API Reference > geometry-core > ArraysAndInterfaces > IndexedCollectionInterval IndexedCollectionInterval<T extends CollectionWithLength> Class Object describing a (contiguous) subset of indices to an IndexedXYZCollection Extended by IndexedXYZCollectionInterval Methods Name Description constructor(points: T extends CollectionWithLength, base: number, limit: number): IndexedCollectionInterval Protected advanceBegin(): boolean Add one to this.begin. advanceEnd(): boolean advance this.end (but do not go beyond this.points.length) return true if the interval is still live. advanceToHead(other: IndexedCollectionInterval<T extends CollectionWithLength>): boolean Advance this.begin to (other.begin), i.e. advanceToTail(other: IndexedCollectionInterval<T extends CollectionWithLength>): boolean Advance this.begin to (other.end-1), i.e. localIndexToParentIndex(localIndex: number): number | undefined Return (if possible) the parent index corresponding to localIndex restrictEnd(): void restrict this.end to this.points.length setFrom(other: IndexedCollectionInterval<T extends CollectionWithLength>, base?: number, limit?: number): void Set this interval from another, with conditional replacements: createBeginEnd<T extends CollectionWithLength>(points: T extends CollectionWithLength, begin: number, end: number): IndexedCollectionInterval<T extends CollectionWithLength> Static Create an interval which matches a collection from start <= i < end. createBeginLength<T extends CollectionWithLength>(points: T extends CollectionWithLength, begin: number, length: number): IndexedCollectionInterval<T extends CollectionWithLength> Static Create an interval which matches a collection from start <= i < end. createComplete<T extends CollectionWithLength>(points: T extends CollectionWithLength): IndexedCollectionInterval<T extends CollectionWithLength> Static Create an interval which matches a complete indexed collection. Properties Name Type Description begin number lower limit of index range end number upper limit (beyond) index range. isNonEmpty Accessor ReadOnly boolean Return true if length is 1 or more isSingleton Accessor ReadOnly boolean Return true if the length is exactly 1 isValidSubset Accessor ReadOnly boolean Return true if length Accessor ReadOnly number Return the number of steps possible with current begin and end points T extends CollectionWithLength Any collection that has a .length member or property Defined in core/geometry/src/geometry3d/IndexedCollectionInterval.ts Line 18 Last Updated: 15 June, 2021