Re: This week's summary
On Mon, 26 Jul 2004 10:29:15 -0700, Brent 'Dax' Royal-Gordon [EMAIL PROTECTED] wrote: The Perl 6 Summarizer wrote: The infinite thread Pushing onto lazy lists continued to exercise the p6l crowd (or at least, a subset of it). Larry said that if someone wanted to hack surreal numbers into Perl 6.1 then that would be cool. Care to explain what those are, O great math teacher? *ducks* Just for those following along from home: http://www.amazon.com/exec/obidos/tg/detail/-/0201038129/qid=1090866301/sr=1-1/ref=sr_1_1/103-7396197-3600620?v=glances=books - Kurt
Re: Unicode in Emacs (was: Semantics of vector operations)
On Feb 03, David Wheeler wrote: On Feb 3, 2004, at 7:13 AM, Kurt Starsinic wrote: No joke. You'll need to have the mule-ucs module installed. A quick Google search turns up plenty of sources. Oh, I have Emacs 21.3.50. Mule is gone. I'm afraid you're on your own, then. I'm using 21.3.1. If you work it out, please post. - Kurt
Re: Semantics of vector operations
On Feb 02, David Wheeler wrote: On Feb 2, 2004, at 9:53 PM, Kurt Starsinic wrote: I realize this is a tad OT, but can anyone tell me how I can get Emacs to properly display Unicode characters? I expect that others on the list could benefit, too. (require 'un-define) Since I really don't understand Lisp, and since that simply didn't work, I'm going to assume it was some kind of joke. :-) Am I right? No joke. You'll need to have the mule-ucs module installed. A quick Google search turns up plenty of sources. You'll also need to have the appropriate fonts installed, of course. You may need to set your $LANG environment variable to a suitable value (I use en_US.UTF-8). - Kurt
Re: Protocols
On Jul 24, chromatic wrote:
On Thursday, July 24, 2003, at 05:28 PM, Benjamin Goldberg wrote:
If this were Java, the way to do this would be to define a Thingie
interface, and then an (archetypical) ThingieObject class... any time
that we want to actually *create* Thingies, we would use new
ThingieObject, but everywhere else, we would use the typename
Thingie. This way, when we want a class which acts like a Thingie,
but without inheriting any of it's innards, simply implement the
Thingie
interface, instead of inheriting the ThingyObject class.
Yes, that's the Java way to do it. Surely we can do it better in Perl
6.
The problem with Java interfaces is that you have to rely on the
library writer to have expected you to use an interface. Given the
amount of CPAN modules that, for example, expect a glob and preclude me
from passing in an IO::Handle with code like this:
croak Need a glob unless ref $thingie eq 'GLOB';
I'm not sure that the Java style is helpful. I'd rather not multiply
entities needlessly.
For our isa operator, and (perhaps more importantly) for
multimethod dispatch and/or sub prototype checking, we only check if an
object inherits from a class's magic parent interface, and *don't*
check
if it *really* inherits from that class itself.
heretic
Why should an implementor inherit from the interface?
If inheritance and polymorphic equivalence are two different things,
they ought to be handled two different ways. If anything, inheritance
is a specific case of the general mechanism of marking polymorphic
equivalence.
Again, the interesting question isn't Does this thing derive from
something I know about? It's Does this thing support the operations I
expect it to support? I don't care how, just that it does.
I don't want to call $mock_foo-isa( 'foo' ) because $mock_foo *isn't*
a foo. I don't want to call $delegates_to_foo-isa( 'foo' ) because
$delegates_to_foo *isn't* a foo. They can both handle foo-methods, but
neither is a foo.
/heretic
My two cents: the best possible use of an interface/protocol is
to define a set of methods *and their semantics*, and *not* their
implementation. In pseudocode:
protocol Window {
method print;
method close;
method bringToFront;
}
class MyWindow: implements Window;
You're saying that MyWindow has print, close, and bringToFront
methods. You're not saying whether they're inherited, or implemented
from scratch. You *are* saying that close() will erase a graphical
rectangle on a display, not disconnect a filehandle or return true
if it's nearby.
So the useful feature of this abstraction is that, given an
anonymous object, you don't ask, do you implement method called
so-and-so, e.g., $anon-can('print'); you ask it, do you do the
things that a Window does, e.g., $anon-implements('Window').
So a class shouldn't inherit from an interface. It should
assert that it implements it.
- Kurt
Re: Protocols
On Jul 24, David Wheeler wrote: On Wednesday, July 23, 2003, at 05:57 PM, chromatic wrote: The first is a deeper question -- besides inheritance, there's delegation, aggregation, and reimplementation (think mock objects) that can make two classes have equivalent interfaces. I'd like some way to mark this equivalence *without* having to inherit from an abstract base class and I wish that interface equivalence were checked before inheritance, as per Luke's idea. Sounds like you want Java-style interfaces to me. Follow the thread back. Objective-C had them way first, and their ur-name is protocols. - Kurt
Re: Perl and *ML
On Mar 26, Robin Berjon wrote: Dan Sugalski wrote: I think that the issue here isn't so much good perl support for XML as it is good support for attributed DAGs, something which would be of general good use for perl, since the ASTs the parser feeds to the compiler will ultimately be DAGs of a sort. ++good So, rather than jumping on the XML [insert verb here]! bandwagon, perhaps we'd be better served figuring out what would be useful operations and support for/on DAGs and suchlike things? Fast and efficient graphs of all sorts would be very useful. A way to define a complex graph of interlinked arbitrary objects while being reasonable on memory and good with GC would be a definitive big win, especially if it can be lazy. Especially with nice ways to write visitors and easy searches in the graph based on object properties (but I could be asking for too much ;). DAGs wouldn't enough though, most XML tree representations aren't really trees, they're very cyclic. Pardon me? Could you please provide an example? - Kurt
