough memory
-to store all the contents of the file.
-If the file is very large or you want to process it while reading it,
-you should use a [stream](#streaming-file-contents).
-
-#### Reading a file as text
-
-When reading a text file, you can read the entire file
-contents with `readAsText()`. When the individual lines are
-important, you can use `readAsLines()`. In both cases,
-a Future object is returned that provides
-the contents of the file as one or more strings.
-
-{% highlight dart %}
-#import('dart:io');
-
-main() {
-  var config = new File('config.txt');
-
-  // Put the whole file in a single string.
-  config.readAsText(Encoding.UTF_8).then((String contents) {
-    print("The entire file is ${contents.length} characters long");
-  });
-
-  // Put each line of the file into its own string.
-  config.readAsLines(Encoding.UTF_8).then((List<String> lines) {
-    print("The entire file is ${lines.length} lines long");
-  });
-}
-{% endhighlight %}
-
-#### Reading a file as binary
-
-The following code reads an entire file into a list of bytes (as ints).
-
-{% highlight dart %}
-#import('dart:io');
-
-main() {
-  var config = new File('config.txt');
-
-  config.readAsBytes().then((List<int> contents) {
-    print("The entire file is ${contents.length} bytes long");
-  });
-}
-{% endhighlight %}
-
-In the examples above, the API uses Future objects to signal completion.
-This asynchronous technique is preferred for performance reasons.
-However, you have the option to use synchronous and blocking
-methods: `readAsTextSync()`, `readAsLinesSync()`, and `readAsBytesSync()`.
-
-#### Handling errors
-
-Errors are thrown as exceptions if you do not
-register an explicit handler. If you want to
-capture an error, you can register a handleException handler
-with the Future object.
-
-{% highlight dart %}
-#import('dart:io');
-
-main() {
-  var config = new File('config.txt');
-  Future<String> readFile = config.readAsText();
-  readFile.handleException((e) {
-    print('Error: $e');
-    // ... other error handling goes here ...
-    return true; // We've handled the exception; no need to propagate it.
-  });       
-
-  readFile.then((text) => print(text));
-}
-{% endhighlight %}
-
-#### Streaming file contents
-
-Use an [InputStream](http://api.dartlang.org/io/InputStream.html)
-to read a file, a little at a time. The `onData`
-callback runs when data
-is ready to be read. When the InputStream
-is finished reading the file, the `onClosed` callback executes.
-
-{% highlight dart %}
-#import('dart:io');
-
-main() {
-  var config = new File('config.txt');
-  var inputStream = config.openInputStream();
-
-  inputStream.onError = (e) => print(e);
-  inputStream.onClosed = () => print("file is now closed");
-  inputStream.onData = () {
-    List<int> bytes = inputStream.read();
-    print("Read ${bytes.length} bytes from stream");
-  };
-}
-{% endhighlight %}
-
-#### Writing file contents
-
-Use an [OutputStream](http://api.dartlang.org/io/OutputStream.html)
-to write data to a file. Open a file
-for writing with `openOutputStream()` and declare a
-mode. Use `FileMode.WRITE` to completely overwrite existing data in the file,
-and `FileMode.APPEND`
-to add to the end.
-
-{% highlight dart %}
-#import('dart:io');
-
-main() {
-  var logFile = new File('log.txt');
-  var out = logFile.openOutputStream(FileMode.WRITE);
-  out.writeString('FILE ACCESSED ${new Date.now()}');
-  out.close();
-}
-{% endhighlight %}
-
-To write binary data, use `write(List<int> buffer)`.
-
-#### Listing files in a directory
-
-Finding all files and subdirectories for a directory is an asynchronous
-operation. The `list()` method returns a
-[DirectoryLister](http://api.dartlang.org/io/DirectoryLister.html),
-on which you can register callback handlers to be notified when
-a file is encountered (using `onFile`) or when a directory is
-encountered (using `onDir`).
-
-{% highlight dart %}
-#import('dart:io');
-
-main() {
-  var dir = new Directory('/tmp');
-
-  DirectoryLister lister = dir.list(recursive:true); //returns immediately
-  lister.onError = (e) => print(e);
-  lister.onFile = (name) => print("Found file $name");
-  lister.onDir = (name) => print("Found dir $name");
-}
-{% endhighlight %}
-
-No equivalent synchronous API exists for walking a directory
-tree.
