Then you're ready to read the Felleisen-Hieb semantics to understand how to handle state (and just about everything else in the universe).
It's a tour de force, which is why I don't recommend it to beginners: they usually have no idea what it's saying or why it matters. But your questions suggest you're at just the right point. Shriram On Wed, Dec 1, 2010 at 9:03 PM, YC <yinso.c...@gmail.com> wrote: > > On Wed, Dec 1, 2010 at 5:25 PM, David Van Horn <dvanh...@ccs.neu.edu> wrote: >> >> An evaluator can implement function application using substitution, i.e. >> you can evaluate ((lambda (x) e) v) by evaluating the substitution of v for >> x in e. >> >> Or, you can be lazy and defer the substitution. In that case, you >> evaluate ((lambda (x) e) v) by evaluating e; you just have to remember that >> v should have been substituted for x should you ever get to evaluating x. >> The data structure you use to remember those deferred substitutions is an >> environment. A simple list of variable, value pairs is a suitable >> representation. > > Thanks - I have read the substitution part of PLAI and thought of using > substitution as well, but it seems that substitution does not constitute the > full solution: > > it only work with side-effect free code > it does not address closure > > Maybe I am looking too far ahead, but it seems like I cannot get away from > needing my own call stack? Or am I missing something? > Thanks, > yc > > _________________________________________________ > For list-related administrative tasks: > http://lists.racket-lang.org/listinfo/users > _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
