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<title>Compose Function Object Adapters</title>
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<td WIDTH="680" BGCOLOR="#DDDDDD"><b><font face="Arial,helvetica" color="#000000" size="+1">Compose
Function Object Adapters</font></b></td>
</tr>
</table>
<p><font face="Arial,Helvetica">The C++ Standard Template Library STL as
part of the C++ Standard Library provides several function objects. Unfortunately,
it doesn't provide the ability to compose these function objects. For example,
it is not possible to combine the result of two unary operations to formulate
a criterion such as ``<i>this <b>and</b> that'</i>'. But this would be
important for building software components out of other components, which
leads to the concept of functional composition. So, here are some adapters
that close this gap.</font>
<p><font face="Arial,Helvetica">In fact, these adapters provide to compose
function objects as follows:</font>
<br>
<table NOSAVE >
<tr NOSAVE>
<td NOSAVE><b><font face="Arial,Helvetica">Functionality</font></b></td>
<td><b><font face="Arial,Helvetica">Boost Name</font></b></td>
<td><b><font face="Arial,Helvetica">SGI STL's Name</font></b></td>
</tr>
<tr>
<td><font face="Times New Roman,Times">f(g(<i>value</i>))</font></td>
<td><font face="Times New Roman,Times">compose_f_gx</font></td>
<td><font face="Times New Roman,Times">compose1</font></td>
</tr>
<tr>
<td><font face="Times New Roman,Times">f(g(<i>value</i>),h(<i>value</i>))</font></td>
<td><font face="Times New Roman,Times">compose_f_gx_hx</font></td>
<td><font face="Times New Roman,Times">compose2</font></td>
</tr>
<tr>
<td><font face="Times New Roman,Times">f(g(<i>value1</i>),h(<i>value2</i>))</font></td>
<td><font face="Times New Roman,Times">compose_f_gx_hy</font></td>
<td></td>
</tr>
<tr>
<td><font face="Times New Roman,Times">f(g(<i>value1</i>,<i>value2</i>))</font></td>
<td><font face="Times New Roman,Times">compose_f_gxy</font></td>
<td></td>
</tr>
<tr>
<td><font face="Times New Roman,Times">f(g())</font></td>
<td><font face="Times New Roman,Times">compose_f_g</font></td>
<td></td>
</tr>
</table>
<p><font face="Arial,Helvetica">As you can see, two of these adapters are
part of the SGI STL already.
However, we changed the names according to
a consistent naming scheme for all adapters.</font>
<p><font face="Arial,Helvetica">In addition, this code also defines a type </font><tt>nullary_function</tt><font face="Arial,Helvetica">
for function objects that have no argument (as supplement to </font><tt>unary_function</tt><font face="Arial,Helvetica">
and </font><tt>binary_function</tt><font face="Arial,Helvetica">) and overloads
</font><tt>ptr_fun</tt><font face="Arial,Helvetica"> for functions that take
no arguments.</font>
<p><font face="Arial,Helvetica">The code is provided "as is" without expressed
or implied warranty.</font>
<p><b><font face="Arial,Helvetica">compose.hpp:</font></b>
<li>
<font face="Arial,Helvetica"><a href="compose.hpp.html">as HTML file</a></font></li>
<li> <font face="Arial,Helvetica"><a href="../../boost/compose.hpp">as plain file</a></font><br>
<br>
<font face="Arial,Helvetica">Example for using </font><b>compose_f_gx</b> </li>
<li>
<tt><a href="compose1.cpp.html">as HTML file</a></tt></li>
<li>
<tt><a href="compose1.cpp">as plain file</a></tt></li>
<br>
<font face="Arial,Helvetica">Example for using </font><b>compose_f_gx_hx</b>
<li>
<tt><a href="compose2.cpp.html">as HTML file</a></tt></li>
<li>
<tt><a href="compose2.cpp">as plain file</a></tt></li>
<br><font face="Arial,Helvetica">Example for using
</font><b>compose_f_gx_hy</b>
<li>
<tt><a href="compose3.cpp.html">as HTML file</a></tt></li>
<li>
<tt><a href="compose3.cpp">as plain file</a></tt></li>
<br><font face="Arial,Helvetica">Example for using
</font><b>compose_f_g</b>
and <b><tt>ptr_fun</tt></b> for functions without arguments
<li>
<a href="compose4.cpp.html">as HTML file</a></li>
<li> <a href="compose4.cpp">as plain file<br>
<br>
</a><b>All files</b> </li>
<li>
<a href="compose.zip">as ZIP file</a></li>
<li> <a href="compose.tgz">as TGZ file<br>
</a><br>
<font face="Arial,Helvetica">To find more details about function objects in
general and about these compose functions, see</font> <br>
<i><font face="Arial,Helvetica"> <a href="http://www.josuttis.com/libbook/">The
C++ Standard Library - A Tutorial and Reference</a></font></i> <br>
<font face="Arial,Helvetica"> by Nicolai M. Josuttis</font>
<br>
<font face="Arial,Helvetica"> Addison Wesley Longman,
1999</font> <br>
<font face="Arial,Helvetica"> ISBN 0-201-37926-0</font>
<br>
<font face="Arial,Helvetica">and the <a href="http://www.sgi.com/Technology/STL/">SGI
STL documentation</a></font> </li>
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