Different ways of declaring a function in C++ [duplicate]

I have come across the following code snippet in C++ and I have no idea what it means;

#include <iostream>

char (&some_function(int (&some_input)));  

int main ()
{
  // main code here 
  return 0;
}

How is some_function a function? what kind of syntax is this? where is the body? I'm sure this is only a C++ syntax as it doesn't compile in C.

Edit: Actual code with above style:

template <typename T, size_t N>  
char (&ArraySizeHelper(T (&array)[N]))[N];  
#define arraysize(array) (sizeof(ArraySizeHelper(array)))