You must use quotes to set a variable to a lone slash, because an unquoted slash is interpreted as a divisionsign.
你必须使用引号去设置一个变量为一个长斜杠,因为一个不被引住的斜杠被解释为一个除号。
3
To avoid any division by zero or overflow, transform all division into multiplication and check for the sign (horizontal lines with Y2=Y1 do not count in the algorithm)