A6: Named vs. Variadic Parameters

[Michael Lazzaro]

A simple question, I hope...

From A6, "Calling Subroutines", comes the following:

    multi push(@array, +$how, [EMAIL PROTECTED]) {...}

    push(@a, how => 'rapidly', 1,2,3);   # OK
    push(@a, 1,2,3);                     # WRONG, $how == 1!
Oops!  What you really wanted to say was:

    multi push(@array, [EMAIL PROTECTED], +$how) {...}

    push(@a, how => 'rapidly', 1,2,3);   # OK
    push(@a, 1,2,3);                     # OK
Note the gotcha part... if you want to use both named arguments and a 
variadic list, you must declare the parameters in the signature in a 
different order than they must appear when actually calling the sub.  
If you put the signatured params and the actual arguments in the _same_ 
order, it will break.  The reason for this is because, in the first 
example, the slurpy array has been placed in the named-only zone, _not_ 
the positional zone.

Clearly, it's going to be a newbie problem, and I guess I'm not 
understanding why we can't enforce What They Really Meant.

When calling a sub that has both named params and a slurpy list, the 
slurpy list should always come last.  If a sub has both a slurpy hash 
and a slurpy list, the slurpy list should still always come last.  You 
simply can't credibly have anything after the slurpy list, or it'll be 
slurped.  So args/params must ALWAYS come in this exact order, if they 
are to be useful:

   sub foo(
       $x,    # required positional
      ?$y,    # optional positional
      +$k,    # optional named
      *%h,    # optional slurpy hash
      *$s,    # optional slurpy scalar
      [EMAIL PROTECTED],    # optional slurpy array
   ) {...}
I guess what I'm not understanding is why you would _EVER_ want [EMAIL PROTECTED] 
to be in the named-only zone, and presuming you never would, why we 
can't syntactically / semantically fix the above gotcha so that the 
params always appear in the "calling" order?

MikeL