Operators without co- or contravariance

[akarnokd]

I'm looking at the operator definition and found a bunch of places where the "lambda" functions do not have wildcard bounds specified, e.g.,

reduce(Func2[T, T, T])
max(Comparator[T])

etc.
Is there a particular reason these are not:

reduce(Func2[? super T, ? super T, ? extends T])
max(Comparator[? super T])

?

[samuelgruetter]

reduce:

That's a long story, see #369 , #360 , and #336 (comment) .
In short:

• It's considered unnecessary (or not necessary enough to complicate the signature)
• Note, though, that the signature of reduce is not entirely correct, because the covariant type parameter T appears in a contravariant position, so you can't use reduce on an Observable<? extends XXX> , but only on an Observable<XXX> . To fix this, one would need lower bounds for type parameters, but Java doesn't support this.

min/max:

IMHO it would be a good idea to add wildcards, what do others think?

[zsxwing]

For min/max, I agree with you. I'll fix it.

[zsxwing]

It seems we can close this issue now.