/* eslint-disable @typescript-eslint/no-unused-vars */
interface Array<T> {
    /**
     * returns the last element of the array or undefined
     */
    lastElement(): T;
    /**
     * if val is in the list, it returns its index, otherwise undefined;
     * @param val
     */
    getIndex(val: T): number | undefined;
}

interface String {
    removeTrailingNewlines(): string;
    hasNewline(): boolean;
}