matrosov daily c++

Повседневный С++: boost и STL

Михаил Матросов[email protected]

[email protected]

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"Повседневный С++: boost и STL", Михаил Матросов, CoreHard C++ Conf 2016

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С++17С++11/14

С++98

С

High level

Expert level

Modern C++

“Within C++ is a smaller, simpler, safer language struggling to get out”

Bjarne Stroustrup


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High level: Парадигма RAII и исключения (exceptions) Алгоритмы и контейнеры STL и boost Семантика перемещения λ-функции Классы и конструкторы Простые шаблоны


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Expert level: Операторы new/delete, владеющие

указатели Пользовательские операции копирования

и перемещения Пользовательские деструкторы Закрытое, защищённое, ромбовидное,

виртуальное наследование Шаблонная магия, SFINAE Все функции языка Си, препроцессор «Голые» циклы

Классический слайд с телом и заголовком


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bool doCompare(const Bakery* oldBakery, const Bakery* newBakery){ if (!oldBakery || !newBakery) { return false; } std::vector<Cookie> oldCookies; std::vector<Cookie> newCookies; std::vector<std::pair<Cookie, int>> diff; collectCookies(*oldBakery, oldCookies); collectCookies(*newBakery, newCookies); std::sort(oldCookies.begin(), oldCookies.end(), compareCookies); std::sort(newCookies.begin(), newCookies.end(), compareCookies); auto oldIt = oldCookies.begin(); auto newIt = newCookies.begin(); while ((oldIt != oldCookies.end()) || (newIt != newCookies.end())) { if (compareCookies(*oldIt, *newIt)) { diff.push_back(std::pair<Cookie, int>(*oldIt, 1)); ++oldIt; } else if (compareCookies(*newIt, *oldIt)) { diff.push_back(std::pair<Cookie, int>(*newIt, 2)); ++newIt; } else { ++oldIt; ++newIt; } } if (oldIt != oldCookies.end()) { for (; oldIt < oldCookies.end(); oldIt++) { diff.push_back(std::pair<Cookie, int>(*oldIt, 1)); } } if (newIt != newCookies.end()) { for (; newIt < newCookies.end(); newIt++) { diff.push_back(std::pair<Cookie, int>(*newIt, 2)); } } for (const auto& item : diff) { std::cout << "Bakery #" << item.second << " has a different cookie \"" << item.first.name << "\" (weight=" << item.first.weight << ", volume=" << item.first.volume << ", tastiness=" << item.first.tastiness << ")." << std::endl; } if (diff.size() > 0) return false; return true;}


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bool doCompare(const Bakery& oldBakery, const Bakery& newBakery){ auto oldCookies = collectSortedCookies(oldBakery); auto newCookies = collectSortedCookies(newBakery); auto reportLost = [](const Cookie& cookie) { std::cout << "We've lost a friend: " << cookie << "." << std::endl; }; auto reportAppeared = [](const Cookie& cookie) { std::cout << "We got a new friend: " << cookie << "." << std::endl; }; boost::range::set_difference(oldCookies, newCookies, boost::make_function_output_iterator(reportLost)); boost::range::set_difference(newCookies, oldCookies, boost::make_function_output_iterator(reportAppeared)); return oldCookies == newCookies;}


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bool doCompare(const Bakery* oldBakery, const Bakery* newBakery){ if (!oldBakery || !newBakery) { return false; } std::vector<Cookie> oldCookies; std::vector<Cookie> newCookies; std::vector<std::pair<Cookie, int>> diff; collectCookies(*oldBakery, oldCookies); collectCookies(*newBakery, newCookies); // ...


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bool doCompare(const Bakery& oldBakery, const Bakery& newBakery){ std::vector<Cookie> oldCookies; std::vector<Cookie> newCookies; std::vector<std::pair<Cookie, int>> diff; collectCookies(oldBakery, oldCookies); collectCookies(newBakery, newCookies); // ...


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bool doCompare(const Bakery& oldBakery, const Bakery& newBakery){ std::vector<Cookie> oldCookies; std::vector<Cookie> newCookies; collectCookies(oldBakery, oldCookies); collectCookies(newBakery, newCookies); // ...


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void collectCookies(const Bakery& bakery, std::vector<Cookie>& o_cookies); bool doCompare(const Bakery& oldBakery, const Bakery& newBakery){ std::vector<Cookie> oldCookies; std::vector<Cookie> newCookies; collectCookies(oldBakery, oldCookies); collectCookies(newBakery, newCookies); // ...


