On Tue, 23 Jan 2001, John Hughes wrote:
> > I had already reached the same conclusion after I saw that
> > everyone would have to remember to say "my Dog $spot;" every time or the
> > whole thing falls apart.
>
> Falls apart? How?
Because you miss one out and its a very difficult to find bug in your
application, mostly because you don't get the compile warnings if you miss
one off, but also you end up wasting time looking for why your application
really isn't any faster (the hint here is that pseudo hashes really don't
make that much speed difference to your application).
Say you miss off a type declaration, and later decide to change your hash
key. All of the declarations with types will produce compile errors, so
you can/will fix them, but the one you missed it from will lie hidden,
never producing an error even when the code is called.
> > If you want something reasonably close, you could do what a lot of the
> > Template Toolkit code does and use arrays with constants for key
> > names. Here's an example:
>
> Yes but then you get neither compile time (my Dog $spot) nor run time
> (my $spot) error checking.
Why not?
Witness:
% perl -Mstrict
use constant FOO => 0;
my @array;
$array[FOD] = 3;
Bareword "FOD" not allowed while "strict subs" in use at - line 3.
Seems like compile time checking to me...
> How are you going to debug the times you use a constant defined for
> one structure to index another?
You use packages, and data hiding.
> Oh, do it all through accessor functions. That'll be nice and
> fast won't it.
Maybe faster than you think. Your bottleneck is elsewhere.
If you are really going:
my Dog $spot = Dog->new("spot");
print "My Dog's name is: ", $spot->{Name}, "\n";
Then I think many people here would think that is a very bad
technique. You should *never* be able to make assumptions about the
underlying data format of an object.
--
<Matt/>
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// || ** http://axkit.org ** ** XSLT, XPathScript, XSP **
// \\| // ** Personal Web Site: http://sergeant.org/ **
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