AdditiveCollection not defined for Seq?

[dimitriye98]

Why isn't AdditiveCollection defined for Seq itself? It makes it pretty much impossible to use sized Seqs, since all of the underlying methods require an AdditiveCollection type class.

[milessabin]

Seq only requires an ordering of it's elements, it doesn't require the additive behaviour that AdditiveCollection requires ... instances of the latter are defined ad hoc for concrete data types which do behave appropriately. Stream would be problematic, for instance. And there's nothing to stop someone from defining a Seq subtype with ordered-set-like behaviour.

[dimitriye98]

Stream already has an applicable AdditiveCollection though? Stream is a LinearSeq, for which an AdditiveCollection conversion exists.

[jxnu-liguobin]

It seems that this question can be used to get started? @joroKr21

[joroKr21]

It seems that this question can be used to get started? @joroKr21

Yes, @jxnu-liguobin sorry I missed your question 🙈 - do you want to work on this issue?
One would have to implement AdditiveCollection[Seq]. Do you have any questions?