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diff --git a/doc/rdoc/markup_reference.rb b/doc/rdoc/markup_reference.rb
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+require 'rdoc'
+
+# \Class \RDoc::MarkupReference exists only to provide a suitable home
+# for a reference document for \RDoc markup.
+#
+# All objects defined in this class -- classes, modules, methods, aliases,
+# attributes, and constants -- are solely for illustrating \RDoc markup,
+# and have no other legitimate use.
+#
+# = \RDoc Markup Reference
+#
+# [Note]
+#
+#   Examples in this reference are Ruby code and comments.
+#   Certain differences among the sources are noted.
+#
+# \RDoc-generated documentation is derived from and controlled by:
+#
+# - Single-line or multi-line comments that precede certain definitions.
+# - \RDoc directives in trailing comments (on the same line as code).
+# - The Ruby code itself.
+#
+# == Markup in Comments
+#
+# A single-line or multi-line comment that immediately precedes
+# the definition of a class, module, method, alias, constant, or attribute
+# becomes the documentation for that defined object.
+#
+# (\RDoc ignores other such comments that do not precede definitions.)
+#
+# === Margins
+#
+# In a multi-line comment,
+# \RDoc looks for the comment's natural left margin,
+# which becomes the <em>base margin</em> for the comment
+# and is the initial <em>current margin</em> for for the comment.
+#
+# The current margin can change, and does so, for example in a list.
+#
+# === Blocks
+#
+# It's convenient to think of markup input as a sequence of _blocks_,
+# such as:
+#
+# - {Paragraphs}[rdoc-ref:RDoc::MarkupReference@Paragraphs].
+# - {Verbatim text blocks}[rdoc-ref:RDoc::MarkupReference@Verbatim+Text+Blocks].
+# - {Code blocks}[rdoc-ref:RDoc::MarkupReference@Code+Blocks].
+# - {Bullet lists}[rdoc-ref:RDoc::MarkupReference@Bullet+Lists].
+# - {Numbered lists}[rdoc-ref:RDoc::MarkupReference@Numbered+Lists].
+# - {Lettered lists}[rdoc-ref:RDoc::MarkupReference@Lettered+Lists].
+# - {Labeled lists}[rdoc-ref:RDoc::MarkupReference@Labeled+Lists].
+# - {Headings}[rdoc-ref:RDoc::MarkupReference@Headings].
+# - {Horizontal rules}[rdoc-ref:RDoc::MarkupReference@Horizontal+Rules].
+# - {Directives}[rdoc-ref:RDoc::MarkupReference@Directives].
+#
+# All of these except paragraph blocks are distinguished by indentation,
+# or by unusual initial or embedded characters.
+#
+# ==== Paragraphs
+#
+# A paragraph consists of one or more non-empty lines of ordinary text,
+# each beginning at the current margin.
+#
+# Note: Here, <em>ordinary text</em> means text that is <em>not identified</em>
+# by indentation, or by unusual initial or embedded characters.
+# See below.
+#
+# Paragraphs are separated by one or more empty lines.
+#
+# Example input:
+#
+#   # \RDoc produces HTML and command-line documentation for Ruby projects.
+#   # \RDoc includes the rdoc and ri tools for generating and displaying
+#   # documentation from the command-line.
+#   #
+#   # You'll love it.
+#
+# Rendered HTML:
+#
+# \RDoc produces HTML and command-line documentation for Ruby projects.
+# \RDoc includes the rdoc and ri tools for generating and displaying
+# documentation from the command-line.
+#
+# You'll love it.
+#
+# A paragraph may contain nested blocks, including:
+#
+# - Verbatim text blocks.
+# - Code blocks.
+# - Lists of any type.
+#
+# ==== Verbatim Text Blocks
+#
+# Text indented farther than the current margin becomes a <em>verbatim text block</em>
+# (or a code block, described next).
+# In the rendered HTML, such text:
+#
+# - Is indented.
+# - Has a contrasting background color.
+#
+# The verbatim text block ends at the first line beginning at the current margin.
