/**
 * Classes and functions for lexing PENMAN strings.
 */
import { DecodeError } from './exceptions';
export declare const PENMAN_RE: RegExp;
export declare const TRIPLE_RE: RegExp;
/**
 * A lexed token.
 */
export type Token = [
    type: string,
    text: string,
    lineno: number,
    offset: number,
    line: string
];
/**
 * An iterator of Tokens with L1 lookahead.
 */
export declare class TokenIterator {
    _next: IteratorResult<Token, Token> | null;
    _last: IteratorResult<Token, Token> | null;
    iterator: IterableIterator<Token>;
    constructor(iterator: IterableIterator<Token>);
    [Symbol.iterator](): this;
    __bool__(): boolean;
    bool(): boolean;
    hasNext(): boolean;
    /**
     * Return the next token but do not advance the iterator.
     *
     * If the iterator is exhausted then a DecodeError is raised.
     */
    peek(): Token;
    /**
     * Advance the iterator and return the next token.
     *
     * @throws {Error} If the iterator is already exhausted.
     */
    next(): IteratorResult<Token, Token>;
    /**
     * Return the next token if its type is in `choices`.
     *
     * The iterator is advanced if successful.
     *
     * @throws {DecodeError} If the next token type is not in `choices`.
     */
    expect(...choices: string[]): Token;
    /**
     * Return the next token if its type is in *choices*.
     *
     * The iterator is advanced if successful. If unsuccessful, `None` is returned.
     */
    accept(...choices: string[]): Token | null;
    error(message: string, token?: Token): DecodeError;
}
/**
 * Yield PENMAN tokens matched in `lines`.
 *
 * By default, this function lexes strings in `lines` using the basic pattern
 * for PENMAN graphs. If `pattern` is provided, it is used for lexing instead.
 *
 * @param lines - An iterable of lines to lex.
 * @param pattern - The pattern to use for lexing instead of the default ones.
 * @returns A `TokenIterator` object.
 */
export declare const lex: (lines: Iterable<string> | string, pattern?: RegExp | string) => TokenIterator;