> 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 racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
