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