+</li>
+
+<li><a name="cl::desc">The <b><tt>cl::desc</tt></b></a> attribute specifies a
+description for the option to be shown in the <tt>--help</tt> output for the
+program.</li>
+
+<li><a name="cl::value_desc">The <b><tt>cl::value_desc</tt></b></a> attribute
+specifies a string that can be used to fine tune the <tt>--help</tt> output for
+a command line option. Look <a href="#value_desc_example">here</a> for an
+example.</li>
+
+<li><a name="cl::init">The <b><tt>cl::init</tt></b></a> attribute specifies an
+inital value for a <a href="#cl::opt">scalar</a> option. If this attribute is
+not specified then the command line option value defaults to the value created
+by the default constructor for the type. <b>Warning</b>: If you specify both
+<b><tt>cl::init</tt></b> and <b><tt>cl::location</tt></b> for an option,
+you must specify <b><tt>cl::location</tt></b> first, so that when the
+command-line parser sees <b><tt>cl::init</tt></b>, it knows where to put the
+initial value. (You will get an error at runtime if you don't put them in
+the right order.)</li>
+
+<li><a name="cl::location">The <b><tt>cl::location</tt></b></a> attribute where to
+store the value for a parsed command line option if using external storage. See
+the section on <a href="#storage">Internal vs External Storage</a> for more
+information.</li>
+
+<li><a name="cl::aliasopt">The <b><tt>cl::aliasopt</tt></b></a> attribute
+specifies which option a <tt><a href="#cl::alias">cl::alias</a></tt> option is
+an alias for.</li>
+
+<li><a name="cl::values">The <b><tt>cl::values</tt></b></a> attribute specifies
+the string-to-value mapping to be used by the generic parser. It takes a
+<b>clEnumValEnd terminated</b> list of (option, value, description) triplets
+that
+specify the option name, the value mapped to, and the description shown in the
+<tt>--help</tt> for the tool. Because the generic parser is used most
+frequently with enum values, two macros are often useful:
+
+<ol>
+
+<li><a name="clEnumVal">The <b><tt>clEnumVal</tt></b></a> macro is used as a
+nice simple way to specify a triplet for an enum. This macro automatically
+makes the option name be the same as the enum name. The first option to the
+macro is the enum, the second is the description for the command line
+option.</li>
+
+<li><a name="clEnumValN">The <b><tt>clEnumValN</tt></b></a> macro is used to
+specify macro options where the option name doesn't equal the enum name. For
+this macro, the first argument is the enum value, the second is the flag name,
+and the second is the description.</li>
+
+</ol>
+
+You will get a compile time error if you try to use cl::values with a parser
+that does not support it.</li>
+
+</ul>
+
+</div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <a name="modifiers">Option Modifiers</a>
+</div>
+
+<div class="doc_text">
+
+<p>Option modifiers are the flags and expressions that you pass into the
+constructors for <tt><a href="#cl::opt">cl::opt</a></tt> and <tt><a
+href="#cl::list">cl::list</a></tt>. These modifiers give you the ability to
+tweak how options are parsed and how <tt>--help</tt> output is generated to fit
+your application well.</p>
+
+<p>These options fall into five main catagories:</p>
+
+<ol>
+<li><a href="#hiding">Hiding an option from <tt>--help</tt> output</a></li>
+<li><a href="#numoccurrences">Controlling the number of occurrences
+ required and allowed</a></li>
+<li><a href="#valrequired">Controlling whether or not a value must be
+ specified</a></li>
+<li><a href="#formatting">Controlling other formatting options</a></li>
+<li><a href="#misc">Miscellaneous option modifiers</a></li>
+</ol>
+
+<p>It is not possible to specify two options from the same catagory (you'll get
+a runtime error) to a single option, except for options in the miscellaneous
+catagory. The CommandLine library specifies defaults for all of these settings
+that are the most useful in practice and the most common, which mean that you
+usually shouldn't have to worry about these.</p>
+
+</div>
+
+<!-- _______________________________________________________________________ -->
