[Haskell-cafe] Haskell 2010 report nit?

[Tom Ellis]

On Mon, Dec 16, 2019 at 01:42:39AM -0500, Viktor Dukhovni wrote:
> Not sure where to post about this, and it has likely been noted
> elsewhere already, but reading through the report I see in Section
> 3.17.2
> 
> > • Consider the following declarations:
> > 
> >   newtype N = N Bool  
> >   data    D = D !Bool
> > 
> > These examples illustrate the difference in pattern matching between types defined by data and newtype:
> > 
> > (\  (N True) -> True) ⊥     ⇒    ⊥
> > (\  (D True) -> True) ⊥     ⇒    ⊥
> > (\ ~(D True) -> True) ⊥     ⇒    True
> > 
> > Additional examples may be found in Section 4.2.3.
> 
> But unlike the examples in 4.2.3, which do show differences
> between "newtype" and "data", the above does not seem to
> show any actual difference.  For that the pattern after the
> constructor would I believe have to be irrefutable, which
> "True" is not.

I think what you're saying is that this doesn't show a difference because

    (\ ~(N True) -> True) ⊥     ⇒    True