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std::vector<Cookie> collectCookies(const Bakery& bakery);

bool doCompare(const Bakery& oldBakery, const Bakery& newBakery){ std::vector<Cookie> oldCookies = collectCookies(oldBakery); std::vector<Cookie> newCookies = collectCookies(newBakery);

// ...


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λλ=:


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bool doCompare(const Bakery& oldBakery, const Bakery& newBakery){ std::vector<Cookie> oldCookies = collectCookies(oldBakery); std::vector<Cookie> newCookies = collectCookies(newBakery); std::sort(oldCookies.begin(), oldCookies.end()); std::sort(newCookies.begin(), newCookies.end());

// ...


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std::vector<Cookie> collectCookies(const Bakery& bakery){ std::vector<Cookie> cookies; // ... // ... return cookies;} bool doCompare(const Bakery& oldBakery, const Bakery& newBakery){ std::vector<Cookie> oldCookies = collectCookies(oldBakery); std::vector<Cookie> newCookies = collectCookies(newBakery); std::sort(oldCookies.begin(), oldCookies.end()); std::sort(newCookies.begin(), newCookies.end());

// ...


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std::vector<Cookie> collectSortedCookies(const Bakery& bakery){ std::vector<Cookie> cookies; // ... std::sort(cookies.begin(), cookies.end()); return cookies;} bool doCompare(const Bakery& oldBakery, const Bakery& newBakery){ std::vector<Cookie> oldCookies = collectSortedCookies(oldBakery); std::vector<Cookie> newCookies = collectSortedCookies(newBakery);

// ...


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// ... std::sort(oldCookies.begin(), oldCookies.end(), compareCookies); std::sort(newCookies.begin(), newCookies.end(), compareCookies); auto oldIt = oldCookies.begin(); auto newIt = newCookies.begin(); while ((oldIt != oldCookies.end()) || (newIt != newCookies.end())) { if (compareCookies(*oldIt, *newIt)) { diff.push_back(std::pair<Cookie, int>(*oldIt, 1)); ++oldIt; } else if (compareCookies(*newIt, *oldIt)) { // ...


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struct Cookie{ double weight; double volume; std::string name; int tastiness;}; bool compareCookies(const Cookie& a, const Cookie& b){ if (a.tastiness != b.tastiness) return a.tastiness < b.tastiness; if (a.weight != b.weight) return a.weight < b.weight; if (a.volume != b.volume) return a.volume < b.volume; return a.name < b.name;}


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struct Cookie{ double weight; double volume; std::string name; int tastiness;}; bool operator<(const Cookie& a, const Cookie& b){ if (a.tastiness != b.tastiness) return a.tastiness < b.tastiness; if (a.weight != b.weight) return a.weight < b.weight; if (a.volume != b.volume) return a.volume < b.volume; return a.name < b.name;}


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// ... std::sort(oldCookies.begin(), oldCookies.end(), compareCookies); std::sort(newCookies.begin(), newCookies.end(), compareCookies); auto oldIt = oldCookies.begin(); auto newIt = newCookies.begin(); while ((oldIt != oldCookies.end()) || (newIt != newCookies.end())) { if (compareCookies(*oldIt, *newIt)) { diff.push_back(std::pair<Cookie, int>(*oldIt, 1)); ++oldIt; } else if (compareCookies(*newIt, *oldIt)) { // ...


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// ... std::sort(oldCookies.begin(), oldCookies.end()); std::sort(newCookies.begin(), newCookies.end()); auto oldIt = oldCookies.begin(); auto newIt = newCookies.begin(); while ((oldIt != oldCookies.end()) || (newIt != newCookies.end())) { if (*oldIt < *newIt) { diff.push_back(std::pair<Cookie, int>(*oldIt, 1)); ++oldIt; } else if (*newIt < *oldIt) { // ...


