[Haskell-cafe] ANN: unordered-containers - a new, faster hashing-based containers library

Johan Tibell johan.tibell at gmail.com
Sat Feb 19 02:38:51 CET 2011

Hi all,

I am delighted to announce the release of preview versions of two new packages:

unordered-containers 0.1
Efficient hashing-based container types.

hashable 1.1
Efficient hashing of common types.

These packages address a need for faster container types in Haskell,
especially for string types like ByteString and Text. The package
achieves better performance by using hashing and a Patricia trie (also
known as a radix tree), instead of a balanced tree, in its

The provided HashMap type is three times faster than Data.Map for
lookups and twice as fast for inserts, for all key types I've tried,
including ByteString, String, and Int.

I'm calling this a preview release, even though the code hash been
well tested both for correctness and performance, as the API is quite
basic and doesn't provide a HashSet type yet. One thing you'll notice
is that the API is split into a value-strict and a value-lazy version,
making it easier to use in a strict setting.

If you want to contribute, please get copies of the source trees from here:

* git clone https://github.com/tibbe/unordered-containers.git
* git clone https://github.com/tibbe/hashable.git

Alternatively, just fork the projects on GitHub:


As I mentioned in my talk on hashing-based containers earlier this
week, I'm working on an even faster version, based on hash-array
mapped tries, but it won't be ready until GHC 7.2.


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