def _fwd6(y, dt):
    """Compute the first derivative of a uniformly-spaced-in-time array with a
    sixth-order forward difference scheme.

    Parameters
    ----------
    y : (7,...) ndarray
        Data to differentiate. The derivative is taken along the first axis.

    dt : float
        Time step (the uniform spacing).

    Returns
    -------
    dy0 : float or (...) ndarray
        Approximate derivative of y at the first entry, i.e., dy[0] / dt.
    """
    return (- 147*y[0] + 360*y[1] - 450*y[2]
            + 400*y[3] - 225*y[4] + 72*y[5] - 10*y[6]) / (60*dt)