ceph/src/boost/libs/ptr_container/doc/tutorial_example.html

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   9     <pre><span class=comment>//
  10 // Boost.Pointer Container
  11 //
  12 //  Copyright Thorsten Ottosen 2003-2005. Use, modification and
  13 //  distribution is subject to the Boost Software License, Version
  14 //  1.0. (See accompanying file LICENSE_1_0.txt or copy at
  15 //  http://www.boost.org/LICENSE_1_0.txt)
  16 //
  17 // For more information, see http://www.boost.org/libs/ptr_container/
  18 //
  19
  20 //
  21 // This example is intended to get you started.
  22 // Notice how the smart container
  23 //
  24 // 1. takes ownership of objects
  25 // 2. transfers ownership
  26 // 3. applies indirection to iterators
  27 // 4. clones objects from other smart containers
  28 //
  29
  30 //
  31 // First we select which container to use.
  32 //</span>
  33 <span class=preprocessor>#include</span> <span class=special>&lt;</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>ptr_container</span><span class=special>/</span><span class=identifier>ptr_deque</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>&gt;</span>
  34
  35 <span class=comment>//
  36 // we need these later in the example
  37 //</span>
  38 <span class=preprocessor>#include</span> <span class=special>&lt;</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>assert</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>&gt;</span>
  39 <span class=preprocessor>#include</span> <span class=special>&lt;</span><span class=identifier>string</span><span class=special>&gt;</span>
  40 <span class=preprocessor>#include</span> <span class=special>&lt;</span><span class=identifier>exception</span><span class=special>&gt;</span>
  41
  42
  43 <span class=comment>//
  44 // Then we define a small polymorphic class
  45 // hierarchy.
  46 //</span>
  47
  48 <span class=keyword>class</span> <span class=identifier>animal</span> <span class=special>:</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>noncopyable</span>
  49 <span class=special>{</span>
  50     <span class=keyword>virtual</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span> <span class=identifier>do_speak</span><span class=special>()</span> <span class=keyword>const</span> <span class=special>=</span> <span class=number>0</span><span class=special>;</span>
  51     <span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span> <span class=identifier>name_</span><span class=special>;</span>
  52
  53 <span class=keyword>protected</span><span class=special>:</span>
  54     <span class=comment>//
  55     // Animals cannot be copied...
  56     //</span>
  57     <span class=identifier>animal</span><span class=special>(</span> <span class=keyword>const</span> <span class=identifier>animal</span><span class=special>&amp;</span> <span class=identifier>r</span> <span class=special>)</span> <span class=special>:</span> <span class=identifier>name_</span><span class=special>(</span> <span class=identifier>r</span><span class=special>.</span><span class=identifier>name_</span> <span class=special>)</span>           <span class=special>{</span> <span class=special>}</span>
  58     <span class=keyword>void</span> <span class=keyword>operator</span><span class=special>=(</span> <span class=keyword>const</span> <span class=identifier>animal</span><span class=special>&amp;</span> <span class=special>);</span>
  59
  60 <span class=keyword>private</span><span class=special>:</span>
  61     <span class=comment>//
  62     // ...but due to advances in genetics, we can clone them!
  63     //</span>
  64
  65     <span class=keyword>virtual</span> <span class=identifier>animal</span><span class=special>*</span> <span class=identifier>do_clone</span><span class=special>()</span> <span class=keyword>const</span> <span class=special>=</span> <span class=number>0</span><span class=special>;</span>
  66
  67 <span class=keyword>public</span><span class=special>:</span>
  68     <span class=identifier>animal</span><span class=special>(</span> <span class=keyword>const</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span><span class=special>&amp;</span> <span class=identifier>name</span> <span class=special>)</span> <span class=special>:</span> <span class=identifier>name_</span><span class=special>(</span><span class=identifier>name</span><span class=special>)</span>        <span class=special>{</span> <span class=special>}</span>
  69     <span class=keyword>virtual</span> <span class=special>~</span><span class=identifier>animal</span><span class=special>()</span> <span class=keyword>throw</span><span class=special>()</span>                              <span class=special>{</span> <span class=special>}</span>
  70
  71     <span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span> <span class=identifier>speak</span><span class=special>()</span> <span class=keyword>const</span>
  72     <span class=special>{</span>
  73         <span class=keyword>return</span> <span class=identifier>do_speak</span><span class=special>();</span>
  74     <span class=special>}</span>
  75
  76     <span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span> <span class=identifier>name</span><span class=special>()</span> <span class=keyword>const</span>
  77     <span class=special>{</span>
  78         <span class=keyword>return</span> <span class=identifier>name_</span><span class=special>;</span>
  79     <span class=special>}</span>
  80
  81     <span class=identifier>animal</span><span class=special>*</span> <span class=identifier>clone</span><span class=special>()</span> <span class=keyword>const</span>
  82     <span class=special>{</span>
  83         <span class=keyword>return</span> <span class=identifier>do_clone</span><span class=special>();</span>
  84     <span class=special>}</span>
  85 <span class=special>};</span>
  86
  87 <span class=comment>//
  88 // An animal is still not Clonable. We need this last hook.
