Data.IntervalSet

An implementation of sets of intervals. The intervals may overlap, and the implementation contains efficient search functions for all intervals containing a point or overlapping a given interval. Closed, open, and half-open intervals can be contained in the same set.

It is an error to insert an empty interval into a set. This precondition is not checked by the various construction functions.

Since many function names (but not the type name) clash with Prelude names, this module is usually imported qualified, e.g.

 import Data.IntervalSet.Strict (IntervalSet)
 import qualified Data.IntervalSet.Strict as IS

It offers most of the same functions as Set, but the member type must be an instance of Interval. The findMin and findMax functions deviate from their set counterparts in being total and returning a Maybe value. Some functions differ in asymptotic performance (for example size) or have not been tuned for efficiency as much as their equivalents in Set.

In addition, there are functions specific to sets of intervals, for example to search for all intervals containing a given point or contained in a given interval.

The implementation is a red-black tree augmented with the maximum upper bound of all keys.

Parts of this implementation are based on code from the Map implementation, (c) Daan Leijen 2002, (c) Andriy Palamarchuk 2008. The red-black tree deletion is based on code from llrbtree by Kazu Yamamoto. Of course, any errors are mine.

re-export

class Ord e => Interval i e | i -> e where

Intervals with endpoints of type e. A minimal instance declaration for a closed interval needs only to define lowerBound and upperBound.

Minimal complete definition

lowerBound, upperBound

Methods

lowerBound :: i -> e

lower bound

upperBound :: i -> e

upper bound

leftClosed :: i -> Bool

Does the interval include its lower bound? Default is True for all values, i.e. closed intervals.

rightClosed :: i -> Bool

Does the interval include its upper bound bound? Default is True for all values, i.e. closed intervals.

before :: i -> i -> Bool

Interval strictly before another? True if the upper bound of the first interval is below the lower bound of the second.

after :: i -> i -> Bool

Interval strictly after another? Same as 'flip before'.

subsumes :: i -> i -> Bool

Does the first interval completely contain the second?

overlaps :: i -> i -> Bool

Do the two intervals overlap?

below :: e -> i -> Bool

Is a point strictly less than lower bound?

above :: e -> i -> Bool

Is a point strictly greater than upper bound?

inside :: e -> i -> Bool

Does the interval contain a given point?

isEmpty :: i -> Bool

Is the interval empty?

Instances

Ord a => Interval (Interval a) a

Set type

data IntervalSet k

A set of intervals of type k.

Constructors

Nil

Node !Color !k !k !(IntervalSet k) !(IntervalSet k)

Instances

Foldable IntervalSet

Eq k => Eq (IntervalSet k)

Ord k => Ord (IntervalSet k)

(Ord k, Read k, Interval i k, Ord i, Read i) => Read (IntervalSet i)

Show k => Show (IntervalSet k)

(Interval i k, Ord i) => Monoid (IntervalSet i)

NFData k => NFData (IntervalSet k)

Operators

(\\) :: (Interval k e, Ord k) => IntervalSet k -> IntervalSet k -> IntervalSet k infixl 9

Same as difference.

Query

null :: IntervalSet k -> Bool

O(1). Is the set empty?

size :: IntervalSet k -> Int

O(n). Number of keys in the set.

Caution: unlike size, this takes linear time!

member :: Ord k => k -> IntervalSet k -> Bool

O(log n). Does the set contain the given value? See also notMember.

notMember :: Ord k => k -> IntervalSet k -> Bool

O(log n). Does the set not contain the given value? See also member.

Interval query

containing :: Interval k e => IntervalSet k -> e -> IntervalSet k

Return the set of all intervals containing the given point.

O(n), since potentially all intervals could contain the point. O(log n) average case. This is also the worst case for sets containing no overlapping intervals.

intersecting :: Interval k e => IntervalSet k -> k -> IntervalSet k

Return the set of all intervals overlapping (intersecting) the given interval.

O(n), since potentially all values could intersect the interval. O(log n) average case, if few values intersect the interval.

within :: Interval k e => IntervalSet k -> k -> IntervalSet k

Return the set of all intervals which are completely inside the given interval.

O(n), since potentially all values could be inside the interval. O(log n) average case, if few keys are inside the interval.

Construction

empty :: IntervalSet k

O(1). The empty set.

singleton :: k -> IntervalSet k

O(1). A set with one entry.

Insertion

insert :: (Interval k e, Ord k) => k -> IntervalSet k -> IntervalSet k

O(log n). Insert a new value. If the set already contains an element equal to the value, it is replaced by the new value.

Delete/Update

delete :: (Interval k e, Ord k) => k -> IntervalSet k -> IntervalSet k

O(log n). Delete an element from the set. If the set does not contain the value, it is returned unchanged.

Combine

union :: (Interval k e, Ord k) => IntervalSet k -> IntervalSet k -> IntervalSet k

O(n+m). The expression (union t1 t2) takes the left-biased union of t1 and t2. It prefers t1 when duplicate elements are encountered.

unions :: (Interval k e, Ord k) => [IntervalSet k] -> IntervalSet k

The union of a list of sets: (unions == foldl union empty).

difference :: (Interval k e, Ord k) => IntervalSet k -> IntervalSet k -> IntervalSet k

O(n+m). Difference of two sets. Return elements of the first set not existing in the second set.

intersection :: (Interval k e, Ord k) => IntervalSet k -> IntervalSet k -> IntervalSet k

O(n+m). Intersection of two sets. Return elements in the first set also existing in the second set.

