Is there any way to tell if a constexpr function gets called at compile   
   time or at runtime? That would open a window of optimizations for the   
   runtime version.   
      
   Something like   
      
   constexpr   
   int   
   myfunc( int i )   
   {   
     return (atCompileTime) ? (i<<1) : (2*i);   
   }   
      
      
   --   
         [ See http://www.gotw.ca/resources/clcm.htm for info about ]   
         [ comp.lang.c++.moderated.    First time posters: Do this! ]   
      
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