1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>List Generation</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. Phoenix 3.2.0"> 8<link rel="up" href="../tutorial_with_examples.html" title="Tutorial with examples"> 9<link rel="prev" href="arithmetic_functions.html" title="Arithmetic functions"> 10<link rel="next" href="../exceptions.html" title="Exceptions"> 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="arithmetic_functions.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../tutorial_with_examples.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="../exceptions.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h4 class="title"> 27<a name="phoenix.lazy_list.tutorial_with_examples.list_generation"></a><a class="link" href="list_generation.html" title="List Generation">List 28 Generation</a> 29</h4></div></div></div> 30<p> 31 One of the most interesting capabilities of <a href="http://cgi.di.uoa.gr/~smaragd/fc++/" target="_top">FC++</a> 32 is the generation of infinite lazy lists which are evaluated only at need. 33 The most simple example of this is 34 </p> 35<pre class="programlisting"><span class="identifier">enum_from</span><span class="special">(</span><span class="number">1</span><span class="special">)</span> 36</pre> 37<p> 38 which returns the generator for integers 1,2,3,..... infinity. 39 </p> 40<pre class="programlisting"><span class="identifier">take</span><span class="special">(</span><span class="number">4</span><span class="special">,</span><span class="identifier">enum_from</span><span class="special">(</span><span class="number">1</span><span class="special">))</span> 41</pre> 42<p> 43 returns a list of the first 4 of the list. 44 </p> 45<pre class="programlisting"><span class="identifier">at</span><span class="special">(</span><span class="identifier">enum_from</span><span class="special">(</span><span class="number">1</span><span class="special">),</span><span class="number">3</span><span class="special">)</span> 46</pre> 47<p> 48 returns the fourth member using zero indexed access. Both of the lists 49 returned are lazy and only evaluated when the list members are accessed. 50 </p> 51</div> 52<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 53<td align="left"></td> 54<td align="right"><div class="copyright-footer">Copyright © 2002-2005, 2010, 2014, 2015 Joel de Guzman, Dan Marsden, Thomas 55 Heller, John Fletcher<p> 56 Distributed under the Boost Software License, Version 1.0. (See accompanying 57 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>) 58 </p> 59</div></td> 60</tr></table> 61<hr> 62<div class="spirit-nav"> 63<a accesskey="p" href="arithmetic_functions.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../tutorial_with_examples.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="../exceptions.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 64</div> 65</body> 66</html> 67
