3 Interval Maps

▼ |  | Data Structures

1 | Imperative Queues
2 | Skip Lists
3 | Interval Maps
4 | Growable vectors

On this page:

make-interval-map
make-numeric-interval-map
interval-map?
interval-map-with-translate?
interval-map-ref
interval-map-set!
interval-map-update*!
interval-map-remove!
interval-map-expand!
interval-map-contract!
interval-map-cons*!
interval-map-iter?

Version: 5.0.1.5
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### 3`` Interval Maps

Ryan Culpepper <ryanc@racket-lang.org>

( require data/interval-map)

An interval-map is a mutable dictionary-like data structure where mappings are added by half-open intervals and queried by discrete points. Interval-maps can be used with any total order. Internally, an interval-map uses a skip-list (data/skip-list) of intervals for efficient query and update.

Interval-maps implement the dictionary (racket/dict) interface to a limited extent. Only dict-ref and the iteraction-based methods (dict-iterate-first, dict-map, etc) are supported. For the iteration-based methods, the mapping’s keys are considered the pairs of the start and end positions of the mapping’s intervals.

Examples:
> ( define r ( make-numeric-interval-map))
> ( interval-map-set! r 1 5 'apple)
> ( interval-map-set! r 6 10 'pear)
> ( interval-map-set! r 3 6 'banana)
> ( dict-map r list)
'(((1 . 3) apple) ((3 . 6) banana) ((6 . 10) pear))

( make-interval-map =? <? [translate]) → interval-map?
=? : ( any/c any/c . -> . any/c)
<? : ( any/c any/c . -> . any/c)

| translate |  | : |  | ( or/c ( any/c any/c . -> . ( any/c . -> . any/c)) #f)
|  |  | = |  | #f

Makes a new empty interval-map. The interval-map uses =? and <? to order the endpoints of intervals.

If translate is a procedure, the interval-map supports contraction and expansion of regions of its domain via interval-map-contract! and interval-map-expand!. See also make-numeric-interval-map.

( make-numeric-interval-map) → interval-map-with-translate?

Makes a new empty interval-map suitable for representing numeric ranges.

Equivalent to
( make-interval-map = < ( lambda (x y) ( lambda (z) (+ z (- y x)))))

( interval-map? v) → boolean?
v : any/c

Returns #t if v is an interval-map, #f otherwise.

( interval-map-with-translate? v) → boolean?
v : any/c

Returns #t if v is an interval-map constructed with support for translation of keys, #f otherwise.

( interval-map-ref |  | interval-map |  |  |  |
|  | position |  |  |  |
| [ | default]) |  | → |  | any/c

interval-map : interval-map?
position : any/c
default : any/c = ( lambda () ( error ....))

Return the value associated with position in interval-map. If no mapping is found, default is applied if it is a procedure, or returned otherwise.

( interval-map-set! |  | interval-map |  |  |  |
|  | start |  |  |  |
|  | end |  |  |  |
|  | value) |  | → |  | void?

interval-map : interval-map?
start : any/c
end : any/c
value : any/c

Updates interval-map, associating every position in [start, end) with value.

Existing interval mappings contained in [start, end) are destroyed, and partly overlapping intervals are truncated. See interval-map-update*! for an updating procedure that preserves distinctions within [start, end).

( interval-map-update*! |  | interval-map |  |  |  |
|  | start |  |  |  |
|  | end |  |  |  |
|  | updater |  |  |  |
| [ | default]) |  | → |  | void?

interval-map : interval-map?
start : any/c
end : any/c
updater : ( any/c . -> . any/c)
default : any/c = ( lambda () ( error ....))

Updates interval-map, associating every position in [start, end) with the result of applying updater to the position’s previously associated value, or to the default value produced by default if no mapping exists.

Unlike interval-map-set!, interval-map-update*! preserves existing distinctions within [start, end).

( interval-map-remove! |  | interval-map |  |  |  |
|  | start |  |  |  |
|  | end) |  | → |  | void?

interval-map : interval-map?
start : any/c
end : any/c

Removes the value associated with every position in [start, end).

( interval-map-expand! |  | interval-map |  |  |  |
|  | start |  |  |  |
|  | end) |  | → |  | void?

interval-map : interval-map-with-translate?
start : any/c
end : any/c

Expands interval-map’s domain by introducing a gap [start, end) and adjusting intervals after start using (translate start end).

If interval-map was not constructed with a translate argument, an exception is raised. If start is not less than end, an exception is raised.

( interval-map-contract! |  | interval-map |  |  |  |
|  | start |  |  |  |
|  | end) |  | → |  | void?

interval-map : interval-map-with-translate?
start : any/c
end : any/c

Contracts interval-map’s domain by removing all mappings on the interval [start, end) and adjusting intervals after end using (translate end start).

If interval-map was not constructed with a translate argument, an exception is raised. If start is not less than end, an exception is raised.

( interval-map-cons*! |  | interval-map |  |  |  |
|  | start |  |  |  |
|  | end |  |  |  |
|  | v |  |  |  |
| [ | default]) |  | → |  | void?

interval-map : interval-map?
start : any/c
end : any/c
v : any/c
default : any/c = null

Same as the following:

( interval-map-update*! interval-map start end
( lambda (old) ( cons v old))
default)

( interval-map-iter? v) → boolean?
v : any/c

Returns #t if v represents a position in an interval-map, #f otherwise.
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