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Postings from July 2006
On Wed, Jul 12, 2006 at 04:16:13PM -0400, Aaron Sherman wrote:
> On Wed, 2006-07-12 at 19:25 +0300, Yuval Kogman wrote:
> > 4. will we have a deep (possibly optimized[1]) equality operator, that
> > *will* return true for @foo = ( [ 1, 2 ], 3 ); @bar = ( [ 1, 2 ], 3 ); op(@foo, @bar)?
> > Is it going to be easy to make the newbies use that when they mean "it's the
> > same", like they currently expect == and eq to work on "simple" values?
>
> Isn't that ~~?
>
> Per S03:
>
> Array Array arrays are comparable match if $_ »~~« $x
>
> ~~ is really the all-purpose, bake-your-bread, clean-your-floors,
> wax-your-cat operator that you're looking for.
Granted, ~~ will return true in that case. I think the main problem
is Yuval wants a guarantee that it will return true if and only if
the things on either side have the same deep structure and values.
Currently, ~~ will also return true for structures where this does
not hold. For example:
@a = ( [ 1, 2] , 3 );
@b = ( sub { return 1 }, sub { return 1 } );
@a ~~ @b; # true
Why is that true? By the rules of hyper-operation, it turns into
this:
[1,2] ~~ sub { return 1 }
3 ~~ sub { return 1 }
which is true if these return true values:
sub { return 1 }->([1,2])
sub { return 1 }->(3)
Which they do.
So, smart-match fails as a "deep equality" operator precisely
because it's so smart.
-Scott
--
Jonathan Scott Duff
duff@pobox.com
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