+#
+# Example input:
+#
+#   # This is not verbatim text.
+#   #
+#   #   This is verbatim text.
+#   #     Whitespace is honored.     # See?
+#   #       Whitespace is honored.     # See?
+#   #
+#   #   This is still the same verbatim text block.
+#   #
+#   # This is not verbatim text.
+#
+# Rendered HTML:
+#
+# This is not verbatim text.
+#
+#   This is verbatim text.
+#     Whitespace is honored.     # See?
+#       Whitespace is honored.     # See?
+#
+#   This is still the same verbatim text block.
+#
+# This is not verbatim text.
+# ==== Code Blocks
+#
+# A special case of verbatim text is the <em>code block</em>,
+# which is merely verbatim text that \RDoc recognizes as Ruby code:
+#
+# In the rendered HTML, the code block:
+#
+# - Is indented.
+# - Has a contrasting background color.
+# - Has syntax highlighting.
+#
+# Example:
+#
+#   def foo(name = '', value = 0)
+#     @name = name      # Whitespace is still honored.
+#     @value = value
+#   end
+#
+# Pro tip:  If your indented Ruby code does not get highlighted,
+# it may contain a syntax error.
+#
+# ==== Lists
+#
+# Each type of list item is marked by a special beginning:
+#
+# - Bullet list item: Begins with a hyphen or asterisk.
+# - Numbered list item: Begins with digits and a period.
+# - Lettered list item: Begins with an alphabetic character and a period.
+# - Labeled list item: Begins with one of:
+#   - Square-bracketed text.
+#   - A word followed by two colons.
+#
+# A list begins with a list item and continues, even across blank lines,
+# as long as list items of the same type are found at the same indentation level.
+#
+# A new list resets the current margin inward.
+# Additional lines of text aligned at that margin
+# are part of the continuing list item.
+#
+# A list item may be continued on additional lines that are aligned
+# with the first line.  See examples below.
+#
+# ===== Bullet Lists
+#
+# A bullet list item begins with a hyphen or asterisk.
+#
+# Example input:
+#
+#   # - An item.
+#   # - Another.
+#   # - An item spanning
+#   #   multiple lines.
+#   #
+#   # * Yet another.
+#   # - Last one.
+#
+# Rendered HTML:
+#
+# - An item.
+# - Another.
+# - An item spanning
+#   multiple lines.
+#
+# * Yet another.
+# - Last one.
+#
+# ===== Numbered Lists
+#
+# A numbered list item begins with digits and a period.
+#
+# The items are automatically re-numbered.
+#
+# Example input:
+#
+#   # 100. An item.
+#   # 10. Another.
+#   # 1. An item spanning
+#   #    multiple lines.
+#   #
+#   # 1. Yet another.
+#   # 1000. Last one.
+#
+# Rendered HTML:
+#
+# 100. An item.
+# 10. Another.
+# 1. An item spanning
+#    multiple lines.
+#
+# 1. Yet another.
+# 1000. Last one.
+#
+# ===== Lettered Lists
+#
+# A numbered list item begins with a letters and a period.
+#
+# The items are automatically "re-lettered."
+#
+# Example input:
+#
+#   # z. An item.
+#   # y. Another.
+#   # x. An item spanning
+#   #    multiple lines.
+#   #
+#   # x. Yet another.
+#   # a. Last one.
+#
+# Rendered HTML:
+#
+# z. An item.
+# y. Another.
+#
+# x. Yet another.
+# a. Last one.
+#
+# ===== Labeled Lists
+#
+# A labeled list item begins with one of:
+#
+# - Square-bracketed text: the label and text are on two lines.
+# - A word followed by two colons: the label and text are on the same line.
+#
+# Example input:
+#
+#   # [foo] An item.
+#   # bat:: Another.
+#   # [bag] An item spanning
+#   #       multiple lines.
+#   #
+#   # [bar baz] Yet another.
+#   # bam:: Last one.
+#
+# Rendered HTML:
+#
+# [foo] An item.
+# bat:: Another.
+# [bag] An item spanning
+#       multiple lines.
