import type { MemoizationFunction } from '../types/memoization-function.type.js';
import type { MappingFunction } from '../types/mapping-function.type.js';
import type { Observable } from '../../../external/rxjs/index.js';
/**
 * @function createObservablePart
 * @param {Observable<T>} source - RxJS Subject to use for this Observable.
 * @param {(mappable: T) => R} mappingFunction - Method to return the part for this Observable to return.
 * @param {(previousResult: R, currentResult: R) => boolean} [memoizationFunction] - Method to Compare if the data has changed. Should return true when data is different.
 * @returns {Observable<T>}
 * @description - Creates a RxJS Observable from RxJS Subject.
 * @example <caption>Example create a Observable for part of the data Subject.</caption>
 * public readonly myPart = CreateObservablePart(this._data, (data) => data.myPart);
 */
export declare function createObservablePart<R, T>(source: Observable<T>, mappingFunction: MappingFunction<T, R>, memoizationFunction?: MemoizationFunction<R>): Observable<R>;