  89 //
  90 // Notice that we pass the animal by const reference
  91 // and return by pointer.
  92 //</span>
  93
  94 <span class=identifier>animal</span><span class=special>*</span> <span class=identifier>new_clone</span><span class=special>(</span> <span class=keyword>const</span> <span class=identifier>animal</span><span class=special>&amp;</span> <span class=identifier>a</span> <span class=special>)</span>
  95 <span class=special>{</span>
  96     <span class=keyword>return</span> <span class=identifier>a</span><span class=special>.</span><span class=identifier>clone</span><span class=special>();</span>
  97 <span class=special>}</span>
  98
  99 <span class=comment>//
 100 // We do not need to define 'delete_clone()' since
 101 // since the default is to call the default 'operator delete()'.
 102 //</span>
 103
 104 <span class=keyword>const</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span> <span class=identifier>muuuh</span> <span class=special>=</span> <span class=string>&quot;Muuuh!&quot;</span><span class=special>;</span>
 105 <span class=keyword>const</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span> <span class=identifier>oiink</span> <span class=special>=</span> <span class=string>&quot;Oiiink&quot;</span><span class=special>;</span>
 106
 107 <span class=keyword>class</span> <span class=identifier>cow</span> <span class=special>:</span> <span class=keyword>public</span> <span class=identifier>animal</span>
 108 <span class=special>{</span>
 109     <span class=keyword>virtual</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span> <span class=identifier>do_speak</span><span class=special>()</span> <span class=keyword>const</span>
 110     <span class=special>{</span>
 111         <span class=keyword>return</span> <span class=identifier>muuuh</span><span class=special>;</span>
 112     <span class=special>}</span>
 113
 114     <span class=keyword>virtual</span> <span class=identifier>animal</span><span class=special>*</span> <span class=identifier>do_clone</span><span class=special>()</span> <span class=keyword>const</span>
 115     <span class=special>{</span>
 116         <span class=keyword>return</span> <span class=keyword>new</span> <span class=identifier>cow</span><span class=special>(</span> <span class=special>*</span><span class=keyword>this</span> <span class=special>);</span>
 117     <span class=special>}</span>
 118
 119 <span class=keyword>public</span><span class=special>:</span>
 120     <span class=identifier>cow</span><span class=special>(</span> <span class=keyword>const</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span><span class=special>&amp;</span> <span class=identifier>name</span> <span class=special>)</span> <span class=special>:</span> <span class=identifier>animal</span><span class=special>(</span><span class=identifier>name</span><span class=special>)</span>          <span class=special>{</span> <span class=special>}</span>
 121 <span class=special>};</span>
 122
 123 <span class=keyword>class</span> <span class=identifier>pig</span> <span class=special>:</span> <span class=keyword>public</span> <span class=identifier>animal</span>
 124 <span class=special>{</span>
 125     <span class=keyword>virtual</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span> <span class=identifier>do_speak</span><span class=special>()</span> <span class=keyword>const</span>
 126     <span class=special>{</span>
 127         <span class=keyword>return</span> <span class=identifier>oiink</span><span class=special>;</span>
 128     <span class=special>}</span>
 129
 130     <span class=keyword>virtual</span> <span class=identifier>animal</span><span class=special>*</span> <span class=identifier>do_clone</span><span class=special>()</span> <span class=keyword>const</span>
 131     <span class=special>{</span>
 132         <span class=keyword>return</span> <span class=keyword>new</span> <span class=identifier>pig</span><span class=special>(</span> <span class=special>*</span><span class=keyword>this</span> <span class=special>);</span>
 133     <span class=special>}</span>
 134
 135 <span class=keyword>public</span><span class=special>:</span>
 136     <span class=identifier>pig</span><span class=special>(</span> <span class=keyword>const</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span><span class=special>&amp;</span> <span class=identifier>name</span> <span class=special>)</span> <span class=special>:</span> <span class=identifier>animal</span><span class=special>(</span><span class=identifier>name</span><span class=special>)</span>          <span class=special>{</span> <span class=special>}</span>
 137 <span class=special>};</span>
 138
 139 <span class=comment>//
 140 // Then we, of course, need a place to put all
 141 // those animals.
