Re: Constraints on definition of `length` should be strengthened

You want tuples in mathematics and tuples in Haskell to be the same, but they aren't. Call it an artifact of the kind system or a misnomer, but that's the state of affairs. It's counter-intuitive and I don't like it myself. My point is that if you want to fix this, it takes more than to delete a few instances from 'base'. See my other message in this thread about defining unbiased products in Haskell. On Tue, Apr 4, 2017 at 9:50 AM, Sven Panne wrote:

2017-04-04 8:15 GMT+02:00 Vladislav Zavialov :

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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.

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Look at their kind:

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: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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