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List:       perl5-porters
Subject:    auto-declaring subs
From:       Ashley Winters <jql () accessone ! com>
Date:       2001-04-15 21:35:43
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Hello all,

I was trying to implement some rather sick voodoo when I encountered a
snag.

# sick voodoo
sub add : args(bar, baz) {
    frob(bar, baz);
}

That works using an lvalue AUTOLOAD which recognizes the named arguments
based on caller() and returns lvalue @_ elements thanks to @DB::args.

The problem is that bar and baz are converted to strings before the use
attributes call has a chance to introduce them as lvalue subs.


However, these work beautifully:

# separate declaration
sub foo : args(bar, baz);
sub foo {
    print bar .  baz;
}
# use parens
sub blurfl : args(baz, bar) {
    print baz() . bar();
}
foo("Hello ", "World!");
blurfl("Hello ", "World!");

Would it be reasonable to have the parser stop and declare the sub before
parsing the block? Can sub foo (proto) : attributes {} be made equivalent
to sub foo (proto) : attributes; sub foo {}? For now, I can live with
the work-arounds.

And on a side note, is @DB::args threadsafe? It seems like running
caller() from multiple threads would cause a race-condition on reading
@DB::args.

Thanks,
Ashley Winters

--
Trust me, you don't wanna know how I implemented :virtual.

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