-
-
-#### Other common functionality
-
-The File and Directory interfaces contain other functionality,
-including but not limited to:
-
-* [creating a file](http://api.dartlang.org/io/File.html#create)
-* [creating a directory](http://api.dartlang.org/io/Directory.html#create)
-* [deleting a file](http://api.dartlang.org/io/File.html#delete)
-* [deleting a directory](http://api.dartlang.org/io/Directory.html#delete)
-* [getting the length of a file](http://api.dartlang.org/io/File.html#length)
-* [random access to a file](http://api.dartlang.org/io/File.html#open)
-
-#### More information
-
-Refer to the full API docs for
-[File](http://api.dartlang.org/io/File.html),
-[Directory](http://api.dartlang.org/io/Directory.html),
-and [DirectoryLister](http://api.dartlang.org/io/DirectoryLister.html)
-for a full list of methods. For more information,
-read [An introduction to the dart:io library](/articles/io/).
-
-[Back to contents.](#toc)
-{:.up-to-toc}
-
-
-{% comment %}
-### Sockets
-
-Coming soon.
-
-### HTTP server and client
-
-Coming soon.
-
-### Web socket server
-
-Coming soon.
-{% endcomment %}
-
-
-## dart:json - Encoding and decoding objects {#json}
-
-[JSON](http://www.json.org/) is a simple text
-format for representing structured objects and collections.
-The [JSON library](http://api.dartlang.org/json.html)
-decodes JSON-formatted strings into Dart objects,
-and encodes objects into JSON-formatted strings.
-
-The Dart JSON library works in both web apps and command-line apps.
-
-### Importing the JSON library
-
-To use the JSON library, import dart:json.
-
-{% highlight dart %}
-#import('dart:json');
-
-main() {
-  // The app
-}
-{% endhighlight %}
-
-### Decoding JSON
-
-Decode a JSON-encoded string into a Dart object with `JSON.parse()`.
-
-{% highlight dart %}
-#import('dart:json');
-
-main() {
-  // NOTE: Be sure to use ", not ', inside the JSON string.
-  var jsonString = '''
-  [
-    {"score": 40},
-    {"score": 80}
-  ]
-  ''';
-
-  var scores = JSON.parse(jsonString);
-  assert(scores is List);
-
-  var firstScore = scores[0];
-  assert(firstScore is Map);
-  assert(firstScore['score'] == 40);
-}
-{% endhighlight %}
-
-### Encoding JSON
-
-Encode a supported Dart object into a JSON-formatted string
-with `JSON.stringify()`.
-
-Only objects of type List, Map, String, int, double, bool, or null can
-be encoded into JSON.
-List and Map objects are encoded recursively.
-
-{% highlight dart %}
-#import('dart:json');
-
-main() {
-  var scores = [
-    {'score': 40},
-    {'score': 80},
-    {'score': 100, 'overtime': true, 'special_guest': null}
-  ];
-
-  var jsonText = JSON.stringify(scores);
-  assert(jsonText == '[{"score":40},{"score":80},'
-                     '{"score":100,"overtime":true,'
-                     '"special_guest":null}]');
-}
-{% endhighlight %}
-
-[Back to contents.](#toc)
-{:.up-to-toc}
-
-## dart:uri - Manipulating URLs {#uri}
-
-The [URI library](http://api.dartlang.org/uri.html) provides functions
-to encode and decode strings for use in URIs. These functions
-handle characters that are special for URIs, such as `&` and `=`.
-
-The URI library also contains the
-[Uri class](http://api.dartlang.org/uri/Uri.html),
-which parses and exposes
-the components of a URI, such as domain, port, and scheme.
-
-The URI library works in both web apps and command-line apps.
-
-### Importing the URI library
-
-To use the URI library, import dart:uri.
-
-{% highlight dart %}
-#import('dart:uri');
-
-main() {
-  // The app
-}
-{% endhighlight %}
-
-### Encoding and decoding fully qualified URIs
-
-To encode and decode characters *except* those with special meaning in a URI
-(such as `/`, `:`, `&`, `#`), use
-[encodeUri()](http://api.dartlang.org/uri.html#encodeUri)
-and [decodeUri()](http://api.dartlang.org/uri.html#decodeUri). Use these
-functions when you need to encode or decode a fully qualified URI,
-leaving intact special URI characters.
