8 Key Standard Library Algorithms

Using Subranges vs Iterator Pairs

What are the use cases for using std::ranges::subrange() versus standard iterator pairs?

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Using std::ranges::subrange() and standard iterator pairs both allow you to define a specific portion of a range, but they have different use cases and benefits.

Iterator Pairs

Iterator pairs have been a traditional way to define subranges in C++. You specify a range by providing two iterators: a beginning and an end. This method is straightforward and has been widely used:

#include <algorithm>
#include <iostream>
#include <vector>

int main() {
  std::vector<int> vec{1, 2, 3, 4, 5};

  auto begin = vec.begin() + 1;
  auto end = vec.begin() + 4;

  std::for_each(begin, end, [](int n) {
    std::cout << n << ", ";
  });
}
2, 3, 4,

std::ranges::subrange

std::ranges::subrange is part of the C++20 ranges library. It provides a more powerful and expressive way to work with subranges. A subrange is a view that encapsulates a pair of iterators and can be used with range-based algorithms seamlessly:

#include <algorithm>
#include <iostream>
#include <ranges>
#include <vector>

int main() {
  std::vector<int> vec{1, 2, 3, 4, 5};

  auto subrange = std::ranges::subrange(
    vec.begin() + 1, vec.begin() + 4);

  std::ranges::for_each(subrange, [](int n) {
    std::cout << n << ", "; });
}
2, 3, 4,

Benefits of std::ranges::subrange

  1. Readability: std::ranges::subrange makes the code more readable and expressive, clearly indicating that you are working with a subrange of a collection.
  2. Range-based Algorithms: It integrates seamlessly with range-based algorithms and views, making it more flexible and powerful.
  3. Type Safety: Provides better type safety and prevents common iterator mistakes.

Use Cases

Iterator Pairs is suited for:

  • Simple cases where defining the range with iterators is sufficient.
  • When working with older codebases that do not use the C++20 ranges library.
  • Performance-critical sections where the minimal overhead of raw iterators is beneficial.

std::ranges::subrange is suited for:

  • Modern C++ projects that leverage the power of the ranges library.
  • Complex operations involving multiple range-based algorithms and views.
  • Codebases where readability, maintainability, and expressiveness are prioritized.

In summary, std::ranges::subrange offers a modern and powerful alternative to iterator pairs, enhancing code readability and integration with range-based algorithms.

However, iterator pairs remain a valid and useful tool, especially in simpler or performance-critical contexts.

Answers to questions are automatically generated and may not have been reviewed.

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