From: dave@boostpro.com   
      
   on Tue May 22 2012, Zoltan Juhasz  wrote:   
      
   > On Monday, 21 May 2012 15:28:09 UTC-4, Gene Bushuyev  wrote:   
   >> To avoid default constructing an object one would need the function   
   >> returning by value, how about simply modifying pop to return a value:   
   >>   
   >> template   
   >> T priority_queue::pop()   
   >> {   
   >>     T tmp(move(container.front()));   
   >>     container.erase(container.begin());   
   >>     make_heap(container.begin(), container.end(), compare);   
   >>     return tmp;   
   >> }   
   >>   
   >> It will not break existing code that relies on copy and assumes pop()   
   >> doesn't return anything.   
   >   
   > Unfortunately this implementation does not provide strong exception   
   > safety guarantees, e.g. if an exception is thrown when you return tmp,   
   > the container has been already modified, in an irreversible way, and   
   > the returned element is lost.   
      
   That's not so terrible.  The basic guarantee is perfectly adequate for   
   many situations.   
      
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