[Haskell-cafe] Structural sharing in haskell data structures?

Jan-Willem Maessen jmaessen at alum.mit.edu
Thu May 14 11:21:21 EDT 2009

On May 14, 2009, at 11:01 AM, Dan Doel wrote:

> On Thursday 14 May 2009 9:03:30 am Jan-Willem Maessen wrote:
>> Hmm, I think neither of the data structures you name actually support
>> both O(lg n) indexing and O(lg n) cons or append.  That said, your
>> point is well taken, so let's instead state it as a challenge:
> Data.Sequence has O(log n) index, concatenation, update, take, drop  
> and
> splitAt, and O(1) cons, snoc, and viewing at both ends, according to  
> the
> documentation.

Yes.  But large sequences end up being quite deep.  Can a wide-fanout  
version be made that is actually faster?  Note that the effective  
fanout of Hinze's finger trees is approximately e; consider effective  
fanouts of e^2 to e^4 (which may require substantially higher maximum  


> -- Dan

More information about the Haskell-Cafe mailing list