[dmd-beta] D 2.059 beta 4

[Walter Bright]

On 4/10/2012 3:59 AM, Steve Schveighoffer wrote:
> If I understand correctly (and I very well might not), the idea is that auto 
> ref is *always* ref, so only one function is generated.

No. Two functions are generated.

>   The main difference between auto ref and ref is that ref doesn't allow 
> rvalues.  Saying auto ref is basically like saying to the compiler: "yeah, I 
> know it's an rvalue, still pass it as ref".
>
> If that's correct, I think the way to look at it is these three situations:
>
> 1. I want to change the value, and/or I want to disallow rvalues: use ref
> 2. I want to pass by reference because the struct is large: use auto ref 
> (includes rvalues), possibly const as well.
> 3. I want to optimize passing large structs for both rvalues and lvalues: use 
> two overloads, one with const ref, one by value.
>
> Andrei, I hate to ask this, because I feel very confused from all the 
> statements you have previously made, but could you explain this again?
>
> To be honest, if what I've said is correct, it still sounds so clunky and 
> awkward...
>
> -Steve
>
>     --------------------------------------------------------------------------------
>     *From:* Walter Bright <walter at digitalmars.com>
>     *To:* Discuss the dmd beta releases for D <dmd-beta at puremagic.com>
>     *Sent:* Monday, April 9, 2012 11:55 PM
>     *Subject:* Re: [dmd-beta] D 2.059 beta 4
>
>
>
>     On 4/9/2012 7:44 PM, Jonathan M Davis wrote:
>     > On Monday, April 09, 2012 19:40:43 Walter Bright wrote:
>     >> On 4/9/2012 7:32 PM, Nick Sabalausky wrote:
>     >>> Although, if there really is good merit to struct lits not veing lvalues,
>     >>> then maybe all we need is to wait until "auto ref" is usable for
>     >>> non-templates? (If that would even be possible...?)
>     >> Not possible, as the binary ABI would be different.
>     > It was my understanding that the auto ref was supposed to work with non-
>     > templated functions - at least what Andrei proposed was - but that you
>     > misunderstood that and made it only work with templates. And as long as it
>     > only works with templates, it's usefulness is very limited. opEquals
>     would be
>     > a _prime_ case for where it would be useful.
>     >
>
>     How could that possibly work for the same function, considering that the code
>     for each would be quite different, including the calling code?
>
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