def isac(c):
    """
    A simple function, which determine whether the
    string element char c is belong to a decimal number
    :param c: a string element type of char
    :return: a bool type of determination
    """
    try:
        int(c)
        return True
    except:
        if c == '.' or c == '-' or c == 'e':
            return True
        else:
            return False