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<h1>Function Output Iterator Adaptor</h1>
Defined in header <a href=
"../../boost/function_output_iterator.hpp">boost/function_output_iterator.hpp</a>
<p>The function output iterator adaptor makes it easier to create
custom output iterators. The adaptor takes a <a
href="http://www.sgi.com/tech/stl/UnaryFunction.html">Unary
Function</a> and creates a model of <a
href="http://www.sgi.com/tech/stl/OutputIterator.html">Output
Iterator</a>. Each item assigned to the output iterator is passed
as an argument to the unary function. The motivation for this
iterator is that creating a C++ Standard conforming output
iterator is non-trivial, particularly because the proper
implementation usually requires a proxy object. On the other hand,
creating a function (or function object) is much simpler.
<h2>Synopsis</h2>
<blockquote>
<pre>
namespace boost {
template <class UnaryFunction>
class function_output_iterator;
template <class UnaryFunction>
function_output_iterator<UnaryFunction>
make_function_output_iterator(const UnaryFunction& f = UnaryFunction())
}
</pre>
</blockquote>
<h3>Example</h3>
In this example we create an output iterator that appends
each item onto the end of a string, using the <tt>string_appender</tt>
function.
<blockquote>
<pre>
#include <iostream>
#include <string>
#include <vector>
#include <boost/function_output_iterator.hpp>
struct string_appender {
string_appender(std::string& s) : m_str(s) { }
void operator()(const std::string& x) const {
m_str += x;
}
std::string& m_str;
};
int main(int, char*[])
{
std::vector<std::string> x;
x.push_back("hello");
x.push_back(" ");
x.push_back("world");
x.push_back("!");
std::string s = "";
std::copy(x.begin(), x.end(),
boost::make_function_output_iterator(string_appender(s)));
std::cout << s << std::endl;
return 0;
}
</pre>
</blockquote>
<hr>
<h2><a name="function_output_iterator">The Function Output Iterator Class</a></h2>
<blockquote>
<pre>
template <class UnaryFunction>
class function_output_iterator;
</pre>
</blockquote>
The <tt>function_output_iterator</tt> class creates an <a
href="http://www.sgi.com/tech/stl/OutputIterator.html">Output
Iterator</a> out of a
<a href="http://www.sgi.com/tech/stl/UnaryFunction.html">Unary
Function</a>. Each item assigned to the output iterator is passed
as an argument to the unary function.
<h3>Template Parameters</h3>
<table border>
<tr>
<th>Parameter
<th>Description
<tr>
<td><tt>UnaryFunction</tt>
<td>The function type being wrapped. The return type of the
function is not used, so it can be <tt>void</tt>. The
function must be a model of <a
href="http://www.sgi.com/tech/stl/UnaryFunction.html">Unary
Function</a>.</td>
</table>
<h3>Concept Model</h3>
The function output iterator class is a model of <a
href="http://www.sgi.com/tech/stl/OutputIterator.html">Output
Iterator</a>.
<h2>Members</h3>
The function output iterator implements the member functions
and operators required of the <a
href="http://www.sgi.com/tech/stl/OutputIterator.html">Output
Iterator</a> concept. In addition it has the following constructor:
<pre>
explicit function_output_iterator(const UnaryFunction& f = UnaryFunction())
</pre>
<br>
<br>
<hr>
<h2><a name="make_function_output_iterator">The Function Output Iterator Object
Generator</a></h2>
The <tt>make_function_output_iterator()</tt> function provides a
more convenient way to create function output iterator objects. The
function saves the user the trouble of explicitly writing out the
iterator types. If the default argument is used, the function
type must be provided as an explicit template argument.
<blockquote>
<pre>
template <class UnaryFunction>
function_output_iterator<UnaryFunction>
make_function_output_iterator(const UnaryFunction& f = UnaryFunction())
</pre>
</blockquote>
<hr>
<p>© Copyright Jeremy Siek 2001. Permission to copy, use,
modify, sell and distribute this document is granted provided this
copyright notice appears in all copies. This document is provided
"as is" without express or implied warranty, and with no claim as
to its suitability for any purpose.
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