docs(guide/filter): Refactor filter guide docs

This refactors the filter guide docs into a single file.
Also removes out of date references to the fact that Angular used to enhance Arrays while evaluating expressions.

docs/content/api/index.ngdoc

@@ -9,7 +9,7 @@ The documentation is organized into **modules** which contain various components
 These components are directives, services, filters, providers, types, global APIs and testing mocks.
 
 <div class="alert alert-info">
-**Angular Namspaces `$` and `$$`**
+**Angular Namespaces `$` and `$$`**
 
 To prevent accidental name collisions with your code,
 Angular prefixes names of public objects with `$` and names of private objects with `$$`.

docs/content/guide/concepts.ngdoc

@@ -86,7 +86,7 @@ in the rest of the documentation.
 Applied to the example above, the markup directs Angular to "take the data we got from the input widgets
 and multiply them together".
 
-The example above also contains a <a name="filter">"{@link dev_guide.templates.filters filter}"</a>.
+The example above also contains a <a name="filter">"{@link filter filter}"</a>.
 A filter formats the value of an expression for display to the user.
 In the example above, the filter {@link api/ng.filter:currency `currency`} formats a number
 into an output that looks like money.
@@ -144,7 +144,7 @@ allow to enter and calculate the costs in different currencies and also pay the
           <span ng-repeat="c in invoice.currencies">
             {{invoice.total(c) | currency:c}}
           </span>
-          <button ng-click="invoice.pay()">Pay</button>
+          <button class="btn" ng-click="invoice.pay()">Pay</button>
         </div>
       </div>
   </file>
@@ -244,7 +244,7 @@ Let's refactor our example and move the currency conversion into a service in an
           <span ng-repeat="c in invoice.currencies">
             {{invoice.total(c) | currency:c}}
           </span>
-          <button ng-click="invoice.pay()">Pay</button>
+          <button class="btn" ng-click="invoice.pay()">Pay</button>
         </div>
       </div>
   </file>
@@ -370,7 +370,7 @@ The following example shows how this is done with Angular:
           <span ng-repeat="c in invoice.currencies">
             {{invoice.total(c) | currency:c}}
           </span>
-          <button ng-click="invoice.pay()">Pay</button>
+          <button class="btn" ng-click="invoice.pay()">Pay</button>
         </div>
       </div>
   </file>

docs/content/guide/controller.ngdoc

@@ -109,7 +109,7 @@ logic. Angular offers {@link databinding databinding} for automatic DOM manipula
 you have to perform your own manual DOM manipulation, encapsulate the presentation logic in
 {@link guide/directive directives}.
 - Input formatting — Use {@link forms angular form controls} instead.
-- Output filtering — Use {@link dev_guide.templates.filters angular filters} instead.
+- Output filtering — Use {@link filter angular filters} instead.
 - Sharing stateless or stateful code across Controllers — Use {@link dev_guide.services angular
 services} instead.
 - Managing the life-cycle of other components (for example, to create service instances).

docs/content/guide/dev_guide.unit-testing.ngdoc

@@ -259,7 +259,7 @@ Notice that the test is not only much shorter but it is easier to follow what is
 that such a test tells a story, rather then asserting random bits which don't seem to be related.
 
 ## Filters
-{@link api/ng.$filter Filters} are functions which transform the data into user readable
+{@link api/ng.$filterProvider Filters} are functions which transform the data into user readable
 format. They are important because they remove the formatting responsibility from the application
 logic, further simplifying the application logic.
 

docs/content/guide/expression.ngdoc

@@ -4,12 +4,11 @@
 
 Expressions are JavaScript-like code snippets that are usually placed in bindings such as `{{
 expression }}`. Expressions are processed by the {@link api/ng.$parse $parse}
-service.
+service. Expressions are often post processed using {@link filter filters} to create a more user-friendly format.
 
 For example, these are all valid expressions in angular:
 
   * `1+2`
-  * `3*10 | currency`
   * `user.name`
 
 
@@ -29,9 +28,6 @@ You can think of Angular expressions as JavaScript expressions with following di
   * **No Control Flow Statements:** you cannot do any of the following in angular expression:
     conditionals, loops, or throw.
 
-  * **Filters:** you can pass result of expression evaluations through filter chains. For example
-    to convert date object into a local specific human-readable format.
-
 If, on the other hand, you do want to run arbitrary JavaScript code, you should make it a
 controller method and call the method. If you want to `eval()` an angular expression from
 JavaScript, use the {@link api/ng.$rootScope.Scope#methods_$eval `$eval()`} method.
@@ -150,37 +146,3 @@ You cannot write a control flow statement in an expression. The reason behind th
 Angular philosophy that application logic should be in controllers, not in the view. If you need a
 conditional, loop, or to throw from a view expression, delegate to a JavaScript method instead.
 