+#
+# [bar baz] Yet another.
+# bam:: Last one.
+#
+# ===== Blocks Nested in Lists
+#
+# A list item may contain nested blocks, including:
+#
+# - Paragraphs.
+# - Verbatim text blocks.
+# - Code blocks.
+# - Other lists of any type.
+#
+# ==== Headings
+#
+# A heading begins with up to six equal-signs, followed by heading text.
+# Whitespace between those and the heading text is optional.
+#
+# Examples:
+#
+#   # = Section 1
+#   # == Section 1.1
+#   # === Section 1.1.1
+#   # === Section 1.1.2
+#   # == Section 1.2
+#   # = Section 2
+#   # = Foo
+#   # == Bar
+#   # === Baz
+#   # ==== Bam
+#   # ===== Bat
+#   # ====== Bad
+#   # ============Still a Heading (Level 6)
+#   # \== Not a Heading
+#
+# ==== Horizontal Rules
+#
+# A horizontal rule begins with three or more hyphens.
+#
+# Example input:
+#
+#   # ------
+#   # Stuff between.
+#   #
+#   # \--- Not a horizontal rule.
+#   #
+#   # -- Also not a horizontal rule.
+#   #
+#   # ---
+#
+# Rendered HTML:
+#
+# ------
+# Stuff between.
+#
+# \--- Not a horizontal rule.
+#
+# -- Also not a horizontal rule.
+#
+# ---
+#
+# === Text Markup
+#
+# Text in a paragraph, list item (any type), or heading
+# may have markup formatting.
+#
+# ==== Italic
+#
+# A single word may be italicized by prefixed and suffixed underscores.
+#
+# Examples:
+#
+#   # _Word_ in paragraph.
+#   # - _Word_ in bullet list item.
+#   # 1. _Word_ in numbered list item.
+#   # a. _Word_ in lettered list item.
+#   # [_word_] _Word_ in labeled list item.
+#   # ====== _Word_ in heading
+#
+# Any text may be italicized via HTML tag +i+ or +em+.
+#
+# Examples:
+#
+#   # <i>Two words</i> in paragraph.
+#   # - <i>Two words</i> in bullet list item.
+#   # 1. <i>Two words</i> in numbered list item.
+#   # a. <i>Two words</i> in lettered list item.
+#   # [<i>Two words</i>] <i>Two words</i> in labeled list item.
+#   # ====== <i>Two words</i> in heading
+#
+# ==== Bold
+#
+# A single word may be made bold by prefixed and suffixed asterisks.
+#
+# Examples:
+#
+#   # *Word* in paragraph.
+#   # - *Word* in bullet list item.
+#   # 1. *Word* in numbered list item.
+#   # a. *Word* in lettered list item.
+#   # [*word*] *Word* in labeled list item.
+#   # ====== *Word* in heading
+#
+# Any text may be made bold via HTML tag +b+.
+#
+# Examples:
+#
+#   # <b>Two words</b> in paragraph.
+#   # - <b>Two words</b> in bullet list item.
+#   # 1. <b>Two words</b> in numbered list item.
+#   # a. <b>Two words</b> in lettered list item.
+#   # [<b>Two words</b>] <b>Two words</b> in labeled list item.
+#   # ====== <b>Two words</b> in heading
+#
+# ==== Monofont
+#
+# A single word may be made monofont -- sometimes called "typewriter font" --
+# by prefixed and suffixed plus-signs.
+#
+# Examples:
+#
+#   # +Word+ in paragraph.
+#   # - +Word+ in bullet list item.
+#   # 1. +Word+ in numbered list item.
+#   # a. +Word+ in lettered list item.
+#   # [+word+] +Word+ in labeled list item.
+#   # ====== +Word+ in heading
+#
+# Any text may be made monofont via HTML tag +tt+ or +code+.
+#
+# Examples:
+#
+#   # <tt>Two words</tt> in paragraph.
+#   # - <tt>Two words</tt> in bullet list item.
+#   # 1. <tt>Two words</tt> in numbered list item.
