ceph/src/boost/libs/spirit/classic/phoenix/doc/tuples.html

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  15       <font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Tuples</b></font>
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  28 <p>
  29 Tuples are the most basic infrastructure that the framework builds with. This sub-library provides a mechanism to bundle objects of arbitrary types in a single structure. Tuples hold heterogeneous types up to a predefined maximum.</p>
  30 <p>
  31 Only the most basic functionality needed are provided. This is a straight-forward and extremely lean and mean library. Unlike other recursive list-like tuple implementations, this tuple library implementation uses simple structs similar to std::pair with specialization for 0 to N tuple elements, where N is a predefined constant. There are only 4 tuple operations to learn:</p>
  32 <p>
  33 1)  Construction</p>
  34 <p>
  35 Here are examples on how to construct tuples:</p>
  36 <code><pre>
  37     <span class=keyword>typedef </span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=keyword>int</span><span class=special>, </span><span class=keyword>char</span><span class=special>&gt; </span><span class=identifier>t1_t</span><span class=special>;
  38     </span><span class=keyword>typedef </span><span class=identifier>tuple</span><span class=special>&lt;</span><span class=keyword>int</span><span class=special>, </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span><span class=special>, </span><span class=keyword>double</span><span class=special>&gt; </span><span class=identifier>t2_t</span><span class=special>;
  39
  40     //  </span><span class=keyword>this </span><span class=identifier>tuple </span><span class=identifier>has </span><span class=identifier>an </span><span class=keyword>int </span><span class=keyword>and </span><span class=keyword>char </span><span class=identifier>members
  41     </span><span class=identifier>t1_t </span><span class=identifier>t1</span><span class=special>(</span><span class=number>3</span><span class=special>, </span><span class=literal>'c'</span><span class=special>);
  42
  43     //  </span><span class=keyword>this </span><span class=identifier>tuple </span><span class=identifier>has </span><span class=identifier>an </span><span class=keyword>int</span><span class=special>, </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string </span><span class=keyword>and </span><span class=keyword>double </span><span class=identifier>members
  44     </span><span class=identifier>t2_t </span><span class=identifier>t2</span><span class=special>(</span><span class=number>3</span><span class=special>, </span><span class=string>&quot;hello&quot;</span><span class=special>, </span><span class=number>3.14</span><span class=special>);
  45 </span></pre></code>
  46 <p>
  47 2)  Member access</p>
  48 <p>
  49 A member in a tuple can be accessed using the tuple's  operator by specifying the Nth tuple_index. Here are some examples:</p>
  50 <code><pre>
  51     <span class=identifier>tuple_index</span><span class=special>&lt;</span><span class=number>0</span><span class=special>&gt; </span><span class=identifier>ix0</span><span class=special>; // </span><span class=number>0</span><span class=identifier>th </span><span class=identifier>index </span><span class=special>== </span><span class=number>1</span><span class=identifier>st </span><span class=identifier>item
  52     </span><span class=identifier>tuple_index</span><span class=special>&lt;</span><span class=number>1</span><span class=special>&gt; </span><span class=identifier>ix1</span><span class=special>; // </span><span class=number>1</span><span class=identifier>st </span><span class=identifier>index </span><span class=special>== </span><span class=number>2</span><span class=identifier>nd </span><span class=identifier>item
  53     </span><span class=identifier>tuple_index</span><span class=special>&lt;</span><span class=number>2</span><span class=special>&gt; </span><span class=identifier>ix2</span><span class=special>; // </span><span class=number>2</span><span class=identifier>nd </span><span class=identifier>index </span><span class=special>== </span><span class=number>3</span><span class=identifier>rd </span><span class=identifier>item
  54
  55     </span><span class=comment>//  Note zero based indexing. 0 = 1st item, 1 = 2nd item
  56
  57     </span><span class=identifier>t1</span><span class=special>[</span><span class=identifier>ix0</span><span class=special>] = </span><span class=number>33</span><span class=special>;       // </span><span class=identifier>sets </span><span class=identifier>the </span><span class=keyword>int </span><span class=identifier>member </span><span class=identifier>of </span><span class=identifier>the </span><span class=identifier>tuple </span><span class=identifier>t1
  58     </span><span class=identifier>t2</span><span class=special>[</span><span class=identifier>ix2</span><span class=special>] = </span><span class=number>6e6</span><span class=special>;      // </span><span class=identifier>sets </span><span class=identifier>the </span><span class=keyword>double </span><span class=identifier>member </span><span class=identifier>of </span><span class=identifier>the </span><span class=identifier>tuple </span><span class=identifier>t2
  59     </span><span class=identifier>t1</span><span class=special>[</span><span class=identifier>ix1</span><span class=special>] = </span><span class=literal>'a'</span><span class=special>;      // </span><span class=identifier>sets </span><span class=identifier>the </span><span class=keyword>char </span><span class=identifier>member </span><span class=identifier>of </span><span class=identifier>the </span><span class=identifier>tuple </span><span class=identifier>t1
  60 </span></pre></code>
  61 <p>
  62 Access to out of bound indexes returns a nil_t value.</p>
  63 <p>
  64 3)  Member type inquiry</p>
  65 <p>
  66 The type of an individual member can be queried. Example:</p>
  67 <code><pre>
  68     <span class=identifier>tuple_element</span><span class=special>&lt;</span><span class=number>1</span><span class=special>, </span><span class=identifier>t2_t</span><span class=special>&gt;::</span><span class=identifier>type
  69 </span></pre></code>
  70 <p>
  71 Refers to the type of the second member (again note zero based indexing, hence 0 = 1st item, 1 = 2nd item) of the tuple.</p>
  72 <p>
  73 Access to out of bound indexes returns a nil_t type.</p>
  74 <p>
  75 4)  Tuple length</p>
  76 <p>
  77 The number of elements in a tuple can be queried. Example:</p>
  78 <code><pre>
  79     <span class=keyword>int </span><span class=identifier>n </span><span class=special>= </span><span class=identifier>t1</span><span class=special>.</span><span class=identifier>length</span><span class=special>;
  80 </span></pre></code>
  81 <p>
  82 gets the number of elements in tuple t1.</p>
  83 <p>
  84 length is a static constant. Thus, TupleT::length also works. Example:</p>
  85 <code><pre>
  86     <span class=keyword>int </span><span class=identifier>n </span><span class=special>= </span><span class=identifier>t1_t</span><span class=special>::</span><span class=identifier>length</span><span class=special>;
  87 </span></pre></code>
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  97 <p class="copyright">Copyright &copy; 2001-2002 Joel de Guzman<br>
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  99 <font size="2">Use, modification and distribution is subject to the Boost Software
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