16 Feb
                
                    2011
                
            
            
                16 Feb
                
                '11
                
            
            
            
        
    
                2:22 p.m.
            
        The finally tagless and "Generics as a Library" styles can - though you loose pattern matching they are arguably still close to grammars. Pablo Nogueira has posted some examples of open types in "Generics as a Library" tagless style to Haskell cafe: http://www.haskell.org/pipermail/haskell-cafe/2008-July/045028.html