+<div class="doc_subsubsection">
+ <a name="hiding">Hiding an option from <tt>--help</tt> output</a>
+</div>
+
+<div class="doc_text">
+
+<p>The <tt>cl::NotHidden</tt>, <tt>cl::Hidden</tt>, and
+<tt>cl::ReallyHidden</tt> modifiers are used to control whether or not an option
+appears in the <tt>--help</tt> and <tt>--help-hidden</tt> output for the
+compiled program:</p>
+
+<ul>
+
+<li><a name="cl::NotHidden">The <b><tt>cl::NotHidden</tt></b></a> modifier
+(which is the default for <tt><a href="#cl::opt">cl::opt</a></tt> and <tt><a
+href="#cl::list">cl::list</a></tt> options) indicates the option is to appear
+in both help listings.</li>
+
+<li><a name="cl::Hidden">The <b><tt>cl::Hidden</tt></b></a> modifier (which is the
+default for <tt><a href="#cl::alias">cl::alias</a></tt> options) indicates that
+the option should not appear in the <tt>--help</tt> output, but should appear in
+the <tt>--help-hidden</tt> output.</li>
+
+<li><a name="cl::ReallyHidden">The <b><tt>cl::ReallyHidden</tt></b></a> modifier
+indicates that the option should not appear in any help output.</li>
+
+</ul>
+
+</div>
+
+<!-- _______________________________________________________________________ -->
+<div class="doc_subsubsection">
+ <a name="numoccurrences">Controlling the number of occurrences required and
+ allowed</a>
+</div>
+
+<div class="doc_text">
+
+<p>This group of options is used to control how many time an option is allowed
+(or required) to be specified on the command line of your program. Specifying a
+value for this setting allows the CommandLine library to do error checking for
+you.</p>
+
+<p>The allowed values for this option group are:</p>
+
+<ul>
+
+<li><a name="cl::Optional">The <b><tt>cl::Optional</tt></b></a> modifier (which
+is the default for the <tt><a href="#cl::opt">cl::opt</a></tt> and <tt><a
+href="#cl::alias">cl::alias</a></tt> classes) indicates that your program will
+allow either zero or one occurrence of the option to be specified.</li>
+
+<li><a name="cl::ZeroOrMore">The <b><tt>cl::ZeroOrMore</tt></b></a> modifier
+(which is the default for the <tt><a href="#cl::list">cl::list</a></tt> class)
+indicates that your program will allow the option to be specified zero or more
+times.</li>
+
+<li><a name="cl::Required">The <b><tt>cl::Required</tt></b></a> modifier
+indicates that the specified option must be specified exactly one time.</li>
+
+<li><a name="cl::OneOrMore">The <b><tt>cl::OneOrMore</tt></b></a> modifier
+indicates that the option must be specified at least one time.</li>
+
+<li>The <b><tt>cl::ConsumeAfter</tt></b> modifier is described in the <a
+href="#positional">Positional arguments section</a>.</li>
+
+</ul>
+
+<p>If an option is not specified, then the value of the option is equal to the
+value specified by the <tt><a href="#cl::init">cl::init</a></tt> attribute. If
+the <tt><a href="#cl::init">cl::init</a></tt> attribute is not specified, the
+option value is initialized with the default constructor for the data type.</p>
+
+<p>If an option is specified multiple times for an option of the <tt><a
+href="#cl::opt">cl::opt</a></tt> class, only the last value will be
+retained.</p>
+
+</div>
+
+<!-- _______________________________________________________________________ -->
+<div class="doc_subsubsection">
+ <a name="valrequired">Controlling whether or not a value must be specified</a>
+</div>
+
+<div class="doc_text">
+
+<p>This group of options is used to control whether or not the option allows a
+value to be present. In the case of the CommandLine library, a value is either
+specified with an equal sign (e.g. '<tt>-index-depth=17</tt>') or as a trailing
+string (e.g. '<tt>-o a.out</tt>').</p>
+
+<p>The allowed values for this option group are:</p>
+
+<ul>
+
+<li><a name="cl::ValueOptional">The <b><tt>cl::ValueOptional</tt></b></a> modifier
+(which is the default for <tt>bool</tt> typed options) specifies that it is
+acceptable to have a value, or not. A boolean argument can be enabled just by
+appearing on the command line, or it can have an explicit '<tt>-foo=true</tt>'.
