Constraints on definition of `length` should be strengthened

[Sven Panne]

2017-04-04 8:15 GMT+02:00 Vladislav Zavialov <vlad.z.4096 at gmail.com>:

> > Tuples are unbiased cartesian products, full stop.
>
> This statement is not correct.


According to probably all the math books in the world, the statement is
correct, at least if we want to see tuples as cartesian products. But if we
don't want to do that, the usage of the name "tuple" in Haskell and the
(...,...) notation would be confusing misnomers.


> Look at their kind:
>
> > :k (,)
> (,) :: * -> * -> *
>
> The same currying business is going on here. [...]


That's an artifact of our kind system, not a consequence of the usual
definition of cartesian products.
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