[Haskell-cafe] Purely Functional Data Structures

G?uenther Schmidt redcom at fedoms.com
Sat Mar 7 20:28:43 EST 2009

Hi Jeremy,

I had used HAppS-IxSet before and was very happy with it, it offered 
pretty much everything I needed. I switched (back) to SQL once I had hit 
a bump in the road that I wasn't able to fix, a stack-overflow that 
occurred once I ran the code against the largest sample data I had. It 
occurred because I could not make the inserts into the set strict.

However since then my haskell skills have improved somewhat and right 
now I'm giving it another go.

At that time it seemed that not many people were using IxSet so no-one 
was really able to help me with it.

I'm glad that even though the original project is discontinued someone 
else took up the torch.


Jeremy Shaw schrieb:
> At Sun, 08 Mar 2009 00:13:14 +0100,
> G?uenther Schmidt wrote:
>> In SQL I would have the data indexed by several 
>> different columns, if I use maps I'd only have one key, so if I need to 
>> lookup data in the map by a value that is not the key the lookups will 
>> become quite expensive.
> happstack-ixset offers a data-type similar to Map except that you can
> have multiple keys. You can even have keys that are calculated from
> the data but don't actually appear in the data itself. For, example,
> if your ixset just contains Strings, one of the keys could be the
> length of the String.
> happstack-ixset (and its dependencies) also offers compact
> serialization/deserialization of the ixset to disk, data migration
> options, and a smattering of other features that may or may not be
> useful to you.
> While happstack-ixset is built to work with happstack, it is does not
> depend on the happstack http server or persistent store layer, so it
> should be useful even if you are not being an application server.
> - jeremy  

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