The lazyset package

[Tags:benchmark, library, mit, test]

A Set and Map implementation that is completly lazy and works for infinite sets and maps.

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Dependencies base (==4.9.*), containers (>= && <0.6), data-ordlist (==0.4.*) [details]
License MIT
Author Carlos Freund
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Source repository head: git clone
Uploaded Thu Dec 15 11:53:11 UTC 2016 by carlos_freund
Distributions NixOS:
Downloads 35 total (11 in the last 30 days)
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Status Docs available [build log]
Last success reported on 2016-12-15 [all 1 reports]
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Readme for lazyset

Readme for lazyset-


A Lazy Set and Map implemented in Haskell. Allows efficient, lazy lookups on sorted lists. The list may be of ininite size. The Source-List must

  • contain elements that implement Ord
  • must be ascending (or descending: see fromDescList)
  • either produce an infinite number of elements or terminate

Set Sample usage

import Data.Set.Lazy

set = fromAscList $ map (*3) [1..]

3 `member` set -> True
4 `member` set -> False

Map Sample usage

import Prelude hiding(lookup)
import Data.Map.Lazier

sqrtmap = fromList $ map (\i->(i, sqrt i)) [1..]
lookup 2 sqrtmap -> Just 1.4142135623730951


Elements from the Source-List will be requested in batches of increasing size. By default the batch-size is increases by two. This would lead to batches of 1,2,4,8,16. This can be changed by using growFromAscList factor list. For Example a factor of 1.3 casues the batches to be 1,2,2,3,3,4,5. Increasing the growth-factor reduces lookup times but increases the batch-size. When it is set to 1.0 it performs like a list. lookup: O(m) = log m where m is the index of the element in the source-list.


This breaks the set, because the underlying list stops producing elements.

set = fromList $ filter (<4) [1..]
5 `member` set