I need to take the address of the arrays, not their contents, and if I'm going to use the same definition of spam_length as the author. This kind of mistake is why one should avoid native arrays in C++ - the abstractions provided by the STL are more expressive and no more expensive.
The STL algorithms have no concept of length of a sequence, they only deal with iterators. This is the definition of for_each that Stroustrup provides in The C++ Programming Language:
template<class In, class Op> Op for_each(In first, In last, Op f)
{
while (first != last) f(*first++);
return f;
}
Notice that first and last can be pointers or STL style iterators, and that f can be a function object or an actual function. The template parameter In resolves to int* at compile time.
