The empty statement ";" - when is it useful?

[Andrei Alexandrescu]

Daniel Keep wrote:
> Andrei Alexandrescu wrote:
>> Bill Baxter wrote:
>>> On Tue, Jul 28, 2009 at 12:09 AM, Don<nospam at nospam.com> wrote:
>>>>> Walter once claimed that it's useful for automatically generated code.
>>>>> Though I'm still not quite sure how.
>>>> Yes. He's recently the claimed the same thing about the comma
>>>> operator, but
>>>> I don't buy that argument. I've never needed to use either of them
>>>> myself.
>>>> (In the case of comma, sure it works as a sequence point when you
>>>> have: a,b,
>>>> return a; but it doesn't work for a,b, return b; which is 50% of the
>>>> cases.
>>>> I think it's a fallacious argument). Interestingly CommaExpression
>>>> doesn't
>>>> seem to be defined anywhere in the D spec.
>>> You meant to say it doesn't work for a,b, return a;  right?
>>> And I don't think that would be 50% of the cases.  a,b,return b seems
>>> much more common.
>>>
>>> But either way the argument is ridiculous.  It doesn't need to be as
>>> basic an operator as a single comma just for the sake of making code
>>> generation easier.
>> I agree. Walter also mentioned the code generation argument in a
>> conversation with me, fully expecting something like "hell yeah" from
>> me, but was disappointed :o). If he were right and the comma operator
>> would be a net win for better code generation, it would be a net win for
>> better handwritten code. But it's not for either; it is some win, but
>> minor.
>>
>> Anyway, if I had my way I'd eliminate the empty statement ";". It's just
>> uselessly hanging in there. It adds half a page total to TDPL just
>> because I must first define it and then explain for all of if, while,
>> switch, for, foreach... that they can't control an empty statement. If
>> the empty statement didn't exist in the first place, I wouldn't be
>> wasting readers' time.
>>
>> BTW, the use of ";" in foreach is not a problem; that use could be
>> easily defined as sheer punctuation.
>>
>>
>> Andrei
> 
> U comma(T,U)(T a, U b) { return b; }
> 
> Is there any reason you couldn't use something like that?

Absolutely! And now that order of evaluation will be defined to be 
left-to-right in D, the semantics would be quite the same.


Andrei