[Haskell-cafe] Re: Non Empty List?

Hi Tom, thanks for replying, no, I'm not looking for streams. I hope I made myself a bit more clear in my response to Jake. Günther Tom Lokhorst schrieb:

Are you looking for something like Streams [1]?

They're infinite sequences, defined like this:

data Stream a = Cons a (Stream a)

They can obviously never be empty (unless you see bottom (undefined) as empty).

- Tom

[1] http://hackage.haskell.org/cgi-bin/hackage-scripts/package/Stream

On Thu, Jun 4, 2009 at 11:53 PM, GüŸnther Schmidt wrote:

...

Hi,

I need to design a container data structure that by design cannot be empty and can hold n elements. Something like a non-empty list.

I started with:

data Container a = Single a | Many a [a]

but the problem above is that the data structure would allow to construct a Many 5 [] :: Container Int.

I can't figure out how to get this right. :(

Please help.

Günther

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