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font-weight: bold ; font-size: larger } p.sidebar-subtitle { font-family: sans-serif ; font-weight: bold } p.topic-title { font-weight: bold } pre.address { margin-bottom: 0 ; margin-top: 0 ; font-family: serif ; font-size: 100% } pre.line-block { font-family: serif ; font-size: 100% } pre.literal-block, pre.doctest-block { margin-left: 2em ; margin-right: 2em ; background-color: #eeeeee } span.classifier { font-family: sans-serif ; font-style: oblique } span.classifier-delimiter { font-family: sans-serif ; font-weight: bold } span.interpreted { font-family: sans-serif } span.option { white-space: nowrap } span.pre { white-space: pre } span.problematic { color: red } span.section-subtitle { /* font-size relative to parent (h1..h6 element) */ font-size: 80% } table.citation { border-left: solid thin gray } table.docinfo { margin: 2em 4em } table.docutils { margin-top: 0.5em ; margin-bottom: 0.5em } table.footnote { border-left: solid thin black } table.docutils td, table.docutils th, table.docinfo td, table.docinfo th { padding-left: 0.5em ; padding-right: 0.5em ; vertical-align: top } table.docutils th.field-name, table.docinfo th.docinfo-name { font-weight: bold ; text-align: left ; white-space: nowrap ; padding-left: 0 } h1 tt.docutils, h2 tt.docutils, h3 tt.docutils, h4 tt.docutils, h5 tt.docutils, h6 tt.docutils { font-size: 100% } tt.docutils { background-color: #eeeeee } ul.auto-toc { list-style-type: none } </style> </head> <body> <div class="document" id="boost-pointer-container-library"> <h1 class="title"><img alt="Boost" src="boost.png" /> Pointer Container Library</h1> <h2 class="subtitle" id="examples">Examples</h2> <p>Some examples are given here and in the accompanying test files:</p> <div class="contents local topic"> <ul class="simple"> <li><a class="reference" href="#null-pointers-cannot-be-stored-in-the-containers" id="id2" name="id2">1. Null pointers cannot be stored in the containers</a></li> <li><a class="reference" href="#iterators-and-other-operations-return-indirected-values" id="id3" name="id3">2. Iterators and other operations return indirected values</a></li> <li><a class="reference" href="#copy-semantics-of-pointer-containers" id="id4" name="id4">3. Copy-semantics of pointer containers</a></li> <li><a class="reference" href="#making-a-non-copyable-type-cloneable" id="id5" name="id5">4. Making a non-copyable type Cloneable</a></li> <li><a class="reference" href="#objects-are-cloned-before-insertion-inserted-pointers-are-owned-by-the-container" id="id6" name="id6">5. Objects are cloned before insertion, inserted pointers are owned by the container</a></li> <li><a class="reference" href="#transferring-ownership-of-a-single-element" id="id7" name="id7">6. Transferring ownership of a single element</a></li> <li><a class="reference" href="#transferring-ownership-of-pointers-between-different-pointer-containers" id="id8" name="id8">7. Transferring ownership of pointers between different pointer containers</a></li> <li><a class="reference" href="#selected-test-files" id="id9" name="id9">8. Selected test files</a></li> <li><a class="reference" href="#a-large-example" id="id10" name="id10">9. A large example</a></li> </ul> </div> <div class="section"> <h1><a class="toc-backref" href="#id2" id="null-pointers-cannot-be-stored-in-the-containers" name="null-pointers-cannot-be-stored-in-the-containers"><span id="example-1"></span>1. Null pointers cannot be stored in the containers</a></h1> <pre class="literal-block"> my_container.push_back( 0 ); // throws bad_ptr my_container.replace( an_iterator, 0 ); // throws bad_ptr my_container.insert( an_iterator, 0 ); // throws bad_ptr std::auto_ptr<T> p( 0 ); my_container.push_back( p ); // throws bad_ptr </pre> </div> <div class="section"> <h1><a class="toc-backref" href="#id3" id="iterators-and-other-operations-return-indirected-values" name="iterators-and-other-operations-return-indirected-values"><span id="example-2"></span>2. Iterators and other operations return indirected values</a></h1> <pre class="literal-block"> ptr_vector<X> pvec; std::vector<X*> vec; *vec.begin() = new X; // fine, memory leak *pvec.begin() = new X; // compile time error ( *vec.begin() )->foo(); // call X::foo(), a bit clumsy pvec.begin()->foo(); // no indirection needed *vec.front() = X(); // overwrite first element pvec.front() = X(); // no indirection needed </pre> </div> <div class="section"> <h1><a class="toc-backref" href="#id4" id="copy-semantics-of-pointer-containers" name="copy-semantics-of-pointer-containers"><span