def hlog_inv(y, b=500, r=_display_max, d=_l_mmax):
    """
    Inverse of base 10 hyperlog transform.
    """
    aux = 1. * d / r * y
    s = sign(y)
    if s.shape:  # to catch case where input is a single number
        s[s == 0] = 1
    elif s == 0:
        s = 1
    return s * 10 ** (s * aux) + b * aux - s
Inverse of base 10 hyperlog transform.