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GHC 9.10.3 · lts/ghc-9.10.x · 248f8f0 · 2026-10-05

Modulepsqueues-0.2.8.2Haskell2010

Data.OrdPSQ

An OrdPSQ uses the Ord instance of the key type to build a priority search queue.

It is based on Ralf Hinze's work.

  • Hinze, R., A Simple Implementation Technique for Priority Search Queues, ICFP 2001, pp. 110-121

http://citeseer.ist.psu.edu/hinze01simple.html

This means it is similar to the PSQueue package but our benchmarks showed it perform quite a bit faster.

  • 1 type
  • 24 values
  • Packagepsqueues-0.2.8.2
  • Exports25
  • LanguageHaskell2010
  • LicenceBSD-3-Clause
  • SourceOrdPSQ.hs

Type

1 declaration
datadata OrdPSQ k p v
#

A mapping from keys k to priorites p and values v. It is strict in keys, priorities and values.

Instances6Functor, Foldable, Traversable, Eq, Show, NFData

Query

5 declarations
valuesize :: OrdPSQ k p v -> Int
#

O(1) The number of elements in a queue.

valuemember :: Ord k => k -> OrdPSQ k p v -> Bool
#

O(log n) Check if a key is present in the the queue.

valuelookup :: Ord k => k -> OrdPSQ k p v -> Maybe (p, v)
#

O(log n) The priority and value of a given key, or Nothing if the key is not bound.

valuefindMin :: OrdPSQ k p v -> Maybe (k, p, v)
#

O(1) The element with the lowest priority.

Construction

2 declarations
valuesingleton :: k -> p -> v -> OrdPSQ k p v
#

O(1) Build a queue with one element.

Insertion

1 declaration
valueinsert :: (Ord k, Ord p) => k -> p -> v -> OrdPSQ k p v -> OrdPSQ k p v
#

O(log n) Insert a new key, priority and value into the queue. If the key is already present in the queue, the associated priority and value are replaced with the supplied priority and value.

Delete/Update

4 declarations
valuedelete :: (Ord k, Ord p) => k -> OrdPSQ k p v -> OrdPSQ k p v
#

O(log n) Delete a key and its priority and value from the queue. When the key is not a member of the queue, the original queue is returned.

valuedeleteMin :: (Ord k, Ord p) => OrdPSQ k p v -> OrdPSQ k p v
#

O(log n) Delete the binding with the least priority, and return the rest of the queue stripped of that binding. In case the queue is empty, the empty queue is returned again.

valuealter
  1. :: (Ord k, Ord p)
  2. => Maybe (p, v) -> (b, Maybe (p, v))
  3. -> k
  4. -> OrdPSQ k p v
  5. -> (b, OrdPSQ k p v)
#

O(log n) The expression alter f k queue alters the value x at k, or absence thereof. alter can be used to insert, delete, or update a value in a queue. It also allows you to calculate an additional value b.

valuealterMin
  1. :: (Ord k, Ord p)
  2. => Maybe (k, p, v) -> (b, Maybe (k, p, v))
  3. -> OrdPSQ k p v
  4. -> (b, OrdPSQ k p v)
#

O(log n) A variant of alter which works on the element with the minimum priority. Unlike alter, this variant also allows you to change the key of the element.

Conversion

4 declarations
valuefromList :: (Ord k, Ord p) => [(k, p, v)] -> OrdPSQ k p v
#

O(n*log n) Build a queue from a list of (key, priority, value) tuples. If the list contains more than one priority and value for the same key, the last priority and value for the key is retained.

valuetoList :: OrdPSQ k p v -> [(k, p, v)]
#

O(n) Convert a queue to a list of (key, priority, value) tuples. The order of the list is not specified.

valuetoAscList :: OrdPSQ k p v -> [(k, p, v)]
#

O(n) Convert to a list in ascending order by key.

valuekeys :: OrdPSQ k p v -> [k]
#

O(n) Obtain the list of present keys in the queue.

Views

4 declarations
valueinsertView
  1. :: (Ord k, Ord p)
  2. => k
  3. -> p
  4. -> v
  5. -> OrdPSQ k p v
  6. -> (Maybe (p, v), OrdPSQ k p v)
#

O(log n) Insert a new key, priority and value into the queue. If the key is already present in the queue, then the evicted priority and value can be found the first element of the returned tuple.

valuedeleteView
  1. :: (Ord k, Ord p)
  2. => k
  3. -> OrdPSQ k p v
  4. -> Maybe (p, v, OrdPSQ k p v)
#

O(log n) Delete a key and its priority and value from the queue. If the key was present, the associated priority and value are returned in addition to the updated queue.

valueminView :: (Ord k, Ord p) => OrdPSQ k p v -> Maybe (k, p, v, OrdPSQ k p v)
#

O(log n) Retrieve the binding with the least priority, and the rest of the queue stripped of that binding.

valueatMostView
  1. :: (Ord k, Ord p)
  2. => p
  3. -> OrdPSQ k p v
  4. -> ([(k, p, v)], OrdPSQ k p v)
#

Return a list of elements ordered by key whose priorities are at most pt, and the rest of the queue stripped of these elements. The returned list of elements can be in any order: no guarantees there.

Traversals

3 declarations
valuemap :: (k -> p -> v -> w) -> OrdPSQ k p v -> OrdPSQ k p w
#

O(n) Modify every value in the queue.

valueunsafeMapMonotonic
  1. :: k -> p -> v -> (q, w)
  2. -> OrdPSQ k p v
  3. -> OrdPSQ k q w
#

O(n) Maps a function over the values and priorities of the queue. The function f must be monotonic with respect to the priorities. I.e. if x < y, then fst (f k x v) < fst (f k y v). The precondition is not checked. If f is not monotonic, then the result will be invalid.

valuefold' :: (k -> p -> v -> a -> a) -> a -> OrdPSQ k p v -> a
#

O(n) Strict fold over every key, priority and value in the queue. The order in which the fold is performed is not specified.

Validity check

1 declaration
valuevalid :: (Ord k, Ord p) => OrdPSQ k p v -> Bool
#

O(n^2) Internal function to check if the OrdPSQ is valid, i.e. if all invariants hold. This should always be the case.