On Wednesday, 26 March 2014 at 23:00:29 UTC, Andrei Alexandrescu
wrote:
> On 3/26/14, 3:13 PM, Timon Gehr wrote:
>> On 03/26/2014 08:49 PM, Andrei Alexandrescu wrote:
>>>>
>>>> I don't agree. It's much better to fix the little breaking changes now,
>>>> and think about non-breaking improvements later. Because later the
>>>> breaking changes will become less and less possible.
>>>
>>> That later is already now.
>>
>> So how come there exists this thread on breaking the comma operator?
>
> Because it's arguably worth it. -- Andrei

Because it has been agreed a long time a ago, but now we are
backpedaling because we can't break code as much as we used to.

That being said, I'm quite satisfied with Andrei's void return
value proposal.

On Wed, 26 Mar 2014 17:32:00 -0400, Nick Sabalausky <SeeWebsiteToContactMe@semitwist.com> wrote:

> On 3/26/2014 7:44 AM, "Marc Schütz" <schuetzm@gmx.net>" wrote:
>> This is valid in both C and C++:
>>
>>    i, j = 0, 1;
>>
>> It is equivalent to the following:
>>
>>    i;
>>    j = 0;
>>    1;
>>
>
> Under the proposal, the "0, 1" would be void, so it wouldn't compile in D. Therefore, the rule about moving C code to D safely is not violated.
>

This part of the subthread is about the future plans to possibly use comma operators to mean tuples. This C/C++ code will still be valid then, and when someone ports to D, might get a nasty silently compiling surprise.

But, I think the proposal to re-introduce ',' as a tuple operator would not affect this code, it would remain a 3-element tuple, with i, j, 1 as elements (after setting j to 0 of course). '=' has precedence over ','.

The second statement would be a problem (i, j) = (0, 1), but clearly, this would not be a valid use case. I can envision there may be some valid use cases of that form, however.

-Steve

On Wed, 26 Mar 2014 13:27:17 -0400, Andrei Alexandrescu <SeeWebsiteForEmail@erdani.org> wrote:

> On 3/26/14, 7:39 AM, Steven Schveighoffer wrote:

>> Frequently, I have situations where I do not put a comma on the last
>> element.
>
> Big mistake :o). -- Andrei

A trailing comma in a list looks so wrong to me :) It looks like an unfinished declaration. I just as frequently have trailing commas because I delete the last element and forget to remove the comma on the "new" last element :D

-Steve

On Thursday, 27 March 2014 at 02:08:50 UTC, Steven Schveighoffer wrote:
> On Wed, 26 Mar 2014 17:32:00 -0400, Nick Sabalausky <SeeWebsiteToContactMe@semitwist.com> wrote:
>
>> On 3/26/2014 7:44 AM, "Marc Schütz" <schuetzm@gmx.net>" wrote:
>>> This is valid in both C and C++:
>>>
>>>   i, j = 0, 1;
>>>
>>> It is equivalent to the following:
>>>
>>>   i;
>>>   j = 0;
>>>   1;
>>>
>>
>> Under the proposal, the "0, 1" would be void, so it wouldn't compile in D. Therefore, the rule about moving C code to D safely is not violated.
>>
>
> This part of the subthread is about the future plans to possibly use comma operators to mean tuples. This C/C++ code will still be valid then, and when someone ports to D, might get a nasty silently compiling surprise.
>
> But, I think the proposal to re-introduce ',' as a tuple operator would not affect this code, it would remain a 3-element tuple, with i, j, 1 as elements (after setting j to 0 of course). '=' has precedence over ','.
>
> The second statement would be a problem (i, j) = (0, 1), but clearly, this would not be a valid use case. I can envision there may be some valid use cases of that form, however.
>
> -Steve

I think you get operator priority wrong and it will be (i), (j = 0), (1). I added extra () to show how operator priority works.

On Wed, 26 Mar 2014 22:02:44 -0000, Timon Gehr <timon.gehr@gmx.ch> wrote:

> On 03/26/2014 05:19 PM, H. S. Teoh wrote:
>> 	int x = 1, 5;	// hands up, how many understand what this does?
>
> Nothing. This fails to parse because at that place ',' is expected to be a separator for declarators.

Spectacularly proving his point :p

R

-- 
Using Opera's revolutionary email client: http://www.opera.com/mail/

On Wednesday, 26 March 2014 at 16:21:01 UTC, H. S. Teoh wrote:
> What we're proposing is to get rid of things like this:
>
> 	int x = 1, 5;	// hands up, how many understand what this does?

This proposal gets rid of this while keeping the comma operator.

On Thursday, 27 March 2014 at 11:32:45 UTC, Kagamin wrote:
> On Wednesday, 26 March 2014 at 16:21:01 UTC, H. S. Teoh wrote:
>> What we're proposing is to get rid of things like this:
>>
>> 	int x = 1, 5;	// hands up, how many understand what this does?
>
> This proposal gets rid of this while keeping the comma operator.

+1 to dropping to comma operator.

This is what I would like to see illegal, forcing a refactor of code:

 if (((vertex= null), same.vertices)) for (blah){}


Every time it catches me out and I misread the code to be:

if(vertex == null && same.vertices) for (blah) {}


Cheers,
ed

On Thursday, 27 March 2014 at 10:39:58 UTC, Regan Heath wrote:
> On Wed, 26 Mar 2014 22:02:44 -0000, Timon Gehr <timon.gehr@gmx.ch> wrote:
>
>> On 03/26/2014 05:19 PM, H. S. Teoh wrote:
>>> 	int x = 1, 5;	// hands up, how many understand what this does?
>>
>> Nothing. This fails to parse because at that place ',' is expected to be a separator for declarators.
>
> Spectacularly proving his point :p

Did he want to kill the declaration statement too?

On Thursday, 27 March 2014 at 11:43:36 UTC, ed wrote:
> On Thursday, 27 March 2014 at 11:32:45 UTC, Kagamin wrote:
>> On Wednesday, 26 March 2014 at 16:21:01 UTC, H. S. Teoh wrote:
>>> What we're proposing is to get rid of things like this:
>>>
>>> 	int x = 1, 5;	// hands up, how many understand what this does?
>>
>> This proposal gets rid of this while keeping the comma operator.
>
> +1 to dropping to comma operator.
>
> This is what I would like to see illegal, forcing a refactor of code:
>
>  if (((vertex= null), same.vertices)) for (blah){}
>
>
> Every time it catches me out and I misread the code to be:
>
> if(vertex == null && same.vertices) for (blah) {}
>
>
> Cheers,
> ed

s/== null/is null/

On Thursday, 27 March 2014 at 11:32:45 UTC, Kagamin wrote:
> On Wednesday, 26 March 2014 at 16:21:01 UTC, H. S. Teoh wrote:
>> What we're proposing is to get rid of things like this:
>>
>> 	int x = 1, 5;	// hands up, how many understand what this does?
>
> This proposal gets rid of this while keeping the comma operator.

The point is that this is not the comma operator, and is already illegal to begin with.

*This* is what is being made illegal
int x = (1, 5);

The point being that most programmers don't actually understand all the subtleties of comma operator vs argument listing. Mysielf included (I also thought that was a comma operator...)

Also, not to mention issues with things like operator precedence...
a = 1, 5 + 2; //What's a?
a = (1 + 2, 5); //What's a?

Speaking of which:
a = 1, 5 + 2;
Why doesn't dmd emit an "operator , has no effect" error?

Or
a = (1 + 2, 5)
Why doesn't dmd emit an "operator + has no effect" error?