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25<div class="section" lang="en">
26<div class="titlepage"><div><div><h3 class="title">
27<a name="string_algo.concept"></a>Concepts</h3></div></div></div>
28<div class="toc"><dl>
29<dt><span class="section"><a href="concept.html#id2745880">Definitions</a></span></dt>
30<dt><span class="section"><a href="concept.html#string_algo.finder_concept">Finder Concept</a></span></dt>
31<dt><span class="section"><a href="concept.html#string_algo.formatter_concept">Formatter concept</a></span></dt>
32</dl></div>
33<div class="section" lang="en">
34<div class="titlepage"><div><div><h4 class="title">
35<a name="id2745880"></a>Definitions</h4></div></div></div>
36<div class="table">
37<a name="id2745884"></a><p class="title"><b>Table 11.12. Notation</b></p>
38<table class="table" summary="Notation">
39<colgroup>
40<col>
41<col>
42</colgroup>
43<tbody>
44<tr>
45<td align="left"><code class="computeroutput">F</code></td>
46<td align="left">A type that is a model of Finder</td>
47</tr>
48<tr>
49<td align="left"><code class="computeroutput">Fmt</code></td>
50<td align="left">A type that is a model of Formatter</td>
51</tr>
52<tr>
53<td align="left"><code class="computeroutput">Iter</code></td>
54<td align="left">
55                            Iterator Type
56                        </td>
57</tr>
58<tr>
59<td align="left"><code class="computeroutput">f</code></td>
60<td align="left">Object of type <code class="computeroutput">F</code>
61</td>
62</tr>
63<tr>
64<td align="left"><code class="computeroutput">fmt</code></td>
65<td align="left">Object of type <code class="computeroutput">Fmt</code>
66</td>
67</tr>
68<tr>
69<td align="left"><code class="computeroutput">i,j</code></td>
70<td align="left">Objects of type <code class="computeroutput">Iter</code>
71</td>
72</tr>
73</tbody>
74</table>
75</div>
76</div>
77<div class="section" lang="en">
78<div class="titlepage"><div><div><h4 class="title">
79<a name="string_algo.finder_concept"></a>Finder Concept</h4></div></div></div>
80<p>
81            Finder is a functor which searches for an arbitrary part of a container.
82            The result of the search is given as an <code class="computeroutput">iterator_range</code> 
83            delimiting the selected part.
84        </p>
85<div class="table">
86<a name="id2745984"></a><p class="title"><b>Table 11.13. Valid Expressions</b></p>
87<table class="table" summary="Valid Expressions">
88<colgroup>
89<col>
90<col>
91<col>
92</colgroup>
93<thead><tr>
94<th align="left">Expression</th>
95<th align="left">Return Type</th>
96<th align="left">Effects</th>
97</tr></thead>
98<tbody><tr>
99<td align="left"><code class="computeroutput">f(i,j)</code></td>
100<td align="left">Convertible to <code class="computeroutput">iterator_range&lt;Iter&gt;</code>
101</td>
102<td align="left">Perform the search on the interval [i,j) and returns the result of the search</td>
103</tr></tbody>
104</table>
105</div>
106<p>
107            Various algorithms need to perform a search in a container and a Finder is a generalization of such
108            search operations that allows algorithms to abstract from searching. For instance, generic replace
109            algorithms can replace any part of the input, and the Finder is used to select the desired one.
110        </p>
111<p>
112            Note, that it is only required that the finder works with a particular iterator type. However,
113            a Finder operation can be defined as a template, allowing the Finder to work with any iterator.
114        </p>
115<p><span class="bold"><strong>Examples</strong></span></p>
116<div class="itemizedlist"><ul type="disc">
117<li>
118                    Finder implemented as a class. This Finder always returns the whole input as a match. <code class="computeroutput">operator()</code>
119                    is templated, so that the finder can be used on any iterator type.
