22 Apr
2020
22 Apr
'20
9:50 a.m.
Hi Marc, On Wed, Apr 22 2020 11:17, Marc Busqué wrote:
For instance, a functor can be both covariant and contravariant
Judging from personal experience, "functor" in mathematics always (for a sufficiently small definition of always) refers to a covariant functor. If something is contravariant you usually declare it explicitly. These concepts are rather related though; one may view any contravariant functor F: C -> D as a covariant one, either by F: C^o -> D or by F: C -> D^o.
Would `Cofunctor` be a better name for it?
Cofunctor has some ambiguity around it. While it might refer to a contravariant functor it may as well refer to the dual of a functor (which is again a functor). Cheers, -- Tony Zorman | PGP: 0xc927de8c7dfd57b8