How to Handle std::Arrays of Varying Sizes in C Functions?

Passing an std::array of Unknown Size to a Function

Question:

How can a function be written to handle std::arrays of known type but varying sizes? For instance, consider the following example:

<code class="cpp">// Hypothetical function
void mulArray(std::array<int, ?>& arr, const int multiplier) {
    for (auto& e : arr) {
        e *= multiplier;
    }
}</code>

How can a function such as mulArray be defined to accommodate arrays of varying sizes like the following:

<code class="cpp">std::array<int, 17> arr1;
std::array<int, 6>  arr2;
std::array<int, 95> arr3;</code>

Answer:

Unfortunately, it is not possible to write a function that accepts std::arrays of unknown sizes without using a function template or employing a different container type, such as std::vector.

Function Templates:

<code class="cpp">template<std::size_t SIZE>
void mulArray(std::array<int, SIZE>& arr, const int multiplier) {
    for (auto& e : arr) {
        e *= multiplier;
    }
}</code>

In this example, the mulArray function is defined as a function template, allowing it to handle arrays of any size. The SIZE parameter specifies the size of the array at compile time.

Example Usage:

<code class="cpp">// Array of size 17
std::array<int, 17> arr1;

// Function call with template instantiation for size 17
mulArray(arr1, 3);</code>

Note: When using function templates, the function definition must be placed in a header file to be accessible during compilation.

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