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<pre>
<span class=comment>//
// 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>smart_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=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>allocate_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>//
// 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>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><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>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><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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