import { AsyncReducer, Reducer } from '../base';
export interface ReduceFunction<T> {
    /**
     * Aggregates the iterable by applying an accumulator function over the elements of the iterable. The specified seed value is used as the initial accumulator value. This is a resolving operation, will cause a full loop through all the elements of the iterable.<br>
     *   Example:<br>
     *     ```
     *     fluent(['anchor', 'almond', 'bound', 'alpine']).reduce(
     *       (current, next) => (next[0] === 'a' ? current + 1 : current),
     *       0
     *     )
     *     ``` returns *3*, the number of words start with 'a' in the iterable.
     * @typeparam R The type of the accumulator value.
     * @param reducer The accumulator function, provides the next accumulator value out of the last accumulator value and the next element in the iterable.
     * @param initial The initial (aka *seed*) value of the accumulator.
     * @returns The aggregated value.
     */
    <R>(reducer: Reducer<T, R>, initial: R): R;
    /**
     * Aggregates the iterable by applying an accumulator function over the elements of the iterable. The specified seed value is used as the initial accumulator value. This is a resolving operation, will cause a full loop through all the elements of the iterable.<br>
     *   Example:<br>
     *     ```
     *     fluent(['anchor', 'almond', 'bound', 'alpine']).reduce(
     *       (current, next) => (next[0] === 'a' ? current + 1 : current),
     *       0
     *     )
     *     ``` returns *3*, the number of words start with 'a' in the iterable.
     * @typeparam R The type of the accumulator value.
     * @param reducer The accumulator function, provides the next accumulator value out of the last accumulator value and the next element in the iterable.
     * @returns The aggregated value.
     */
    <R = T>(reducer: (current: R | T, next: T) => R): R | T;
}
export interface AsyncReduceFunction<T> {
    /**
     * Aggregates the iterable by applying an asynchronous accumulator function over the elements of the iterable. The specified seed value is used as the initial accumulator value. This is a resolving operation, will cause a full loop through all the elements of the iterable.
     * @typeparam R The type of the accumulator value.
     * @param reducer The asynchronous accumulator function, provides the next accumulator value out of the last accumulator value and the next element in the iterable.
     * @param initial The initial (aka *seed*) value of the accumulator.
     * @returns A promise of the aggregated value.
     */
    <R>(reducer: AsyncReducer<T, R>, initial: R): Promise<R>;
    /**
     * Aggregates the iterable by applying an asynchronous accumulator function over the elements of the iterable. The specified seed value is used as the initial accumulator value. This is a resolving operation, will cause a full loop through all the elements of the iterable.
     * @typeparam R The type of the accumulator value.
     * @param reducer The asynchronous accumulator function, provides the next accumulator value out of the last accumulator value and the next element in the iterable.
     * @returns A promise of the aggregated value.
     */
    <R = T>(reducer: (current: R | T, next: T) => Promise<R> | R): Promise<R | T>;
}