Re: [Caml-list] First-class Functor Forgetting for Free

[Leo White <lpw25@cam.ac.uk>]

>> So,
>>
>>    let g x = let module X = (val x : D) in X.(f x)
>>
>> would have a type:
>>
>>    (module D with ..) -> int
>
> This certainly is a nice suggestive syntax, but it is assuming an underlying semantic similarity that does not
> exist. Semantically, the type sharing equations on signatures have very little in common with rows, and I have a hard
> time imagining what interpreting the above as a row would even mean or how it would fit in with either core or module 
> typing. 

I don't see what is hard to imagine. The row variable represents
possible extra with-constraints. The type above can be unified with any
package type with signature D.

With-constraints are essentially sets of label and type pairs, row
polymorphism provides a mechanism for typing sets of label and type
pairs. I don't see where they differ "semantically".

> (I could go into boring technical details here, but I'll leave it at
> that. :) )

I would prefer it if you did (off-list if you prefer).

Regards,

Leo