Why don't people like lisp?

[Erann Gat]

In article <8Nnlb.619$I04.380 at newsread4.news.pas.earthlink.net>, "Andrew
Dalke" <adalke at mindspring.com> wrote:

> Me:
> > Python has the ability to do exactly
> > what you're saying (domain language -> AST -> Python code or AST ->
> > compiler).  It's rarely needed (I've used it twice now in my six years
> > or so of Python), so why should a language cater to make that
> > easy at the expense of making frequent things harder?
> 
> As an example, here's a quick hack of a way to parse a simple
> stack-based language and make a native Python function out
> of it.  I am the first to admit that it's ugly code, but it does work.
> 
> I am curious to see the equivalent code in Lisp.

Here's a quick and dirty version:


(defvar *operations* '(+ - * / **))

(defun ** (n e) (expt n e))

(defun rpn-compile (expr)
  (let ( stack free-vars )
    (dolist (term expr)
      (cond ( (numberp term) (push term stack) )
            ( (member term *operations*)
              (push (list term (pop stack) (pop stack)) stack)
              (rotatef (second (first stack)) (third (first stack))) )
            (t (push term stack)
               (pushnew term free-vars))))
    (unless (= (length stack) 1) (error "Syntax error"))
    (eval `(lambda (&key , at free-vars) ,(first stack)))))


? (funcall (rpn-compile '(0 b - b 2 ** 4 a c * * - 0.5 ** + 2 a * /))
           :a 1 :b 6 :c 3)
-0.5505102572168221
? 


E.