1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 2 3<html> 4<head> 5 <meta http-equiv="Content-Language" content="en-us"> 6 <meta http-equiv="Content-Type" content="text/html; charset=us-ascii"> 7 8 <title>Generator Iterator Adaptor Documentation</title> 9</head> 10 11<body bgcolor="#FFFFFF" text="#000000"> 12 <img src="../../boost.png" alt="boost.png (6897 bytes)" align="middle" 13 width="277" height="86"> 14 15 <h1>Generator Iterator Adaptor</h1> 16 17 <p>Defined in header <a href= 18 "../../boost/generator_iterator.hpp">boost/generator_iterator.hpp</a></p> 19 20 <p>The generator iterator adaptor makes it easier to create custom input 21 iterators from 0-ary functions and function objects. The adaptor takes a 22 <a href="http://www.sgi.com/tech/stl/Generator.html">Generator</a> and 23 creates a model of <a href= 24 "http://www.sgi.com/tech/stl/InputIterator.html">Input Iterator</a>. Each 25 increment retrieves an item from the generator and makes it available to be 26 retrieved by dereferencing. The motivation for this iterator is that some 27 concepts can be more naturally expressed as a generator, while most STL 28 algorithms expect an iterator. An example is the <a href= 29 "../random/index.html">Random Number</a> library.</p> 30 31 <h2>Synopsis</h2> 32 33 <blockquote> 34 <pre> 35namespace boost { 36 template <class Generator> 37 class generator_iterator_policies; 38 39 template <class Generator> 40 class generator_iterator_generator; 41 42 template <class Generator> 43 typename generator_iterator_generator<Generator>::type 44 make_generator_iterator(Generator & gen); 45} 46</pre> 47 </blockquote> 48 <hr> 49 50 <h2>The Generator Iterator Generator Class</h2> 51 52 <p>The class generator_iterator_generator is a helper class whose purpose 53 is to construct a generator iterator type. The template parameter for this 54 class is the Generator function object type that is being wrapped. The 55 generator iterator adaptor only holds a reference (or pointer) to the 56 function object, therefore the function object must outlive the generator 57 iterator adaptor constructed from it.</p> 58 <pre> 59template <class Generator> 60class generator_iterator_generator 61{ 62public: 63 typedef <i>unspecified</i> type; // the resulting generator iterator type 64} 65</pre> 66 67 <h3>Template Parameters</h3> 68 69 <table border summary=""> 70 <tr> 71 <th>Parameter</th> 72 73 <th>Description</th> 74 </tr> 75 76 <tr> 77 <td><tt><a href= 78 "http://www.sgi.com/tech/stl/Generator.html">Generator</a></tt></td> 79 80 <td>The generator (0-ary function object) type being wrapped. The 81 return type of the function must be defined as 82 <tt>Generator::result_type</tt>. The function object must be a model of 83 <a href= 84 "http://www.sgi.com/tech/stl/Generator.html">Generator</a>.</td> 85 </tr> 86 </table> 87 88 <h3>Concept Model</h3> 89 90 <p>The generator iterator class is a model of <a href= 91 "http://www.sgi.com/tech/stl/InputIterator.html">Input Iterator</a>.</p> 92 93 <h3>Members</h3> 94 95 <p>The generator iterator implements the member functions and operators 96 required of the <a href= 97 "http://www.sgi.com/tech/stl/InputIterator.html">Input Iterator</a> 98 concept.<br></p> 99 <hr> 100 101 <h2><a name="make_generator_iterator" id="make_generator_iterator">The 102 Generator Iterator Object Generator</a></h2> 103 104 <p>The <tt>make_generator_iterator()</tt> function provides a convenient 105 way to create generator iterator objects. The function saves the user the 106 trouble of explicitly writing out the iterator types.</p> 107 108 <blockquote> 109 <pre> 110template <class Generator> 111typename generator_iterator_generator<Generator>::type 112make_generator_iterator(Generator & gen); 113</pre> 114 </blockquote> 115 <hr> 116 117 <h3>Example</h3> 118 119 <p>The following program shows how <code>generator_iterator</code> 120 transforms a generator into an input iterator.</p> 121 122 <blockquote> 123 <pre> 124#include <iostream> 125#include <boost/generator_iterator.hpp> 126 127class my_generator 128{ 129public: 130 typedef int result_type; 131 my_generator() : state(0) { } 132 int operator()() { return ++state; } 133private: 134 int state; 135}; 136 137int main() 138{ 139 my_generator gen; 140 boost::generator_iterator_generator<my_generator>::type it = boost::make_generator_iterator(gen); 141 for(int i = 0; i < 10; ++i, ++it) 142 std::cout << *it << std::endl; 143} 144</pre> 145 </blockquote> 146 <hr> 147 148 <p><a href="http://validator.w3.org/check?uri=referer"><img border="0" src= 149 "../../doc/images/valid-html401.png" alt="Valid HTML 4.01 Transitional" 150 height="31" width="88"></a></p> 151 152 <p>Revised 153 <!--webbot bot="Timestamp" s-type="EDITED" s-format="%d %B, %Y" startspan -->05 December, 2006<!--webbot bot="Timestamp" endspan i-checksum="38516" --></p> 154 155 <p><i>Copyright © 2001 <a href= 156 "http://www.boost.org/people/jens_maurer.htm">Jens Maurer</a></i></p> 157 158 <p><i>Distributed under the Boost Software License, Version 1.0. (See 159 accompanying file <a href="../../LICENSE_1_0.txt">LICENSE_1_0.txt</a> or 160 copy at <a href= 161 "http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</a>)</i></p> 162</body> 163</html> 164