+#   # a. <tt>Two words</tt> in lettered list item.
+#   # [<tt>Two words</tt>] <tt>Two words</tt> in labeled list item.
+#   # ====== <tt>Two words</tt> in heading
+#
+# ==== Character Conversions
+#
+# Certain combinations of characters may be converted to special characters;
+# whether the conversion occurs depends on whether the special character
+# is available in the current encoding.
+#
+# - <tt>(c)</tt> converts to (c) (copyright character); must be lowercase.
+#
+# - <tt>(r)</tt> converts to (r) (registered trademark character); must be lowercase.
+#
+# - <tt>'foo'</tt> converts to 'foo' (smart single-quotes).
+#
+# - <tt>"foo"</tt> converts to "foo" (smart double-quotes).
+#
+# - <tt>foo ... bar</tt> converts to foo ... bar (1-character ellipsis).
+#
+# - <tt>foo -- bar</tt> converts to foo -- bar (1-character en-dash).
+#
+# - <tt>foo --- bar</tt> converts to foo --- bar (1-character em-dash).
+#
+# ==== Links
+#
+# Certain strings in \RDoc text are converted to links.
+# Any such link may be suppressed by prefixing a backslash.
+# This section shows how to link to various
+# targets.
+#
+# [Class]
+#
+#   - On-page: <tt>DummyClass</tt> links to DummyClass.
+#   - Off-page: <tt>RDoc::Alias</tt> links to RDoc::Alias.
+#
+# [Module]
+#
+#   - On-page: <tt>DummyModule</tt> links to DummyModule.
+#   - Off-page: <tt>RDoc</tt> links to RDoc.
+#
+# [Constant]
+#
+#   - On-page: <tt>DUMMY_CONSTANT</tt> links to DUMMY_CONSTANT.
+#   - Off-page: <tt>RDoc::Text::MARKUP_FORMAT</tt> links to RDoc::Text::MARKUP_FORMAT.
+#
+# [Singleton Method]
+#
+#   - On-page: <tt>::dummy_singleton_method</tt> links to ::dummy_singleton_method.
+#   - Off-page<tt>RDoc::TokenStream::to_html</tt> links to RDoc::TokenStream::to_html.
+#     to \RDoc::TokenStream::to_html.
+#
+#   Note: Occasionally \RDoc is not linked to a method whose name
+#   has only special characters. Check whether the links you were expecting
+#   are actually there.  If not, you'll need to put in an explicit link;
+#   see below.
+#
+#   Pro tip: The link to any method is available in the alphabetical table of contents
+#   at the top left of the page for the class or module.
+#
+# [Instance Method]
+#
+#   - On-page: <tt>#dummy_instance_method</tt> links to #dummy_instance_method.
+#   - Off-page: <tt>RDoc::Alias#html_name</tt> links to RDoc::Alias#html_name.
+#
+#     See the Note and Pro Tip immediately above.
+#
+# [Attribute]
+#
+#   - On-page: <tt>#dummy_attribute</tt> links to #dummy_attribute.
+#   - Off-page: <tt>RDoc::Alias#name</tt> links to RDoc::Alias#name.
+#
+# [Alias]
+#
+#   - On-page: <tt>#dummy_instance_alias</tt> links to #dummy_instance_alias.
+#   - Off-page: <tt>RDoc::Alias#new_name</tt> links to RDoc::Alias#new_name.
+#
+# [Protocol +http+]
+#
+#   - Linked: <tt>http://yahoo.com</tt> links to http://yahoo.com.
+#
+# [Protocol +https+]
+#
+#   - Linked: <tt>https://github.com</tt> links to https://github.com.
+#
+# [Protocol +www+]
+#
+#   - Linked: <tt>www.yahoo.com</tt> links to www.yahoo.com.
+#
+# [Protocol +ftp+]
+#
+#   - Linked: <tt>ftp://nosuch.site</tt> links to ftp://nosuch.site.
+#
+# [Protocol +mailto+]
+#
+#   - Linked:  <tt>mailto:/foo@bar.com</tt> links to mailto://foo@bar.com.
