Self optimizing container types.
Self optimizing polymorphic container types.
Adaptive containers are polymorphic container types that use class associated data types to specialize particular element types to a more efficient container representation. The resulting structures tend to be both more time and space efficient.
A self-optimizing pair, for example, will unpack the constructors, yielding a representation for (Int,Char) requiring 8 bytes, instead of 24.
This difference can be visualized. Consider the expression:
[ (x,y) | x <- [1..3], y <- [x..3] ]
[(Int,Int)]: A regular list of pairs http://code.haskell.org/~dons/images/vacuum/tuple-list.png
[Pair Int Int]: An adaptive list of pairs http://code.haskell.org/~dons/images/vacuum/pair-list.png
List (Pair Int Int): An adaptive list of adaptive pairs http://code.haskell.org/~dons/images/vacuum/list-pair.png
Currently supported adaptive containers: pairs, lists, maybes
Most unboxed element types are supported.