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bool operator<(const Cookie& a, const Cookie& b){ if (a.tastiness != b.tastiness) return a.tastiness < b.tastiness; if (a.weight != b.weight) return a.weight < b.weight; if (a.volume != b.volume) return a.volume < b.volume; return a.name < b.name;}


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bool operator<(const Cookie& a, const Cookie& b){ return std::make_tuple(a.tastiness, a.weight, a.volume, a.name) < std::make_tuple(b.tastiness, b.weight, b.volume, b.name); }


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struct Cookie{ double weight; double volume; std::string name; int tastiness;}; bool operator<(const Cookie& a, const Cookie& b){ return std::make_tuple(a.tastiness, a.weight, a.volume, a.name) < std::make_tuple(b.tastiness, b.weight, b.volume, b.name); }


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struct Cookie{ double weight; double volume; std::string name; int tastiness;}; bool operator<(const Cookie& a, const Cookie& b){ return std::tie(a.tastiness, a.weight, a.volume, a.name) < std::tie(b.tastiness, b.weight, b.volume, b.name); }


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struct Cookie{ double weight; double volume; std::string name; int tastiness; auto rank() const { return std::tie(tastiness, weight, volume, name); } bool operator<(const Cookie& rhs) const { return rank() < rhs.rank(); } };

См. http://stackoverflow.com/q/6218812/261217

http://stackoverflow.com/q/6218812/261217

http://stackoverflow.com/q/6218812/261217


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struct Cookie{ double weight; double volume; std::string name; int tastiness; auto rank() const // -> std::tuple<const int&, const double&, { const double&, const std::string&> return std::tie(tastiness, weight, volume, name); } bool operator<(const Cookie& rhs) const { return rank() < rhs.rank(); } };


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struct Cookie{ double weight; double volume; std::string name; int tastiness; auto rank() const // -> std::tuple<const int&, const double&, { const double&, const std::string&> return std::tie(tastiness, weight, volume, name); } bool operator<(const Cookie& rhs) const { return rank() < rhs.rank(); } bool operator==(const Cookie& rhs) const { return rank() == rhs.rank(); } };


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std::vector<std::pair<Cookie, int>> diff;

// ...

if (*oldIt < *newIt){ diff.push_back(std::pair<Cookie, int>(*oldIt, 1)); ++oldIt;}else if (*newIt < *oldIt){ diff.push_back(std::pair<Cookie, int>(*newIt, 2)); ++newIt;}


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// ...

if (*oldIt < *newIt){ diff.push_back(std::make_pair(*oldIt, 1)); ++oldIt;}else if (*newIt < *oldIt){ diff.push_back(std::make_pair(*newIt, 2)); ++newIt;}


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// ...

if (*oldIt < *newIt){ diff.emplace_back(*oldIt, 1); ++oldIt;}else if (*newIt < *oldIt){ diff.emplace_back(*newIt, 2); ++newIt;}

for (const auto& item : diff) // item is std::pair<Cookie, int>{ std::cout << "Bakery #" << item.second << " has a different cookie \"" << item.first.name << "\" (weight=" << item.first.weight << ", volume=" << item.first.volume << ", tastiness=" << item.first.tastiness << ")." << std::endl;}


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for (const auto& item : diff) // item is std::pair<Cookie, int>{ std::cout << "Bakery #" << item.second << " has a different cookie " << item.first << "." << std::endl;}

std::ostream& operator<<(std::ostream& stream, const Cookie& cookie){ return stream << "\"" << cookie.name << "\" (weight=" << cookie.weight << ", volume=" << cookie.volume << ", tastiness=" << cookie.tastiness << ")";}


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if (diff.size() > 0) return false;return true;


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return diff.empty();


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std::vector<std::pair<Cookie, int>> diff; auto oldIt = oldCookies.begin();auto newIt = newCookies.begin(); while ((oldIt != oldCookies.end()) || (newIt != newCookies.end())){ if (*oldIt < *newIt) { diff.emplace_back(*oldIt, 1); ++oldIt; } else if (*newIt < *oldIt) { diff.emplace_back(*newIt, 2); ++newIt; } else { ++oldIt; ++newIt; }} for (; oldIt != oldCookies.end(); oldIt++){ diff.emplace_back(*oldIt, 1);} for (; newIt != newCookies.end(); newIt++){ diff.emplace_back(*newIt, 2);}

1 2 5 7 8 9

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oldCookies

newCookies

diff

Ошибка. Должно быть &&


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std::vector<Cookie> lostCookies;std::set_difference(oldCookies.begin(), oldCookies.end(), newCookies.begin(), newCookies.end(), std::back_inserter(lostCookies)); std::vector<Cookie> appearedCookies;std::set_difference(newCookies.begin(), newCookies.end(), oldCookies.begin(), oldCookies.end(), std::back_inserter(appearedCookies));


