Counting Algorithms

Using std::ranges Algorithms with Container Views

How do std::ranges algorithms interact with container views like std::span or std::string_view?

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std::ranges algorithms work seamlessly with container views like std::span and std::string_view, providing a flexible way to operate on sub-ranges or specific sections of data without copying it.

Using std::span

std::span is a non-owning view over a contiguous sequence of elements. Here’s an example using std::ranges::count() with std::span:

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

int main() {
  std::vector<int> numbers {1, 2, 3, 4, 4, 5};
  std::span<int> numbersView(
    numbers.data(), numbers.size());

  auto foursCount = std::ranges::count(
    numbersView, 4); 
  std::cout << "Count of fours: " << foursCount;
}
Count of fours: 2

Using std::string_view

std::string_view provides a view over a string without owning the actual string data. Here's an example using std::ranges::count() with std::string_view:

#include <algorithm>
#include <iostream>
#include <string>
#include <string_view>

int main() {
  std::string text = "hello world";
  std::string_view textView(text);

  auto lCount = std::ranges::count(textView, 'l');  
  std::cout << "Count of 'l': " << lCount;
}
Count of 'l': 3

Benefits

  • Efficiency: Views avoid copying data, leading to more efficient code.
  • Flexibility: They allow operations on subsections of containers.
  • Safety: Views can be safely used without worrying about managing the underlying data's lifetime.

Practical Usage

  • Sub-ranges: Use views to process parts of a container.
  • Read-only Access: std::string_view is great for read-only string operations.
  • API Design: Pass views to functions to make them more versatile.

By using container views with std::ranges algorithms, you can write efficient, flexible, and clear code. This approach is particularly useful in modern C++ for handling large datasets and optimizing performance.

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

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