Declaring Ref Variables Inside Function Calls

[Andrei Alexandrescu]

Bill Baxter wrote:
> On Wed, Apr 1, 2009 at 6:16 AM, Andrei Alexandrescu
> <SeeWebsiteForEmail at erdani.org> wrote:
>> Bill Baxter wrote:
>>> On Wed, Apr 1, 2009 at 5:03 AM, Sergey Gromov <snake.scaly at gmail.com>
>>> wrote:
>>>> Tue, 31 Mar 2009 12:18:21 -0700, Andrei Alexandrescu wrote:
>>>>
>>>>> Jarrett Billingsley wrote:
>>>>>> On Tue, Mar 31, 2009 at 1:32 PM, Andrei Alexandrescu
>>>>>> <SeeWebsiteForEmail at erdani.org> wrote:
>>>>>>> Jarrett Billingsley wrote:
>>>>>>>> 2009/3/30 dsimcha <dsimcha at yahoo.com>:
>>>>>>>>> // How it works now:
>>>>>>>>> uint foo;
>>>>>>>>> string bar;
>>>>>>>>> unpack(foo, bar) = someFunction();
>>>>>>>>>
>>>>>>>>> // vs. how I want it to work:
>>>>>>>>> unpack(auto foo, auto bar) = someFunction();
>>>>>>>> Cute, but uh, I'd much rather see tuples just be returnable.
>>>>>>> They are.
>>>>>> template Tuple(T...)
>>>>>> {
>>>>>>     alias T Tuple;
>>>>>> }
>>>>>>
>>>>>> Tuple!(int, float) foo()
>>>>>> {
>>>>>>     return Tuple!(3, 4.5);
>>>>>> }
>>>>>>
>>>>>> foo.d(10): Error: functions cannot return a tuple
>>>>>>
>>>>>> Unless you're using some prerelease compiler, they are not.
>>>>> import std.typecons;
>>>>>
>>>>> Tuple!(int, float) foo()
>>>>> {
>>>>>     return tuple(2, 4.5);
>>>>> }
>>>>>
>>>>> The addition of the alias this feature and of constructor templates
>>>>> makes std.typecons.Tuple even better.
>>>>>
>>>>> Andrei
>>>> Unfair---std.typecons.Tuple is actually a struct!
>>>>
>>>> Well, basically struct is a run-time tuple, anyway.
>>>>
>>>> I think that all the buzz around "actual tuple support" boils down to
>>>> requests for syntax sugar for construction and decomposition of
>>>> anonymous structs.  While typecons.Tuple is sorta OK for construction,
>>>> things are still pretty ugly on the "decomposition" end.
>>> Right.  In my ideal world I could use tuples like this:
>>>
>>> (int,float) a;
>> That sucks. Is int(int, float) a function type or a juxtaposition of two
>> types?
> 
> I should say that by "in my ideal world" what I meant was "forgetting
> about all the baggage that D already has for a moment and starting
> from a more or less clean slate".   Things like the useless comma
> operator.
> 
> But isn't a juxtaposition of two types a syntax error?  So the above
> would be a function type, not a juxtaposition of two types.
> 
>> Is (A, B) an expression or a type? And so on.
> 
> How does that differ from asking   "Is A an expression or a type?"
> 
> If A and B are types, then (A,B) is a type.
> 
> 
>>> (int,float) z = returns_tuple();
>> Blech.
> 
> Blech to that, but you like
>    Tuple!(int,float) z = returns_tuple();
> correct?
> 
>>> (int x, float y) = returns_tuple();
>> I'd like that too, but what we should have is make any definition an
>> expression.
>>
>>> auto tup = (2, 3.4);
>> Belch (sic).
> 
> Belch to that, but again, you're saying this is great
>    auto tup = Tuple!(2, 3.4);
> correct?
> 
> --bb

Yah, sorry for the dismissive comments... what I meant was that the 
literal you suggested is so ambiguous grammatically, it's a 
non-improvement compared to just writing Tuple! there.

Andrei