On Aug 21, 2009, at 5:11 PM, Job Vranish wrote:
I also added an extra phantom type parameter to the collection (and key) so that I can prevent keys from being used on different collections even if they hold elements of the same type.
I have the impression that this requires explicit type annotations with your current solution which seems a bit tiresome. If not instantiated to specific different types, the additional phantom types of different collections can just be unified which does not lead to a type error. As you seem to implement a monadic interface, you might be able to steal the idea of using higher-rank polymorphism (that is used in the ST monad implementation) to ensure that the phantom types of different collections cannot be unified. But that would probably mean to implement your own monad that carries this phantom type too.. Cheers, Sebastian -- Underestimating the novelty of the future is a time-honored tradition. (D.G.)