+#
+# [Protocol +irc+]
+#
+#   - link: <tt>irc://irc.freenode.net/ruby</tt> links to irc://irc.freenode.net/ruby.
+#
+# [Image Filename Extensions]
+#
+#   - Link: <tt>https://www.ruby-lang.org/images/header-ruby-logo@2x.png</tt> is
+#     converted to an in-line HTML +img+ tag, which displays the image in the HTML:
+#
+#     https://www.ruby-lang.org/images/header-ruby-logo@2x.png
+#
+#     Also works for +bmp+, +gif+, +jpeg+, and +jpg+ files.
+#
+#     Note: Works only for a fully qualified URL.
+#
+# [Heading]
+#
+#   - Link: <tt>RDoc::RD@LICENSE</tt> links to RDoc::RDoc::RD@LICENSE.
+#
+#   Note that spaces in the actual heading are represented by <tt>+</tt> characters
+#   in the linkable text.
+#
+#   - Link: <tt>RDoc::Options@Saved+Options</tt>
+#     links to RDoc::Options@Saved+Options.
+#
+#   Punctuation and other special characters must be escaped like CGI.escape.
+#
+#   Pro tip: The link to any heading is available in the alphabetical table of contents
+#   at the top left of the page for the class or module.
+#
+# [Section]
+#
+#   See {Directives for Organizing Documentation}[#class-RDoc::MarkupReference-label-Directives+for+Organizing+Documentation].
+#
+#   - Link: <tt>RDoc::Markup::ToHtml@Visitor</tt> links to RDoc::Markup::ToHtml@Visitor.
+#
+#   If a section and a heading share the same name, the link target is the section.
+#
+# [Single-Word Text Link]
+#
+#   Use square brackets to create single-word text link:
+#
+#   - <tt>GitHub[https://github.com]</tt> links to GitHub[https://github.com].
+#
+# [Multi-Word Text Link]
+#
+#   Use square brackets and curly braces to create a multi-word text link.
+#
+#   - <tt>{GitHub home page}[https://github.com]</tt> links to
+#     {GitHub home page}[https://github.com].
+#
+# [<tt>rdoc-ref</tt> Scheme]
+#
+#   A link with the <tt>rdoc-ref:</tt> scheme links to the referenced item,
+#   if that item exists.
+#   The referenced item may be a class, module, method, file, etc.
+#
+#   - Class: <tt>Alias[rdoc-ref:RDoc::Alias]</tt> links to Alias[rdoc-ref:RDoc::Alias].
+#   - Module: <tt>RDoc[rdoc-ref:RDoc]</tt> links to RDoc[rdoc-ref:RDoc].
+#   - Method: <tt>foo[rdoc-ref:RDoc::Markup::ToHtml#handle_regexp_RDOCLINK]</tt>
+#     links to foo[rdoc-ref:RDoc::Markup::ToHtml#handle_regexp_RDOCLINK].
+#   - Constant: <tt>bar[rdoc-ref:RDoc::Markup::ToHtml::LIST_TYPE_TO_HTML]</tt>
+#     links to bar[rdoc-ref:RDoc::Markup::ToHtml::LIST_TYPE_TO_HTML].
+#   - Attribute: <tt>baz[rdoc-ref:RDoc::Markup::ToHtml#code_object]</tt>
+#     links to baz[rdoc-ref:RDoc::Markup::ToHtml#code_object].
+#   - Alias: <tt>bad[rdoc-ref:RDoc::MarkupReference#dummy_instance_alias]</tt> links to
+#     bad[rdoc-ref:RDoc::MarkupReference#dummy_instance_alias].
+#
+#   If the referenced item does not exist, no link is generated
+#   and entire <tt>rdoc-ref:</tt> square-bracketed clause is removed
+#   from the resulting text.
+#
+#   - <tt>Nosuch[rdoc-ref:RDoc::Nosuch]</tt> is rendered as
+#     Nosuch[rdoc-ref:RDoc::Nosuch].
