Re: Dynamic languages (again)

In Java, we only have reflection objects, such as Class, Methods,
those are 'semi'-Runtime-MOP. You could only read meta-info from those
things.Some other framework provide some full MOP thing, but those
things are not working well

On 3/21/06, cao jing <[email protected]> wrote:
> so, runtime MOP and runtime metaobjects do not belong to dynamic languages
> only, static languages also can have runtime MOP.
> i think maybe JAVA just has some runtime metaobjects. In java, does every
> class exist as a metaobject?
>
> 2006/3/21, Jim Haungs <[email protected]>:
> > There's nothing inherently reflective about dynamic languages, nor vice
> versa. The concepts are orthogonal.
> >
> > Dynamic (at least in my definition) means that variables are bound to
> values at run-time, and methods are dispatched via run-time look-up. True,
> this requires the VM to introspect the method dictionaries, but nothing
> requires the running user-level program to actively introspect anything.
> >
> > And Java has reflection without fully-dynamic typing. By "not
> fully-dynamic" I mean you can declare a variable to be of type Object, and
> put any reference type in there, but you can't put an unboxed primitive in
> there, something you can do in Smalltalk and Ruby because everything
> inherits from Object, even so-called "primitives."
> >
> >
> >
> > On 3/20/06, Cristina Videira Lopes < [email protected]> wrote:
> > >
> > >
> > > Let me second the last sentence of the previous message. As a dynamic
> reflective language, Ruby rocks! It's really cute. And it's quite amazing
> what people are doing with it -- if you're into learning about it, don't
> miss Ruby on Rails. I recently taught an undergrad course on PLs, where I
> used Ruby at some point. The students were fascinated.
> > >
> > > (I have objections about some of the assumptions behind reflective
> languages, in general, but that's another story...)
> > >
> > >
> > >
> > > ________________________________
>  From: [email protected] [mailto:[email protected]] On Behalf
> Of Jim Haungs
> > > Sent: Monday, March 20, 2006 8:06 AM
> > > To: Pascal Costanza
> > > Cc: cao jing; [email protected]
> > > Subject: Re: [aosd-discuss] discuss Digest, Vol 30, Issue 7
> > >
> > >
> > > In Smalltalk, dynamic typing and dynamic dispatch are closely related.
> In Smalltalk, variables are merely slots for pointers; they can hold
> anything. Everything is an Object, including booleans, integers and strings,
> even blocks of code.
> > >
> > > When a message is sent to an object in a slot, the message name is
> looked up dynamically, and if a matching method is found, it is executed.
> This sounds egregiously slow, but good VM's play all sorts of tricks to
> optimize the overhead away.
> > >
> > > It's also possible to handle the doesNotUnderstand: error raised by the
> VM when an appropriate method is not found, yielding delicious possibilities
> like faulting an object into memory from a database and then returning to
> the original failed call with the correct object now reified.
> > >
> > > If you think Smalltalk is interesting but passe, check out Ruby. It's
> basically Smalltalk reincarnated as a scripting language.
> > >
> > >
> > > On 3/20/06, Pascal Costanza <[email protected]> wrote:
> > > >
> > > > On 20 Mar 2006, at 02:10, cao jing wrote:
> > > >
> > > > > so, i think SMALLTALK is a kind of Dynamic language, right?
> > > >
> > > > Definitely yes.
> > > >
> > > > > or, maybe SMALLTALK has some features of static languages, if
> > > > > it has, then what are they?
> > > >
> > > > Since Smalltalk allows you to change almost anything at runtime,
> > > > including the class hierarchy, method definitions, etc., it's hard to
> > > > state that anything about Smalltalk is static. However, I am no
> > > > expert about Smalltalk, it may be that some things you can do have
> > > > implications that I am not aware which would render them as
> > > > practically static. It may be a better idea to ask these questions in
> > > > a Smalltalk-related mailing list or newsgroup, like
> comp.lang.smalltalk.
> > > >
> > > > > BTW, is dynamic typing  the main feature  of  Dynamic language?
> > > >
> > > > It's certainly one of the main features. Dynamic dispatch is another
> > > > one.
> > > >
> > > >
> > > > Pascal
> > > >
> > > > --
> > > > Pascal Costanza, mailto:[email protected], http://p-cos.net
> > > > Vrije Universiteit Brussel, Programming Technology Lab
> > > > Pleinlaan 2, B-1050 Brussel, Belgium
> > > >
> > > >
> > > >
> > > >
> > > >
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> > >
> > >
> >
> >
>
>
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