[Issue 1839] New: Give D a modern varargs system that allows forwarding

[Lars Ivar Igesund]

Jarrett Billingsley wrote:

> <d-bugmail at puremagic.com> wrote in message
> news:bug-1839-3 at http.d.puremagic.com/issues/...
>> http://d.puremagic.com/issues/show_bug.cgi?id=1839
>>
>>           Summary: Give D a modern varargs system that allows forwarding
>>           Product: D
>>           Version: 2.010
>>          Platform: PC
>>        OS/Version: Windows
>>            Status: NEW
>>          Severity: enhancement
>>          Priority: P2
>>         Component: DMD
>>        AssignedTo: bugzilla at digitalmars.com
>>        ReportedBy: wbaxter at gmail.com
>>
>>
>> Given function
>>
>> void A(...) {
>> ...
>> }
>>
>> It should be possible to write a function wrapsA of this sort:
>>
>> void wrapsA(...) {
>>    pre_call();
>>    A(...); // or whatever syntax you want for forwarding the varargs.
>>    post_call();
>> }
>>
>> That D --  a supposedly modern, easy-to-use languages -- can't do this
>> conceptually simple thing is sad.
>>
>> The whole point of procedural programming is that code is encapsulated
>> into
>> reusable blocks.  Not being able to forward varargs means that a big
>> chunk of
>> that reusability is lost any time you write a varargs function.
>>
>> The workaround is to write every varargs function in two flavors, one
>> thats got
>> (...) args, and one that's got (_argptr,_arguments) args.  But if the
>> solution
>> is so mechanical and straightforward then why can't the compiler at just
>> do
>> that for us?  I'm not saying that's the right way to implement vararg
>> forwarding, but barring a more elegant solution, that sounds like at
>> least a
>> plausible solution.
> 
> 
> I'll suggest it again:  given a typesafe variadic function whose variadic
> parameter's array element type is a struct:
> 
> void A(Variant[] args...)
> 
> calling that function:
> 
> A(1, 2, "hi")
> 
> should be sugar for:
> 
> A(Variant(1), Variant(2), Variant("hi"))
> 
> This alone would obviate the need for ... style vararg functions.  A
> Variant array is far, far more useful than the platform-dependent
> hard-to-use
> inflexible _arguments/_argptr crap.  And at the same time, solves the "OMG
> template bloat!!" problem.

Only that that would move Variant into the runtime which is unfortunate.