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| 9 | |
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| 10 | <title>Boost Char Separator</title> |
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| 11 | </head> |
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| 12 | |
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| 13 | <body bgcolor="#FFFFFF" text="#000000" link="#0000EE" vlink="#551A8B" alink= |
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| 14 | "#FF0000"> |
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| 15 | <p><img src="../../boost.png" alt="C++ Boost" width="277" height= |
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| 16 | "86"><br></p> |
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| 17 | |
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| 18 | <h1>char_separator<Char, Traits></h1> |
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| 19 | |
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| 20 | <p>The <tt>char_separator</tt> class breaks a sequence of characters into |
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| 21 | tokens based on character delimiters much in the same way that |
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| 22 | <tt>strtok()</tt> does (but without all the evils of non-reentrancy and |
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| 23 | destruction of the input sequence).</p> |
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| 24 | |
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| 25 | <p>The <tt>char_separator</tt> class is used in conjunction with the |
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| 26 | <a href="token_iterator.htm"><tt>token_iterator</tt></a> or <a href= |
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| 27 | "tokenizer.htm"><tt>tokenizer</tt></a> to perform tokenizing.</p> |
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| 28 | |
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| 29 | <h2>Definitions</h2> |
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| 30 | |
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| 31 | <p>The <tt>strtok()</tt> function does not include matches with the |
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| 32 | character delimiters in the output sequence of tokens. However, sometimes |
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| 33 | it is useful to have the delimiters show up in the output sequence, |
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| 34 | therefore <tt>char_separator</tt> provides this as an option. We refer to |
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| 35 | delimiters that show up as output tokens as <b><i>kept delimiters</i></b> |
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| 36 | and delimiters that do now show up as output tokens as <b><i>dropped |
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| 37 | delimiters</i></b>.</p> |
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| 38 | |
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| 39 | <p>When two delimiters appear next to each other in the input sequence, |
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| 40 | there is the question of whether to output an <b><i>empty token</i></b> or |
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| 41 | to skip ahead. The behaviour of <tt>strtok()</tt> is to skip ahead. The |
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| 42 | <tt>char_separator</tt> class provides both options.</p> |
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| 43 | |
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| 44 | <h2>Examples</h2> |
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| 45 | |
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| 46 | <p>This first examples shows how to use <tt>char_separator</tt> as a |
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| 47 | replacement for the <tt>strtok()</tt> function. We've specified three |
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| 48 | character delimiters, and they will not show up as output tokens. We have |
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| 49 | not specified any kept delimiters, and by default any empty tokens will be |
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| 50 | ignored.</p> |
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| 51 | |
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| 52 | <blockquote> |
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| 53 | <pre> |
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| 54 | // char_sep_example_1.cpp |
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| 55 | #include <iostream> |
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| 56 | #include <boost/tokenizer.hpp> |
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| 57 | #include <string> |
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| 58 | |
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| 59 | int main() |
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| 60 | { |
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| 61 | std::string str = ";;Hello|world||-foo--bar;yow;baz|"; |
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| 62 | typedef boost::tokenizer<boost::char_separator<char> > |
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| 63 | tokenizer; |
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| 64 | boost::char_separator<char> sep("-;|"); |
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| 65 | tokenizer tokens(str, sep); |
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| 66 | for (tokenizer::iterator tok_iter = tokens.begin(); |
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| 67 | tok_iter != tokens.end(); ++tok_iter) |
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| 68 | std::cout << "<" << *tok_iter << "> "; |
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| 69 | std::cout << "\n"; |
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| 70 | return EXIT_SUCCESS; |
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| 71 | } |
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| 72 | </pre> |
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| 73 | </blockquote>The output is: |
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| 74 | |
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| 75 | <blockquote> |
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| 76 | <pre> |
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| 77 | <Hello> <world> <foo> <bar> <yow> <baz> |
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| 78 | </pre> |
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| 79 | </blockquote> |
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| 80 | |
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| 81 | <p>The next example shows tokenizing with two dropped delimiters '-' and |
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| 82 | ';' and a single kept delimiter '|'. We also specify that empty tokens |
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| 83 | should show up in the output when two delimiters are next to each |
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| 84 | other.</p> |
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| 85 | |
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| 86 | <blockquote> |
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| 87 | <pre> |
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| 88 | // char_sep_example_2.cpp |
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| 89 | #include <iostream> |
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| 90 | #include <boost/tokenizer.hpp> |
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| 91 | #include <string> |
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| 92 | |
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| 93 | int main() |
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| 94 | { |
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| 95 | std::string str = ";;Hello|world||-foo--bar;yow;baz|"; |
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| 96 | typedef boost::tokenizer<boost::char_separator<char> > |
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| 97 | tokenizer; |
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| 98 | boost::char_separator<char> sep("-;", "|", boost::keep_empty_tokens); |
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| 99 | tokenizer tokens(str, sep); |
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| 100 | for (tokenizer::iterator tok_iter = tokens.begin(); |
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| 101 | tok_iter != tokens.end(); ++tok_iter) |
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| 102 | std::cout << "<" << *tok_iter << "> "; |
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| 103 | std::cout << "\n"; |
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| 104 | return EXIT_SUCCESS; |
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| 105 | } |
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| 106 | </pre> |
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| 107 | </blockquote>The output is: |
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| 108 | |
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| 109 | <blockquote> |
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| 110 | <pre> |
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| 111 | <> <> <Hello> <|> <world> <|> <> <|> <> <foo> <> <bar> <yow> <baz> <|> <> |
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| 112 | </pre> |
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| 113 | </blockquote> |
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| 114 | |
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| 115 | <p>The final example shows tokenizing on punctuation and whitespace |
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| 116 | characters using the default constructor of the |
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| 117 | <tt>char_separator</tt>.</p> |
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| 118 | |
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| 119 | <blockquote> |
