import type { Comparator } from './types';
export declare function isDefined<T>(value: T): value is NonNullable<T>;
export declare function spaceList(...values: ReadonlyArray<string | undefined | Record<string, boolean>>): string;
export declare function baseComparator<S, T>(selector: (source: S) => T, matcher: Comparator<NonNullable<T>>): Comparator<S>;
export declare function textComparator<T>(selector: (source: T) => string | null | undefined, locales?: string | string[], collatorOptions?: Intl.CollatorOptions): Comparator<T>;
export declare function numberComparator<T>(selector: (source: T) => number | null | undefined): Comparator<T>;