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std::vector<Cookie> lostCookies;boost::range::set_difference(oldCookies, newCookies, std::back_inserter(lostCookies)); std::vector<Cookie> appearedCookies;boost::range::set_difference(newCookies, oldCookies, std::back_inserter(appearedCookies));


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std::vector<Cookie> lostCookies;boost::range::set_difference(oldCookies, newCookies, std::back_inserter(lostCookies)); std::vector<Cookie> appearedCookies;boost::range::set_difference(newCookies, oldCookies, std::back_inserter(appearedCookies));

for (const auto& cookie : lostCookies){ std::cout << "We've lost a friend: " << cookie << "." << std::endl;}for (const auto& cookie : appearedCookies){ std::cout << "We got a new friend: " << cookie << "." << std::endl;}


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auto reportLost = [](const Cookie& cookie) { std::cout << "We've lost a friend: " << cookie << "." << std::endl;};auto reportAppeared = [](const Cookie& cookie) { std::cout << "We got a new friend: " << cookie << "." << std::endl;}; boost::range::set_difference(oldCookies, newCookies, boost::make_function_output_iterator(reportLost));boost::range::set_difference(newCookies, oldCookies, boost::make_function_output_iterator(reportAppeared));


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bool doCompare(const Bakery& oldBakery, const Bakery& newBakery){ std::vector<Cookie> oldCookies = collectSortedCookies(oldBakery); std::vector<Cookie> newCookies = collectSortedCookies(newBakery); auto reportLost = [](const Cookie& cookie) { std::cout << "We've lost a friend: " << cookie << "." << std::endl; }; auto reportAppeared = [](const Cookie& cookie) { std::cout << "We got a new friend: " << cookie << "." << std::endl; }; boost::range::set_difference(oldCookies, newCookies, boost::make_function_output_iterator(reportLost)); boost::range::set_difference(newCookies, oldCookies, boost::make_function_output_iterator(reportAppeared)); return oldCookies == newCookies;}


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Код, использующий стандартные алгоритмы и контейнеры:КорочеПрощеНадёжнееОбычно эффективнееПроще переиспользоватьНе привязан к конкретной платформе


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И ещё немного по

теме…"Повседневный С++: boost и STL", Михаил Матросов, CoreHard C++ Conf

201650


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struct Cookie{ double weight; double volume; std::string name; int tastiness; auto rank() const { return std::tie(tastiness, weight, volume, name); } };


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struct Cookie{ double weight; double volume; std::string name; int tastiness; double density() const { return weight / volume; } auto rank() const { return std::tie(tastiness, density(), name); // Any problems here?.. }};


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struct Cookie{ double weight; double volume; std::string name; int tastiness; double density() const { return weight / volume; } auto rank() const { return std::make_tuple(tastiness, density(), std::ref(name)); }};


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struct Cookie{ double weight; double volume; std::string name; int tastiness; double density() const { return weight / volume; } auto rank() const // -> std::tuple<int, double, const std::string&> { return std::make_tuple(tastiness, density(), std::ref(name)); }};


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auto f = [](/* ... */) { /* ... */ };

boost::make_function_output_iterator(f) -> boost::iterators::function_output_iterator<LambdaAnonymousType>

template <class UnaryFunction>class function_output_iterator { // ... UnaryFunction m_f;};

auto it1 = boost::make_function_output_iterator(f); // Not assignableauto it2 = boost::make_function_output_iterator(std::ref(f)); // Assignable

Советы:Мыслите на высоком уровнеКод должен ясно выражать намерениеЗнайте свои инструменты и используйте их к месту


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// references// auto variables// auto function return type// move semantics// lambda functionsoperator<();std::make_tuple();std::tie();std::ref();

std::make_pair();std::vector<T>::emplace_back();std::vector<T>::empty();operator<<();std::back_inserter();std::set_difference();boost::range::set_difference();boost::make_function_output_iterator();

Мыслите на высоком уровнеКод должен ясно выражать намерениеЗнайте свои инструменты и используйте их к месту


std::make_pair();std::vector<T>::emplace_back();std::vector<T>::empty();operator<<();std::back_inserter();std::set_difference();boost::range::set_difference();boost::make_function_output_iterator();

Спасибо за внимание!

// references// auto variables// auto function return type// move semantics// lambda functionsoperator<();std::make_tuple();std::tie();std::ref();

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