import { GraphNode, NodeDefinition, StatelessGraphNode, StatelessNodeDefinition, StatelessNodeType } from '../../types/graph';
import { IteratorResultNode } from '../graph/iterator-result';
import { NilNode } from '../graph/nil';
export interface ReduceNode extends StatelessGraphNode<'reduce', ReduceNodeProperties> {
}
export interface ReduceNodeDefinition extends StatelessNodeDefinition<'reduce', ReduceNodeProperties> {
}
export interface ReduceNodeProperties {
    source: NodeDefinition | GraphNode;
    reducer: NodeDefinition | GraphNode;
    initialState: any;
}
export declare const ReduceNodeType: StatelessNodeType<'reduce', ReduceNodeProperties>;
export declare function reduce(source: NodeDefinition | GraphNode, reducer: NodeDefinition | GraphNode, initialState: any): ReduceNodeDefinition;
export declare const isValidReducerStepResult: {
    predicate(node: GraphNode): boolean;
    errorMessage(node: GraphNode): string;
};
export declare function getNextIteratorResult(iterable: GraphNode, callback: (value: IteratorResultNode | NilNode) => GraphNode): NodeDefinition;