Checking if two Stacks are Equal using Friend Functions in C++

int equal(const stack& s1, const stack& s2)
{
    int i;  
    if (s1.c != s2.c)
        return (0);

    for (i = 0; i < s1.c; ++i) {

        assert((i >= 0) && 
               (i < sizeof(s1.info)/sizeof(s1.info[0])));

        assert((i >= 0) && 
               (i < sizeof(s2.info)/sizeof(s2.info[0])));

        if (s1.info[i] != s2.info[i])
            return (0);
    }
    return (1);
}