Portability | portable |
---|---|

Stability | provisional |

Maintainer | libraries@haskell.org |

Safe Haskell | Safe |

*Note:* You should use Data.Map.Strict instead of this module if:

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

An efficient implementation of ordered maps from keys to values (dictionaries).

These modules are intended to be imported qualified, to avoid name clashes with Prelude functions, e.g.

import qualified Data.Map as Map

The implementation of `Map`

is based on *size balanced* binary trees (or
trees of *bounded balance*) as described by:

- 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.

Note that the implementation is *left-biased* -- the elements of a
first argument are always preferred to the second, for example in
`union`

or `insert`

.

Operation comments contain the operation time complexity in the Big-O notation (http://en.wikipedia.org/wiki/Big_O_notation).

- module Data.Map.Lazy
- insertWith' :: Ord k => (a -> a -> a) -> k -> a -> Map k a -> Map k a
- insertWithKey' :: Ord k => (k -> a -> a -> a) -> k -> a -> Map k a -> Map k a
- insertLookupWithKey' :: Ord k => (k -> a -> a -> a) -> k -> a -> Map k a -> (Maybe a, Map k a)
- fold :: (a -> b -> b) -> b -> Map k a -> b
- foldWithKey :: (k -> a -> b -> b) -> b -> Map k a -> b

# Documentation

module Data.Map.Lazy

insertWith' :: Ord k => (a -> a -> a) -> k -> a -> Map k a -> Map k aSource

*Deprecated.* As of version 0.5, replaced by `insertWith`

.

*O(log n)*. Same as `insertWith`

, but the value being inserted to the map is
evaluated to WHNF beforehand.

For example, to update a counter:

insertWith' (+) k 1 m

insertWithKey' :: Ord k => (k -> a -> a -> a) -> k -> a -> Map k a -> Map k aSource

*Deprecated.* As of version 0.5, replaced by
`insertWithKey`

.

*O(log n)*. Same as `insertWithKey`

, but the value being inserted to the map is
evaluated to WHNF beforehand.

insertLookupWithKey' :: Ord k => (k -> a -> a -> a) -> k -> a -> Map k a -> (Maybe a, Map k a)Source

*Deprecated.* As of version 0.5, replaced by
`insertLookupWithKey`

.

*O(log n)*. Same as `insertLookupWithKey`

, but the value being inserted to
the map is evaluated to WHNF beforehand.

foldWithKey :: (k -> a -> b -> b) -> b -> Map k a -> bSource

*Deprecated.* As of version 0.4, replaced by `foldrWithKey`

.

*O(n)*. Fold the keys and values in the map using the given right-associative
binary operator. This function is an equivalent of `foldrWithKey`

and is present
for compatibility only.