How to Pass an std::array of Unknown Size to a Function in C ?

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

In C , how can you create a function that accepts a std::array of a known type, but an unknown size?

Consider the following example:

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

Given this function, you can create std::arrays of different sizes and pass them to mulArray:

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

mulArray(arr1, 3);
mulArray(arr2, 5);
mulArray(arr3, 2);</code>

Is there a simpler way to achieve this, akin to using plain C-style arrays?

No, it is not possible to perform this operation without using function templates or alternative containers like std::vector.

Function Templates Solution

To create a generic function that can handle std::arrays of any size, you need to use a function template:

<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>

This template defines a function that takes an array of integers of any size and multiplies each element by the given multiplier.

A live example of this implementation can be found here: [Live Example](https://godbolt.org/z/Y932XW)

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