[Haskell-beginners] why is there no typeclass common to all containers?

Tony Morris tonymorris at gmail.com
Wed Jun 1 05:14:38 UTC 2016


Map and Set are not.
On 01/06/2016 8:57 AM, "Jeffrey Brown" <jeffbrown.the at gmail.com> wrote:

> In Haskell typeclasses are based on what you want to do with something.
> If, for instance, you want to be able to map over a container, you can make
> it an instance of class Functor -- which all the standard containers (List,
> Map, Set, Tree, Maybe ...) already are.
>
> On Tue, May 31, 2016 at 3:26 PM, Silent Leaf <silent.leaf0 at gmail.com>
> wrote:
>
>> In fact it all comes down to trying to add partially a feature absent
>> from the Haskell language, which is the ability to distinguish values both
>> on name *and* on type --thus allowing two variables of the same name if
>> they have different types.
>> Honestly i don't see the drawback of that name system, but i guess there
>> must be one otherwise it'd have been chosen by default instead of the
>> typeblind current name system.
>>
>>
>> Le mercredi 1 juin 2016, Silent Leaf <silent.leaf0 at gmail.com> a écrit :
>> > All in the title. I haven't used them much, but I saw Map or Vector
>> types were forcing the user to use qualified functions unless you want
>> nameclash with the more basic, typically list-oriented functions.
>> > So, why not have a massive, general purpose interface so the type only
>> can separate between containers --which would allow for cross-container
>> polymorphism, i suppose, more easily, even though it's not necessarily the
>> most widespread need.
>> > So, do i miss something? Is there in fact a class of that kind? If so
>> why not?
>> > Thanks in advance! :)
>>
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>>
>
>
> --
> Jeffrey Benjamin Brown
>
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