import { NodeDefinition, NodeLike, StatelessGraphNode, StatelessNodeDefinition, StatelessNodeType } from '../../types/graph';
/**
 * An instance of the [[charAt]] node.
 * See the [[charAt]] documentation to find out more.
 */
export interface CharAtNode extends StatelessGraphNode<'char-at', CharAtNodeProperties> {
}
/**
 * A definition of the [[charAt]] node.
 * See the [[charAt]] documentation to find out more.
 */
export interface CharAtNodeDefinition extends StatelessNodeDefinition<'char-at', CharAtNodeProperties> {
}
export interface CharAtNodeProperties {
    index: NodeDefinition;
    subject: NodeDefinition;
}
/**
 * The implementation of the [[charAt]] node.
 * See the [[charAt]] documentation to learn more.
 */
export declare const CharAtNodeType: StatelessNodeType<'char-at', CharAtNodeProperties>;
/**
 * Creates a new instance of a [[charAt]] node, which is used when extracting a specific character from string. The node expects
 * the subject to be a [[value]] that contains a string value. It work in a similar way as
 * the `string.charAt(...)` function from JS.
 *
 *
 * @example **Extract char at**
 * ```js
 * import muster, { charAt } from '@dws/muster';
 *
 * const app = muster({});
 *
 * await app.resolve(charAt(1, 'Hello world'));
 * // === 'e'
 *
 * await app.resolve(charAt(20, 'Hello world'));
 * // === null
 * ```
 */
export declare function charAt(index: NodeLike, subject: NodeLike): CharAtNodeDefinition;
export declare function isCharAtNodeDefinition(value: NodeDefinition): value is CharAtNodeDefinition;