[Haskell-cafe] Re: Non Empty List?

[GüŸnther Schmidt]

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 <gue.schmidt at web.de> 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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