+#
+#
+# [<tt>rdoc-label</tt> Scheme]
+#
+#   [Simple]
+#
+#     You can specify a link target using this form,
+#     where the second part cites the id of an HTML element.
+#
+#     This link refers to the constant +DUMMY_CONSTANT+ on this page:
+#
+#     - <tt>{DUMMY_CONSTANT}[rdoc-label:DUMMY_CONSTANT]</tt>
+#
+#     Thus:
+#
+#     {DUMMY_CONSTANT}[rdoc-label:DUMMY_CONSTANT]
+#
+#   [With Return]
+#
+#     You can specify both a link target and a local label
+#     that can be used as the target for a return link.
+#     These two links refer to each other:
+#
+#     - <tt>{go to addressee}[rdoc-label:addressee:sender]</tt>
+#     - <tt>{return to sender}[rdoc-label:sender:addressee]</tt>
+#
+#     Thus:
+#
+#     {go to addressee}[rdoc-label:addressee:sender]
+#
+#     Some text.
+#
+#     {return to sender}[rdoc-label:sender:addressee]
+#
+# [<tt>link:</tt> Scheme]
+#
+#   - <tt>link:README_rdoc.html</tt> links to link:README_rdoc.html.
+#
+# [<tt>rdoc-image</tt> Scheme]
+#
+#   Use the <tt>rdoc-image</tt> scheme to display an image that is also a link:
+#
+#     # {rdoc-image:path/to/image}[link_target]
+#
+#   - Link: <tt>{rdoc-image:https://www.ruby-lang.org/images/header-ruby-logo@2x.png}[https://www.ruby-lang.org]</tt>
+#     displays image <tt>https://www.ruby-lang.org/images/header-ruby-logo@2x.png</tt>
+#     as a link to <tt>https://www.ruby-lang.org</tt>.
+#
+#     {rdoc-image:https://www.ruby-lang.org/images/header-ruby-logo@2x.png}[https://www.ruby-lang.org]
+#
+#   A relative path as the target also works:
+#
+#   - Link: <tt>{rdoc-image:https://www.ruby-lang.org/images/header-ruby-logo@2x.png}[./Alias.html]</tt> links to <tt>./Alias.html</tt>
+#
+#     {rdoc-image:https://www.ruby-lang.org/images/header-ruby-logo@2x.png}[./Alias.html]
+#
+# === Directives
+#
+# ==== Directives for Allowing or Suppressing Documentation
+#
+# Each directive described in this section must appear on a line by itself.
+#
+# - [<tt>:stopdoc:</tt>]
+# Specifies that \RDoc should ignore markup
+# until next <tt>:startdoc:</tt> directive or end-of-file.
+# - [<tt>:startdoc:</tt>]
+#   Specifies that \RDoc should resume parsing markup.
+# - [<tt>:enddoc:</tt>]
+#   Specifies that \RDoc should ignore markup to end-of-file
+#   regardless of other directives.
+#
+# For Ruby code, but not for other \RDoc sources,
+# there is a shorthand for [<tt>:stopdoc:</tt>] and [<tt>:startdoc:</tt>]:
+#
+#   # Documented.
+#   #--
+#   # Not documented.
+#   #++
+#   # Documented.
+#
+# ==== Directive for Specifying \RDoc Source Format
+#
+# This directive described must appear on a line by itself.
+#
+# - [<tt>:markup: _type_</tt>]
+#   Specifies the format for the \RDoc input.
+#   Parameter +type+ is one of +markdown+, +rd+, +rdoc+, +tomdoc+.
+#
+# ==== Directives for HTML Output
+#
+# Each directive described in this section must appear on a line by itself.
+#
+# - [<tt>:title: _text_</tt>]
+#   Specifies the title for the HTML output.
+# - [<tt>:main: _file_name_</tt>]
+#   Specifies the HTML file to be displayed first.
+#
+# ==== Directives for Method Documentation
+#
+# - [<tt>:call-seq:</tt>]
+#   For the given method, specifies the calling sequence to be reported in the HTML,
+#   overriding the actual calling sequence in the Ruby code.
