Haskell Foldable Wats

[Matthias Hörmann]

> Has there ever been a discussion to only allow instance definitions in
> the same library as the data type definition or the class definition?

Not allowing orphans at all would be problematic in the presence of type
classes and data types in packages which are hard to impossible to
upgrade (like base).

You couldn't even locally experiment with new instances that way.

On Thu, Feb 25, 2016 at 10:21 AM, Daniel Trstenjak
<daniel.trstenjak at gmail.com> wrote:
> On Wed, Feb 24, 2016 at 11:27:48AM -0600, Chris Allen wrote:
>> You can't not-include the instances because we'll just end up with orphans so
>> that's not cricket I think.
>
> What was the design decision behind orphans? Why were they considered a good idea?
>
> Has there ever been a discussion to only allow instance definitions in
> the same library as the data type definition or the class definition?
>
> Greetings,
> Daniel
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