Proposal: Add a strict version of <$> for monads

David Luposchainsky dluposchainsky at
Fri Nov 29 12:35:52 UTC 2013

On 29.11.2013 13:23, Johan Tibell wrote:
> On Fri, Nov 29, 2013 at 1:19 PM, Twan van Laarhoven
>     I don't like that this function is implemented for Monads, I think
>     that it makes sense for some other functors as well. Though to do
>     this 'properly' we would probably end up with another typeclass
>     "StrictFunctor" or something, and that is perhaps too much
>     unnecessary complexity.
> Do you have an example of such a functor?

Async is a Functor (but not Applicative). When asyncs finish and you
poll their result with `wait`, you potentially get back an IO <thunk>.
(Just the first example that came to mind.)


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