+If an option is specified with this mode, it is illegal for the value to be
+provided without the equal sign. Therefore '<tt>-foo true</tt>' is illegal. To
+get this behavior, you must use the <a
+href="#cl::ValueRequired">cl::ValueRequired</a> modifier.</li>
+
+<li><a name="cl::ValueRequired">The <b><tt>cl::ValueRequired</tt></b></a> modifier
+(which is the default for all other types except for <a
+href="#onealternative">unnamed alternatives using the generic parser</a>)
+specifies that a value must be provided. This mode informs the command line
+library that if an option is not provides with an equal sign, that the next
+argument provided must be the value. This allows things like '<tt>-o
+a.out</tt>' to work.</li>
+
+<li><a name="cl::ValueDisallowed">The <b><tt>cl::ValueDisallowed</tt></b></a>
+modifier (which is the default for <a href="#onealternative">unnamed
+alternatives using the generic parser</a>) indicates that it is a runtime error
+for the user to specify a value. This can be provided to disallow users from
+providing options to boolean options (like '<tt>-foo=true</tt>').</li>
+
+</ul>
+
+<p>In general, the default values for this option group work just like you would
+want them to. As mentioned above, you can specify the <a
+href="#cl::ValueDisallowed">cl::ValueDisallowed</a> modifier to a boolean
+argument to restrict your command line parser. These options are mostly useful
+when <a href="#extensionguide">extending the library</a>.</p>
+
+</div>
+
+<!-- _______________________________________________________________________ -->
+<div class="doc_subsubsection">
+ <a name="formatting">Controlling other formatting options</a>
+</div>
+
+<div class="doc_text">
+
+<p>The formatting option group is used to specify that the command line option
+has special abilities and is otherwise different from other command line
+arguments. As usual, you can only specify one of these arguments at most.</p>
+
+<ul>
+
+<li><a name="cl::NormalFormatting">The <b><tt>cl::NormalFormatting</tt></b></a>
+modifier (which is the default all options) specifies that this option is
+"normal".</li>
+
+<li><a name="cl::Positional">The <b><tt>cl::Positional</tt></b></a> modifier
+specifies that this is a positional argument that does not have a command line
+option associated with it. See the <a href="#positional">Positional
+Arguments</a> section for more information.</li>
+
+<li>The <b><a href="#cl::ConsumeAfter"><tt>cl::ConsumeAfter</tt></a></b> modifier
+specifies that this option is used to capture "interpreter style" arguments. See <a href="#cl::ConsumeAfter">this section for more information</a>.</li>
+
+<li><a name="cl::Prefix">The <b><tt>cl::Prefix</tt></b></a> modifier specifies
+that this option prefixes its value. With 'Prefix' options, the equal sign does
+not separate the value from the option name specified. Instead, the value is
+everything after the prefix, including any equal sign if present. This is useful
+for processing odd arguments like <tt>-lmalloc</tt> and <tt>-L/usr/lib</tt> in a
+linker tool or <tt>-DNAME=value</tt> in a compiler tool. Here, the
+'<tt>l</tt>', '<tt>D</tt>' and '<tt>L</tt>' options are normal string (or list)
+options, that have the <b><tt><a href="#cl::Prefix">cl::Prefix</a></tt></b>
+modifier added to allow the CommandLine library to recognize them. Note that
+<b><tt><a href="#cl::Prefix">cl::Prefix</a></tt></b> options must not have the
+<b><tt><a href="#cl::ValueDisallowed">cl::ValueDisallowed</a></tt></b> modifier
+specified.</li>
+
+<li><a name="cl::Grouping">The <b><tt>cl::Grouping</tt></b></a> modifier is used
+to implement Unix-style tools (like <tt>ls</tt>) that have lots of single letter
+arguments, but only require a single dash. For example, the '<tt>ls -labF</tt>'