id="example-3"></span>3. Copy-semantics of pointer containers</a></h1> <pre class="literal-block"> ptr_vector<T> vec1; ... ptr_vector<T> vec2( vec1.clone() ); // deep copy objects of 'vec1' and use them to construct 'vec2', could be very expensive vec2 = vec1.release(); // give up ownership of pointers in 'vec1' and pass the ownership to 'vec2', rather cheap vec2.release(); // give up ownership; the objects will be deallocated if not assigned to another container vec1 = vec2; // deep copy objects of 'vec2' and assign them to 'vec1', could be very expensive ptr_vector<T> vec3( vec1 ); // deep copy objects of 'vec1', could be very expensive </pre> </div> <div class="section"> <h1><a class="toc-backref" href="#id5" id="making-a-non-copyable-type-cloneable" name="making-a-non-copyable-type-cloneable"><span id="example-4"></span>4. Making a non-copyable type Cloneable</a></h1> <pre class="literal-block"> // a class that has no normal copy semantics class X : boost::noncopyable { public: X* clone() const; ... }; // this will be found by the library by argument dependent lookup (ADL) X* new_clone( const X& x ) { return x.clone(); } // we can now use the interface that requires cloneability ptr_vector<X> vec1, vec2; ... vec2 = vec1.clone(); // 'clone()' requires cloning <g> vec2.insert( vec2.end(), vec1.begin(), vec1.end() ); // inserting always means inserting clones </pre> </div> <div class="section"> <h1><a class="toc-backref" href="#id6" id="objects-are-cloned-before-insertion-inserted-pointers-are-owned-by-the-container" name="objects-are-cloned-before-insertion-inserted-pointers-are-owned-by-the-container"><span id="example-5"></span>5. Objects are cloned before insertion, inserted pointers are owned by the container</a></h1> <pre class="literal-block"> class X { ... }; // assume 'X' is Cloneable X x; // and 'X' can be stack-allocated ptr_list<X> list; list.push_back( new_clone( x ) ); // insert a clone list.push_back( new X ); // always give the pointer directly to the container to avoid leaks list.push_back( &x ); // don't do this!!! std::auto_ptr<X> p( new X ); list.push_back( p ); // give up ownership BOOST_ASSERT( p.get() == 0 ); </pre> </div> <div class="section"> <h1><a class="toc-backref" href="#id7" id="transferring-ownership-of-a-single-element" name="transferring-ownership-of-a-single-element"><span id="example-6"></span>6. Transferring ownership of a single element</a></h1> <pre class="literal-block"> ptr_deque<T> deq; typedef ptr_deque<T>::auto_type auto_type; // ... fill the container somehow auto_type ptr = deq.pop_back(); // remove back element from container and give up ownership auto_type ptr2 = deq.release( deq.begin() + 2 ); // use an iterator to determine the element to release ptr = deq.pop_front(); // supported for 'ptr_list' and 'ptr_deque' deq.push_back( ptr.release() ); // give ownership back to the container </pre> </div> <div class="section"> <h1><a class="toc-backref" href="#id8" id="transferring-ownership-of-pointers-between-different-pointer-containers" name="transferring-ownership-of-pointers-between-different-pointer-containers"><span id="example-7"></span>7. Transferring ownership of pointers between different pointer containers</a></h1> <pre class="literal-block"> ptr_list<X> list; ptr_vector<X> vec; ... // // note: no cloning happens in these examples // list.transfer( list.begin(), vec.begin(), vec ); // make the first element of 'vec' the first element of 'list' vec.transfer( vec.end(), list.begin(), list.end(), list ); // put all the lists element into the vector </pre> <p>We can also transfer objects from <tt class="docutils literal"><span class="pre">ptr_container<Derived></span></tt> to <tt class="docutils literal"><span class="pre">ptr_container<Base></span></tt> without any problems.</p> </div> <div class="section"> <h1><a class="toc-backref" href="#id9" id="selected-test-files" name="selected-test-files"><span id="example-8"></span>8. Selected test files</a></h1> <table class="docutils field-list" frame="void" rules="none"> <col class="field-name" /> <col class="field-body" /> <tbody valign="top"> <tr class="field"><th class="field-name" colspan="2"><a class="reference" href="../test/incomplete_type_test.cpp">incomplete_type_test.cpp</a>:</th></tr> <tr><td> </td><td class="field-body">Shows how to implement the Composite pattern.