On 24 December 2010 02:16, Mario Blažević
To turn the proof obligation around, what could possibly be the downside of adding a puny Cofunctor class to the base library?
Hi Mario For the record I'm personally neutral on Cofunctor and on balance would like to see Comonad added to Base. My reservation is really at the "meta-level" - I suspect there are a lot of candidates for adding to Base if you want to Base to be systematic about "modeling structures". At the moment and possibly by accident rather than explicit intention, the structures in Base (Monoid, Applicative, Monad, Arrow) add good sets of operational combinators as well as modeling structures (in Monoid's case it only adds one operational combinator but it is the basis for Foldable, the Writer Monad and more). For Comonad, Cofunctor (Bifunctor, Semigroup...) not having the visibility of being in Base certainly means there is less motivation to discover valuable operations that use them, but should they go into Base without an initial strong operational value, instead maybe something between Base and Hackage is needed? Certainly, Hackage isn't great for developing "Base candidates". The bike shedding on the Libraries list, whilst frustrating for a proposer, is valuable for teasing out more regular designs than single authored packages often manage, and having lots of small packages for Base-like things is a dependency burden that hinders adoption. Best wishes Stephen