Ranges library (C++20)

The ranges library provides components for dealing with ranges of elements, including a variety of view adapters.

namespace std {
    namespace view = ranges::view;
}

The namespace alias std::view is provided as a shorthand for std::ranges::view.

Range factories

Range adaptors

Range adaptors accept ViewableRange as their first arguments and returns a View. They can also be chained using the pipe operator: if C and D are a range adaptors and R is a ViewableRange, these two expressions are equivalent:

D(C(R))
R | C | D

If an adaptor takes multiple arguments, these forms are equivalent:

adaptor(range, args...)
adaptor(args...)(range)
range | adaptor(args...)

Some range adaptors wrap their element or function object with the semiregular wrapper.

Helper concepts

Following exposition-only concepts are used for several types, but they are not parts of the interface of standard library.

template<class R>
  concept __SimpleView =                         // exposition only
    View<R> && Range<const R> &&
    Same<std::ranges::iterator_t<R>, std::ranges::iterator_t<const R>> &&
    Same<std::ranges::sentinel_t<R>, std::ranges::sentinel_t<const R>>;

template<class T, class U>
  concept __NotSameAs =                          // exposition only
    !Same<std::remove_cvref_t<T>, std::remove_cvref_t<U>>;

Example

#include <vector>
#include <ranges>
#include <iostream>
 
int main()
{
  std::vector<int> ints{0,1,2,3,4,5};
  auto even = [](int i){ return 0 == i % 2; };
  auto square = [](int i) { return i * i; };
 
  for (int i : ints | std::view::filter(even) | std::view::transform(square)) {
    std::cout << i << ' ';
  }
}

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