Sets

A set is an ordered collection of distinct values of a single type. Unlike a span set (which holds ranges), a set holds individual discrete values.

MEOS.js provides four set types:

Class	Value type	Unit
IntSet	Integer	-
FloatSet	Float (IEEE 754 double)	-
DateSet	Calendar date	Days since 2000-01-01
TsTzSet	Timestamp with time zone	Microseconds since 2000-01-01 UTC

Creating a set

From a WKT string

import { initMeos, IntSet, FloatSet, DateSet, TsTzSet } from 'meos.js';
await initMeos();

const a = IntSet.fromString('{1, 3, 7, 15}');
const b = FloatSet.fromString('{1.5, 3.0, 7.25}');
const c = DateSet.fromString('{2020-01-01, 2020-06-15, 2020-12-31}');
const d = TsTzSet.fromString('{2020-01-01, 2020-06-15, 2020-12-31}');

From hex WKB

const hexwkb = a.asHexWKB();
const copy   = IntSet.fromHexWKB(hexwkb);

Navigating values

const s = IntSet.fromString('{1, 3, 7, 15}');

s.numValues();    // 4
s.startValue();   // 1   (smallest)
s.endValue();     // 15  (largest)
s.valueN(0);      // 1   (0-based index)
s.valueN(2);      // 7

Topological predicates

const a = IntSet.fromString('{1, 3, 7}');
const b = IntSet.fromString('{3, 7, 20}');

a.overlaps(b);        // true  (share {3, 7})
a.isContainedIn(b);   // false (1 not in b)
b.contains(a);        // false
a.eq(b);              // false

Position predicates

const a = IntSet.fromString('{1, 3}');
const b = IntSet.fromString('{7, 15}');

a.isBefore(b);        // true  (max(a)=3 < min(b)=7)
a.isOverOrBefore(b);  // true
b.isAfter(a);         // true
b.isOverOrAfter(a);   // true

Distance

const a = IntSet.fromString('{1, 3}');
const b = IntSet.fromString('{7, 15}');

a.distance(b); // 4  (gap between 3 and 7)

Set operations

const a = IntSet.fromString('{1, 3, 7}');
const b = IntSet.fromString('{3, 7, 20}');

const u = a.union(b);          // {1, 3, 7, 20}
const i = a.intersection(b);  // {3, 7}  (null if disjoint)
const m = a.minus(b);         // {1}     (null if empty)

u.free(); i?.free(); m?.free();

Shifting and scaling

const s = IntSet.fromString('{1, 3, 7}');

const shifted = s.shiftScale(10, 0, true, false);  // {11, 13, 17}
shifted.free(); s.free();

Conversions

const i = IntSet.fromString('{1, 3, 7}');
const f = new FloatSet(i.toFloatSet()); // {1.0, 3.0, 7.0}
i.free(); f.free();

const d = DateSet.fromString('{2020-01-01, 2020-06-15}');
const t = new TsTzSet(d.toTsTzSet()); // timestamps at midnight UTC
d.free(); t.free();

Bounding span and span set

Every set can be projected to its bounding span or a span set of unit spans:

const s = IntSet.fromString('{1, 3, 7}');

const span    = s.toSpan();    // raw Ptr: bounding IntSpan [1, 7]
const spanset = s.toSpanSet(); // raw Ptr: IntSpanSet {[1,1],[3,3],[7,7]}