Timon Gehr <timon.g...@gmx.ch> wrote:
> On 08/19/2011 03:46 PM, kennytm wrote:
>> Timon Gehr<timon.g...@gmx.ch> wrote:
>>
>>> auto ref currently treats struct literals as lvalues too. (therefore, as
>>> ref). And passing by value would be considerably less efficient for large
>>> structs.
>>>
>>> As I understand it, the only issue with allowing literals and function
>>> results as lvalues is that generic code cannot detect if it is working
>>> with a temporary or not. I don't know if this would be useful in D though.
>>>
>>> each code segment of the form:
>>>
>>> void foo(ref S);
>>> ...
>>> foo(S(...));
>>>
>>> is equivalent to one explicitly declaring the temporary:
>>>
>>> {auto __temp=S(...); foo(__temp);}
>>>
>>> The difference is that the first is more pleasant to write. If
>>> temporaries would become rvalues everyone would always have to write the
>>> second form manually. So imho it is just a syntax sugar issue.
>>>
>>> I'd actually argue that ref-passing should work for arbitrary function
>>> results too.
>>
>> Here I propose that we go a step further and abolish the notion of rvalue
>> and lvalue entirely, and let the compiler insert necessary temporary
>> variable when needed, so that we can finally write things like
>>
>> uint w;
>> memcpy(w,&5.0f, w.sizeof);
>> 13u = w;
>>
>> </joking>
>
> And then of course you could do:
>
> 5=6;
> assert(5==6);
>
> It hasn't been working since the good ol' days of fortran =(.
Actually that assignment would just become an expensive no-op because it
will be rewritten into
(int __lvalue1243 = 5, __lvalue1243) = 6;
So the assert would still assert.
