Variance of Ordered, PartiallyOrdered?

EDIT : Looked further and find some explanation in the documentation for Ordered to not be covariant anymore For the case of tryCompare in PartiallyOrdered the signature set more restriction on passed parameter : def tryCompareTo B >: A (that: B)(implicit arg0: (B) ⇒ PartiallyOrderedB): OptionInt Here the implicit arg0 implies that to be seen as a PartiallyOrderedB instance and thus that it has access to all method defined in this trait.

EDIT : Looked further and find some explanation in the documentation for Ordered to not be covariant anymore. For the case of tryCompare in PartiallyOrdered, the signature set more restriction on passed parameter : def tryCompareTo B >: A (that: B)(implicit arg0: (B) ⇒ PartiallyOrderedB): OptionInt Here the implicit arg0 implies that to be seen as a PartiallyOrderedB instance and thus that it has access to all method defined in this trait.

Thanks for the answer. I guess I understand tryCompareTo, after staring for the signature for a little while. Any insights on the variance of OrderedA, though?

– Daniel Jun 11 at 1:42 I won't edit yet the answer because I'm not sure about this point but I think it is because you can't be sure that OrderedA is equals to OrderedB even if B.

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