The arguments of Ian Lynagh, Ganesh Sittampalam, Claus Reinke and Cale Gibbard about restricting k patterns to class Integral, introducing a class Natural and the role of class Eq prove my point that k patterns are special, different from data constructors or character literals. They are special, far more complex than most people think, and very easy to avoid. I do understand that probably everybody learning functional programming learned k patterns very early on (in other languages such as Miranda there is no overloading problem) and hence find it hard to make the small change of using explicit equality instead. (And yes, removing k-patterns will break a lot of Haskell programs.) Higher-order functions substantially increase the expressivity of the programming language. k-patterns are just an odd decorative element. I was probably wrong to start my argument with talking about Hat. This is just what made me personally look into k, n+k and ~ patterns. The general argument is just that every language feature has its costs (for tools, for research, for teaching,...) and hence any language feature should be truely useful, not just convenient (naturally the distinction is not clear cut). Ciao, Olaf