</td> </tr> <tr class="field"><th class="field-name" colspan="2"><a class="reference" href="../test/simple_test.cpp">simple_test.cpp</a>:</th></tr> <tr><td> </td><td class="field-body">Shows how the usage of pointer container compares with a container of smart pointers</td> </tr> <tr class="field"><th class="field-name" colspan="2"><a class="reference" href="../test/view_example.cpp">view_example.cpp</a>:</th></tr> <tr><td> </td><td class="field-body">Shows how to use a pointer container as a view into other container</td> </tr> <tr class="field"><th class="field-name"><a class="reference" href="../test/tree_test.cpp">tree_test.cpp</a>:</th><td class="field-body">Shows how to make a tree-structure</td> </tr> <tr class="field"><th class="field-name"><a class="reference" href="../test/ptr_array.cpp">array_test.cpp</a>:</th><td class="field-body">Shows how to make an n-ary tree</td> </tr> </tbody> </table> </div> <div class="section"> <h1><a class="toc-backref" href="#id10" id="a-large-example" name="a-large-example">9. A large example</a></h1> <p>This example shows many of the most common features at work. The example provide lots of comments. The source code can also be found <a class="reference" href="../test/tut1.cpp">here</a>.</p> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title> </title> <link rel="stylesheet" href="default.css" type="text/css"> </head> <body> <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><</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>></span> <span class=comment>// // we need these later in the example //</span> <span class=preprocessor>#include</span> <span class=special><</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>></span> <span class=preprocessor>#include</span> <span class=special><</span><span class=identifier>string</span><span class=special>></span> <span class=preprocessor>#include</span> <span class=special><</span><span class=identifier>exception</span><span class=special>></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>&</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>&</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>&</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>&</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>"Muuuh!"</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>"Oiiink"</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>&</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>&</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><</span><span class=identifier>animal</span><span class=special>></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<T>' ... this means you can expect // // T* operator->() // 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><</span><span class=identifier>barn_type</span><span class=special>></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><</span><span class=identifier>barn_type</span><span class=special>></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>-></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>"Betty"</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>"Benny"</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>"Jeltzin"</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>"Hanz"</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>"Mary"</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>"Frederik"</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>()-></span><span class=identifier>name</span><span class=special>()</span> <span class=special>==</span> <span class=string>"Betty"</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>-></span><span class=identifier>name</span><span class=special>()</span> <span class=special>==</span> <span class=string>"Mary"</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>-></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> </body> </html> <!-- 10. Changing the Clone Allocator ++++++++++++++++++++++++++++++++ This example shows how we can change the Clone Allocator to use the pointer containers as view into other containers: .. raw:: html :file: tut2.html --> <hr><p><strong>Navigate:</strong></p> <ul class="simple"> <li><a class="reference" href="ptr_container.html">home</a></li> <li><a class="reference" href="reference.html">reference</a></li> </ul> <hr><table class="docutils field-list" frame="void" rules="none"> <col class="field-name" /> <col class="field-body" /> <tbody valign="top"> <tr class="field"><th class="field-name">Copyright:</th><td class="field-body">Thorsten Ottosen 2004-2006. Use, modification and distribution is subject to the Boost Software License, Version 1.0 (see <a class="reference" href="http://www.boost.org/LICENSE_1_0.txt">LICENSE_1_0.txt</a>).</td> </tr> </tbody> </table> </div> </div> </body> </html>