- You will eventually need all the values stored.
- The stored values don't represent large virtual data structures to be lazily computed.

import qualified Data.Map as MapThe implementation of Map is based on

- Stephen Adams, "
*Efficient sets: a balancing act*", Journal of Functional Programming 3(4):553-562, October 1993, http://www.swiss.ai.mit.edu/~adams/BB/. - J. Nievergelt and E.M. Reingold, "
*Binary search trees of bounded balance*", SIAM journal of computing 2(1), March 1973.

- Guy Blelloch, Daniel Ferizovic, and Yihan Sun, "
*Just Join for Parallel Ordered Sets*", https://arxiv.org/abs/1602.02120v3.

An efficient implementation of maps from integer keys to values
(dictionaries).
This module re-exports the value lazy Data.IntMap.Lazy API,
plus several deprecated value strict functions. Please note that these
functions have different strictness properties than those in
Data.IntMap.Strict: they only evaluate the result of the
combining function. For example, the default value to
insertWith' is only evaluated if the combining function is
called and uses it.
These modules are intended to be imported qualified, to avoid name
clashes with Prelude functions, e.g.
*big-endian patricia trees*. This
data structure performs especially well on binary operations like
union and intersection. However, my benchmarks show that
it is also (much) faster on insertions and deletions when compared to
a generic size-balanced map implementation (see Data.Map).
*O(min(n,W))*. This
means that the operation can become linear in the number of elements
with a maximum of *W* -- the number of bits in an Int (32
or 64).

import Data.IntMap (IntMap) import qualified Data.IntMap as IntMapThe implementation is based on

- Chris Okasaki and Andy Gill, "
*Fast Mergeable Integer Maps*", Workshop on ML, September 1998, pages 77-86, http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.37.5452 - D.R. Morrison, "
*PATRICIA -- Practical Algorithm To Retrieve Information Coded In Alphanumeric*", Journal of the ACM, 15(4), October 1968, pages 514-534.

**Packages**- is:exact