naturalToWord vs 'clampNaturalToWord'

[Sylvain Henry]

We can easily add this function to ghc-bignum.

I've opened https://gitlab.haskell.org/ghc/ghc/-/issues/18697 to track this.

Sylvain

On 16/09/2020 04:19, Keith wrote:
> The short of it is,
>
> clampNaturalToWord :: Natural → Word
> clampNaturalToWord n = case n of
> NatS# w -> W# w
> _ -> maxBound
>
> results in much better space and time use than naturalToWord, which 
> always takes the least significant Word of the Natural.
>
>
> Because naturalToWord takes the least significant Word, you always 
> have to check for size before conversion. Even though you do check, 
> GHC has to assume that, after conversion, the big Natural could have 
> resulted in a small Word and will uselessly duplicate all branches for 
> both cases.
>
> Is there anything wrong with clamping by default in this case?
>
> --Keith
>
> Sent from my phone with K-9 Mail.
>
> _______________________________________________
> Libraries mailing list
> Libraries at haskell.org
> http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.haskell.org/pipermail/libraries/attachments/20200916/19f6e839/attachment.html>