1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Upgrading from the old Boost Iterator Adaptor Library</title> 5<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../index.html" title="Chapter 1. Boost.Iterator"> 8<link rel="up" href="../index.html" title="Chapter 1. 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In the new library 34 design, you'll move those same core operations into the body of the iterator 35 class itself. If you were writing a family of iterators, you probably wrote 36 a <a href="http://www.boost.org/more/generic_programming.html#type_generator" target="_top">type 37 generator</a> to build the <code class="computeroutput"><span class="identifier">iterator_adaptor</span></code> 38 specialization you needed; in the new library design you don't need a type 39 generator (though may want to keep it around as a compatibility aid for older 40 code) because, due to the use of the Curiously Recurring Template Pattern (CRTP) 41 [Cop95]_, you can now define the iterator class yourself and acquire functionality 42 through inheritance from <code class="computeroutput"><span class="identifier">iterator_facade</span></code> 43 or <code class="computeroutput"><span class="identifier">iterator_adaptor</span></code>. As a result, 44 you also get much finer control over how your iterator works: you can add additional 45 constructors, or even override the iterator functionality provided by the library. 46 </p> 47<p> 48 If you're looking for the old <code class="computeroutput"><span class="identifier">projection_iterator</span></code> 49 component, its functionality has been merged into <span class="underline">transform_iterator</span>: 50 as long as the function object's <code class="computeroutput"><span class="identifier">result_type</span></code> 51 (or the <code class="computeroutput"><span class="identifier">Reference</span></code> template 52 argument, if explicitly specified) is a true reference type, <span class="underline">transform_iterator</span> 53 will behave like <code class="computeroutput"><span class="identifier">projection_iterator</span></code> 54 used to. 55 </p> 56</div> 57<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 58<td align="left"></td> 59<td align="right"><div class="copyright-footer">Copyright © 2003, 2005 David Abrahams Jeremy Siek Thomas 60 Witt<p> 61 Distributed under the Boost Software License, Version 1.0. (See accompanying 62 file LICENSE_1_0.txt or copy at <ulink url="http://www.boost.org/LICENSE_1_0.txt"> 63 http://www.boost.org/LICENSE_1_0.txt </ulink>) 64 </p> 65</div></td> 66</tr></table> 67<hr> 68<div class="spirit-nav"> 69<a accesskey="p" href="algorithms/next_prior.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="history.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 70</div> 71</body> 72</html> 73
