[racket] Is eval very slow?

Just now, John Clements wrote:
> 
> I don't think you should be shocked; I believe that calls to eval
> are essentially triggering full passes of the parser and compiler,
> dynamically. It's true that you could optimize for certain special
> cases (such as yours), but generally speaking these use cases are
> rare, particularly since I'm guessing that the places where this
> optimization would be possible are also the places where eval isn't
> needed.

As a sidenote, this is not something that is unique to racket or that
is new in any way...  I first "encountered" this in 1995 in a project
written in Allegro Lisp -- I was surprised about how slow `eval' was,
and when I asked about it, the advice I was given is that in extreme
cases where you really need a fast evaluation of dynamically generated
code, you're better off writing a mini-evaluator instead.

(Another sidenote: there are some languages with a "very fast" eval,
like elisp and newlisp.  In these languages it can be as fast as
running normal code, but this is because there is little to no
compilation done.)

-- 
          ((lambda (x) (x x)) (lambda (x) (x x)))          Eli Barzilay:
                    http://barzilay.org/                   Maze is Life!