ANNOUNCE: GHC 7.4.1 Release Candidate 1
la at iki.fi
Thu Dec 29 00:44:06 CET 2011
Quoting "Wolfgang Jeltsch" <g9ks157k at acme.softbase.org>:
> Am Mittwoch, den 28.12.2011, 12:48 +0000 schrieb Simon Peyton-Jones:
>> Only that BOX is a sort (currently the one and only sort), whereas
>> Constraint is a kind. I'm not sure that BOX should ever be displayed
>> to users.
> Okay, this makes sense then. However, note that the GHC User’s manual
> mixes the terminology (“kind” vs. “sort”) at one point:
> Note that List, for instance, does not get kind BOX -> BOX, because
> we do not further classify kinds; all kinds have sort BOX.
> I think, it should say “sort BOX -> BOX”.
I don't think that would be quite correct. Sorts are typically
constants, and there are usually a finite amount of them, each
presenting a "level" of the type system. For instance, * and BOX are
both sorts, even though we also have * :: BOX. In a system where BOX
-> BOX would be well-formed, it should probably be called something
else, maybe "kind-classifying term" (whose sort would be something
new, maybe TRIANGLE).
But it seems a bit funny to spend a lot of time thinking about what to
call things that don't exist in GHC. Maybe it'd be easiest to just
drop that awkward hypothetical "BOX -> BOX" altogether from the manual.
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