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 *
 * 
 *
 * Copyright (C) 1997-2014 by Dimitri van Heesch.
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 * Permission to use, copy, modify, and distribute this software and its
 * documentation under the terms of the GNU General Public License is hereby 
 * granted. No representations are made about the suitability of this software 
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 * See the GNU General Public License for more details.
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/*! \page grouping Grouping

Doxygen has three mechanisms to group things together. 
One mechanism works at a global level, creating a new page
for each group. These groups are called \ref modules "'modules'" in the documentation.
The second mechanism works within a member list of some compound entity,
and is referred to as a \ref memgroup "'member groups'". 
For \ref cmdpage "pages" there is a third grouping mechanism referred to 
as \ref subpaging "subpaging".

\section modules Modules

Modules are a way to group things together on a separate page. You
can document a group as a whole, as well as all individual members.
Members of a group can be files, namespaces, classes, functions,
variables, enums, typedefs, and defines, but also other groups.

To define a group, you should put the \ref cmddefgroup "\\defgroup"
command in a special comment block. The first argument of the command 
is a label that should uniquely identify the group.  
The second argument is the name or title of the group as it should appear 
in the documentation.

You can make an entity a member of a specific group by putting 
a \ref cmdingroup "\\ingroup" command inside its documentation block.

To avoid putting \ref cmdingroup "\\ingroup" commands in the documentation
for each member you can also group members together by the 
open marker <code>\@{</code> before the group and the 
closing marker <code>\@}</code> after the group. The markers can 
be put in the documentation of the group definition or in a separate 
documentation block. 

Groups themselves can also be nested using these grouping markers.

You will get an error message when you use the same group label more than once.
If you don't want doxygen to enforce unique labels, then you can 
use \ref cmdaddtogroup "\\addtogroup" instead of
\ref cmddefgroup "\\defgroup". 
It can be used exactly like \ref cmddefgroup "\\defgroup",
but when the group has been defined already, then it silently merges the 
existing documentation with the new one.
The title of the group is optional for this command, so you can use
\verbatim
/** \addtogroup <label> 
 *  @{
 */
...

/** @}*/
\endverbatim
to add additional members to a group that is defined in more detail elsewhere.

Note that compound entities (like classes, files and namespaces) can
be put into multiple groups, but members (like variable, functions, typedefs
and enums) can only be a member of one group 
(this restriction is in place to avoid ambiguous linking targets in case 
a member is not documented in the context of its class, namespace
or file, but only visible as part of a group).

Doxygen will put members into the group whose definition has
the highest "priority": e.g. An explicit \ref cmdingroup "\\ingroup" overrides 
an implicit grouping definition via <code>\@{</code> <code>\@}</code>. 
Conflicting grouping definitions with the same priority trigger a warning, 
unless one definition was for a member without any explicit documentation. 

The following example puts VarInA into group A and silently resolves 
the conflict for IntegerVariable by putting it into group IntVariables, 
because the second instance of IntegerVariable
is undocumented:

\verbatim

/**
 * \ingroup A
 */
extern int VarInA;

/**
 * \defgroup IntVariables Global integer variables
 * @{
 */

/** an integer variable */
extern int IntegerVariable;

/**@}*/

....

/**
 * \defgroup Variables Global variables
 */
/**@{*/

/** a variable in group A */
int VarInA;

int IntegerVariable;

/**@}*/
\endverbatim

The \ref cmdref "\\ref" command can be used to refer to a group.
The first argument of the \\ref command should be group's label.
To use a custom link name, you can put the name of the links in 
double quotes after the label, as shown by the following example
\verbatim
This is the \ref group_label "link" to this group.
\endverbatim

The priorities of grouping definitions are (from highest to lowest):
\ref cmdingroup "\\ingroup", \ref cmddefgroup "\\defgroup",
\ref cmdaddtogroup "\\addtogroup", \ref cmdweakgroup "\\weakgroup".
The last command is exactly like \ref cmdaddtogroup "\\addtogroup"
with a lower priority. It was added to allow "lazy" grouping
definitions: you can use commands with a higher priority in your .h
files to define the hierarchy and \ref cmdweakgroup "\\weakgroup"
in .c files without having to duplicate the hierarchy exactly.

\par Example:
\verbinclude group.cpp

\htmlonly
Click <a href="$(DOXYGEN_DOCDIR)/examples/group/html/modules.html">here</a> 
for the corresponding HTML documentation that is generated by Doxygen.
\endhtmlonly

\section memgroup Member Groups

If a compound (e.g. a class or file) has many members, it is often 
desired to group them together. Doxygen already automatically groups 
things together on type and protection level, but maybe you feel that 
this is not enough or that that default grouping is wrong. 
For instance, because you feel that members of different (syntactic) 
types belong to the same (semantic) group.

A member group is defined by 
a 
\verbatim
///@{ 
  ...
///@}
\endverbatim 
block or a 
\verbatim
/**@{*/ 
  ... 
/**@}*/ 
\endverbatim 
block if you prefer C style 
comments. Note that the members of the group should be 
physically inside the member group's body.

Before the opening marker of a block a separate comment block may be 
placed. This block should contain the \ref cmdname "@@name" 
(or \ref cmdname "\\name") command and is used to specify the header 
of the group. Optionally, the comment block may also contain more
detailed information about the group.

Nesting of member groups is not allowed. 

If all members of a member group inside a class have the same type 
and protection level (for instance all are static public members), 
then the whole member group is displayed as a subgroup of 
the type/protection level group (the group is displayed as a 
subsection of the "Static Public Members" section for instance). 
If two or more members have different types, then the group is put 
at the same level as the automatically generated groups.
If you want to force all member-groups of a class to be at the top level, 
you should put a \ref cmdnosubgrouping "\\nosubgrouping" command inside the
documentation of the class. 

\par Example:
\verbinclude memgrp.cpp

\htmlonly
Click <a href="$(DOXYGEN_DOCDIR)/examples/memgrp/html/class_test.html">here</a> 
for the corresponding HTML documentation that is generated by Doxygen.
\endhtmlonly

Here Group1 is displayed as a subsection of the "Public Members". And
Group2 is a separate section because it contains members with
different protection levels (i.e. public and protected).

\section subpaging Subpaging

Information can be grouped into pages using the \ref cmdpage "\\page" and
\ref cmdsubpage "\\mainpage" commands. Normally, this results in a
flat list of pages, where the "main" page is the first in the list. 

Instead of adding structure using the approach described in section
\ref modules "modules" it is often more natural and convenient to add 
additional structure to the pages using the \ref cmdsubpage "\\subpage" 
command. 

For a page A the \\subpage command adds a link to another page B and at 
the same time makes page B a subpage of A. This has the effect of making
two groups GA and GB, where GB is part of GA, page A is put in group GA, 
and page B is put in group GB.

\htmlonly
Go to the <a href="formulas.html">next</a> section or return to the
 <a href="index.html">index</a>.
\endhtmlonly

*/