Sounds similar to https://ghc.haskell.org/trac/ghc/wiki/UnliftedDataTypes
Simon
| -----Original Message-----
| From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of
| David Feuer
| Sent: 07 February 2018 01:11
| To: ghc-devs
| Subject: Strict unlifted types
|
| Sometimes there's an awkward expressive tension between saying that a
| type is *unboxed* and saying that it is *strict* in a field. For
| example, I can write
|
| data SMaybe a = SNothing | SJust !a
|
| or I can write
|
| type Maybe# a = (# (# #) | a #)
|
| but there doesn't seem to be a way to simultaneously get both unboxed
| and strict. I'm wondering if it might make sense to add a type to
| serve the purpose
|
| Strict# :: Type -> TYPE 'UnliftedRep
|
| mkStrict# :: a -> Strict# a -- force the argument getStrict# ::
| Strict# a -> a -- do nothing, but know the result is in WHNF
|
| Then one could write, for example,
|
| type SMaybe# a = (# (# #) | Strict# a #)
|
| at which point SMaybe is *precisely* isomorphic to the alternative
| representation
|
| data SMaybe' a = SMaybe' (SMaybe# a)
|
| David
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