export declare function initArray<T>(length: number, makeElement: (i: number) => T): T[];
export declare function mapValues<K, V1, V2>(map: Map<K, V1>, valueMapper: (value: V1) => V2): Map<K, V2>;
export declare function mapDefined<T, U>(arr: Iterable<T>, mapper: (t: T) => U | undefined): U[];
export declare function mapDefinedAsync<T, U>(arr: Iterable<T>, mapper: (t: T) => Promise<U | undefined>): Promise<U[]>;
export declare function sort<T>(values: Iterable<T>, comparer?: (a: T, b: T) => number): T[];
export declare function join<T>(values: Iterable<T>, joiner?: string): string;
/** Returns [values that cb returned undefined for, defined results of cb]. */
export declare function split<T, U>(inputs: readonly T[], cb: (t: T) => U | undefined): [readonly T[], readonly U[]];
/**
 * Appends a range of value to an array, returning the array.
 *
 * @param to The array to which `value` is to be appended. If `to` is `undefined`, a new array
 * is created if `value` was appended.
 * @param from The values to append to the array. If `from` is `undefined`, nothing is
 * appended. If an element of `from` is `undefined`, that element is not appended.
 * @param start The offset in `from` at which to start copying values.
 * @param end The offset in `from` at which to stop copying values (non-inclusive).
 */
export declare function addRange<T>(to: T[], from: readonly T[] | undefined, start?: number, end?: number): T[];
export declare function addRange<T>(to: T[] | undefined, from: readonly T[] | undefined, start?: number, end?: number): T[] | undefined;
/**
 * Appends a value to an array, returning the array.
 *
 * @param to The array to which `value` is to be appended. If `to` is `undefined`, a new array
 * is created if `value` was appended.
 * @param value The value to append to the array. If `value` is `undefined`, nothing is
 * appended.
 */
export declare function append<TArray extends any[] | undefined, TValue extends NonNullable<TArray>[number] | undefined>(to: TArray, value: TValue): [undefined, undefined] extends [TArray, TValue] ? TArray : NonNullable<TArray>[number][];
export declare function append<T>(to: T[], value: T | undefined): T[];
export declare function append<T>(to: T[] | undefined, value: T): T[];
export declare function append<T>(to: T[] | undefined, value: T | undefined): T[] | undefined;
/**
 * Tests whether a value is an array.
 */
export declare function isArray(value: any): value is readonly {}[];
/**
 * Maps an array. The mapped value is spread into the result.
 *
 * @param array The array to map.
 * @param mapfn The callback used to map the result into one or more values.
 */
export declare function flatMap<T, U>(array: readonly T[] | undefined, mapfn: (x: T, i: number) => readonly U[]): readonly U[];
export declare function unique<T>(arr: Iterable<T>): T[];
export declare function min<T>(array: readonly [T, ...(T | undefined)[]]): T;
export declare function min<T>(array: readonly T[], compare?: (a: T, b: T) => number): T | undefined;
export declare function max<T>(array: readonly [T, ...(T | undefined)[]]): T;
export declare function max<T>(array: readonly T[], compare?: (a: T, b: T) => number): T | undefined;
export declare function compact<T>(array: readonly (T | undefined)[]): T[];
export declare function symmetricDifference<T>(a: Set<T>, b: Set<T>): Set<T>;