Misleading strictness annotations in Data.List.NonEmpty

[David Feuer]

Well, more reasonable from a performance standpoint anyway.
Semantically, it makes sense as it is.

On Fri, Jan 8, 2021 at 2:33 PM David Feuer <david.feuer at gmail.com> wrote:
>
> I agree that your implementation of (<|) is more reasonable. I'll take
> a look at groupBy1 in a bit.
>
> On Fri, Jan 8, 2021 at 2:27 PM Keith <keith.wygant at gmail.com> wrote:
> >
> > There are a couple other ones that I'm less sure about.
> >
> > cons:
> > a <| ~(b :| bs) = a :| b : bs
> >
> > Unsugared this is
> > a <| bs = a :|
> > (case bs of b :| _ -> b ) :
> > case bs of _ :| bs -> bs
> >
> > Would this make more sense?
> > a <| bs = a :| case bs of b :| bs' -> b : bs'
> >
> > Then
> > cons x undefined = x :| undefined
> > not
> > x :| undefined : undefined
> >
> >
> > groupBy1 matches strictly, could be lazy. (Is this a performance issue or an oversight?)
> > —
> > Sent from my phone with K-9 Mail.
> >
> > On January 8, 2021 6:36:58 PM UTC, Keith <keith.wygant at gmail.com> wrote:
> >>
> >> Thanks, will do.
> >>
> >> On January 8, 2021 5:07:25 PM UTC, David Feuer <david.feuer at gmail.com> wrote:
> >>>
> >>> The first one. Neither twiddles nor bangs are useful or add clarity.
> >>>
> >>> On Fri, Jan 8, 2021, 11:53 AM Keith <keith.wygant at gmail.com> wrote:
> >>>
> >>>>  Currently:
> >>>>
> >>>>  head ~(a :| _) = a
> >>>>  tail ~(_ :| as) = as
> >>>>
> >>>>  But head and tail are both strict. At best the '~'s have no effect.
> >>>>
> >>>>  Should I open a PR to change it to
> >>>>
> >>>>  head (a :| _) = a
> >>>>  tail (_ :| as) = as
> >>>>
> >>>>  or maybe even more clearly
> >>>>
> >>>>  head !(a :l _) = a
> >>>>  tail !(_ :| as) = as
> >>>>
> >>>>  ?
> >>>>  --Keith
> >>>>  Sent from my phone with K-9 Mail.
> >>
> >>
> >>
> >> Good to know! Wasn't aware that that was in the works.
> >>
> >> And sorry for accidentally threading this onto something unrelated.
> >>
> >> -- Keith
> >> Sent from my phone with K-9 Mail.
> >>
> >> On January 8, 2021 5:13:31 PM UTC, Henning Thielemann <lemming at henning-thielemann.de> wrote:
> >>>
> >>>
> >>> On Fri, 8 Jan 2021, Keith wrote:
> >>>
> >>>> Currently:
> >>>>
> >>>> head ~(a :| _) = a
> >>>> tail ~(_ :| as) = as
> >>>>
> >>>> But head and tail are both strict. At best the '~'s have no effect.
> >>>>
> >>>> Should I open a PR to change it to
> >>>>
> >>>> head (a :| _) = a
> >>>> tail (_ :| as) = as
> >>>>
> >>>> or maybe even more clearly
> >>>>
> >>>> head !(a :l _) = a
> >>>> tail !(_ :| as) = as
> >>>>
> >>>> ?
> >>>
> >>>
> >>> The last one would trigger the "redundant bang pattern" warning that is
> >>> going to be implemented/released:
> >>>     https://gitlab.haskell.org/ghc/ghc/issues/17340
> >
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