FastInt = Int#, so newtype doesn't work here.
Cheers,
Simon
On 15/08/2014 14:01, Edward Z. Yang wrote:
The definition dates back to 1996, so it seems plausible that
newtype is the way to go now.
Edward
Excerpts from p.k.f.holzenspies's message of 2014-08-15 11:52:47 +0100:
Dear all,
I'm working with Alan to instantiate everything for Data.Data, so that we can
do better SYB-traversals (which should also help newcomers significantly to get
into the GHC code base). Alan's looking at the AST types, I'm looking at the
basic types in the compiler.
Right now, I'm looking at Unique and two questions come up:
data Unique = MkUnique FastInt
1) As someone already commented: Is there a specific reason (other than
history) that this isn't simply a newtype around an Int? If we're boxing
anyway, we may as well use the default Int boxing and newtype-coerce to the
specific purpose of Unique, no?
2) As a general question for GHC hacking style; what is the reason for hiding
the constructors in the first place?
I understand about abstraction and there are reasons for hiding, but there's a
"public GHC API" and then there are all these modules that people can import at
their own peril. Nothing is guaranteed about their consistency from version to version of
GHC. I don't really see the point about hiding constructors (getting in the way of
automatically deriving things) and then giving extra functions like (in the case of
Unique):
getKeyFastInt (MkUnique x) = x
mkUniqueGrimily x = MkUnique (iUnbox x)
I would propose to just make Unique a newtype for an Int and making the
constructor visible.
Regards,
Philip
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