import { AsyncPredicate, Predicate } from 'augmentative-iterable';
export interface FirstFunction<T> {
    /**
     * Returns the first element of the iterable matching a predicate, or `undefined` value if no such element is found. This is a partial resolving operation, will cause a partial or - if needed - a full loop through the elements of the iterable.<br>
     *   Examples:<br>
     *     * `fluent(['anchor', 'almond', 'bound', 'alpine']).first()` returns *anchor*<br>
     *     * `fluent([]).first()` returns `undefined`<br>
     *     * `fluent(['anchor', 'almond', 'bound', 'alpine']).first(word => word[0] === 'b')` returns *bound*<br>
     *     * `fluent(['anchor', 'almond', 'bound', 'alpine']).first(word => word[0] === 'c')` returns `undefined`
     * @param predicate The first element is to be returned which matches this predicate. Defaults to the always true function and thus, returns the first element in the iterable if omitted.
     * @returns The first element matching the specified predicate, or `undefined` if no such element found.
     */
    (predicate?: Predicate<T>): T | undefined;
    /**
     * Returns the first element of the iterable matching a predicate, or `undefined` value if no such element is found. This is a partial resolving operation, will cause a partial or - if needed - a full loop through the elements of the iterable.<br>
     *   Examples:<br>
     *     * `fluent(['anchor', 'almond', 'bound', 'alpine']).first()` returns *anchor*<br>
     *     * `fluent([]).first()` returns `undefined`<br>
     *     * `fluent(['anchor', 'almond', 'bound', 'alpine']).first(word => word[0] === 'b')` returns *bound*<br>
     *     * `fluent(['anchor', 'almond', 'bound', 'alpine']).first(word => word[0] === 'c')` returns `undefined`
     * @param predicate The first element is to be returned which matches this predicate. Defaults to the always true function and thus, returns the first element in the iterable if omitted.
     * @returns The first element matching the specified predicate, or `undefined` if no such element found.
     */
    (predicate: keyof T): T | undefined;
}
export interface AsyncFirstFunction<T> {
    /**
     * Returns the first element of the iterable matching an asynchronous predicate, or `undefined` value if no such element is found. This is a partial resolving operation, will cause a partial or - if needed - a full loop through the elements of the iterable.
     * @param predicate The first element is to be returned which matches this asynchronous predicate.
     * @returns A promise of the first element matching the specified predicate, or `undefined` if no such element found.
     */
    (predicate?: AsyncPredicate<T>): Promise<T | undefined>;
    /**
     * Returns the first element of the iterable matching an asynchronous predicate, or `undefined` value if no such element is found. This is a partial resolving operation, will cause a partial or - if needed - a full loop through the elements of the iterable.
     * @param predicate The first element is to be returned which matches this asynchronous predicate.
     * @returns A promise of the first element matching the specified predicate, or `undefined` if no such element found.
     */
    (predicate: keyof T): Promise<T | undefined>;
}