Feature request: extending comma operator's functionality

[Timon Gehr]

On 10/05/2012 03:35 PM, monarch_dodra wrote:
> On Friday, 5 October 2012 at 00:22:04 UTC, Jonathan M Davis wrote:
>> On Friday, October 05, 2012 02:08:14 bearophile wrote:
>>> [SNIP]
>>> Regarding definition of variables in D language constructs, there
>>> is one situation where sometimes I find D not handy. This code
>>> can't work:
>>>
>>> do {
>>> const x = ...;
>>> } while (predicate(x));
>>>
>>>
>>> You need to use:
>>>
>>> T x;
>>> do {
>>> x = ...;
>>> } while (predicate(x));
>>
>> Yeah. That comes from C/C++ (and is the same in Java and C#, I
>> believe). I
>> don't know why it works that way. It's definitely annoying.
>>
>> [SNIP]
>>
>> - Jonathan M Davis
>
> Because it's the only way to guarantee that x exits when you reach the
> end of the loop.
>


s/only/simplest/

> do {
>    if(true) continue; //Yawn... skip.
>    const x = ... ;
> } while (predicate(x)); //What's x?
>
> Basic goto limitations. Unlike goto though, inserting a "continue"
> should never create a compile error, so the compiler *has* to guarantee
> that the if condition references nothing inside its own block.
>
> It is annoying, but nothing that can't be fixed with a scope bloc.