boost_ptr_container 0.1.0

Boost C++ library boost_ptr_container packaged using Zanbil
Documentation 
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    <pre><span class="comment">//
// Boost.Pointer Container
//
//  Copyright Thorsten Ottosen 2003-2005. Use, modification and
//  distribution is subject to the Boost Software License, Version
//  1.0. (See accompanying file LICENSE_1_0.txt or copy at
//  http://www.boost.org/LICENSE_1_0.txt)
//
// For more information, see http://www.boost.org/libs/ptr_container/
//

//
// This example is intended to get you started.
// Notice how the smart container
//
// 1. takes ownership of objects
// 2. transfers ownership
// 3. applies indirection to iterators 
// 4. clones objects from other smart containers
// 

//
// First we select which container to use.
//</span>
<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>

<span class="comment">//
// we need these later in the example
//</span>
<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>
<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">string</span><span class="special">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">exception</span><span class="special">&gt;</span>


<span class="comment">//
// Then we define a small polymorphic class
// hierarchy.
//</span> 

<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>
<span class="special">{</span>
    <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>
    <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">protected</span><span class="special">:</span>
    <span class="comment">//
    // Animals cannot be copied...
    //</span>
    <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>
    <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>

<span class="keyword">private</span><span class="special">:</span>
    <span class="comment">//
    // ...but due to advances in genetics, we can clone them!
    //</span>

    <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>
        
<span class="keyword">public</span><span class="special">:</span>
    <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>
    <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>
    
    <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>
    <span class="special">{</span>
        <span class="keyword">return</span> <span class="identifier">do_speak</span><span class="special">();</span>
    <span class="special">}</span>

    <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>
    <span class="special">{</span>
        <span class="keyword">return</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">clone</span><span class="special">()</span> <span class="keyword">const</span>
    <span class="special">{</span>
        <span class="keyword">return</span> <span class="identifier">do_clone</span><span class="special">();</span>
    <span class="special">}</span>
<span class="special">};</span>

<span class="comment">//
// An animal is still not Clonable. We need this last hook.
//
// Notice that we pass the animal by const reference
// and return by pointer.
//</span>

<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>
<span class="special">{</span>
    <span class="keyword">return</span> <span class="identifier">a</span><span class="special">.</span><span class="identifier">clone</span><span class="special">();</span>
<span class="special">}</span>

<span class="comment">//
// We do not need to define 'delete_clone()' since
// since the default is to call the default 'operator delete()'.
//</span>

<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>
<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>

<span class="keyword">class</span> <span class="identifier">cow</span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">animal</span>
<span class="special">{</span>
    <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="keyword">return</span> <span class="identifier">muuuh</span><span class="special">;</span>
    <span class="special">}</span>

    <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="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>
    <span class="special">}</span>

<span class="keyword">public</span><span class="special">:</span>
    <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>
<span class="special">};</span>

<span class="keyword">class</span> <span class="identifier">pig</span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">animal</span>
<span class="special">{</span>
    <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="keyword">return</span> <span class="identifier">oiink</span><span class="special">;</span>
    <span class="special">}</span>

    <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="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>
    <span class="special">}</span>
    
<span class="keyword">public</span><span class="special">:</span>
    <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>
<span class="special">};</span>

<span class="comment">//
// Then we, of course, need a place to put all
// those animals.
//</span>

<span class="keyword">class</span> <span class="identifier">farm</span>
<span class="special">{</span>
    <span class="comment">//
    // This is where the smart containers are handy
    //</span>
    <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>
    <span class="identifier">barn_type</span>                        <span class="identifier">barn</span><span class="special">;</span>

    <span class="comment">//
    // A convenience typedef for the compiler-appropriate
    // smart pointer used to manage barns
    //</span>    
    <span class="keyword">typedef</span> <span class="identifier"><a href="compatible_smart_ptr.html"><em>compatible-smart-ptr</em></a></span><span class="special">&lt;</span><span class="identifier">barn_type</span><span class="special">&gt;</span> <span class="identifier">raii_ptr</span><span class="special">;</span>

    <span class="comment">//
    // An error type
    //</span>
    <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>

<span class="keyword">public</span><span class="special">:</span>
    <span class="comment">// 
    // We would like to make it possible to
    // iterate over the animals in the farm
    //</span>
    <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>

    <span class="comment">//
    // We also need to count the farm's size...
    //</span>
    <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>
    
    <span class="comment">//
    // And we also want to transfer an animal
    // safely around. The easiest way to think
    // about '::auto_type' is to imagine a simplified
    // 'std::auto_ptr&lt;T&gt;' ... this means you can expect
    // 
    //   T* operator-&gt;()
    //   T* release()
    //   deleting destructor
    //
    // but not more.
    //</span>
    <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>

    <span class="comment">// 
    // Create an empty farm.
    //</span>
    <span class="identifier">farm</span><span class="special">()</span>                                                 <span class="special">{</span> <span class="special">}</span>
    
