[Haskell-cafe] Re: Data.Ring -- Pre-announce

John Van Enk vanenkj at gmail.com
Mon Jan 4 09:19:53 EST 2010

I've heard this a few times and am slowly becoming convinced of it. I'll try
my current use without the Empty and see how it goes.

Given that I've heard this from several places, I'll probably drop Empty.

On Mon, Jan 4, 2010 at 9:17 AM, Luke Palmer <lrpalmer at gmail.com> wrote:

> On Mon, Jan 4, 2010 at 6:51 AM, Maciej Piechotka <uzytkownik2 at gmail.com>
> wrote:
> > About comonad - not exactly as every comonad is copointed and the only
> > possible way is extract Empty = _|_
> I think this module could be cleaned up by disallowing empty lists.
> You have this nice semantic property that "every clist has a focus",
> but when you add empty you have to add "unless it's empty".  focus
> returns a Maybe, isEmpty is necessary.
> I mean, it could be that your use case requires empty clists and would
> be uglier without empty, but think about it.  I find in Haskell that
> simplicity breeds simplicity; i.e. I'm willing to wager that whatever
> algorithm you are using clist for will actually be cleaner if you got
> rid of empty and modify the algorithm accordingly.  We shall see
> though...
> Luke
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