[NumericPrelude] NP bug reports

Henning Thielemann lemming at henning-thielemann.de
Sat Aug 27 06:30:37 BST 2016

On Thu, 25 Aug 2016, Eric Crockett wrote:

> Is there a github (or similar) repo for this library where I can file bug reports and feature requests?

E-mail to me is ok, you may also mail to 
numeric-prelude at projects.haskell.org. However, the mailing list had 
problems. I could move to darcs-hub. It includes a bug tracker, but 
requires conversion to darcs-2 format. So I did not perform the move so 
far because of low volume of issues.

> With the NP equivalent:
> {-# LANGUAGE NoImplicitPrelude, RebindableSyntax #-}

Btw. you may omit NoImplicitPrelude. It is implied by RebindableSyntax.

> module Main where
> import NumericPrelude
> main :: IO ()
> main = do
>   let x = sqrt $ -1.0 :: Double
>   print x -- NaN
>   let y = round x :: Int
>   print y -- crashes
> When compiled with -O0, I get NaN and 0, respectively (same as Prelude). When compiled with -O1, I get NaN and
> "Prelude.Enum.pred{Int}: tried to take `pred' of minBound".

I think the behavior is better than that of Prelude, yet, the error 
message is confusing. I think it is caused by Algebra.RealRing.roundInt. I 
wrote 'pred n' instead of 'n-1'. In general I did such things in order to 
avoid working with number literals because they are not available in all 
numeric-prelude modules. However, in this case 'n-1' should also work.

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