Should we deprecate comma?

[monarch_dodra]

On Monday, 24 March 2014 at 02:31:46 UTC, Andrei Alexandrescu 
wrote:
> On 3/23/14, 7:21 PM, Kenji Hara wrote:
>> At least I can imagine two reasonable cases.
>>
>> 1. If the code is ported from C/C++, breaking it is not 
>> reasonable.
>>
>> 2. If the two expressions are strongly related, using comma 
>> operator is
>> reasonable to represent the intensity. I think rather it's an 
>> *ability*
>> to represent code meaning by using code style.
>>
>> Kenji Hara
>
> One concession we could make would be to disallow using the 
> result of the operator. That might actually catch all bugs 
> discussed herein.
>
> if (condition) ++i, ++j; // fine
> foreach (e; exp1, exp2) {}   // ERROR
> if(pMgr->ShouldRecordEvent(eSE_Weapon), pOwnerRaw) // ERROR
> return pMgr->RecordEvent(eSE_Weapon), pOwnerRaw; // ERROR
>
> I think this would be a compromise worth looking into.

I like it a lot. Almost *all* the "abusive" uses of "operator 
comma" I've seen use this trait of operator comma. So this would 
kill those:
//----
auto a = fun(), 5; //WTF is wrong with you?
//----

On the other hand, the "legit" cases of comma never seem to use 
the return value. The "only" execute two statements in a single 
context. For example:

//----
for (size_t i, j ; someCondition() ; ++i, ++j )
{...}
//----

I think this is *the* single most common use of operator comma, 
and I also think it is perfectly legit. Sure, it can easily be 
migrated away from, but I think it would be gratuitous breakage 
of good code.

--------

So this has my +1 vote.