From: musiphil@bawi.org   
      
   On 2012-05-21 14:24, Wil Evers wrote:   
   > Seungbeom Kim wrote:   
   >> On 2012-05-20 21:19, Zoltan Juhasz wrote:   
   >>> The pop( value_type& e ), on the other hand, does not suffer from   
   >>> these kind of problems;   
   >>   
   >> But then you need to default construct an object of value_type and   
   >> ask the top element to be move-assigned to it. It may not be always   
   >> possible or desirable to default construct such an object, just to   
   >> be overwritten later.   
   >   
   > I agree.  Paradoxically, a movable type without a default   
   > constructor seems like a strange beast, because it presumably   
   > implements a "valid, but resourceless" state for its objects to be   
   > left in after having been moved from.   
   >   
   > I would say that a type with a default constructor clearly   
   > advertises that such a state exists and must be reckoned with.   
      
   You have a good point. Then in most sensible cases, the default   
   constructor should be available and its cost should reduce to   
   initializing a few small scalar objects such as pointers or booleans.   
      
   The remaining problem is that of aesthetics: "value_type e = q.pop();"   
   is much more elegant than "value_type e; q.pop(e);" and I'd love to be   
   able to write so.   
      
   --   
   Seungbeom Kim   
      
      
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