[Haskell-cafe] Monad laws in presence of bottoms

Roman Cheplyaka roma at ro-che.info
Tue Feb 21 08:17:05 CET 2012

* Sebastian Fischer <fischer at nii.ac.jp> [2012-02-21 00:28:13+0100]
> On Mon, Feb 20, 2012 at 7:42 PM, Roman Cheplyaka <roma at ro-che.info> wrote:
> > Is there any other interpretation in which the Reader monad obeys the
> > laws?
> If "selective strictness" (the  seq  combinator) would exclude function
> types, the difference between  undefined  and  \_ -> undefined  could not
> be observed. This reminds me of the different language levels used by the
> free theorem generator [1] and the discussions whether  seq  should have a
> type-class constraint..

It's not just about functions. The same holds for the lazy Writer monad,
for instance.

Roman I. Cheplyaka :: http://ro-che.info/

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