How to reliably get size of C-style array?

Question

How do I reliably get the size of a C-style array? The method often recommended seems to be to use sizeof, but it doesn\'t work in the foo function

Answer 1

I also agree that Corwin's method above is very good.

template 
void foo(int (&x)[N]) 
{
    std::cerr << N;
}

I don't think anybody gave a really good reason why this is not a good idea.
In java, for example, we can write things like:

int numbers [] = {1, 2, 3, 4};
for(int i = 0; i < numbers.length(); i++)
{
   System.out.println(numbers[i]+"\n");
}

In C++ it would be nice instead of saying

int numbers [] = {1, 2, 3, 4};
int size = sizeof(numbers)/sizeof(int);
for(int i = 0; i < size; i++)
{
    cout << numbers[i] << endl;
}

We could take it a step further and go

template 
int size(int (&X)[N])
{
   return N;
}

Or if that causes problems I suppose you could write explicitly:

template < int N >
int size(int (&X)[N])
{
   int value = (sizeof(X)/sizeof(X[0]));
   return value;
}

Then we just have to go in main:

int numbers [] = {1, 2, 3, 4};
for(int i = 0; i < size(numbers); i++)
{
   cout << numbers[i] << endl;
}

makes sense to me :-)