Suggestion: add a lazy_vector<T> example

[greole]

First, thanks for creating yap! I am trying to extend the lazy_vector example to create a lazy_vector<T> version. This would need another template parameter for the lazy_vector_expr struct, like

template <boost::yap::expr_kind Kind, typename Tuple, typename I>
struct lazy_vector_expr
{
    static const boost::yap::expr_kind kind = Kind;

    Tuple elements;

    // Note that this does not return an expression; it is greedily evaluated.
    I operator[] (std::size_t n) const;
};

However, this doesn't work with the provided macros BOOST_YAP_USER_BINARY_OPERATOR. Does it mean i should implement a different version of BOOST_YAP_USER_BINARY_OPERATOR? What is the best way to achieve this?

[tzlaine]

Interesting! I think maybe making macros that take a variadic number of arguments at the end might work -- that way, we can provide the extra "typename I" in your example, or "std::size_t N" in some other case. Those would get passe through. PR welcome; otherwise, I may take a while to get to this -- I'm readying another library for including into Boost.

[greole]

@tzlaine Ok I'll see if I can't implement it myself and do a PR.