120                   
121                    <pre class="programlisting">
122struct simple_finder
123{
124    template&lt;typename ForwardIteratorT&gt;
125    boost::iterator_range&lt;ForwardIterator&gt; operator()(
126        ForwardIteratorT Begin,
127        ForwardIteratorT End )
128    {
129        return boost::make_range( Begin, End );
130    }
131};
132        </pre>
133</li>
134<li>
135                    Function Finder. Finder can be any function object. That is, any ordinary function with the
136                    required signature can be used as well. However, such a function can be used only for
137                    a specific iterator type.
138                   
139                    <pre class="programlisting">
140boost::iterator_range&lt;std::string&gt; simple_finder(
141    std::string::const_iterator Begin,
142    std::string::const_iterator End )
143{
144    return boost::make_range( Begin, End );
145}
146        </pre>
147</li>
148</ul></div>
149</div>
150<div class="section" lang="en">
151<div class="titlepage"><div><div><h4 class="title">
152<a name="string_algo.formatter_concept"></a>Formatter concept</h4></div></div></div>
153<p>
154            Formatters are used by <a href="design.html#string_algo.replace" title="Replace Algorithms">replace algorithms</a>.
155            They are used in close combination with finders.
156            A formatter is a functor, which takes a result from a Finder operation and transforms it in a specific way.
157            The operation of the formatter can use additional information provided by a specific finder,
158            for example <code class="computeroutput"><a href="../id2586835.html" title="Function template regex_formatter">regex_formatter()</a></code> uses the match information from
159            <code class="computeroutput"><a href="../id2559243.html" title="Function template regex_finder">regex_finder()</a></code> to format the result of formatter operation.
160        </p>
161<div class="table">
162<a name="id2746137"></a><p class="title"><b>Table 11.14. Valid Expressions</b></p>
163<table class="table" summary="Valid Expressions">
164<colgroup>
165<col>
166<col>
167<col>
168</colgroup>
169<thead><tr>
170<th align="left">Expression</th>
171<th align="left">Return Type</th>
172<th align="left">Effects</th>
173</tr></thead>
174<tbody><tr>
175<td align="left"><code class="computeroutput">fmt(f(i,j))</code></td>
176<td align="left">A container type, accessible using container traits</td>
177<td align="left">Formats the result of the finder operation</td>
178</tr></tbody>
179</table>
180</div>
181<p>
182            Similarly to finders, formatters generalize format operations. When a finder is used to
183            select a part of the input, formatter takes this selection and performs some formating
184            on it. Algorithms can abstract from formating using a formatter.
185        </p>
186<p><span class="bold"><strong>Examples</strong></span></p>
187<div class="itemizedlist"><ul type="disc">
188<li>
189                    Formatter implemented as a class. This Formatter does not perform any formating and
190                    returns the match, repackaged. <code class="computeroutput">operator()</code>
191                    is templated, so that the Formatter can be used on any Finder type.
192                   
193                    <pre class="programlisting">
194struct simple_formatter
195{
196    template&lt;typename FindResultT&gt;
197    std::string operator()( const FindResultT&amp; Match )
198    {
199        std::string Temp( Match.begin(), Match.end() );
200        return Temp;
201    }
202};
203                </pre>
204</li>
205<li>
206                    Function Formatter. Similarly to Finder, Formatter can be any function object.
207                    However, as a function, it can be used only with a specific Finder type.
208                 
209                    <pre class="programlisting">
210std::string simple_formatter( boost::iterator_range&lt;std::string::const_iterator&gt;&amp; Match )
211{
212    std::string Temp( Match.begin(), Match.end() );
213    return Temp;
214}
215                    </pre>
216</li>
217</ul></div>
218</div>
219</div>
220<table width="100%"><tr>
221<td align="left"><small><p>Last revised: July 16, 2004 at 09:06:39 GMT</p></small></td>
222<td align="right"><small>Copyright © 2002-2004 Pavol Droba</small></td>
223</tr></table>
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