Should the comma operator be removed in D2?

Ellery Newcomer ellery-newcomer at utulsa.edu
Tue Nov 17 15:27:43 PST 2009


Ellery Newcomer wrote:
> Bill Baxter wrote:
>> On Tue, Nov 17, 2009 at 3:01 PM, Ellery Newcomer
>> <ellery-newcomer at utulsa.edu> wrote:
>>> Bill Baxter wrote:
>>>> On Tue, Nov 17, 2009 at 1:51 PM, KennyTM~ <kennytm at gmail.com> wrote:
>>>>> On Nov 18, 09 05:40, Ellery Newcomer wrote:
>>>>>> Bill Baxter wrote:
>>>>>>> However, I think for the good of humanity we can accept that one
>>>>>>> little bizarre example of legal C syntax not doing the same thing in
>>>>>>> D.
>>>>>> int[] i;
>>>>>>
>>>>>> auto a = (i)[0];
>>>>>>
>>>>>> what does this do?
>>>>> (i) should not construct a tuple. Probably (i,).
>>>> That's Python's solution and it seems to work out ok.
>>>>
>>>> --bb
>>> How do we express tuple types? ...
>>> These won't work:
>>> ...
>>> (int,int) [] lst; //want
>> Why won't that work?  You may be right, but that particular
>> declaration doesn't seem ambiguous to me.
>>
>> --bb
> 
> foo!( (i,i) ) ();
> 
> compiler doesn't know if 'i' is a type or a variable.

by compiler I mean parser. compiler eventually will figure it out.

> Like I said, the problem already exists for eg
> 
> foo!( i ) ();
> 
> and isn't semantically ambiguous (as far as I know..), so it is doable.
> 
> at statement level, it would require a lot of lookahead to distinguish eg
> 
> (i,i)[0] = blah;
> (i,i)[0] blah;
> 
> Not my idea of good language design (one character deep in the
> production - can you say fortran :) actually fortran is worse, it
> discards whitespace as token separators)



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