Re: Fancy sub arg handling: ability to expand error message?

[The Sidhekin]

On Sat, Mar 28, 2015 at 2:53 PM, Moritz Lenz <mor...@faui2k3.org> wrote:
> On 28.03.2015 12:27, Tom Browder wrote:
> > I like the subroutine arg handling in Perl 6.  Is there any simple
> > way to attach a short error msg in place of or additive to the
> > default for, say, a missing arg?
>
> You can always use multi subs, and use a catch-all candidate which
> produces the error message.
>
> multi thingy($x) { $x + 42 }
> multi thingy(|c) { die "Must call &thingy with exactly one argument" }


  Multis?  I guess my mind went elsewhere:

sidhekin@purplehat[00:25:02]~$ cat > tom.p6
sub foo($x = (warn "&foo called without argument; using default (42)"; 42)
) {
  $x + 42;
}

sub bar($x = (die "&bar called without argument; failing") ) {
  $x + 42;
}

say foo(-2);
say foo();
say bar(-2);
say bar();
sidhekin@purplehat[00:25:21]~$ perl6 tom.p6
40
&foo called without argument; using default (42)  in sub foo at tom.p6:1

84
40
&bar called without argument; failing
  in sub bar at tom.p6:5
  in block  at tom.p6:12

sidhekin@purplehat[00:25:27]~$


Eirik