From: jm@bourguet.org   
      
   torbenm@diku.dk (Torben Cgidius Mogensen) writes:   
      
   > You can also reverse the question: Given that you have records and   
   > (tagged) unions (== sum types), will classes provide significant value?   
      
   Classes provides modular addition of types, but unmodular addition of   
   operation.   
      
   Unions provides modular addition of operation, and unmodular addition of   
   types.   
      
   I choose one or the other depending on which evolution is more needed.   
      
   The problem is when both kinds is probable.  Some names that the   
   expression problem (and last time I looked, it has no good solution)   
      
   Yours,   
      
   --   
   Jean-Marc   
      
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