Re: embedding question: defining symbols?

[Han-Wen Nienhuys <hanwen@cs.uu.nl>]

jimb@red-bean.com writes:
> Use the function scm_ihashv in hash.c to get a hash value for a
> symbol's name.

OK.

> > > That is, find some way to use
> > > symbols as the keys in your table.
> > > 
> > > When Guile acquires real first-class environments, then you may want
> > > to change your code.
> > 
> > So what you are saying is, that I also cannot recode C++ methods in
> > Scheme? Hmm...
> 
> Hmm.  I'm absolutely positive I don't understand what you mean here.
> :(  Can you explain?  Would you like to replace some of your methods
> written in C++ with methods written in Scheme?

My actual objective is to go from code that looks like


	class Foo { 
		int bla;
		Bar * bar_p;
		void do_something ()
		{
			if (!bla)
				bla = bar_p->blub * 2;
		}
		Foo ()
		{
			
		}
	}

to something that is written in Scheme, and where methods can be
overriden at runtime.  I know that I am sounding very sketchy, but to
do the things I want to do, I feel that I must somehow use GUILE
evaluation and namespace stuff.  So I am trying to get  a grip on how
they work.  Perhaps the below demonstrates what I want:


	(define (make-foo)
	  (define (Foo fun)
	    (define bla 1)
	    (define bar-pointer '())
	    (define (calculate-bla)
	      (set! bla (* 2 ((bar-pointer 'access) 'blub)))
	      )

	    (define (access-fun sym) (eval sym))

	    (if (eq? fun 'access)
		access-fun
		)

	  )
	  Foo
	)


I want to make the change from C++ to scheme gradually, so I must
integrate the semantics of Scheme and C++ somewhat: I want to
associate a namespace / environment / whatever to every Foo class I
create, and one by one, move the C++ variables (and their associated
code) to the SCM variables and SCM code..

> Actually, it's an interface supported by Guile's object system that
> allows users to customize its implementation.  I'm not very familiar
> with its abilities myself at the moment.

But I've got some links, though.  Is  MOP usable right now?  Does it
work in GUILE 1.3?


> 

-- 

Han-Wen Nienhuys, hanwen@cs.uu.nl ** GNU LilyPond - The Music Typesetter 
      http://www.cs.uu.nl/people/hanwen/lilypond/index.html