def read_tle_decimal(pack):
    """Convert *pack* to decimal value.
    For example, the packed value -12345-6 corresponds to -0.12345 × 10-6
    Empty corresponds to a zero value.
    """
    if pack[0] in ['-', ' ', '+']:
        digits = pack[1:-2].strip()
        val = pack[0] + '.' + digits + 'e' + pack[-2:]
    else:
        digits = pack[:-2].strip()
        val = '.' + digits + 'e' + pack[-2:]
    return float(val)
