25 Feb
2011
25 Feb
'11
7:15 p.m.
On Fri, Feb 25, 2011 at 5:42 PM, Ross Paterson
On Fri, Feb 25, 2011 at 05:34:18PM -0500, roconnor@theorem.ca wrote:
In the applicative documentation, it says for an Applicative functor f:
The Functor instance should satisfy
fmap f x = pure f <*> x
I think the documentation should be clarified that this does not need to be checked because it is a consequence of the other applicative laws.
Do you have a proof that Functor instances are uniquely determined?
Given fmap id = id, the uniqueness of fmap for a given type follows trivially from the free theorem. -Edward Kmett