The first stage of the formal review for DIP 1009 [1], "Improve Contract Syntax", is now underway. From now until 11:59 PM ET on September 13 (3:59 AM GMT on September 14), the community has the opportunity to provide last-minute feedback. If you missed either of the two preliminary review rounds [2][3], this is your chance to provide input.

At the end of the feedback period, I will submit the DIP to Walter and Andrei for their final decision. Thanks in advance to those of you who participate.

[1] https://github.com/dlang/DIPs/blob/98052839441fdb8c6cc05afccb9a81d084051c4d/DIPs/DIP1009.md

[2] http://forum.dlang.org/post/gjtsfysvtyxcfcmuutez@forum.dlang.org

[3] http://forum.dlang.org/post/luhdbjnsmfomtgpydser@forum.dlang.org

On Wednesday, 30 August 2017 at 12:26:43 UTC, Mike Parker wrote:
> The first stage of the formal review for DIP 1009 [1], "Improve Contract Syntax", is now underway. From now until 11:59 PM ET on September 13 (3:59 AM GMT on September 14), the community has the opportunity to provide last-minute feedback. If you missed either of the two preliminary review rounds [2][3], this is your chance to provide input.
>
> At the end of the feedback period, I will submit the DIP to Walter and Andrei for their final decision. Thanks in advance to those of you who participate.
>
> [1] https://github.com/dlang/DIPs/blob/98052839441fdb8c6cc05afccb9a81d084051c4d/DIPs/DIP1009.md
>
> [2] http://forum.dlang.org/post/gjtsfysvtyxcfcmuutez@forum.dlang.org
>
> [3] http://forum.dlang.org/post/luhdbjnsmfomtgpydser@forum.dlang.org

I see that in the previous review rounds some people suggested various keywords for designating the return value of a function ("return", "result", ...) in an `out` contract. What about using a plain old underscore? For example:

int abs(int x)
out(_ >= 0)
{
    return x>0 ? x : -x;
}

On Wednesday, 30 August 2017 at 14:05:40 UTC, Mark wrote:
> [...]
>
> int abs(int x)
> out(_ >= 0)
> {
>     return x>0 ? x : -x;
> }

The ambiguity issue of having two results in one scope [1] applies.

[1] http://forum.dlang.org/post/oihbot$134s$1@digitalmars.com

On Wednesday, 30 August 2017 at 14:57:38 UTC, Moritz Maxeiner wrote:
> On Wednesday, 30 August 2017 at 14:05:40 UTC, Mark wrote:
>> [...]
>>
>> int abs(int x)
>> out(_ >= 0)
>> {
>>     return x>0 ? x : -x;
>> }
>
> The ambiguity issue of having two results in one scope [1] applies.
>
> [1] http://forum.dlang.org/post/oihbot$134s$1@digitalmars.com

Ah, I see the problem.

On Wednesday, 30 August 2017 at 14:05:40 UTC, Mark wrote:
> I see that in the previous review rounds some people suggested various keywords for designating the return value of a function ("return", "result", ...) in an `out` contract. What about using a plain old underscore? For example:
>
> int abs(int x)
> out(_ >= 0)
> {
>     return x>0 ? x : -x;
> }

I think it's good to be consistent with existing out contracts which require declaring the variable first. The identifier `__result` currently works, but the thing is, it takes fewer characters to write `out(r; r >= 0)` than to write `out(;__result >= 0)` (or `out(__result >= 0)`). The possibility of using a single character as the return identifier makes it hard, in my opinion, to justify complaints about the syntax being "too verbose."