 142 //</span>
 143
 144 <span class=keyword>class</span> <span class=identifier>farm</span>
 145 <span class=special>{</span>
 146     <span class=comment>//
 147     // This is where the smart containers are handy
 148     //</span>
 149     <span class=keyword>typedef</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>ptr_deque</span><span class=special>&lt;</span><span class=identifier>animal</span><span class=special>&gt;</span> <span class=identifier>barn_type</span><span class=special>;</span>
 150     <span class=identifier>barn_type</span>                        <span class=identifier>barn</span><span class=special>;</span>
 151
 152     <span class=comment>//
 153     // An error type
 154     //</span>
 155     <span class=keyword>struct</span> <span class=identifier>farm_trouble</span> <span class=special>:</span> <span class=keyword>public</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>exception</span>           <span class=special>{</span> <span class=special>};</span>
 156
 157 <span class=keyword>public</span><span class=special>:</span>
 158     <span class=comment>//
 159     // We would like to make it possible to
 160     // iterate over the animals in the farm
 161     //</span>
 162     <span class=keyword>typedef</span> <span class=identifier>barn_type</span><span class=special>::</span><span class=identifier>iterator</span>  <span class=identifier>animal_iterator</span><span class=special>;</span>
 163
 164     <span class=comment>//
 165     // We also need to count the farm's size...
 166     //</span>
 167     <span class=keyword>typedef</span> <span class=identifier>barn_type</span><span class=special>::</span><span class=identifier>size_type</span> <span class=identifier>size_type</span><span class=special>;</span>
 168
 169     <span class=comment>//
 170     // And we also want to transfer an animal
 171     // safely around. The easiest way to think
 172     // about '::auto_type' is to imagine a simplified
 173     // 'std::auto_ptr&lt;T&gt;' ... this means you can expect
 174     //
 175     //   T* operator-&gt;()
 176     //   T* release()
 177     //   deleting destructor
 178     //
 179     // but not more.
 180     //</span>
 181     <span class=keyword>typedef</span> <span class=identifier>barn_type</span><span class=special>::</span><span class=identifier>auto_type</span>  <span class=identifier>animal_transport</span><span class=special>;</span>
 182
 183     <span class=comment>//
 184     // Create an empty farm.
 185     //</span>
 186     <span class=identifier>farm</span><span class=special>()</span>                                                 <span class=special>{</span> <span class=special>}</span>
 187
 188     <span class=comment>//
 189     // We need a constructor that can make a new
 190     // farm by cloning a range of animals.
 191     //</span>
 192     <span class=identifier>farm</span><span class=special>(</span> <span class=identifier>animal_iterator</span> <span class=identifier>begin</span><span class=special>,</span> <span class=identifier>animal_iterator</span> <span class=identifier>end</span> <span class=special>)</span>
 193      <span class=special>:</span>
 194         <span class=comment>//
 195         // Objects are always cloned before insertion
 196         // unless we explicitly add a pointer or
 197         // use 'release()'. Therefore we actually
 198         // clone all animals in the range
 199         //</span>
 200         <span class=identifier>barn</span><span class=special>(</span> <span class=identifier>begin</span><span class=special>,</span> <span class=identifier>end</span> <span class=special>)</span>                               <span class=special>{</span> <span class=special>}</span>
 201
 202     <span class=comment>//
 203     // ... so we need some other function too
 204     //</span>
 205
 206     <span class=identifier>animal_iterator</span> <span class=identifier>begin</span><span class=special>()</span>
 207     <span class=special>{</span>
 208         <span class=keyword>return</span> <span class=identifier>barn</span><span class=special>.</span><span class=identifier>begin</span><span class=special>();</span>
 209     <span class=special>}</span>
 210
 211     <span class=identifier>animal_iterator</span> <span class=identifier>end</span><span class=special>()</span>
 212     <span class=special>{</span>
 213         <span class=keyword>return</span> <span class=identifier>barn</span><span class=special>.</span><span class=identifier>end</span><span class=special>();</span>
 214     <span class=special>}</span>
 215
 216     <span class=comment>//
 217     // Here it is quite ok to have an 'animal*' argument.