+#   See method #call_seq_directive.
+# - [<tt>:args: _arg_names_</tt> (aliased as <tt>:arg</tt>)]
+#   For the given method, specifies the arguments to be reported in the HTML,
+#   overriding the actual arguments in the Ruby code.
+#   See method #args_directive.
+# - [<tt>:yields: _arg_names_</tt> (aliased as <tt>:yield:</tt>)]
+#   For the given method, specifies the yield arguments to be reported in the HTML,
+#   overriding the actual yield in the Ruby code.
+#   See method #yields_directive.
+#
+# Note that \RDoc can build the calling sequence for a Ruby-coded method,
+# but not for other languages.
+# You may want to override that by explicitly giving a <tt>:call-seq:</tt>
+# directive if you want to include:
+#
+# - A return type, which is not automatically inferred.
+# - Multiple calling sequences.
+#
+# ==== Directives for Organizing Documentation
+#
+# By default, \RDoc groups:
+#
+# - Singleton methods together in alphabetical order.
+# - Instance methods and their aliases together in alphabetical order.
+# - Attributes and their aliases together in alphabetical order.
+#
+# You can use directives to modify those behaviors.
+#
+# - [<tt>:section: _section_title_</tt>]
+#
+#   Directive <tt>:section: <em>section_title</em></tt> specifies that
+#   following methods are to be grouped into a section
+#   with the given <em>section_title</em> as its heading.
+#   This directive remains in effect until another such directive is given,
+#   but may be temporarily overridden by directive <tt>:category:</tt>.
+#   See below.
+#
+#   Directive <tt>:section:</tt> with no title reverts to the default section.
+#
+#   The comment block containing this directive:
+#
+#   - Must be separated by a blank line from the documentation for the next item.
+#   - May have one or more lines preceding the directive.
+#     These will be removed, along with any trailing lines that match them.
+#     Such lines may be visually helpful.
+#   - Lines of text that are not so removed become the descriptive text
+#     for the section.
+#
+#   Example:
+#
+#     # ----------------------------------------
+#     # :section: My Section
+#     # This is the section that I wrote.
+#     # See it glisten in the noon-day sun.
+#     # ----------------------------------------
+#
+#     ##
+#     # Comment for some_method
+#     def some_method
+#       # ...
+#     end
+#
+#   You can use directive <tt>:category:</tt> to temporarily
+#   override the current section.
+#
+# - [<tt>:category: _section_title_</tt>]
+#
+#   Directive <tt>:category: <em>section_title</em></tt> specifies that
+#   just one following method is to be included in the given section.
+#   Subsequent methods are to be grouped into the current section.
+#
+#   Directive <tt>:category:</tt> with no title specifies that just one
+#   following method is to be included in the default section.
+#
+# ==== Directive for Including a File
+#
+# - [<tt>:include: _filename_</tt>]
+#
+#   Include the contents of the named file at this point.
+#   This directive must appear alone on one line, possibly preceded by spaces.
+#   In this position, it can be escaped with a backslash in front of the first colon.
+#
+#   The file is searched for in the directories
+#   given with the <tt>--include</tt> command-line option,
+#   or in the current directory by default.
+#   The file content is shifted to have the same indentation as the colon
+#   at the start of the directive.
+#
+# == Markup in Code
+#
+# === Directives in Trailing Comments
+#
+# Each \RDoc directive in this section appears in a trailing
+# comment in a line of code.
+#
+# - [<tt>:nodoc:</tt>]
+#   - Appears in a trailing comment on a line of code
+#     that defines a class, module, method, alias, constant, or attribute.
+#   - Specifies that the defined object should not be documented.
+# - [<tt>:nodoc: all</tt>]
+#   - Appears in a trailing comment on a line of code
+#     that defines a class or module.
+#   - Specifies that the class or module should not be documented.
+#     By default, however, a nested class or module _will_ be documented
+# - [<tt>:doc:</tt>]
+#   - Appears in a trailing comment on a line of code
+#     that defines a class, module, method, alias, constant, or attribute.
