Re: Eval - Pro's and Con's (was Re: Dylan rather than CL -- why?)

[Jeff Dalton <jeff@aiai.edinburgh.ac.uk>]

> >From jeff@aiai.edinburgh.ac.uk Tue Dec  8 07:14:57 1992
> /// In my experience, meta-interpreters and rule-based systems can usually
> /// get by w/o EVAL.  A typical trick is to take an expression in a macro-
> /// call that might be evaluated and have the macro expand to something that
> /// includes
> /// 
> ///   #'(lambda () <expr>)
> /// 
> /// rather than
> /// 
> ///   (quote <expr>)
> 
> While this is true, sometimes one wants to allow a rule to given actual code
> to execute, thus temporarily losing some of the interpretter/search engine's
> overhead.  Eval is one of the cleanest ways to do this I know of.

I'm not sure what you mean.  If I have a rule like this:

(defrule rule-1
  (if <conditions>
      then <Lisp code>))

then I can handle it as above.

-- jd