-
-{% highlight dart %}
-#import('dart:uri');
-
-main() {
-  var uri = 'http://example.org/api?foo=some message';
-  var encoded = encodeUri(uri);
-  assert(encoded == 'http://example.org/api?foo=some%20message');
-
-  var decoded = decodeUri(encoded);
-  assert(uri == decoded);
-}
-{% endhighlight %}
-
-Notice how only the space between `some` and `message` was encoded.
-
-### Encoding and decoding URI components
-
-To encode and decode all characters in a string that have special meaning
-in a URI, including (but not limited to)
-`/`, `&`, and `:`, use
-[encodeUriComponent()](http://api.dartlang.org/uri.html#encodeUriComponent) and
-[decodeUriComponent()](http://api.dartlang.org/uri.html#decodeUriComponent).
-
-{% highlight dart %}
-#import('dart:uri');
-
-main() {
-  var uri = 'http://example.org/api?foo=some message';
-  var encoded = encodeUriComponent(uri);
-  assert(encoded == 'http%3A%2F%2Fexample.org%2Fapi%3Ffoo%3Dsome%20message');
-
-  var decoded = decodeUriComponent(encoded);
-  assert(uri == decoded);
-}
-{% endhighlight %}
-
-Notice how every special character was encoded. For example, `/` was encoded
-to `%2F`.
-
-### Parsing URIs
-
-You can parse a URI into its parts with the
-[Uri.fromString() constructor](http://api.dartlang.org/uri/Uri.html#Uri).
-
-{% highlight dart %}
-#import('dart:uri');
-
-main() {
-  var uri = new Uri.fromString('http://example.org/foo/bar#frag');
-
-  assert(uri.scheme == 'http');
-  assert(uri.domain == 'example.org');
-  assert(uri.path == '/foo/bar');
-  assert(uri.fragment == 'frag');
-}
-{% endhighlight %}
-
-The Uri class exposes more URI components. Learn more by
-reading the [Uri API docs](http://api.dartlang.org/uri/Uri.html).
-
-### Building URIs
-
-You can build up a URI from individual parts using the
-[Uri() constructor](http://api.dartlang.org/uri/Uri.html#Uri).
-
-{% highlight dart %}
-#import('dart:uri');
-
-main() {
-  var uri = new Uri(scheme: 'http', domain: 'example.org', path: '/foo/bar',
-                    fragment: 'frag');
-  assert(uri.toString() == 'http://example.org/foo/bar#frag');
-}
-{% endhighlight %}
-
-[Back to contents.](#toc)
-{:.up-to-toc}
-
-
-## dart:utf - Strings and Unicode {#utf}
-
-The [UTF library](http://api.dartlang.org/utf.html) helps bridge the gap
-between strings and UTF8/UTF16/UTF32 encodings.
-
-### Importing the UTF library
-
-To use the UTF library, import dart:utf.
-
-{% highlight dart %}
-#import('dart:utf');
-
-main() {
-  // The app
-}
-{% endhighlight %}
-
-### Decoding UTF8 characters
-
-Use `decodeUtf8()` to decode UTF8-encoded bytes to a Dart string.
-
-{% highlight dart %}
-#import('dart:utf');
-
-main() {
-  var string = decodeUtf8([0xc3, 0x8e, 0xc3, 0xb1, 0xc5, 0xa3, 0xc3, 0xa9,
-                           0x72, 0xc3, 0xb1, 0xc3, 0xa5, 0xc5, 0xa3, 0xc3,
-                           0xae, 0xc3, 0xb6, 0xc3, 0xb1, 0xc3, 0xa5, 0xc4,
-                           0xbc, 0xc3, 0xae, 0xc5, 0xbe, 0xc3, 0xa5, 0xc5,
-                           0xa3, 0xc3, 0xae, 0xe1, 0xbb, 0x9d, 0xc3, 0xb1]);
-  assert(string == "Îñţérñåţîöñåļîžåţîờñ");
-}
-{% endhighlight %}
-
-### Encoding strings to UTF8 bytes
-
-Use `encodeUtf8()` to encode a Dart string as a list of UTF8-encoded bytes.
