> Robby’s message dominates mine but I don’t get why you can’t work your way > thru what I provided. >
I don’t see the connection between the issue I brought up and what you provided. In your program ‘r-r/tick’ is a form to define a reduction relation which manages ‘clock’, but then ‘clock’ can’t determine the behavior of the reduction relation (and it isn’t cached by Redex). Note that ‘r-r/tick’ says ‘(where _ ,(begin (set! clock (u clock)) (o clock)))’, which means the outputs of the ‘observer’ are ignored. Now, we could modify ‘r-r/tick’ to take a pattern ‘p’ and say ‘(where p ,(begin (set! clock (u clock)) (o clock)))’. But then we’re getting further and further away from my intent: having ‘k’ as an implicit argument to a collection of definitions (metafunctions, judgment forms, and so forth), beyond a single reduction relation. > HUH? This is something that you control with the initialization function. > The REDEX results are the same. It is up to your init function to cache or > not cache. But if my function doesn’t cache and the reduction relation depends on ‘clock’ (see previous paragraph), then the Redex results would differ. > > No, ‘#:initial’ let’s you parameterize ‘clock’ when *defining* the > reduction relation (‘r-r/tick’), not when *calling* it (‘traces’, > ‘apply-reduction-relation’ and friends). > > > Really? > > (define *foo 0) > (define (init) .. *foo ..) I assume you’re proposing to pass ‘init’ to ‘#:initial’, and then ‘(set! *foo ___)’ to control the reduction relation’s behavior. And that starts to look like a dynamically bound variable—better yet, a Racket parameter. We’re on the right track: Racket parameters is how we got started, and I’m proposing we need them at the Redex level as well 😀 > > (define-metafunction X > > [(my-metafunction _) clock]) ;; <= ‘clock’ is just a symbol here, not > a bound (meta-)variable > > > What does this even mean? Racket-Redex is about variables not symbols. Right, Racket–Redex is about variables, but ‘clock’ in ‘my-metafunction’ isn’t a variable, it’s literally the symbol ‘'clock’. * * * I feel we’re getting into the weeds and having different conversations. Can I kindly ask you re-read my original message with a fresh pair of eyes? By the way: *thank you all* for the conversation thus far, and for building Redex in the first place. As usual I’m learning a lot from interacting with you. -- 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 [email protected]. For more options, visit https://groups.google.com/d/optout.
