On 2015-02-10 at 09:46:37 +0100, Edward Z. Yang wrote:
I propose the following (abstract) data type, functions, and instance be added to deepseq (naming amenable to bikeshedding):
newtype NF a = NF a -- abstract makeNF :: NFData a => a -> NF a getNF :: NF a -> a
instance NFData (NF a) where rnf x = x `seq` ()
I generally like it, so count me as +1 bikeshed-wondering though, why did you make it abstract w/ separate construct/deconstructors? as a related concept (and hoping not to derail the discussion too much), I had attempted some time ago to implement TH predicates that could infer if WHNF=NF holds: http://hackage.haskell.org/package/deepseq-th-0.1.0.4/docs/Control-DeepSeq-T... and back then I was wondering, if GHC couldn't help us out here (maybe by providing an implicit NF=WHNF class-instance -- and btw, I recently found out, Haskell 1.4 had an implicit 'Eval'-class declaring `seq`-ability) I'm not sure though if WHNF=NF can always be decided... Cheers, hvr