著者: Marc Perkel 日付: To: Exim Mailing List 題目: Re: [exim] More integer annoyances in 4.65
Dean Brooks wrote: > On Wed, Jan 03, 2007 at 05:06:54PM +0000, Dave Evans wrote:
>
>> On Wed, Jan 03, 2007 at 08:46:28AM -0800, Marc Perkel wrote:
>>
>>> A null and a blank string are not the same thing either. Are you going
>>> to treat strings that way too?
>>>
>> Not a fair comparison IMO, because although variables can be null, the result
>> of string expansion can (AFAIK) never be null. (e.g. h_Cc may be null, but
>> expanding $h_Cc: yields the empty string). Since the operands of string ops
>> (e.g. eq) are always acquired by first performing a string expansion, which
>> can *only* yield a (possibly empty) string, the operands can never be anything
>> but strings. Unless I've missed something.
>>
>
> Exim has no concept of nulls in its string expansions, only blank
> strings. The word "null" should not be used in this discussion as
> nulls do not exist in the constructs being discussed. That is, Exim's
> "def:" condition simply tests to see if the variable is equal to an
> empty string.
>
> That being said, empty strings in integer comparisons seem completely
> reasonable given that Exim is *already* doing a conversion from string
> to integer form in this process.
>
> By documenting that an empty value is equal to zero, and informing the
> user to be aware of this and to depend on it seems completely
> reasonable. Especially if it helps avoid breaking otherwise simple
> expressions and confusing the heck out of new users.
>
> --
> Dean Brooks
> dean@???
>
>