 218     // The smart container will handle all ownership
 219     // issues.
 220     //</span>
 221     <span class=keyword>void</span> <span class=identifier>buy_animal</span><span class=special>(</span> <span class=identifier>animal</span><span class=special>*</span> <span class=identifier>a</span> <span class=special>)</span>
 222     <span class=special>{</span>
 223         <span class=identifier>barn</span><span class=special>.</span><span class=identifier>push_back</span><span class=special>(</span> <span class=identifier>a</span> <span class=special>);</span>
 224     <span class=special>}</span>
 225
 226     <span class=comment>//
 227     // The farm can also be in economical trouble and
 228     // therefore be in the need to sell animals.
 229     //</span>
 230     <span class=identifier>animal_transport</span> <span class=identifier>sell_animal</span><span class=special>(</span> <span class=identifier>animal_iterator</span> <span class=identifier>to_sell</span> <span class=special>)</span>
 231     <span class=special>{</span>
 232         <span class=keyword>if</span><span class=special>(</span> <span class=identifier>to_sell</span> <span class=special>==</span> <span class=identifier>end</span><span class=special>()</span> <span class=special>)</span>
 233             <span class=keyword>throw</span> <span class=identifier>farm_trouble</span><span class=special>();</span>
 234
 235         <span class=comment>//
 236         // Here we remove the animal from the barn,
 237         // but the animal is not deleted yet...it's
 238         // up to the buyer to decide what
 239         // to do with it.
 240         //</span>
 241         <span class=keyword>return</span> <span class=identifier>barn</span><span class=special>.</span><span class=identifier>release</span><span class=special>(</span> <span class=identifier>to_sell</span> <span class=special>);</span>
 242     <span class=special>}</span>
 243
 244     <span class=comment>//
 245     // How big a farm do we have?
 246     //</span>
 247     <span class=identifier>size_type</span> <span class=identifier>size</span><span class=special>()</span> <span class=keyword>const</span>
 248     <span class=special>{</span>
 249         <span class=keyword>return</span> <span class=identifier>barn</span><span class=special>.</span><span class=identifier>size</span><span class=special>();</span>
 250     <span class=special>}</span>
 251
 252     <span class=comment>//
 253     // If things are bad, we might choose to sell all animals :-(
 254     //</span>
 255     <span class=identifier>std</span><span class=special>::</span><span class=identifier>auto_ptr</span><span class=special>&lt;</span><span class=identifier>barn_type</span><span class=special>&gt;</span> <span class=identifier>sell_farm</span><span class=special>()</span>
 256     <span class=special>{</span>
 257         <span class=keyword>return</span> <span class=identifier>barn</span><span class=special>.</span><span class=identifier>release</span><span class=special>();</span>
 258     <span class=special>}</span>
 259
 260     <span class=comment>//
 261     // However, if things are good, we might buy somebody
 262     // else's farm :-)
 263     //</span>
 264
 265     <span class=keyword>void</span> <span class=identifier>buy_farm</span><span class=special>(</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>auto_ptr</span><span class=special>&lt;</span><span class=identifier>barn_type</span><span class=special>&gt;</span> <span class=identifier>other</span> <span class=special>)</span>
 266     <span class=special>{</span>
 267         <span class=comment>//
 268         // This line inserts all the animals from 'other'
 269         // and is guaranteed either to succeed or to have no
 270         // effect
 271         //</span>
 272         <span class=identifier>barn</span><span class=special>.</span><span class=identifier>transfer</span><span class=special>(</span> <span class=identifier>barn</span><span class=special>.</span><span class=identifier>end</span><span class=special>(),</span> <span class=comment>// insert new animals at the end</span>
 273                          <span class=special>*</span><span class=identifier>other</span> <span class=special>);</span>     <span class=comment>// we want to transfer all animals,
 274                                        // so we use the whole container as argument
 275         //
 276         // You might think you would have to do
 277         //
 278         // other.release();
 279         //
