C++ :: Calculate Mean Of Array Class?

I am trying to create a small function that can return the mean of an object of array class, not a simple array.

Declare and initiate the array:

array<double, 100> myArray = {};
myArray.fill(1.0);

function to calculate mean:

double mean_array(double *array)
{
double sum = 0.0;
for(int i=0; i<sizeof(array); i++)
sum += array[i];
return sum / sizeof(array);
}

However, it does not work. It seems it is incompatible with the array definition.