Hi all,
TL;DR:
Value based promotion seems complex both for users and ufunc-
dispatching/promotion logic. Is there any way we can move forward here,
and if we do, could we just risk some possible (maybe not-existing)
corner cases to break early to get on the way?
...
I have realized that this got much too long, so I hope it makes sense.
I will continue to dabble along on these things a bit, so if nothing
else maybe writing it helps me to get a bit clearer on things...
Your email was long but very clear. The part I'm missing is "why are things the way they are?". Before diving into casting rules and all other wishes people may have, can you please try to answer that? Because there's more to it than "(maybe not-existing) corner cases".
Marten's first sentence ("a balance between unexpected memory blow-up and unexpected wrapping") is in the right direction. As is Stephan's "Too many users rely upon arithmetic like "x + 1" having a predictable dtype."
The problem is clear, however you need to figure out the constraints first, then decide within the wiggle room you have what the options are.
Cheers,
Ralf