Traversal

Map

map :: (Interval a e1, Interval b e2, Ord b) => (a -> b) -> IntervalSet a -> IntervalSet b

O(n log n). Map a function over all values in the set.

The size of the result may be smaller if f maps two or more distinct elements to the same value.

mapMonotonic :: (Interval k2 e, Ord k2) => (k1 -> k2) -> IntervalSet k1 -> IntervalSet k2

O(n). mapMonotonic f s == map f s, but works only when f is strictly monotonic. That is, for any values x and y, if x < y then f x < f y. The precondition is not checked.

Fold

foldr :: (k -> b -> b) -> b -> IntervalSet k -> b

O(n). Fold the values in the set using the given right-associative binary operator, such that foldr f z == foldr f z . elems.

foldl :: (b -> k -> b) -> b -> IntervalSet k -> b

O(n). Fold the values in the set using the given left-associative binary operator, such that foldl f z == foldl f z . elems.

foldl' :: (b -> k -> b) -> b -> IntervalSet k -> b

O(n). A strict version of foldl. Each application of the operator is evaluated before using the result in the next application. This function is strict in the starting value.

foldr' :: (k -> b -> b) -> b -> IntervalSet k -> b

O(n). A strict version of foldr. Each application of the operator is evaluated before using the result in the next application. This function is strict in the starting value.

Conversion

elems :: IntervalSet k -> [k]

O(n). List of all values in the set, in ascending order.

Lists

toList :: IntervalSet k -> [k]

O(n). The list of all values in the set, in no particular order.

fromList :: (Interval k e, Ord k) => [k] -> IntervalSet k

O(n log n). Build a set from a list of elements. See also fromAscList. If the list contains duplicate values, the last value is retained.

Ordered lists

toAscList :: IntervalSet k -> [k]

O(n). The list of all values contained in the set, in ascending order.

toDescList :: IntervalSet k -> [k]

O(n). The list of all values in the set, in descending order.

fromAscList :: (Interval k e, Eq k) => [k] -> IntervalSet k

O(n). Build a set from an ascending list in linear time. The precondition (input list is ascending) is not checked.

fromDistinctAscList :: Interval k e => [k] -> IntervalSet k

O(n). Build a set from an ascending list of distinct elements in linear time. The precondition is not checked.

Filter

filter :: Interval k e => (k -> Bool) -> IntervalSet k -> IntervalSet k

O(n). Filter values satisfying a predicate.

partition :: Interval k e => (k -> Bool) -> IntervalSet k -> (IntervalSet k, IntervalSet k)

O(n). Partition the set according to a predicate. The first set contains all elements that satisfy the predicate, the second all elements that fail the predicate. See also split.

split :: (Interval i k, Ord i) => i -> IntervalSet i -> (IntervalSet i, IntervalSet i)

O(n). The expression (split k set) is a pair (set1,set2) where the elements in set1 are smaller than k and the elements in set2 larger than k. Any key equal to k is found in neither set1 nor set2.

splitMember :: (Interval i k, Ord i) => i -> IntervalSet i -> (IntervalSet i, Bool, IntervalSet i)

O(n). The expression (splitMember k set) splits a set just like split but also returns member k set.

Subset

isSubsetOf :: Ord k => IntervalSet k -> IntervalSet k -> Bool

O(n+m).

isProperSubsetOf :: Ord k => IntervalSet k -> IntervalSet k -> Bool

O(n+m). Is this a proper subset? (ie. a subset but not equal).

Min/Max

findMin :: IntervalSet k -> Maybe k

O(log n). Returns the least interval in the set.

findMax :: IntervalSet k -> Maybe k

O(log n). Returns the largest interval in the set.

findLast :: Interval k e => IntervalSet k -> Maybe k

Returns the interval with the largest endpoint. If there is more than one interval with that endpoint, return the rightmost.

O(n), since all intervals could have the same endpoint. O(log n) average case.

deleteMin :: (Interval k e, Ord k) => IntervalSet k -> IntervalSet k

O(log n). Remove the smallest element from the set. Return the empty set if the set is empty.

deleteMax :: (Interval k e, Ord k) => IntervalSet k -> IntervalSet k

O(log n). Remove the largest element from the set. Return the empty set if the set is empty.

deleteFindMin :: (Interval k e, Ord k) => IntervalSet k -> (k, IntervalSet k)

O(log n). Delete and return the smallest element.

deleteFindMax :: (Interval k e, Ord k) => IntervalSet k -> (k, IntervalSet k)

O(log n). Delete and return the largest element.

minView :: (Interval k e, Ord k) => IntervalSet k -> Maybe (k, IntervalSet k)

O(log n). Retrieves the minimal element of the set, and the set stripped of that element, or Nothing if passed an empty set.

maxView :: (Interval k e, Ord k) => IntervalSet k -> Maybe (k, IntervalSet k)

O(log n). Retrieves the maximal element of the set, and the set stripped of that element, or Nothing if passed an empty set.

Debugging

valid :: (Interval i k, Ord i) => IntervalSet i -> Bool

Check red-black-tree and interval search augmentation invariants. For testing/debugging only.