 280         // but '*other' is empty and can go out of scope as it wants
 281         //</span>
 282         <span class=identifier>BOOST_ASSERT</span><span class=special>(</span> <span class=identifier>other</span><span class=special>-&gt;</span><span class=identifier>empty</span><span class=special>()</span> <span class=special>);</span>
 283     <span class=special>}</span>
 284
 285 <span class=special>};</span> <span class=comment>// class 'farm'.</span>
 286
 287 <span class=keyword>int</span> <span class=identifier>main</span><span class=special>()</span>
 288 <span class=special>{</span>
 289     <span class=comment>//
 290     // First we make a farm
 291     //</span>
 292     <span class=identifier>farm</span> <span class=identifier>animal_farm</span><span class=special>;</span>
 293     <span class=identifier>BOOST_ASSERT</span><span class=special>(</span> <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>size</span><span class=special>()</span> <span class=special>==</span> <span class=number>0u</span> <span class=special>);</span>
 294
 295     <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>buy_animal</span><span class=special>(</span> <span class=keyword>new</span> <span class=identifier>pig</span><span class=special>(</span><span class=string>&quot;Betty&quot;</span><span class=special>)</span> <span class=special>);</span>
 296     <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>buy_animal</span><span class=special>(</span> <span class=keyword>new</span> <span class=identifier>pig</span><span class=special>(</span><span class=string>&quot;Benny&quot;</span><span class=special>)</span> <span class=special>);</span>
 297     <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>buy_animal</span><span class=special>(</span> <span class=keyword>new</span> <span class=identifier>pig</span><span class=special>(</span><span class=string>&quot;Jeltzin&quot;</span><span class=special>)</span> <span class=special>);</span>
 298     <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>buy_animal</span><span class=special>(</span> <span class=keyword>new</span> <span class=identifier>cow</span><span class=special>(</span><span class=string>&quot;Hanz&quot;</span><span class=special>)</span> <span class=special>);</span>
 299     <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>buy_animal</span><span class=special>(</span> <span class=keyword>new</span> <span class=identifier>cow</span><span class=special>(</span><span class=string>&quot;Mary&quot;</span><span class=special>)</span> <span class=special>);</span>
 300     <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>buy_animal</span><span class=special>(</span> <span class=keyword>new</span> <span class=identifier>cow</span><span class=special>(</span><span class=string>&quot;Frederik&quot;</span><span class=special>)</span> <span class=special>);</span>
 301     <span class=identifier>BOOST_ASSERT</span><span class=special>(</span> <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>size</span><span class=special>()</span> <span class=special>==</span> <span class=number>6u</span> <span class=special>);</span>
 302
 303     <span class=comment>//
 304     // Then we make another farm...it will actually contain
 305     // a clone of the other farm.
 306     //</span>
 307     <span class=identifier>farm</span> <span class=identifier>new_farm</span><span class=special>(</span> <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>begin</span><span class=special>(),</span> <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>end</span><span class=special>()</span> <span class=special>);</span>
 308     <span class=identifier>BOOST_ASSERT</span><span class=special>(</span> <span class=identifier>new_farm</span><span class=special>.</span><span class=identifier>size</span><span class=special>()</span> <span class=special>==</span> <span class=number>6u</span> <span class=special>);</span>
 309
 310     <span class=comment>//
 311     // Is it really clones in the new farm?
 312     //</span>
 313     <span class=identifier>BOOST_ASSERT</span><span class=special>(</span> <span class=identifier>new_farm</span><span class=special>.</span><span class=identifier>begin</span><span class=special>()-&gt;</span><span class=identifier>name</span><span class=special>()</span> <span class=special>==</span> <span class=string>&quot;Betty&quot;</span> <span class=special>);</span>
 314
 315     <span class=comment>//
 316     // Then we search for an animal, Mary (the Crown Princess of Denmark),
 317     // because we would like to buy her ...
