On 2011-01-27 13:07 +0200, Boris Lykah wrote: > I think it would be convenient to allow adding variables and > functions, which are not members of the class, to a class instance so > that they are visible only in the instance scope. It will help if the > same functions are used by several class functions. > > Example: > When implementing Num class for my datatype, I found that I routinely > do unwrapping in each operator definition. I extracted it into > functions, but as they are used only in instance definition, I want to > put them there and restrict them to that scope. It would be neater > than leaving them in the global scope or copypasting into each > operator.
One problem with this proposal is that it hurts modularity, as there is no distinction in the instance declarations between the definitions of "instance-local" functions and those of class methods. This means that you cannot add new methods to an existing class (together with a default implementation in terms of the existing methods) without potentially breaking the existing instances. -- Nick Bowler, Elliptic Technologies (http://www.elliptictech.com/) _______________________________________________ Haskell-prime mailing list Haskell-prime@haskell.org http://www.haskell.org/mailman/listinfo/haskell-prime
