/** Functions for working with constant values. */
import { Constant } from './types';
export declare enum ConstantType {
    SYMBOL = "Symbol",//: Symbol constants (e.g., :code:`(... :polarity -)`)
    STRING = "String",//: String constants (e.g., :code:`(... :op1 "Kim")`)
    INTEGER = "Integer",//: Integer constants (e.g., :code:`(... :value 12)`)
    FLOAT = "Float",//: Float constants (e.g., :code:`(... :value 1.2)`)
    NULL = "Null"
}
/**
 * Return the type of constant encoded by `constantString`.
 *
 * @param constantString - The string representation of the constant.
 * @returns The type of the constant.
 * @example
 * import { constantType } from 'penman-js';
 *
 * console.log(constantType('-')); // Outputs: 'Symbol'
 * console.log(constantType('"foo"')); // Outputs: 'String'
 * console.log(constantType('1')); // Outputs: 'Integer'
 * console.log(constantType('1.2')); // Outputs: 'Float'
 * console.log(constantType('')); // Outputs: 'Null'
 */
export declare const constantType: (constant_string: string | null | undefined) => ConstantType;
/**
 * Evaluate and return the value of `constantString`.
 *
 * If `constantString` is `null` or an empty symbol (`''`), this
 * function returns `null`. An empty string constant (`'""'`) returns an empty string (`''`).
 * Symbols are returned unchanged, while strings get quotes removed and escape sequences unescaped.
 * Note that this means it is impossible to recover the original type of
 * strings and symbols once they have been evaluated. For integer and
 * float constants, this function returns the equivalent JavaScript
 * `Number` object.
 *
 * @param constantString - The string representation of the constant.
 * @returns The evaluated value of the constant.
 * @example
 * import { evaluateConstant } from 'penman-js';
 *
 * console.log(evaluateConstant('-')); // Outputs: '-'
 * console.log(evaluateConstant('"foo"')); // Outputs: 'foo'
 * console.log(evaluateConstant('1')); // Outputs: 1
 * console.log(evaluateConstant('1.2')); // Outputs: 1.2
 * console.log(evaluateConstant('') === null); // Outputs: true
 */
export declare const evaluateConstant: (constantString: string | null | undefined) => Constant;
/**
 * Return `constant` as a quoted string.
 *
 * If `constant` is `null`, this function returns an empty string
 * constant (`'""'`). All other types are cast to a string and
 * quoted.
 *
 * @param constant - The value to quote.
 * @returns The quoted string representation of the constant.
 * @example
 * import { quoteConstant } from 'penman-js';
 *
 * console.log(quoteConstant(null)); // Outputs: '""'
 * console.log(quoteConstant('')); // Outputs: '""'
 * console.log(quoteConstant('foo')); // Outputs: '"foo"'
 * console.log(quoteConstant('"foo"')); // Outputs: '"\\"foo\\""'
 * console.log(quoteConstant(1)); // Outputs: '"1"'
 * console.log(quoteConstant(1.5)); // Outputs: '"1.5"'
 */
export declare const quoteConstant: (constant: Constant) => string;