Views are sequences that do not actually contain data, but instead impart an
alternative presentation over the data from one or more underlying sequences.
Views are proxies. They provide an efficient yet purely functional way to work
on potentially expensive sequence operations. Views are inherently lazy. Their
elements are only computed on demand only when the elements of the underlying
sequence(s) are actually accessed. Views' lazy nature make them very cheap
to copy and be passed around by value.
#include <boost/fusion/view.hpp>
#include <boost/fusion/include/view.hpp>
