How to pass a VLA to a function template?

Question

I have the following code which could not be complied.

using namespace std;
void f(int);
template
void array_ini_1d(T1 (&x)[         


        

Answer 1

As you use Variable length array (VLA) (compiler extension), compiler cannot deduce N.

You have to pass it by pointer and give the size:

template
void array_ini_1d(T* a, std::size_t n)
{
    for (std::size_t i = 0; i != n; ++i) {
        a[i] = 0;
    }
}

void f(int n)
{
    int arr[n];
    array_ini_1d(arr);
}

Or use std::vector. (no extension used so). Which seems cleaner:

template
void array_ini_1d(std::vector& v)
{
    for (std::size_t i = 0, size = v.size(); i != n; ++i) {
        a[i] = 0; // or other stuff.
    }
}

void f(int n)
{
    std::vector arr(n); // or arr(n, 0).
    array_ini_1d(arr);
}