    <span class="comment">//
    // We need a constructor that can make a new
    // farm by cloning a range of animals.
    //</span>
    <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>
     <span class="special">:</span> 
        <span class="comment">//
        // Objects are always cloned before insertion
        // unless we explicitly add a pointer or 
        // use 'release()'. Therefore we actually
        // clone all animals in the range
        //</span>
        <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>
    
    <span class="comment">//
    // ... so we need some other function too
    //</span>

    <span class="identifier">animal_iterator</span> <span class="identifier">begin</span><span class="special">()</span>
    <span class="special">{</span>
        <span class="keyword">return</span> <span class="identifier">barn</span><span class="special">.</span><span class="identifier">begin</span><span class="special">();</span>
    <span class="special">}</span>

    <span class="identifier">animal_iterator</span> <span class="identifier">end</span><span class="special">()</span>
    <span class="special">{</span>
        <span class="keyword">return</span> <span class="identifier">barn</span><span class="special">.</span><span class="identifier">end</span><span class="special">();</span>
    <span class="special">}</span>
    
    <span class="comment">//
    // Here it is quite ok to have an 'animal*' argument.
    // The smart container will handle all ownership
    // issues.
    //</span>
    <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>
    <span class="special">{</span>
        <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>
    <span class="special">}</span>

    <span class="comment">//
    // The farm can also be in economical trouble and
    // therefore be in the need to sell animals.
    //</span>
    <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>
    <span class="special">{</span>
        <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>
            <span class="keyword">throw</span> <span class="identifier">farm_trouble</span><span class="special">();</span>

        <span class="comment">//
        // Here we remove the animal from the barn,
        // but the animal is not deleted yet...it's
        // up to the buyer to decide what
        // to do with it.
        //</span>
        <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>
    <span class="special">}</span>

    <span class="comment">//
    // How big a farm do we have?
    //</span>
    <span class="identifier">size_type</span> <span class="identifier">size</span><span class="special">()</span> <span class="keyword">const</span>
    <span class="special">{</span>
        <span class="keyword">return</span> <span class="identifier">barn</span><span class="special">.</span><span class="identifier">size</span><span class="special">();</span>
    <span class="special">}</span>

    <span class="comment">//
    // If things are bad, we might choose to sell all animals :-(
      //</span>

    <span class="identifier">raii_ptr</span> <span class="identifier">sell_farm</span><span class="special">()</span>
    <span class="special">{</span>
        <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="special">}</span>

    <span class="comment">//
    // However, if things are good, we might buy somebody
    // else's farm :-)
    //</span>

    <span class="keyword">void</span> <span class="identifier">buy_farm</span><span class="special">(</span> <span class="identifier">raii_ptr</span> <span class="identifier">other</span> <span class="special">)</span>
    <span class="special">{</span>
        <span class="comment">//
        // This line inserts all the animals from 'other'
        // and is guaranteed either to succeed or to have no
        // effect
        //</span>
        <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>
                         <span class="special">*</span><span class="identifier">other</span> <span class="special">);</span>     <span class="comment">// we want to transfer all animals,
                                       // so we use the whole container as argument
        //
        // You might think you would have to do
        //
        // other.release();
        //
        // but '*other' is empty and can go out of scope as it wants
        //</span>
        <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>
    <span class="special">}</span>
    
<span class="special">};</span> <span class="comment">// class 'farm'.</span>

<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
<span class="special">{</span>
    <span class="comment">//
    // First we make a farm
    //</span>
    <span class="identifier">farm</span> <span class="identifier">animal_farm</span><span class="special">;</span>
    <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>
    
    <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>
    <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>
    <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>
    <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>
    <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>
    <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>
    <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>

    <span class="comment">//
    // Then we make another farm...it will actually contain
    // a clone of the other farm.
    //</span>
    <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>
    <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>

    <span class="comment">//
    // Is it really clones in the new farm?
    //</span>
    <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>
    
    <span class="comment">//
    // Then we search for an animal, Mary (the Crown Princess of Denmark),
    // because we would like to buy her ...
    //</span>
    <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>
    <span class="identifier">iterator</span> <span class="identifier">to_sell</span><span class="special">;</span>
    <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>
                  <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>
         <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>
    <span class="special">{</span>
        <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>
        <span class="special">{</span>
            <span class="identifier">to_sell</span> <span class="special">=</span> <span class="identifier">i</span><span class="special">;</span>
            <span class="keyword">break</span><span class="special">;</span>
        <span class="special">}</span>
    <span class="special">}</span>

    <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>


    <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>
        <span class="comment">//
        // Great, Mary is a cow, and she may live longer
        //</span>
        <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>
    <span class="keyword">else</span>
        <span class="comment">//
        // Then the animal would be destroyed (!)
        // when we go out of scope.
        //</span>
        <span class="special">;</span>

    <span class="comment">//
    // Now we can observe some changes to the two farms...
    //</span>
    <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>
    <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>

    <span class="comment">//
    // The new farm has however underestimated how much
    // it cost to feed Mary and its owner is forced to sell the farm...
    //</span>
    <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>

    <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>
    <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>     
<span class="special">}</span>
</pre>
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