Evaluation order of index expressions

[Andrei Alexandrescu via Digitalmars-d]

On 5/24/15 3:36 PM, Iain Buclaw via Digitalmars-d wrote:
> On 25 May 2015 00:20, "Andrei Alexandrescu via Digitalmars-d"
> <digitalmars-d at puremagic.com <mailto:digitalmars-d at puremagic.com>> wrote:
>  >
>  > On 5/24/15 1:29 PM, Timon Gehr wrote:
>  >>
>  >> BTW, the documentation contradicts itself on evaluation order:
>  >> http://dlang.org/expression.html
>  >
>  >
>  > This comes up once in a while. We should stick with left to right
> through and through. It's a "simple" matter of getting somebody on the
> compiler team to find the time for it. -- Andrei
>  >
>
> I find it is not as clear cut as that.  In gdc, there is a compiler flag
> that tells the optimizer to honour left to right evaluation, and because
> of both what you say and the agreement of others, it seems natural to
> have this turned on by default.

Even better - the front end could force the sequencing.

> However, this has an interesting side effect with operations with side
> effects.  Ie: foo += bar() could either produce expected or surprising
> results.
>
> Hint, the LTR order - foo = foo + bar() - gives the most surprise in my
> experience from users.

I think LTR is the most sensible in all cases. -- Andrei