From: musiphil@bawi.org   
      
   On 2013-11-13 10:47, peter koch larsen wrote:   
   > Hi group,   
   >   
   > I hope this text looks okay. Unfortunately, I am currently   
   > forced to use google groups.   
      
   Your text looks very good; thanks for taking the care.   
      
   > I have a question regarding differentiating templated classes.   
   > Assume I have (the real code is more complex):   
   >   
   > template< .... > class my_template;   
   > typedef my_template lat_long;   
   > typedef my_template complex;   
   >   
   > I still have only one type, so I could input a complex to   
   > a function expecting a complex - reducing typesafety.   
   > What is perhaps worse, I can't overload on the two types.   
   > std::ostream operator<< must be the same for both types.   
      
   One solution would be to use differentiating tag types.   
      
   template<..., typename tag = void> class my_template;   
      
   struct lat_long_tag { };   
   typedef my_template lat_long;   
   struct complex_tag { };   
   typedef my_template complex;   
      
   The tag type is never used in the definition of my_template, but   
   different tags still serve to differentiate the resulting types.   
      
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   Seungbeom Kim   
      
      
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