/**
 * @packageDocumentation
 * @module Utility
 */
import { MonoTypeOperatorFunction, Subscribable } from 'rxjs';
import { SupportedLengths } from '../types/length';
/**
 * Returns an Observable that converts the source value through [[Lengths]] conversion
 *
 * @category Conversion
 *
 * @param fromLength The length type of the source value
 * @param toLength The length type of the output value
 * @param precision The number of decimal places to return, default is `3`
 *
 * @example
 * Convert a value from Miles to Meters
 * ```ts
 * const source$ = from([100, 200, 300, 500]);
 *
 * source$.pipe(length(Lengths.MILES, Lengths.METERS, 0)).subscribe()
 * ```
 * Output: `160934, 321869, 482803, 804672`
 *
 * @example
 * Convert a value from Inches to Yards to precision `2`
 * ```ts
 * const source$ = from([100, 200, 300, 500]);
 *
 * source$.pipe(length('inches', 'yards', 2)).subscribe()
 * ```
 * Output: `2.78, 5.56, 8.33, 13.89`
 *
 * @returns Observable that emits a number that is the `from` [[Lengths]] converted to the `to` [[Lengths]]
 */
export declare function length<I extends SupportedLengths, O extends SupportedLengths>(fromLength: Subscribable<I> | I, toLength: Subscribable<O> | O, precision?: Subscribable<number> | number): MonoTypeOperatorFunction<number>;