Proposal: NF newtype

[Roman Cheplyaka]

Sounds great, +1.

On 10/02/15 10:46, 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` ()
> 
> NF is an abstract data type representing data which has been evaluated
> to normal form; the guarantee specifically is, if NF is in whnf, then
> it is in nf.  Crucially, when we have 'NF a', we ONLY need to seq it
> in order to assure that it is fully evaluated.
> 
> This guarantee is sufficient for a variety of cases where
> normal data is necessary, e.g. when transmitting data over Channels.
> For example, from the monad-par library 'put_' could be used in place
> of 'put' with this type signature.
> 
>     put_ :: IVar (NF a) -> (NF a) -> Par () 
> 
> Cheers,
> Edward
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