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| 120 | <pre> |
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| 121 | // char_sep_example_3.cpp |
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| 122 | #include <iostream> |
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| 123 | #include <boost/tokenizer.hpp> |
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| 124 | #include <string> |
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| 125 | |
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| 126 | int main() |
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| 127 | { |
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| 128 | std::string str = "This is, a test"; |
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| 129 | typedef boost::tokenizer<boost::char_separator<char> > Tok; |
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| 130 | boost::char_separator<char> sep; // default constructed |
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| 131 | Tok tok(str, sep); |
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| 132 | for(Tok::iterator tok_iter = tok.begin(); tok_iter != tok.end(); ++tok_iter) |
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| 133 | std::cout << "<" << *tok_iter << "> "; |
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| 134 | std::cout << "\n"; |
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| 135 | return EXIT_SUCCESS; |
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| 136 | } |
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| 137 | </pre> |
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| 138 | </blockquote>The output is: |
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| 139 | |
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| 140 | <blockquote> |
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| 141 | <pre> |
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| 142 | <This> <is> <,> <a> <test> |
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| 143 | </pre> |
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| 144 | </blockquote> |
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| 145 | |
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| 146 | <h2>Template parameters</h2> |
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| 147 | |
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| 148 | <table border summary=""> |
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| 149 | <tr> |
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| 150 | <th>Parameter</th> |
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| 151 | |
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| 152 | <th>Description</th> |
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| 153 | |
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| 154 | <th>Default</th> |
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| 155 | </tr> |
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| 156 | |
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| 157 | <tr> |
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| 158 | <td><tt>Char</tt></td> |
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| 159 | |
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| 160 | <td>The type of elements within a token, typically <tt>char</tt>.</td> |
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| 161 | |
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| 162 | <td> </td> |
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| 163 | </tr> |
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| 164 | |
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| 165 | <tr> |
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| 166 | <td><tt>Traits</tt></td> |
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| 167 | |
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| 168 | <td>The <tt>char_traits</tt> for the character type.</td> |
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| 169 | |
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| 170 | <td><tt>char_traits<char></tt></td> |
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| 171 | </tr> |
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| 172 | </table> |
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| 173 | |
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| 174 | <h2>Model of</h2><a href="tokenizerfunction.htm">Tokenizer Function</a> |
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| 175 | |
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| 176 | <h2>Members</h2> |
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| 177 | <hr> |
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| 178 | <pre> |
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| 179 | explicit char_separator(const Char* dropped_delims, |
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| 180 | const Char* kept_delims = "", |
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| 181 | empty_token_policy empty_tokens = drop_empty_tokens) |
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| 182 | </pre> |
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| 183 | |
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| 184 | <p>This creates a <tt>char_separator</tt> object, which can then be used to |
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| 185 | create a <a href="token_iterator.htm"><tt>token_iterator</tt></a> or |
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| 186 | <a href="tokenizer.htm"><tt>tokenizer</tt></a> to perform tokenizing. The |
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| 187 | <tt>dropped_delims</tt> and <tt>kept_delims</tt> are strings of characters |
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| 188 | where each character is used as delimiter during tokenizing. Whenever a |
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| 189 | delimiter is seen in the input sequence, the current token is finished, and |
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| 190 | a new token begins. The delimiters in <tt>dropped_delims</tt> do not show |
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| 191 | up as tokens in the output whereas the delimiters in <tt>kept_delims</tt> |
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| 192 | do show up as tokens. If <tt>empty_tokens</tt> is |
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| 193 | <tt>drop_empty_tokens</tt>, then empty tokens will not show up in the |
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| 194 | output. If <tt>empty_tokens</tt> is <tt>keep_empty_tokens</tt> then empty |
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| 195 | tokens will show up in the output.</p> |
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| 196 | <hr> |
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| 197 | <pre> |
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| 198 | explicit char_separator() |
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| 199 | </pre> |
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| 200 | |
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| 201 | <p>The function <tt>std::isspace()</tt> is used to identify dropped |
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| 202 | delimiters and <tt>std::ispunct()</tt> is used to identify kept delimiters. |
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| 203 | In addition, empty tokens are dropped.</p> |
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| 204 | <hr> |
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| 205 | <pre> |
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| 206 | template <typename InputIterator, typename Token> |
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| 207 | bool operator()(InputIterator& next, InputIterator end, Token& tok) |
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| 208 | </pre> |
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| 209 | |
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| 210 | <p>This function is called by the <a href= |
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| 211 | "token_iterator.htm"><tt>token_iterator</tt></a> to perform tokenizing. The |
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| 212 | user typically does not call this function directly.</p> |
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| 213 | <hr> |
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| 214 | |
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| 215 | <p><a href="http://validator.w3.org/check?uri=referer"><img border="0" src= |
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| 216 | "http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01 Transitional" |
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| 217 | height="31" width="88"></a></p> |
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| 218 | |
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| 219 | <p>Revised |
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| 220 | <!--webbot bot="Timestamp" s-type="EDITED" s-format="%d %B, %Y" startspan -->25 |
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| 221 | December, 2006<!--webbot bot="Timestamp" endspan i-checksum="38518" --></p> |
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| 222 | |
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| 223 | <p><i>Copyright © 2001-2002 Jeremy Siek and John R. Bandela</i></p> |
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| 224 | |
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| 225 | <p><i>Distributed under the Boost Software License, Version 1.0. (See |
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| 226 | accompanying file <a href="../../LICENSE_1_0.txt">LICENSE_1_0.txt</a> or |
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| 227 | copy at <a href= |
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| 228 | "http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</a>)</i></p> |
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| 229 | </body> |
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| 230 | </html> |
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