Re: Minor containers API changes

On 29 November 2011 14:09, Johan Tibell wrote:

On Mon, Nov 28, 2011 at 5:29 PM, Kazu Yamamoto wrote:

...

Hello,

This is off-topic but I'm curious.

Why the container package does not provide a type-class to unify APIs? Are there any technical/historical reasons?

Mostly technical I would say. I hope we should be able to do this right now when we have constraint kinds [1] i.e. we can do something like:

class Map m where    type C :: Constraints    insert :: C => k -> v -> Map k v -> Map k v

instance Map HashMap where    type C = Ord    insert = ...

1. http://blog.omega-prime.co.uk/?p=127

Definitely: this kind of thing was what stopped me when I tried to do something similar last year. There's still the tension of whether to put particular functions as class methods or not though (e.g. just look at these proposals about whether to include certain functions). -- Ivan Lazar Miljenovic Ivan.Miljenovic@gmail.com IvanMiljenovic.wordpress.com