Hello, I think that if we want something along those lines, we should consider a more general construct that allows declarations to scope over other declarations (like SML's `local` construct). It would be quite arbitrary to restrict this only to instances. -Iavor On Mon, Apr 29, 2013 at 2:41 PM, Max Bolingbroke

wrote:

You could probably get away with just using two "where" clauses:

instance Foo a where bar = ... where auxilliary = ...

On 28 April 2013 18:42, Edward Kmett wrote:

...

Makes sense. I'm not sure what a good syntactic story would be for that feature though. Just writing down member names that aren't in the class seems to be too brittle and error prone, and new keywords seems uglier than the current situation.

Sent from my iPad

On Apr 28, 2013, at 1:24 PM, Doug McIlroy wrote:

...

Not always. For example, you can't mess with the declaration of a standard class, such as Num.

On Sun, Apr 28, 2013 at 12:06 PM, Edward Kmett wrote:

...

You can always put those helper functions in the class and then just not export them from the module.

On Sun, Apr 28, 2013 at 10:49 AM, Doug McIlroy

...

Is there any strong reason why the where clause in an instance declaration cannot declare anything other than class operators? If not, I suggest relaxing the restriction.

It is not unusual for declarations of class operators to refer to special auxiliary functions. Under current rules such functions have to be declared outside the scope in which they are used.

Doug McIlroy

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