1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>FAQ</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. Range 2.0"> 8<link rel="up" href="../index.html" title="Chapter 1. Range 2.0"> 9<link rel="prev" href="portability.html" title="Portability"> 10<link rel="next" href="history_ack.html" title="History and Acknowledgement"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../boost.png"></td> 15<td align="center"><a href="../../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="portability.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_ack.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h2 class="title" style="clear: both"> 27<a name="range.faq"></a><a class="link" href="faq.html" title="FAQ">FAQ</a> 28</h2></div></div></div> 29<p> 30 1. <span class="emphasis"><em><span class="bold"><strong>Why is there no difference between <code class="computeroutput"><span class="identifier">range_iterator</span><span class="special"><</span><span class="identifier">C</span><span class="special">>::</span><span class="identifier">type</span></code> 31 and <code class="computeroutput"><span class="identifier">range_const_iterator</span><span class="special"><</span><span class="identifier">C</span><span class="special">>::</span><span class="identifier">type</span></code> 32 for <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special"><</span><span class="identifier">iterator</span><span class="special">,</span> <span class="identifier">iterator</span><span class="special">></span></code>?</strong></span></em></span> 33 </p> 34<div class="blockquote"><blockquote class="blockquote"><p> 35 In general it is not possible nor desirable to find a corresponding <code class="computeroutput"><span class="identifier">const_iterator</span></code>. When it is possible to 36 come up with one, the client might choose to construct a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special"><</span><span class="identifier">const_iterator</span><span class="special">,</span><span class="identifier">const_iterator</span><span class="special">></span></code> object. 37 </p></blockquote></div> 38<div class="blockquote"><blockquote class="blockquote"><p> 39 Note that an <a class="link" href="reference/utilities/iterator_range.html" title="Class iterator_range"><code class="computeroutput"><span class="identifier">iterator_range</span></code></a> is somewhat more 40 convenient than a <code class="computeroutput"><span class="identifier">pair</span></code> and 41 that a <a class="link" href="reference/utilities/sub_range.html" title="Class sub_range"><code class="computeroutput"><span class="identifier">sub_range</span></code></a> does propagate const-ness. 42 </p></blockquote></div> 43<p> 44 2. <span class="emphasis"><em><span class="bold"><strong>Why is there not supplied more types or 45 more functions?</strong></span></em></span> 46 </p> 47<div class="blockquote"><blockquote class="blockquote"><p> 48 The library has been kept small because its current interface will serve 49 most purposes. If and when a genuine need arises for more functionality, 50 it can be implemented. 51 </p></blockquote></div> 52<p> 53 3. <span class="emphasis"><em><span class="bold"><strong>How should I implement generic algorithms 54 for ranges?</strong></span></em></span> 55 </p> 56<div class="blockquote"><blockquote class="blockquote"><p> 57 One should always start with a generic algorithm that takes two iterators 58 (or more) as input. Then use Boost.Range to build handier versions on top 59 of the iterator based algorithm. Please notice that once the range version 60 of the algorithm is done, it makes sense not to expose the iterator version 61 in the public interface. 62 </p></blockquote></div> 63<p> 64 4. <span class="emphasis"><em><span class="bold"><strong>Why is there no Incrementable Range concept?</strong></span></em></span> 65 </p> 66<div class="blockquote"><blockquote class="blockquote"><p> 67 Even though we speak of incrementable iterators, it would not make much sense 68 for ranges; for example, we cannot determine the size and emptiness of a 69 range since we cannot even compare its iterators. 70 </p></blockquote></div> 71<div class="blockquote"><blockquote class="blockquote"><p> 72 Note also that incrementable iterators are derived from output iterators 73 and so there exist no output range. 74 </p></blockquote></div> 75</div> 76<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 77<td align="left"></td> 78<td align="right"><div class="copyright-footer">Copyright © 2003-2010 Thorsten Ottosen, 79 Neil Groves<p> 80 Distributed under the Boost Software License, Version 1.0. (See accompanying 81 file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) 82 </p> 83</div></td> 84</tr></table> 85<hr> 86<div class="spirit-nav"> 87<a accesskey="p" href="portability.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_ack.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 88</div> 89</body> 90</html> 91
