Philip McGrath writes: > Alternatively, here is a little example of how you might define lambda-box: > > #lang racket > > (struct lambda-box ([proc #:mutable]) > #:property prop:procedure > (make-keyword-procedure > (λ (kws kw-args this . by-pos-args) > (keyword-apply (lambda-box-proc this) > kws > kw-args > by-pos-args)))) > > (define f > (lambda-box (λ () 1))) > > (f) > > (set-lambda-box-proc! f (λ () 2)) > > (f)
Thanks! This is a very helpful. I guess if used in combination with namespace-variable-value one could extend or freshly define depending on whether or not things are defined in (current-namespace). > I guess my bigger question is whether making everything redefinable is > really the best mechanism to achieve what you want. I would bet that, even > in your example, you don't usually want to dynamically redefine cons or +. > I think it would probably be better to be explicit about where you want to > allow redefinition and where you want identifiers to refer to a specific > binding. > > If I were thinking about "a multiplayer game … where you could change the > world while players are in it without kicking them out," I might think > about a current-world parameter that can be mutated and having certain > functions consult the current-world. Using the class-based object system or > racket/generic for the world value might be particularly suitable. (Of > course, the details would depend on exactly what about the world you want > to be able to change.) It could be that there are per-instance ways to handle things. I'm partly coming from the perspective of other lisps where there's a very *general purpose* option with a mutable toplevel. It could be that in various applications there may be a more *specific* options that are better. But a lot of my question is whether or not the general route *can* be brought to Racket. It looks like it can be, even if Racket folks will in general not like it :) > -Philip -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
