If any of those take the value of the attribute outside it's defined range, then no, I don't want it to "Just work". I want it to "Just NOT work".

Most of the time, this isn't needed. A normal variable $foo can have any value and I don't understand why instance variables should be different in this.

Still, because value validation is a nice thing to have, tie with a STORE handler isn't a bad idea. But this shouldn't be specific to OO - the solution should apply to all variables. Our implementation, however, cheats by ignoring normal variables. This was easier :) 

sub foo : Property { $_ < 10 }

main->foo = 9;
main->foo++;  # dies

[download]

Perl 6 will provide a real solution, with a nice syntax even! In fact, more than one nice syntax! 

has $foo where { $_ < 10 };

[download]
This extends to non-instance variables too. Just use "our" or "my" instead of "has". 
my $foo where { $_ < 10 };

$foo = 9;
$foo++;  # dies

[download]

Juerd # { site => 'juerd.nl', plp_site => 'plp.juerd.nl', do_not_use => 'spamtrap' }

In reply to Re^7: Experimenting with Lvalue Subs by Juerd
in thread Experimenting with Lvalue Subs by Limbic~Region

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.