[Haskell-cafe] Announcing OneTuple-0.1.0

[Derek Elkins]

On Fri, 2008-10-03 at 15:38 -0400, David Menendez wrote:
> On Fri, Oct 3, 2008 at 3:17 AM, Jason Dusek <jason.dusek at gmail.com> wrote:
> >  Perhaps I am lacking in imagination, but I still can't see the
> >  value of one tuples.
> 
> You can use them to defeat seq.
> 
> undefined `seq` x == undefined
> OneTuple undefined `seq` x == x
> 
> That might be useful if a polymorphic function is using seq to force
> evaluation, and you don't want it to. But I can't imagine that coming
> up much in practice.

Think element strict polymorphic containers, e.g.

data HeadStrictList a = Nil | Cons !a (HeadStrictList a)

then

type LazyList a = HeadStrictList (OneTuple a)