1 files changed, 52 insertions, 3 deletions
diff --git a/guides/source/active_support_core_extensions.md b/guides/source/active_support_core_extensions.md
index c012ded888..7f65d920df 100644
--- a/guides/source/active_support_core_extensions.md
+++ b/guides/source/active_support_core_extensions.md
@@ -418,6 +418,14 @@ TIP: Since `with_options` forwards calls to its receiver they can be nested. Eac
 
 NOTE: Defined in `active_support/core_ext/object/with_options.rb`.
 
+### JSON support
+
+Active Support provides a better implemention of `to_json` than the +json+ gem ordinarily provides for Ruby objects. This is because some classes, like +Hash+ and +OrderedHash+ needs special handling in order to provide a proper JSON representation.
+
+Active Support also provides an implementation of `as_json` for the <tt>Process::Status</tt> class.
+
+NOTE: Defined in `active_support/core_ext/object/to_json.rb`.
+
 ### Instance Variables
 
 Active Support provides several methods to ease access to instance variables.
@@ -439,6 +447,22 @@ C.new(0, 1).instance_values # => {"x" => 0, "y" => 1}
 
 NOTE: Defined in `active_support/core_ext/object/instance_variables.rb`.
 
+#### `instance_variable_names`
+
+The method `instance_variable_names` returns an array.  Each name includes the "@" sign.
+
+```ruby
+class C
+  def initialize(x, y)
+    @x, @y = x, y
+  end
+end
+
+C.new(0, 1).instance_variable_names # => ["@x", "@y"]
+```
+
+NOTE: Defined in `active_support/core_ext/object/instance_variables.rb`.
+
 ### Silencing Warnings, Streams, and Exceptions
 
 The methods `silence_warnings` and `enable_warnings` change the value of `$VERBOSE` accordingly for the duration of their block, and reset it afterwards:
@@ -1038,7 +1062,7 @@ For convenience `class_attribute` also defines an instance predicate which is th
 
 When `:instance_reader` is `false`, the instance predicate returns a `NoMethodError` just like the reader method.
 
-If you do not want the instance predicate,  pass `instance_predicate: false` and it will not be defined.
+If you do not want the instance predicate, pass `instance_predicate: false` and it will not be defined.
 
 NOTE: Defined in `active_support/core_ext/class/attribute.rb`
 
@@ -1423,7 +1447,7 @@ The method `pluralize` returns the plural of its receiver:
 
 As the previous example shows, Active Support knows some irregular plurals and uncountable nouns. Built-in rules can be extended in `config/initializers/inflections.rb`. That file is generated by the `rails` command and has instructions in comments.
 
-`pluralize` can also take an optional `count` parameter.  If `count == 1` the singular form will be returned.  For any other value of `count` the plural form will be returned:
+`pluralize` can also take an optional `count` parameter. If `count == 1` the singular form will be returned. For any other value of `count` the plural form will be returned:
 
 ```ruby
 "dude".pluralize(0) # => "dudes"
@@ -2011,8 +2035,33 @@ NOTE: Defined in `active_support/core_ext/integer/inflections.rb`.
 
 Extensions to `BigDecimal`
 --------------------------
+### `to_s`
 
-...
+The method `to_s` is aliased to `to_formatted_s`. This provides a convenient way to display a BigDecimal value in floating-point notation:
+
+```ruby
+BigDecimal.new(5.00, 6).to_s  # => "5.0"
+```
+
+### `to_formatted_s`
+
+Te method `to_formatted_s` provides a default specifier of "F".  This means that a simple call to `to_formatted_s` or `to_s` will result in floating point representation instead of engineering notation:
+
+```ruby
+BigDecimal.new(5.00, 6).to_formatted_s  # => "5.0"
+```
+
+and that symbol specifiers are also supported:
+
+```ruby
+BigDecimal.new(5.00, 6).to_formatted_s(:db)  # => "5.0"
+```
+
+Engineering notation is still supported:
+
+```ruby
+BigDecimal.new(5.00, 6).to_formatted_s("e")  # => "0.5E1"
+```
 
 Extensions to `Enumerable`
 --------------------------