C++2019 May 2026

int main() for (const auto& entry : fs::directory_iterator(".")) auto [path, status] = std::pairentry.path(), entry.status(); if (fs::is_regular_file(status)) std::cout << "File: " << path.filename() << '\n';

// Error: add("a", "b") – string not numeric c++2019

If you’ve heard “C++2019,” it likely refers to the work leading up to C++20 (finalized in 2020) or the post-C++17 era of feature development. C++17 was completed in 2017; C++20 followed as one of the largest updates in the language’s history. C++17: Polishing the Foundation C++17 bridged the gap between “modern C++” (C++11/14) and the ambitious goals of C++20. It focused on usability, performance, and reducing boilerplate. Key Features of C++17 | Feature | Benefit | |---------|---------| | std::optional | Express “no value” without sentinels or pointers | | std::variant | Type-safe unions | | std::visit | Pattern matching over variants | | std::any | Type-safe opaque containers | | std::string_view | Non-owning string references (avoid copies) | | Structured bindings | auto [x, y] = returns_pair(); | | if constexpr | Compile-time conditional code | | Inline variables | Define globals in headers without ODR issues | | std::filesystem | Cross-platform file operations | | Parallel STL | std::sort(std::execution::par, …) | Example: Structured Bindings + std::filesystem #include <filesystem> #include <iostream> namespace fs = std::filesystem; int main() for (const auto& entry : fs::directory_iterator("

Concepts replace SFINAE with readable, checkable template requirements. #include <ranges> #include <vector> namespace rv = std::ranges::views; generator&lt;int&gt; fibonacci() int a = 0, b =

auto result = std::vector1,2,3,4,5 | rv::filter([](int x) return x%2==0; ) | rv::transform([](int x) return x*x; ); // result = 4, 16

No more messy iterator pairs; lazy evaluation and chaining. generator<int> fibonacci() int a = 0, b = 1; while (true) co_yield a; // suspend and return a auto next = a + b; a = b; b = next;

for (int f : fibonacci() | rv::take(10)) std::cout << f << ' ';