Control.Monad.Writer.Strict not as strict as expected

[Edward Kmett]

Yes. Hence why I pointed out some (myself included) would argue that the lazy versions are not properly monads.

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On Sep 15, 2011, at 5:12 PM, Henning Thielemann <lemming at henning-thielemann.de> wrote:

> 
> On Thu, 15 Sep 2011, Edward Kmett wrote:
> 
>> The Strict/Lazy writer split has nothing to do with the strictness of your monoid, but
>> rather whether or not operations such as:
>> > fmap f ~(w, a) = (w, f a)
> 
> Doesn't this violate the fmap law
> 
>  fmap id = id
> 
> because
> 
>  fmap id undefined = (undefined, undefined)
> 
> ?