Constraints on definition of `length` should be strengthened

[amindfv at gmail.com]

I don't totally understand this viewpoint. It sounds like what you're saying is it's unfortunate that tuples (and everything else) are biased in Haskell, but because they are we're obligated to make all the legal instances we can for them.

E.g. if I define a datatype "data Foo x y z", I'm powerless and sort of obligated to define "instance Functor (Foo x y)" if there's a legal one, regardless of if that's what I want Foo to mean.

Tom


> El 3 abr 2017, a las 15:29, Nathan Bouscal <nbouscal at gmail.com> escribió:
> 
> I expect most people probably agree that it'd be nice to have tuples be an unbiased cartesian product, but the actual fact of the matter is that tuples as they exist in Haskell are biased. We can't just ignore that and pretend they're unbiased. It definitely sucks that the answer people would naively give to "what is a tuple in Haskell" is not the correct answer, but we're stuck in that situation. The question is how to make the best of it.
> 
>> On Mon, Apr 3, 2017 at 12:56 PM, Henning Thielemann <lemming at henning-thielemann.de> wrote:
>> 
>> On Mon, 3 Apr 2017, Sven Panne wrote:
>> 
>>> Of course such an interpretation is possible, but let's remember Abelson's famous quote:
>>> 
>>>    "Programs must be written for people to read, and only incidentally for machines to execute."
>>> 
>>> When you show somebody a pair and ask "What is this?", how many people do you *seriously* expect to say "Oh, yeah, I've seen that: It's a value on the right decorated by another one on the left!" compared to people telling you something about e.g. cartesian products (which are totally symmetric with no bias to the right or left)? The point is: Using a pair for a decorated one-element container is completely miscommunicating your intent, even if you find a sensible mathematical interpretation for it.
>> 
>> That's what I am saying all the time.
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