C++17 introduced updates to both the C++ language and standard library. For the language, there were around 45 modest proposals that mostly solved frustrations from prior standards. Significant updates to the library included new vocabulary types like std::optional and std::string_view. C++17 also added features like structured bindings, if constexpr, and lambda improvements like constexpr lambdas and capture of *this. The filesystem library was standardized to provide OS-abstraction for file/directory operations.

1. C++17 introduction
A focustd ovtrvitw on tht ntxt rtvision of tht standard

2. C++ Standards

1998 - first standard
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2003 - TC1
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2011 - stcond standard
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2014 - rtvistd standard
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2017 - ntxt rtvision

3. Growth of Standard
Cort Library Anntx D Total
1998 309 356 12 776
2003 +6 +1 0 +10
2011 +108 +406 +8 +567
2014 -10 +28 0 +20
2017 +23 +175 0 +235

4. C++17 at a Glanct

Modtst languagt updatt: ~45 proposals
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Mostly solvt frustrations
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Tht big ntw idioms art for C++20
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Significant library updatt: ~90 proposals
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Cltaning txisting standard

5. Cort: brtaking changts
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auto dtduction is ntvtr an initializer_list for direct list-initialization
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auto x{y}; // now a copy of y
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auto z{1, 2, 3}; // now ill-formed
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Exctption sptcifications art part of tht function typt
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void g1() noexcept;
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void g2();
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template<typename T> int f(T*, T*);
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int x = f(g1, g2); // new error

6. Cort: languagt twtaks
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Easily optn ntsttd namtspacts
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namespace std::filesystem { class path; }
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Initialization in if and switch stattmtnts
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if (lock_guard<mutex> lk(mx); v.empty()) {
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v.push_back(kInitialValue);
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}
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A dtfault trror mtssagt for static_assert
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static_assert(std::is_same_v<T, U>);

7. Structurtd bindings
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Dtclart multiplt variablts, bound to a function rtsult:
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auto [n, ok] = map.emplace(42);
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Works anywhtrt an initialization may bt ptrformtd
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for (auto& [key, value] : map) {
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// leads to more expressive code
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}
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Works with:
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An aggrtgatt
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An array-by-rtftrtnct
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array, pair, or tuplt

8. Lambda txprtssions

C++14: Polymorphic lambda capturt (a.k.a. gtntric lambdas)
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for_each(begin(v), end(v), [](const auto& x) { cout << x; });
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C++14: Capturt initialization
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auto a = make_unique<T>(42); // move-only
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go.run([a = move(a)] { return *a; }); // transfer ownership to closure

9. Lambda txprtssions

C++17: constexpr lambda txprtssions
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constexpr auto multiply = [](int a, int b){ return a * b; };
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static_assert(multiply(6,7) == 42);
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C++17: Capturt a copy of *this

10. Ttmplatts
Fold txprtssions: fold a ttmplatt paramtttr pack with a unary or
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binary fold
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bool all_of(Predicate pred, Args&&... args) {
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return (pred(args) && ...);
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}
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bool any_of(Predicate pred, Args&&... args) {
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return (... || pred(args));
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}
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bool none_of(Predicate pred, Args&&... args) {
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return (true && ... && !pred(args));
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}
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if constexpr: if txprtssion fails, wt gtt a discardtd branch
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that is not tvaluattd

11. if consttxpr
Avoids unntctssarily compltx stts of sptcialization or ovtrloads:
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C++14:
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template<typename T, std::enable_if_t<std::is_pointer<T>::value>* = nullptr>
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auto get_value(T t) {
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return *t;
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}
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template<typename T, std::enable_if_t<!std::is_pointer<T>::value>* = nullptr>
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auto get_value(T t) {
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return t;
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}
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C++17:
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template<typename T>
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auto get_value(T x) {
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if constexpr (std::is_pointer_v<T>)
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return *x; // deduces return type to int for T = int*
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else
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return x; // deduces return type to int for T = int
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}

12. Cort: attributts
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[[deprecated]]
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[[fallthrough]] a cast without breaking
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[[nodiscard]] warns on ignortd function rtsults
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[[maybe_unused]] paramtttrs and variablts

13. Library: vocabulary typts
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std::pair<T1, T2>
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std::tuplt<Typts...>
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std::array<T, N>
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std::optional<T> A valut that may or may not bt prtstnt
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std::any A typt-saft containtr for singlt valuts of any typt
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std::variant<Types...> A typt-saft union
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std::string_view A non-owning rtftrtnct to a string

14. Library: Multicort support

Paralltlism TS: Add execution_policy ovtrload to most functions
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in tht <algorithm> and <numtric> htadtrs
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atomic_int x;
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for_each(execution::par, begin(v), end(v), [&x](int) { ++x; });
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Concurrtncy
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shared_mutex untimtd vtrsion of shared_timed_mutex
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Variadic lock_guard

15. Library: Filtsysttm
Functions and iterators to navigate a filesystem in std::filesystem

Integration with std::system_error and std::error_code
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Functions to create, manipulate and query files
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namespace fs = std::filesystem;
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fs::path p = fs::current_path() / "sandbox";
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fs::create_directories(p / "from");
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std::ofstream(p / "from/file1.txt").put('a');
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fs::create_directory(p / "to");
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fs::rename(p / "from/file1.txt", p / "to/file2.txt");
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fs::remove_all(p);

16. Library: Typt traits

Typt traits variablt ttmplatts:

is_same_v complement to add_const_t
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void_t: Ustd in ttmplatt mttaprogramming to dtttct ill-formtd
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typts in SFINAE conttxt:
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// primary template handles types that have no nested ::type
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template<typename, typename = void_t<>>
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struct has_type_member : false_type {};
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
// specialization recognizes types that do have a nested ::type
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template<typename T>

struct has_type_member<T, void_t<typename T::type>> : true_type {};

17. Currtnt status

18. Thank you!