[Haskell-cafe] Need an example of new type constructor with zero data constructors

[Jack Henahan]

I think they mean "new type" to mean a data declaration, rather than a
newtype. I had to read it a few times before it clicked for me. Just a
confusion in terminology.

Adam Bergmark <adam at bergmark.nl> writes:

> What you posted is the format for data declarations, not newtypes. Newtypes
> are required to have exactly one constructor:
>
> newtype [context =>] simpletype = newconstr [deriving]
>
>
> Adam
>
> On Fri, Aug 12, 2016 at 4:43 PM, James Brown <james.brown5374 at gmail.com>
> wrote:
>
>> In the Haskell report 2010, a data declaration has the format of:
>>
>>
>> <https://lh3.googleusercontent.com/-G-z92n-50B0/V63XKCCrJDI/AAAAAAAAAGA/w-Zdi9DaR18hX67n-OeQNkDB1iUR0IP7gCLcB/s1600/Screen%2BShot%2B2016-08-12%2Bat%2B10.03.00%2BAM.png>
>>
>> For a new type, there could be zero or more data constructors. What's the
>> use case for a new type that has zero data constructor?
>>
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--
Jack
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