<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>