Re: Re: New, from-scratch implementation of backquote.

Kaz Kylheku <kaz@xxxxxxxxxxxxxxxxxxx> writes:

> On Fri, 11 Apr 2003, Hoehle, Joerg-Cyril wrote:
> 
> > Date: Fri, 11 Apr 2003 13:22:31 +0200
> > From: "Hoehle, Joerg-Cyril" <Joerg-Cyril.Hoehle@xxxxxxxxxxxxx>
> > To: clisp-list@xxxxxxxxxxxxxxxxxxxxx
> > Cc: kaz@xxxxxxxxxxxxxxxxxxx
> > Subject: New, from-scratch implementation of backquote.
> > 
> > Hi,
> > 
> > I found the following thread from 1999 quite intriguing:
> > 
> > Christopher R. Barry in cll on: quasiquote reference implementation
> > http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&selm=87vh8hk0dj.fsf%402xtreme.net&rnum=8
> > (defmacro defclass* (name supers slots &rest options)
> >   `(macrolet ((do-it ()
> >        `(defclass ,,name ,,supers ,,slots ,,@options)))
> >      (do-it)))
> 
> Interesting; basically this uses macrolet solely to obtain an extra
> level of macroexpansion, so that the name, supers, slots and options
> are all evaluated.

Which maybe means that you probably don't want a macro, but a function
instead...

> [... lucid comments elided ...]
> 
> To solve this problem you need the help of EVAL. Your loop must
> actually construct the *source code* of a DEFCLASS construct into which
> it has inserted all the right pieces, and then EVAL that source code
> so that its effect takes place.

Defining defclass* as a function avoids the need for eval:

(defun defclass* (name supers slots &rest options)
  (funcall (lambda () `(defclass ,name ,supers ,slots ,@options))))

(loop for i from 1 to 3
   collect (defclass* ( (intern (format nil "FOO-~D" i)) () ())


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