interval.js

Library implementing mathematical real numbers intervals arithmetics. Available operations:

• union (A∪B)
• difference (A\B)
• intersection (A∩B)
• exclusion (A△B)
• inversion (A')
• subset (A⊆B)
• superset (A⊇B)
• contains (A∍x)

Utils functions:

• toString()
• count()
• forEach()
• forEachPoint()
• intervals()

Installation

Install with npm: npm install intervaljs

Install with bower: bower install intervaljs

Initializations

new Interval(start, [end=start])

Create Interval object.

new Interval().toString(); // ''
new Interval(2).toString(); // '{2}'
new Interval(1, 3).toString(); // [1;3]

new Interval.Endpoint(value, [open=false])

Create complex interval Endpoint.

var eStart = new Interval.Endpoint(2, false); // 'endpoint closed'
var eEnd = new Interval.Endpoint(3, true); // 'endpoint open'

new Interval(eStart, eEnd).toString() // [2, 3) - left closed, right open

API

.union(intervalObj) or .union(start, [end=start])

A∪B - Add intervals to interval.

new Interval(1, 3)
  .union(5, 7)
  .union(new Interval(6, Infinity))
  .toString();
// [1;3], [5;Infinity)

.difference(interval) or .difference(start, [end=start])

A\B - Substract interval from interval.

new Interval(1, 8)
  .diference(5, 9)
  .diference(3)
  .toString();
// [1;3), (3,5)

.intersection(interval) or .intersection(start, [end=start])

A∩B - Common part of intervals.

var interval = new Interval(2, 6)
  .intersection(4, 8);
// [4;6]

.exclusion(interval) or .exclusion(start, [end=start])

A△B - Exclusive OR or intervals.

var interval = new Interval(2, 6)
  .exclusion(4, 8);
// [2;4), (6;8]

.inversion()

A' - Invert interval.

new Interval(1, 8)
  .inversion()
// (-Infinity;1), (8,Infinity)

.subset(interval) or .subset(start, [end=start])

A⊆B - Check if interval is a subset of other interval

new Interval(5, 8)
  .subset(1, 8)
// true
new Interval(1, 8)
  .subset(2, 5);
// false

.superset(interval) or .superset(start, [end=start])

A⊇B - Check if interval is a superset for other interval

new Interval(1, 8)
  .superset(5, 8)
// true
new Interval(1, 8)
  .diference(5, 9)
  .superset(2, 5);
// false

var i1 = new Interval(1, 4)
  .union(6, 9)
var i2 = new Interval(1, 9)
  .diference(4, 6)
i1.superset(i2)
// true

.contains(value)

A∍x - Check if interval contains a memeber.

new Interval(1, 8)
  .contains(5)
// true

Utils

.intervals()

Return intervals array

var arr = new Interval(1, 6)
  .union(8)
  .intervals()
  
arr.length;
// 2

.forEach(callback(start, end), [step=0])

Iterate throught interval parts borders, with minimal step for open endpoints. For step equal 0, function return border values skipping open/close atributes.

new Interval(1, 6)
  .difference(4, 8) // we have [1;4)
  .forEach(function(start, end) {
    // start is 1
    // end = 4
  }, 0) // step = 0

// same case with step value
new Interval(1, 6)
  .difference(4, 8) // we have [1;4)
  .forEach(function(start, end) {
    // start is 1
    // end = 3.5
  }, 0.5) // step = 0.5

.forEachPoint(callback(point), [step=1])

Iterate throught interval points with assigned step (default 1)

new Interval(1, 6)
  .diference(4, 8)
  .forEach(function(point) {
    // point = 1, then 2, then 3
  })

.count()

Return count of intervals

new Interval(1, 6)
  .union(8)
  .count()
// 2

.toString()

Output intervals string

new Interval(1, 6)
  .diference(3, 4)
  .union(8)
  .toString()
// [1;3), (4,6], {8}