repeated parameter names and default values

[Allen Wirfs-Brock]

On Sep 27, 2012, at 10:09 AM, Jason Orendorff wrote:

> On Thu, Sep 27, 2012 at 11:19 AM, Allen Wirfs-Brock
> <allen at wirfs-brock.com> wrote:
>>   function f(a, b=a, a=3, c=a) {
>>      return a+" "+b+" "+c
>>   }
>>   console.log(f(1));
>> 
>> Based upon the conclusions about argument binding at the recent TC39 meeting this will display:
>>  "3 1 3"
> 
> Not having been at the meeting, I had a little trouble coming up with
> a desugaring where this worked. Is this the idea?
> 
>    function f(a, b, a, c) {
>        var %args = a copy of arguments;
>        a = %args[0];
>        b = %args[1] === void 0 ? a : %args[1];
>        a = %args[2] === void 0 ? 3 : %args[2];
>        c = %args[3] === void 0 ? a : %args[3];
>        return a+" "+b+" "+c;
>    }

Yes, essentially that plus presumably appropriate length checks on %args.

Also, I assume by "arguments" you mean the actual passed argument vector rather than the arguments object.

Allen