DIP19: Remove comma operator from D and provision better syntactic support for tuples

[Don Clugston]

On 24/09/12 17:19, Andrei Alexandrescu wrote:
> On 9/24/12 4:17 AM, Don Clugston wrote:
>> Regarding the comma operator: I'd love to deprecate it, but even if we
>> don't, could we at least ensure that this kind of rubbish doesn't
>> compile:
>>
>> void main()
>> {
>> int x;
>> x > 0, x += 5;
>> }
>>
>> At present, because comma expressions are expressions, not statements,
>> the "x > 0" doesn't generate a "statement has no effect" error, despite
>> the fact that it is meaningless and gets completely discarded.
>
> Interesting. The comma operator is probably the only one in which an
> expression is evaluated only for the sake of its side effects. So
> eliminating the comma operator would just get rid of that case by design.

Yes. Comma is a special case in a number of ways.

> Of course, there's always the option of adding more checks or rewriting
> the comma operator from "expr1, expr2, expr3" to "{ expr1; expr2; return
> expr3; }()".

We hit this one often in real-world code. On German keyboards , and ; 
are on the same key, so it's a fairly easy typo. I don't think it 
happens as often when using a US keyboard.