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

[Jarrett Billingsley]

<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.