export function kernelLength(xs: any[]): number {
    return xs.length;
}

export function kernelEmptyList<a>(): a[] {
    return [ ];
}

export function kernelSort<a>(xs: a[]): a[] {
    const ys = [ ...xs ];
    ys.sort();
    return ys;
}

export function kernelSortBy<a>(fn: (_0: a, _1: a) => number, xs: a[]): a[] {
    const ys = [ ...xs ];
    ys.sort(fn);
    return ys;
}

export function kernelStatefulFold<item, state>(
    fn: (item: item, state: state) => state,
    init: state,
    items: item[]
): state {
    let currentState = init;
    for (const item of items) {
        currentState = fn(item, currentState);
    }
    return currentState;
}