/**
 * Generate a fractional index which is a sortable string(s) between a and b. Use an empty string or null/undefined to
 * represent the start and end of the range.
 *
 * Pass a count to generate N fractional indexes between a and b.
 *
 * See https://www.figma.com/blog/realtime-editing-of-ordered-sequences/#fractional-indexing and
 * https://observablehq.com/@dgreensp/implementing-fractional-indexing for more information.
 */
export declare function fractionalIndex(a: string | undefined | null, b: string | undefined | null): string;
export declare function fractionalIndex(a: string | undefined | null, b: string | undefined | null, count: number): string[];