-
-{% highlight dart %}
-#import('dart:utf');
-
-main() {
-  List<int> expected = [0xc3, 0x8e, 0xc3, 0xb1, 0xc5, 0xa3, 0xc3, 0xa9, 0x72,
-                        0xc3, 0xb1, 0xc3, 0xa5, 0xc5, 0xa3, 0xc3, 0xae, 0xc3,
-                        0xb6, 0xc3, 0xb1, 0xc3, 0xa5, 0xc4, 0xbc, 0xc3, 0xae,
-                        0xc5, 0xbe, 0xc3, 0xa5, 0xc5, 0xa3, 0xc3, 0xae, 0xe1,
-                        0xbb, 0x9d, 0xc3, 0xb1];
-
-  List<int> encoded = encodeUtf8("Îñţérñåţîöñåļîžåţîờñ");
-
-  assert(() {
-    if (encoded.length != expected.length) return false;
-    for (var i = 0; i < encoded.length; i++) {
-      if (encoded[i] != expected[i]) return false;
-    }
-    return true;
-  });
-}
-{% endhighlight %}
-
-### Other functionality
-
-The UTF library can decode and encode UTF16 and UTF32 bytes.
-The library can also convert directly to and from Unicode codepoints
-and UTF8-encoded bytes. Learn more about the
-[UTF library](http://api.dartlang.org/utf.html).
-
-[Back to contents.](#toc)
-{:.up-to-toc}
-
-
-## dart:crypto - Hash codes and more {#crypto}
-
-The [Dart crypto library](http://api.dartlang.org/crypto.html)
-contains functions useful for cryptographic applications,
-such as creating cryptographic hashes and generating
-has-based message authentication codes.
-
-### Importing the crypto library
-
-To use the crypto library, import dart:crypto.
-
-{% highlight dart %}
-#import('dart:crypto');
-
-main() {
-  // The app
-}
-{% endhighlight %}
-
-### Generating cryptographic hashes
-
-You can generate [SHA256](http://api.dartlang.org/crypto/SHA256.html),
-[SHA1](http://api.dartlang.org/crypto/SHA1.html), and
-[MD5](http://api.dartlang.org/crypto/MD5.html) hashes
-(also known as *digests* or *message digests*)
-with dart:crypto. We
-recommend using SHA256, but we have included SHA1 and MD5 for
-compatibility with older systems.
-
-Learn more about
-[cryptographic hash functions](http://en.wikipedia.org/wiki/Cryptographic_hash_function).
-
-{% highlight dart %}
-#import('dart:crypto');
-
-main() {
-  var sha256 = new SHA256();
-  var digest = sha256.update("message".charCodes()).digest();
-  var hexString = CryptoUtils.bytesToHex(digest);
-  assert(hexString ==
-      'ab530a13e45914982b79f9b7e3fba994cfd1f3fb22f71cea1afbf02b460c6d1d');
-}
-{% endhighlight %}
-
-If the message content changes, the digest value also changes
-(with a very high probability).
-
-### Generating message authentication codes
-
-Use a hash-based message authentication code (HMAC) to combine a
-cryptographic hash function with a secret key.
-Learn more about [HMACs](http://en.wikipedia.org/wiki/HMAC).
-
-{% highlight dart %}
-#import('dart:crypto');
-main() {
-  var hmac = new HMAC(new SHA256(), "secretkey".charCodes());
-  var hmacDigest = hmac.update("message".charCodes()).digest();
-  var hmacHex = CryptoUtils.bytesToHex(hmacDigest);
-  assert(hmacHex ==
-      '5c3e2f56de9411068f675ef32ffa12735210b9cbfee2ba521367a3955334a343');
-}
-{% endhighlight %}
-
-If either the message contents or key changes,
-the digest value also changes (with a very high probability).
-
-### Generating Base64 strings
-
-You can represent binary data as a character string by using the
-[Base64](http://en.wikipedia.org/wiki/Base_64) encoding scheme. Use the
-`CryptoUtils.bytesToBase64()` utility method to convert a list
-of bytes into a base64-encoded string.
-
-{% highlight dart %}
-#import('dart:crypto');
-#import('dart:io');
-
-main() {
-  var file = new File('icon.ico');
-  var bytes = file.readAsBytesSync();
-  var base64 = CryptoUtils.bytesToBase64(bytes);
-  assert(base64 ==
-    "iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38G"
-    "IAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==");
-}
-{% endhighlight %}
-
-[Back to contents.](#toc)
-{:.up-to-toc}
-
-