import type { OptLazy } from '@rimbu/common';
/**
 * An iterator that extends the default `Iterator` interface with methods that give more performance.
 * @typeparam T - the element type
 */
export interface FastIterator<T> extends Iterator<T> {
    /**
     * Returns the next iterator value, or the given `otherwise` `OptLazy` value instead.
     * @param otherwise - (default: undefined) the value to return if the iterator has no more values
     */
    fastNext(): T | undefined;
    fastNext<O>(otherwise: OptLazy<O>): T | O;
    /**
     * Returns the next `IteratorResult`.
     */
    next(): IteratorResult<T>;
}