Re: RFC 265 (v1) Interface polymorphism considered lovely

Nathan Wiger <[email protected]> writes:

> By specifying "use interface" explicitly, you can make sure that your
> class follows the interface spec. Otherwise, you rely on other classes
> in the hierarchy above you doing so, and then you indirectly inheriting
> from that interface. So "use interface" is really the only way you can
> make sure somebody else didn't screw up. ;-) On large projects I think
> this would be an essential safety check, just like "use strict".
> 
> -Nate
> 
>    package Pet : interface;
> 
>    sub isborn (@);
>    sub scratches ($\@;@);
>    sub annoys (\@);
>    sub costsmoney ($$$$$$$$);
>    sub poopsonfurniture ($);

Whoa Nellie. When did we get prototyping for methods. (Not that I'm
objecting, I think strict interfaces might actually make this
possible. The wisdom of it is left as an exercise...)

>    package Cat;
> 
>    use interface 'Pet';
> 
>    sub isborn {
>        bless { @_ }, self;   # ;-)
>    }
>    sub scratches ($\@;@) {
>        ...
>    }
>    sub annoys (\@) {
>        ...
>    }
>    sub costsmoney ($$$$$$$$) {
>        ...
>    }
>    sub poopsonfurniture ($) {
>        ...
>    }
> 
> 
>    package Doggie;
> 
>    sub isborn {
>        bless { @_ }, self;   # ;-)
>    }
>    sub scratches ($\@;@) {
>        ...
>    }
> 
> 
>    package Doggie::Cute;
> 
>    use base 'Doggie';
>    use interface 'Pet';
> 
>    # Our base class is 'Doggie', which does not use the 'Pet'
>    # interface (perhaps unbeknownst to us!). Nonetheless, we use
>    # the 'Pet' interface to make sure that our class is implemented
>    # correctly.
> 
>    # code would follow...

This could still be C<use base 'Pet'> and it would work you know. The
reasoning behind seperating C<use base> and C<use interface> (for me)
is simply because of the mnemonic assistance to the programmer.
interface.pm could easily be a duplicate of base.pm with the added
restriction that that the package so included *must* be an interface.
I'm not irrevocably tied to it...

-- 
Piers