Topic: diamond problem
Sean Leather (Sep 06 2018 at 09:05):
I'm not sure if this is an instance of the type class diamond problem, but what do you do when you have
add_comm_monoid and need
distrib, given that you have
[add_comm_monoid α] [distrib α]? One solution seems to be to use
[semiring α] instead, but that seems to me to add unnecessary constraints, since
semiring also extends
mul_zero_class. I'm guessing there is another, better way.
Reid Barton (Sep 06 2018 at 09:16):
I think you should avoid being in that situation in the first place.
But I don't understand why there isn't a problem with
Maybe old_structure_cmd magic?
Reid Barton (Sep 06 2018 at 09:19):
Maybe you could make your own "old structure" containing just what you need?
Sean Leather (Sep 06 2018 at 09:20):
Sorry, Reid, I haven't used
old_structure_cmd and don't know what you mean.
Last updated: May 08 2021 at 03:17 UTC