On Tue, Jan 5, 2010 at 1:07 AM, Ovid
<publiustemp-perl6langua...@yahoo.com>wrote:
> --- On Mon, 4/1/10, yary <not....@gmail.com> wrote:
>
> > From: yary <not....@gmail.com>
>
> > How about
> > multi sub foo(Any $name) { die "Houston, we have a major
> > malfunction."}
>
> Looks like tha would work, but it forces the developer to remember to write
> this extra code every time they may have a constraint failure, if they
> forget, we're back to the old, cryptic message. It would be much nicer to
> be able to do this (psuedo-code, obviouly):
>
> subset Filename of Str where { $_ ~~ :f }
> :OnFail { "No such file: '$_'" }
> subset Celsius of Num where { $_ >= -273.15 }
> :OnFail { "Celsius temperature should be a Num >= -273.15, not '$_' " }
>
> With something akin to that, developers won't have to write extra
> boilerplate every time a constraint fails. Plus, the code is friendlier :)
>
I'd imagine that the functionality will fall out of the ability to have
nice failures because surely something like the following works now:
subset Filename of Str where { $_ ~~ :f or fail "No such file: '$_'" }
Perhaps s/fail/die/, but that seems like a means to your desired end.
-Scott
--
Jonathan Scott Duff
perlpi...@gmail.com
