On Fri, Nov 2, 2012 at 11:20 AM, Robert Ramey
Nathan Ridge wrote:
"This library therefore provides the means to adapt standard-like containers, null terminated strings, std::pairs of iterators, and raw arrays (and more), such that the same generic code can work with them all. The basic idea is to add another layer of indirection using metafunctions and free-standing functions so syntactic and/or semantic differences can be removed."
This is all beside the point.
My concern is very simple:
The page http://www.boost.org/doc/libs/1_51_0/libs/range/doc/html/range/concepts/sing... is crystal clear. It says that any SinglePassRange must implement the expression boost::begin(a) where a is a model of a SinglePassRange.
On the page you reference, it describes that a particular expression must be valid for types modeling the SinglePassRange concept. It doesn't claim that you must implement it. I admit that it's a fine distinction. I thought that the "See Also" section on that same page was helpful, however -- the link titled "Extending the library for UDTs" seems to provide the information you're looking for.
This is not actually a requirement on any model of a SinglePassRange but rather a requirement on boost::begin. But boost::begin is not supplied by the user! This documentation doesn't tell me what operation the type argument has to support in order to be used as argument to a range. It's just non-sensical and therefore confusing. There is nothing on this page which would indicate to me that something like <vector> would satisify the concept. The page is does not document a "concept" in the C++ manner. I'd be interested to hear opinions on this also -- it made sense to me, but I didn't start adapting my own ranges until I was fairly comfortable with using the library with the standard containers.
Nate