swift234

Pages document on range concepts.  This is by no means a completed design.  This is a statement of direction to let you guys know that there is activity here.  I've been heavily influenced by Andrei Alexandrescu's work with D.  I'm trying to see if I can keep from exposing begin() and end() iterators.  Even Andrei has yet to admit that is practical.  However we both think it is a possibility.  The document syntactically appears to expose begin and end iterators, but it does not.  The begin and end that appear in the document are nothing but generic tag types, and are not actual iterator factory functions. The client 'apparent interface' is fairly small.  However I'm concerned that the range author's implementation effort is rather large at this point once one gets to bidirectional and random_access ranges.

Swift SVN r494