+command actually enables four different options, all of which are single
+letters. Note that <b><tt><a href="#cl::Grouping">cl::Grouping</a></tt></b>
+options cannot have values.</li>
+
+</ul>
+
+<p>The CommandLine library does not restrict how you use the <b><tt><a
+href="#cl::Prefix">cl::Prefix</a></tt></b> or <b><tt><a
+href="#cl::Grouping">cl::Grouping</a></tt></b> modifiers, but it is possible to
+specify ambiguous argument settings. Thus, it is possible to have multiple
+letter options that are prefix or grouping options, and they will still work as
+designed.</p>
+
+<p>To do this, the CommandLine library uses a greedy algorithm to parse the
+input option into (potentially multiple) prefix and grouping options. The
+strategy basically looks like this:</p>
+
+<div class="doc_code"><tt>parse(string OrigInput) {</tt>
+
+<ol>
+<li><tt>string input = OrigInput;</tt>
+<li><tt>if (isOption(input)) return getOption(input).parse();</tt> <i>// Normal option</i>
+<li><tt>while (!isOption(input) && !input.empty()) input.pop_back();</tt> <i>// Remove the last letter</i>
+<li><tt>if (input.empty()) return error();</tt> <i>// No matching option</i>
+<li><tt>if (getOption(input).isPrefix())<br>
+ return getOption(input).parse(input);</tt>
+<li><tt>while (!input.empty()) { <i>// Must be grouping options</i><br>
+ getOption(input).parse();<br>
+ OrigInput.erase(OrigInput.begin(), OrigInput.begin()+input.length());<br>
+ input = OrigInput;<br>
+ while (!isOption(input) && !input.empty()) input.pop_back();<br>
+}</tt>
+<li><tt>if (!OrigInput.empty()) error();</tt></li>
+</ol>
+
+<p><tt>}</tt></p>
+</div>
+
+</div>
+
+<!-- _______________________________________________________________________ -->
+<div class="doc_subsubsection">
+ <a name="misc">Miscellaneous option modifiers</a>
+</div>
+
+<div class="doc_text">
+
+<p>The miscellaneous option modifiers are the only flags where you can specify
+more than one flag from the set: they are not mutually exclusive. These flags
+specify boolean properties that modify the option.</p>
+
+<ul>
+
+<li><a name="cl::CommaSeparated">The <b><tt>cl::CommaSeparated</tt></b></a> modifier
+indicates that any commas specified for an option's value should be used to
+split the value up into multiple values for the option. For example, these two
+options are equivalent when <tt>cl::CommaSeparated</tt> is specified:
+"<tt>-foo=a -foo=b -foo=c</tt>" and "<tt>-foo=a,b,c</tt>". This option only
+makes sense to be used in a case where the option is allowed to accept one or
+more values (i.e. it is a <a href="#cl::list">cl::list</a> option).</li>
+
+<li><a name="cl::PositionalEatsArgs">The
+<b><tt>cl::PositionalEatsArgs</tt></b></a> modifier (which only applies to
+positional arguments, and only makes sense for lists) indicates that positional
+argument should consume any strings after it (including strings that start with
+a "-") up until another recognized positional argument. For example, if you
+have two "eating" positional arguments, "<tt>pos1</tt>" and "<tt>pos2</tt>", the
+string "<tt>-pos1 -foo -bar baz -pos2 -bork</tt>" would cause the "<tt>-foo -bar
+-baz</tt>" strings to be applied to the "<tt>-pos1</tt>" option and the
+"<tt>-bork</tt>" string to be applied to the "<tt>-pos2</tt>" option.</li>
+
+<li><a name="cl::Sink">The <b><tt>cl::Sink</tt></b></a> modifier is
+used to handle unknown options. If there is at least one option with
+<b><tt>cl::Sink</tt></b></a> modifier specified, the parser passes
+unrecognized option strings to it as values instead of signaling an
+error. As with <b><tt>cl::CommaSeparated</tt></b></a>, this modifier
+only makes sense with a <a href="#cl::list">cl::list</a> option.</li>
+
+
+</ul>
+
+<p>So far, these are the only three miscellaneous option modifiers.</p>