[Haskell-cafe] [External] Resources on how to implement (Haskell 98) kind-checking?

[Benjamin Redelings]

Thanks, I didn't know about that list.

I would be happy to document what I find out, though I'm sure other 
people would need to correct it.

-BenRI

On 10/14/21 10:28 AM, Brandon Allbery wrote:
> At this point you might want to ask on ghc-devs. They might ask you to 
> document what you find out, though.
>
> On Thu, Oct 14, 2021 at 10:25 AM Benjamin Redelings 
> <benjamin.redelings at gmail.com> wrote:
>
>     Thanks!  Yes, that introduces the idea that requires kind inference.
>
>     Interestingly, it contains a (kind-aware) type-inference
>     algorithm, but no kind inference algorithm!
>
>     Perhaps kind-inference is considered too "obvious" to require an
>     algorithm.  The closest it comes is the rule:
>
>     C :: k' -> k   and   C' :: k'  => C C' :: k
>
>     This is helpful, but it would probably be beneficial for better
>     documentation to exist SOMEWHERE.
>
>     -BenRI
>
>     On 10/13/21 3:49 PM, Ingle, Apoorv N wrote:
>>     Along with what Emil suggests,
>>     Sec 4. of A system of constructor classes: overloading and
>>     implicit higher-order polymorphism[1] may also be useful.
>>
>>     — Apoorv
>>
>>     [1]: http://web.cecs.pdx.edu/~mpj/pubs/fpca93.pdf
>>
>>
>>>     On Oct 13, 2021, at 14:22, Emil Axelsson <78emil at gmail.com> wrote:
>>>
>>>     Maybe Typing Haskell in Haskell
>>>     <http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.134.7274&rep=rep1&type=pdf>
>>>     is what you're looking for?
>>>
>>>     / Emil
>>>     Den 2021-10-12 kl. 21:35, skrev Benjamin Redelings:
>>>>     Hi,
>>>>
>>>>     1. I'm looking for resources that describe how to implement
>>>>     kind Haskell 98 checking.  Does anyone have any suggestions?
>>>>
>>>>     * I've looked at the PolyKinds paper, but it doesn't cover type
>>>>     classes.
>>>>
>>>>     * I've looked at the source code to GHC, but it is hard to
>>>>     follow for a variety of reasons.  It isn't laid out like an
>>>>     algorithm description, and the complexity to handle options
>>>>     like PolyKinds and DataKinds makes the code harder to follow.
>>>>
>>>>
>>>>     2. One question that came up is how to handle type variables
>>>>     that are present in class methods, but are not type class
>>>>     parameters. If there are multiple types/classes in a single
>>>>     recursive group, the kind of such type variables might not be
>>>>     fully resolved until a later type-or-class is processed.  Is
>>>>     there a recommended approach?
>>>>
>>>>     I can see two ways to proceed:
>>>>
>>>>     i) First determine the kinds of all the data types, classes,
>>>>     and type synonyms.  Then perform a second pass over each type
>>>>     or class to determine the kinds of type variables (in class
>>>>     methods) that are not type class parameters.
>>>>
>>>>     ii) Alternatively, record the kind of each type variable as it
>>>>     is encountered -- even though such kinds may contain
>>>>     unification kind variables.  After visiting all
>>>>     types-or-classes in the recursive group, replace any kind
>>>>     variables with their definition, or with a * if there is no
>>>>     definition.
>>>>
>>>>     I've currently implement approach i), which requires doing kind
>>>>     inference on class methods twice.  Is this the recommended
>>>>     approach?
>>>>
>>>>
>>>>     3. Also, is Haskell 98 kind checking the same as Haskell 2010
>>>>     kind checking?
>>>>
>>>>     -BenRI
>>>>
>>>>
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>
> -- 
> brandon s allbery kf8nh
> allbery.b at gmail.com
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