<ranges>

<ranges> provides the ranges library (C++20): a new way to express algorithms that works on ranges directly instead of iterator pairs. Instead of std::sort(v.begin(), v.end()), you write std::ranges::sort(v). Range adapters like std::views::filter compose transformations lazily.

It's more expressive and composable than the classic iterator-based algorithms, but requires C++20 or later.

This example sorts a vector and filters even numbers using range-based algorithms and views with the pipe operator.

// compile: g++ -std=c++20 -o rangesexample rangesexample.cpp
// run: ./rangesexample
// description: ranges library with views
 
#include <ranges>
#include <vector>
#include <iostream>
 
int main() {
    std::vector<int> nums = {1, 2, 3, 4, 5};
 
    std::ranges::sort(nums);
 
    auto evens = nums | std::views::filter([](int x) { return x % 2 == 0; });
    for (int x : evens) {
        std::cout << x << " ";
    }
    std::cout << "\n";
 
    return 0;
}