That certainly doesn't seem right. It should prefer the pair check, but it's supposed to treat calling embedded expressions as slow. I'll take a look at that. On Oct 6, 2011 7:13 PM, "Jay McCarthy" <<a href="mailto:jay.mccarthy@gmail.com">jay.mccarthy@gmail.com</a>> wrote: > > Given all this talk of optimization, I'm still amazed that my original > example failed. Basically, the ordering optimization decided that > > (and (pair? (cdr e)) > (parse (car (cdr e)))) > > is cheaper than > > (equal? '+ (car e)) > > Jay > > -- > Jay McCarthy <<a href="mailto:jay@cs.byu.edu">jay@cs.byu.edu</a>> > Assistant Professor / Brigham Young University > <a href="http://faculty.cs.byu.edu/~jay">http://faculty.cs.byu.edu/~jay</a> > > "The glory of God is Intelligence" - D&C 93