Hmm, it looks like you forgot to write a Traversable instance. I don't believe:
sequenceA (OneTuple [1,2,3,4]) = _|_
is correct. Here is my contribution!
instance Traversable OneTuple where
sequenceA (OneTuple x) = fmap OneTuple x
Luke
On Thu, Oct 2, 2008 at 12:56 AM, John Dorsey
Fellow Haskellers,
Much attention has been paid over the years to the regrettable omission of singleton tuples from Haskell.
I am pleased to announce OneTuple, a humble implementation of the singleton tuple for Haskell. Now you can:
* Wrap a single value of any type in a OneTuple !
* Pattern match to retrieve your value !
* Solve any of the software problems that cannot be solved without the singleton tuple !
* Enjoy instances for all the classes normal tuples have, plus more !
* Proclaim feature parity with Python !
Note: the singleton tuple does not support tuple syntax.
Contributions are welcome. The project could use a tutorial, and a decent test suite. Strict singleton tuples are planned for the next version.
Enjoy!
Regards, John Dorsey
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