std::ranges::contains(range, value)

does exactly that:

 - works over different container types

 - provides a standardized way for checking for the presence of a value

 

So please state the advantages or differences of your proposal compared to it.


 

-----Ursprüngliche Nachricht-----
Von: Robert Sitton via Std-Proposals <std-proposals@lists.isocpp.org>
Gesendet: Sa 23.12.2023 21:33
Betreff: Re: [std-proposals] Addition of std::contains to Simplify Container Value Checks
An: std-proposals@lists.isocpp.org;
CC: Robert Sitton <robert.sitton@gmail.com>;
Thank you for your prompt response and valuable information, and I appreciate your input. I want to clarify the motivation behind the proposed std::contains function and its potential benefits.

I understand that C++20 has introduced std::ranges::contains. However, my proposal for std::contains aims to create a standardized way of checking for the presence of a particular value in various container types. This common interface can significantly improve code consistency and simplify the logic for dealing with different container types.

Recently, I came across a fascinating scenario where I had to generate a template function that could effortlessly function with a wide range of container types such as vectors, maps, sets, and even std::pair<>. This was while I was parsing data that was stored in a CSV. In this particular context, I could experiment with and modify containers and search for specific values across multiple container types without any difficulty.

Adding such a feature to the C++ standard library would be highly valuable as it aligns with the code simplicity and consistency principles highly valued in the C++ community.

Thanks again,

Robert
 

On Sat, Dec 23, 2023 at 3:51 AM ஜெய்கணேஷ் குமரன் via Std-Proposals <std-proposals@lists.isocpp.org> wrote:
There is already one in C++20: std::ranges::contains (https://en.cppreference.com/w/cpp/algorithm/ranges/contains).

On 23-Dec-2023, at 14:50, Robert Sitton via Std-Proposals <std-proposals@lists.isocpp.org> wrote:

Dear std-proposals community, 

I hope this email finds you well. I am writing to introduce a proposal for the addition of a new utility function, std::contains, to the C++ standard library. This function aims to streamline the common task of checking whether a container contains a specific element and enhance the overall readability of C++ code.

Motivation:
One of the frequent operations in C++ programming involves checking whether a container (e.g., std::vector, std::list, std::set) contains a particular value. While C++ provides mechanisms to achieve this, such as custom loops or std::find, these approaches may not always be as intuitive and efficient as desired.

Proposal Overview:
The proposed std::contains function is designed to simplify this operation and make code more expressive. It offers a straightforward and concise way to check if a container contains a specified element, reducing the need for manual iterations and enhancing code clarity.

Function Signature:
template <typename Container, typename T>
bool std::contains(const Container& container, const T& value);

Example Usage:
std::vector<int> numbers = {1, 2, 3, 4, 5};
bool containsThree = std::contains(numbers, 3); // true
bool containsTen = std::contains(numbers, 10);  // false
bool containsOne = std::contains(numbers, {1, 4, 5}); // true
bool containsTwo = std::contains(numbers, {7, 8});  // false

Your Feedback:
I would greatly appreciate your feedback and insights on this proposal. Before formally submitting it to the C++ committee, I believe it is essential to gather input from the community to ensure that the proposal aligns with the needs and expectations of C++ developers.

Please feel free to share your thoughts, suggestions, or concerns regarding the proposed std::contains function. Your expertise and feedback are invaluable in refining and improving this idea. Thank you for your time and attention. I look forward to engaging in constructive discussions and working together to enhance the C++ standard library.

Sincerely,

Robert
 
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