Proposal: generalise Monoid's mconcat
fumiexcel at gmail.com
Tue Sep 1 10:39:02 UTC 2015
I would rather propose removing mconcat from Monoid. I've never seen
2015-09-01 17:04 GMT+09:00 Edward Kmett <ekmett at gmail.com>:
> To be clear I was referring to the generalization of mconcat, not to
> Petr's Dual suggestion
> That said, I have a very strong issue with the proposed change to Dual's
> mconcat. The issue with the Dual suggestion is that reverse requires the
> list to be finite. This means that even if the monoid could be productive
> before with Dual it can't with that definition.
> On Tue, Sep 1, 2015 at 12:56 AM, Edward Kmett <ekmett at gmail.com> wrote:
>> I'm personally -1 from a base organizational standpoint following Reid's
>> This is just me expressing my own personal opinion rather than any
>> official core libraries committee stance at this time.
>> On Mon, Aug 31, 2015 at 1:19 PM, Petr Pudlák <petr.mvd at gmail.com> wrote:
>>> 2015-08-31 21:00 GMT+02:00 David Feuer <david.feuer at gmail.com>:
>>>> The theory of mconcat is that it should handle monoids that need to be
>>>> summed in some special way. I don't know if anyone actually uses it so,
>>>> however. Still, Reid is right that the circular dependency sets a very high
>>>> I guess the [a] monoid is a good example where using mconcat can make a
>>> What seems to be an omission is that Dual has no implementation of
>>> mconcat. It'd make sense to define 'mconcat = mconcat . reverse' - if the
>>> original monoid benefits from a certain order of operations, we should keep
>>> the order.
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