+#   - Specifies the defined object should be documented, even if otherwise
+#     would not be documented.
+# - [<tt>:notnew:</tt> (aliased as <tt>:not_new</tt> and <tt>:not-new:</tt>)]
+#   - Appears in a trailing comment on a line of code
+#     that defines instance method +initialize+.
+#   - Specifies that singleton method +new+ should not be documented.
+#     By default, Ruby fakes a corresponding singleton method +new+,
+#     which \RDoc includes in the documentaton.
+#     Note that instance method +initialize+ is private, and so by default
+#     is not documented.
+#
+# == Documentation Derived from Ruby Code
+#
+# [Class]
+#
+#   By default, \RDoc documents:
+#
+#   - \Class name.
+#   - Parent class.
+#   - Singleton methods.
+#   - Instance methods.
+#   - Aliases.
+#   - Constants.
+#   - Attributes.
+#
+# [Module]
+#
+#   By default, \RDoc documents:
+#
+#   - \Module name.
+#   - \Singleton methods.
+#   - Instance methods.
+#   - Aliases.
+#   - Constants.
+#   - Attributes.
+#
+# [Method]
+#
+#   By default, \RDoc documents:
+#
+#   - \Method name.
+#   - Arguments.
+#   - Yielded values.
+#
+#   See #method.
+#
+# [Alias]
+#
+#   By default, \RDoc documents:
+#
+#   - Alias name.
+#   - Aliased name.
+#
+#   See #dummy_instance_alias and #dummy_instance_method.
+#
+# [Constant]
+#
+#   By default, \RDoc documents:
+#
+#   - \Constant name.
+#
+#   See DUMMY_CONSTANT.
+#
+# [Attribute]
+#
+#   By default, \RDoc documents:
+#
+#   - Attribute name.
+#   - Attribute type (<tt>[R]</tt>, <tt>[W]</tt>, or <tt>[RW]</tt>)
+#
+#   See #dummy_attribute.
+#
+class RDoc::MarkupReference
+
+  class DummyClass; end
+  module DummyModule; end
+  def self.dummy_singleton_method(foo, bar); end
+  def dummy_instance_method(foo, bar); end;
+  alias dummy_instance_alias dummy_instance_method
+  attr_accessor :dummy_attribute
+  alias dummy_attribute_alias dummy_attribute
+  DUMMY_CONSTANT = ''
+
+  # :call-seq:
+  #   call_seq_directive(foo, bar)
+  #   Can be anything -> bar
+  #   Also anything more -> baz or bat
+  #
+  # The <tt>:call-seq:</tt> directive overrides the actual calling sequence
+  # found in the Ruby code.
+  #
+  # - It can specify anything at all.
+  # - It can have multiple calling sequences.
+  #
+  # This one includes <tt>Can be anything -> foo</tt>, which is nonsense.
+  #
+  # Note that the "arrow" is two characters, hyphen and right angle-bracket,
+  # which is made into a single character in the HTML.
+  #
+  # Click on the calling sequence to see the code.
+  #
+  # Here is the <tt>:call-seq:</tt> directive given for the method:
+  #
+  #   # :call-seq:
+  #   #   call_seq_directive(foo, bar)
+  #   #   Can be anything -> bar
+  #   #   Also anything more -> baz or bat
+  #
+  def call_seq_directive
+    nil
+  end
+
+  # The <tt>:args:</tt> directive overrides the actual arguments found in the Ruby code.
+  #
+  # Click on the calling sequence to see the code.
+  #
+  def args_directive(foo, bar) # :args: baz
+    nil
+  end
+
+  # The <tt>:yields:</tt> directive overrides the actual yield found in the Ruby code.
+  #
+  # Click on the calling sequence to see the code.
+  #
+  def yields_directive(foo, bar) # :yields: 'bat'
+    yield 'baz'
+  end
+
+  # This method is documented only by \RDoc, except for these comments.
+  #
+  # Click on the calling sequence to see the code.
+  #
+  def method(foo, bar)
+    yield 'baz'
+  end
+
+end
\ No newline at end of file