http://qs321.pair.com?node_id=756075


in reply to Re: The value of declarations
in thread The value of declarations

The one place where the design of Perl 6 doesn't quite jibe with this meditation is that, while Perl 6 can do compile-time checking of named arguments on subroutines, it refuses to do so for method calls. (It does this by supplying a default slurpy %_ parameter to methods.) The reasoning for this is that base methods should be allowed to ignore named parameters that are intended only for derived methods, and vice versa. Perhaps there is some way to check named arguments against all the candidates at run time, but it seems as though this could get expensive, and we're at least trying to maintain the hope that Perl 6 could be very fast in theory, even if 6.0.0 doesn't actually achieve that. (And we don't expect it to, since we're optimizing for correct over fast for now.) Anyway, we're still open to ideas in this area, maybe an optional check that only runs first time when dispatch order is established (or reestablished).

Replies are listed 'Best First'.
Re^3: The value of declarations
by moritz (Cardinal) on Apr 07, 2009 at 17:38 UTC
    I wonder, can you do any reliable compile time checks on methods at all? I think this is valid: 
    my $x = eval 'class A { method foo($bar, $baz} }; A.new';
$x.foo();

    [download]

    Any compile time check would complain about a missing method.

[reply]
[d/l]

      Some checks could be done if you had a way to tell the compiler you weren't going to do something like this. 

      __PACKAGE__->no_monkey_business;  # no new methods/method signatures c
+an happen now. 

# or perhaps

use static_methods qw( MyClass );  #compile this class with only expli
+citly declared methods allowed.

      [download]

      Where the declaration says that only the methods that exist for the class at that time, or perhaps those that have been explicitly declared are available.

      Even better if you could turn it off from outside the class file, so you could do some monkey patching if needed: 

      # in main:
no static_methods MyClass;  # uses MyClass with static_methods turned 
+off.

      [download]


      TGI says moo

[reply]
[d/l]
[select]

In Section Meditations