-
-## Filters
-
-When presenting data to the user, you might need to convert the data from its raw format to a
-user-friendly format. For example, you might have a data object that needs to be formatted
-according to the locale before displaying it to the user. You can pass expressions through a chain
-of filters like this:
-
-       name | uppercase
-
-The expression evaluator simply passes the value of name to {@link
-api/ng.filter:uppercase `uppercase`} filter.
-
-Chain filters using this syntax:
-
-       value | filter1 | filter2
-
-You can also pass colon-delimited arguments to filters, for example, to display the number 123
-with 2 decimal points:
-
-       123 | number:2
-
-# The $
-
-You might be wondering, what is the significance of the $ prefix? It is simply a prefix that
-angular uses, to differentiate its API names from others. If angular didn't use $, then evaluating
-`a.length()` would return undefined because neither a nor angular define such a property.
-
-Consider that in a future version of Angular we might choose to add a length method, in which case
-the behavior of the expression would change. Worse yet, you, the developer, could create a length
-property and then we would have a collision. This problem exists because Angular augments existing
-objects with additional behavior. By prefixing its additions with $ we are reserving our namespace
-so that angular developers and developers who use Angular can develop in harmony without collisions.
-

docs/content/guide/filter.ngdoc

@@ -0,0 +1,123 @@
+@ngdoc overview
+@name Filters
+@description
+
+A filter formats the value of an expression for display to the user. They can be used in view templates,
+controllers or services and it is easy to define your own filter.
+
+The underlying API is the {@link api/ng.$filterProvider filterProvider}.
+
+## Using filters in view templates
+
+Filters can be applied to expressions in view templates using the following syntax:
+
+        {{ expression | filter }}
+
+E.g. the markup `{{ 12 | currency }}` formats the number 12 as a currency using the {@link api/ng.filter:currency `currency`}
+filter. The resulting value is `$12.00`.
+
+Filters can be applied to the result of another filter. This is called "chaining" and uses
+the following syntax:
+
+        {{ expression | filter1 | filter2 | ... }}
+
+Filters may have arguments. The syntax for this is
+
+        {{ expression | filter:argument1:argument2:... }}
+
+E.g. the markup `{{ 1234 | number:2 }}` formats the number 1234 with 2 decimal points using the
+{@link api/ng.filter:number `number`} filter. The resulting value is `1,234.00`.
+
+
+## Using filters in controllers and services
+
+You can also use filters in controllers and services. For this, add a dependency with the name `<filterName>Filter`
+to your controller or service. E.g. using the dependency `numberFilter` will inject the number filter.
+The injected argument is a function that takes the value to format as first argument and filter parameters
+starting with the second argument.
+
+The example below uses the filter called {@link api/ng.filter:filter `filter`}.
+This filter reduces arrays into sub arrays based on
+conditions. The filter can be applied in the view template with markup like
+`{{ctrl.array | filter:'a'}}`, which would do a fulltext search for "a".
+However, using a filter in a view template will reevaluate the filter on
+every digest, which can be costly if the array is big.
+
+The example below therefore calls the filter directly in the controller.
+By this, the controller is able to call the filter only when needed (e.g. when the data is loaded from the backend
+or the filter expression is changed).
+
+<doc:example module="FilterInControllerModule">
+<doc:source>
+<script>
+  angular.module('FilterInControllerModule', []).
+    controller('FilterController', ['filterFilter', function(filterFilter) {
+      this.array = [
+        {name: 'Tobias'},
+        {name: 'Jeff'},
+        {name: 'Brian'},
+        {name: 'Igor'},
+        {name: 'James'},
+        {name: 'Brad'}
+      ];
+      this.filteredArray = filterFilter(this.array, 'a');
+    }]);
+</script>
+
+<div ng-controller="FilterController as ctrl">
+  <div>
+    All entries:
+    <span ng-repeat="entry in ctrl.array">{{entry.name}} </span>
+  </div>
+  <div>
+    Entries that contain an "a":
+    <span ng-repeat="entry in ctrl.filteredArray">{{entry.name}} </span>
+  </div>
+</div>
+</doc:source>
+</doc:example>
+
+
+## Creating custom filters
+
+Writing your own filter is very easy: just register a new filter factory function with
+your module. Internally, this uses the {@link api/ng.$filterProvider `filterProvider`}.
+This factory function should return a new filter function which takes the input value
+as the first argument. Any filter arguments are passed in as additional arguments to the filter
+function.
+
+The following sample filter reverses a text string. In addition, it conditionally makes the
+text upper-case.
+
+<doc:example module="MyReverseModule">
+<doc:source>
+<script>
+  angular.module('MyReverseModule', []).
+    filter('reverse', function() {
+      return function(input, uppercase) {
+        var out = "";
+        for (var i = 0; i < input.length; i++) {
+          out = input.charAt(i) + out;
+        }
+        // conditional based on optional argument
+        if (uppercase) {
+          out = out.toUpperCase();
+        }
+        return out;
+      }
+    });
+
+  function Ctrl($scope) {
+    $scope.greeting = 'hello';
+  }
+</script>
+
+<div ng-controller="Ctrl">
+  <input ng-model="greeting" type="greeting"><br>
+  No filter: {{greeting}}<br>
+  Reverse: {{greeting|reverse}}<br>
+  Reverse + uppercase: {{greeting|reverse:true}}<br>
+</div>
+</doc:source>
+</doc:example>
+

docs/content/guide/index.ngdoc

@@ -36,7 +36,7 @@ In Angular applications, you move the job of filling page templates with data fr
 
 * {@link api/ngRoute.$route Views and routes (see the example)}
 
-* {@link guide/dev_guide.templates.filters Filters}
+* {@link guide/filter Filters}
 
 * {@link guide/forms Forms} and [Concepts of AngularJS Forms](http://mrbool.com/the-concepts-of-angularjs-forms/29117)