Functor, Applicative, Monad, Foldable, Traversable instances for (, , ) a b

[Henning Thielemann]

On Sat, 1 Apr 2017, Jakub Daniel wrote:

> And I imagine nobody would argue that doesn't make sense. I kind of see 
> why people want better name than length but I see no really good 
> argument why the instance is bad. There are no doubt other generalised 
> notions. It also was an unfair question to ask what mathematicians would 
> think the length of (1,1) was. Because the question is not asked in 
> context where we ask about length for the type (a,-) not (-,-).

And for me the context (a,-) is artificial.