[boost] is_single_element?

From: Damien Fisher (damien_at_[hidden])
Date: 2002-05-15 09:18:41

I would like to see something like this in Boost:

template<typename Container>
bool is_single_element(const Container &cont)
{
    return boost::next(cont.begin()) == cont.end();
}

In a current project, I am finding the need to continually check for
single element std::lists, and I have to keep restraining myself from
using size().  I think the above would fit nicely into
boost/utility.hpp (or maybe some sort of algorithm header file?).

The following is a more general, possibly useful extension of the above
(although I have no need for it ATM):

template<typename Container>
bool is_n_elements(const Container &cont, unsigned int n)
{
    // ...
}

Of course, this should be specialized for containers where calling
size() isn't an issue, to just call size().

Comments?