[Haskell-cafe] Constraints on <$> vs <$!>

[Will Yager]

What about

f <$!> x = (f $!) <$> x 

?

--Will



> On Aug 10, 2015, at 14:20, Christopher Allen <cma at bitemyapp.com> wrote:
> 
> http://stackoverflow.com/questions/9423622/strict-fmap-using-only-functor-not-monad seems to cover it.
> 
>> On Mon, Aug 10, 2015 at 4:17 PM, Alexey Egorov <electreg at list.ru> wrote:
>> Hello haskellers,
>> 
>> I wonder why <$> and <$!> have different typeclass constraints?
>> 
>> (<$>) :: Functor f => (a -> b) -> f a -> f b
>> (<$!>) :: Monad m => (a -> b) -> m a -> m b
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> 
> 
> -- 
> Chris Allen
> Currently working on http://haskellbook.com
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