d1b2136b   
   From: daniel.kruegler@googlemail.com   
      
   On 2012-01-29 23:42, Daryle Walker wrote:   
   > Now I have a couple more thoughts on this.   
   >   
   > 1. If you use this recursive-call technique to get the return type within   
   the function,   
   > do you need to use "std::move" in the function for arguments that are   
   r-value references?   
      
   I don't know, what you mean with "do you need to use [..]", but it   
   surely makes a difference and I would suggest to do that for the   
   preparation of an expression with the wanted value category.   
      
   > 2. If a reference is returned, will "decltype" on the recursive call include   
   the reference marker,   
   > or just be the referenced type?  I'm not sure which way I prefer it.   
    Including the marker would   
   > be consistent, but it wouldn't be useful (since references aren't   
   objects themselves).  Any non-dangling   
   > reference that you could return would have to be based on a non-local   
   object, and then you could   
   > just return the expression that generates that reference.  (Hmm, now   
   I wonder if you could return   
   > a local object as a r-value reference.)  For manipulation purposes,   
   getting the referenced type   
   > would be more useful.   
      
   It depends on the expression and the way how you form the decltype   
   expression (e.g. with a surrounding pair of parentheses or not), but in   
   general an xvalue expression will result in an rvalue reference and an   
   lvalue expression will result in an lvalue reference. I suggest to   
   discuss more concrete examples. I don't understand what you mean with   
   "but it wouldn't be useful (since references aren't objects   
   themselves)", because references are generally stripped away when   
   interpreting expressions, see Clause 5 p5:   
      
   "If an expression initially has the type “reference to T” (8.3.2,   
   8.5.3), the type is adjusted to T prior to any further analysis. The   
   expression designates the object or function denoted by the reference,   
   and the expression is an lvalue or an xvalue, depending on the expression."   
      
   And yes, it is possible (albeit not recommended) to return an rvalue   
   reference of a variable with automatic storage duration.   
      
   HTH & Greetings from Bremen,   
      
   Daniel Krügler   
      
      
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