 318     //</span>
 319     <span class=keyword>typedef</span> <span class=identifier>farm</span><span class=special>::</span><span class=identifier>animal_iterator</span> <span class=identifier>iterator</span><span class=special>;</span>
 320     <span class=identifier>iterator</span> <span class=identifier>to_sell</span><span class=special>;</span>
 321     <span class=keyword>for</span><span class=special>(</span> <span class=identifier>iterator</span> <span class=identifier>i</span>   <span class=special>=</span> <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>begin</span><span class=special>(),</span>
 322                   <span class=identifier>end</span> <span class=special>=</span> <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>end</span><span class=special>();</span>
 323          <span class=identifier>i</span> <span class=special>!=</span> <span class=identifier>end</span><span class=special>;</span> <span class=special>++</span><span class=identifier>i</span> <span class=special>)</span>
 324     <span class=special>{</span>
 325         <span class=keyword>if</span><span class=special>(</span> <span class=identifier>i</span><span class=special>-&gt;</span><span class=identifier>name</span><span class=special>()</span> <span class=special>==</span> <span class=string>&quot;Mary&quot;</span> <span class=special>)</span>
 326         <span class=special>{</span>
 327             <span class=identifier>to_sell</span> <span class=special>=</span> <span class=identifier>i</span><span class=special>;</span>
 328             <span class=keyword>break</span><span class=special>;</span>
 329         <span class=special>}</span>
 330     <span class=special>}</span>
 331
 332     <span class=identifier>farm</span><span class=special>::</span><span class=identifier>animal_transport</span> <span class=identifier>mary</span> <span class=special>=</span> <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>sell_animal</span><span class=special>(</span> <span class=identifier>to_sell</span> <span class=special>);</span>
 333
 334
 335     <span class=keyword>if</span><span class=special>(</span> <span class=identifier>mary</span><span class=special>-&gt;</span><span class=identifier>speak</span><span class=special>()</span> <span class=special>==</span> <span class=identifier>muuuh</span> <span class=special>)</span>
 336         <span class=comment>//
 337         // Great, Mary is a cow, and she may live longer
 338         //</span>
 339         <span class=identifier>new_farm</span><span class=special>.</span><span class=identifier>buy_animal</span><span class=special>(</span> <span class=identifier>mary</span><span class=special>.</span><span class=identifier>release</span><span class=special>()</span> <span class=special>);</span>
 340     <span class=keyword>else</span>
 341         <span class=comment>//
 342         // Then the animal would be destroyed (!)
 343         // when we go out of scope.
 344         //</span>
 345         <span class=special>;</span>
 346
 347     <span class=comment>//
 348     // Now we can observe some changes to the two farms...
 349     //</span>
 350     <span class=identifier>BOOST_ASSERT</span><span class=special>(</span> <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>size</span><span class=special>()</span> <span class=special>==</span> <span class=number>5u</span> <span class=special>);</span>
 351     <span class=identifier>BOOST_ASSERT</span><span class=special>(</span> <span class=identifier>new_farm</span><span class=special>.</span><span class=identifier>size</span><span class=special>()</span>    <span class=special>==</span> <span class=number>7u</span> <span class=special>);</span>
 352
 353     <span class=comment>//
 354     // The new farm has however underestimated how much
 355     // it cost to feed Mary and its owner is forced to sell the farm...
 356     //</span>
 357     <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>buy_farm</span><span class=special>(</span> <span class=identifier>new_farm</span><span class=special>.</span><span class=identifier>sell_farm</span><span class=special>()</span> <span class=special>);</span>
 358
 359     <span class=identifier>BOOST_ASSERT</span><span class=special>(</span> <span class=identifier>new_farm</span><span class=special>.</span><span class=identifier>size</span><span class=special>()</span>    <span class=special>==</span> <span class=number>0u</span> <span class=special>);</span>
 360     <span class=identifier>BOOST_ASSERT</span><span class=special>(</span> <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>size</span><span class=special>()</span> <span class=special>==</span> <span class=number>12u</span> <span class=special>);</span>
 361 <span class=special>}</span>
 362 </pre>
 363 </body>
 364
 365 </html>