How do I use emplace vs push with std::span?

In C++, both `emplace` and `push` are used to add elements to containers, but there are some differences in how they operate. When dealing with `std::span`, which is a lightweight view over a contiguous sequence of objects, it's essential to note that `std::span` itself does not support `emplace` or `push` directly, as it is not a container but rather a wrapper around an array or a contiguous data structure.

The `emplace` method typically constructs an object in place at the end of a container (like `std::vector`), while `push` simply adds an object to the container. When using fixed-size spans, the structure of the data should already be established at the time of creating the `std::span`, making both `emplace` and `push` methods irrelevant for spans.

Example of Push vs Emplace in Containers


        // Example in C++
        #include 
        #include 

        class Example {
            int value;
        public:
            Example(int v) : value(v) {}
            void show() { std::cout << value << std::endl; }
        };

        int main() {
            std::vector vec;

            // Using push (if we had an existing Example object)
            Example ex1(1);
            vec.push_back(ex1); // Copying the object

            // Using emplace (to construct the object directly in place)
            vec.emplace_back(2); // Constructs Example(2) in place

            for (auto& item : vec) {
                item.show();
            }

            return 0;
        }

C++ std::span emplace push vectors containers

How do I use emplace vs push with std::span?

Example of Push vs Emplace in Containers

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How do I use emplace vs push with std::span?

Example of Push vs Emplace in Containers

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