Thanks for the feedback! Some of these were not concerns for my use case, so I’ll do a bit more design before submitting something.
-- Sent from my phoneamajig > On Oct 30, 2020, at 12:36, George Neuner <[email protected]> wrote: > > >> On 10/30/2020 3:08 PM, William J. Bowman wrote: >> Let me aid this discussion by copying in the ~10 lintes of code in question: >> >> > (define-syntax (dictof syn) >> > (syntax-parse syn >> > [(_ (k:id pred?) ...) >> > (quasisyntax/loc syn >> > (dictof/proc `((k . ,pred?) ...)))])) >> > > (define ((dictof/proc spec) h) >> > (and (eq? (dict-keys h) (dict-keys spec)) >> > (for/and ([(k pred?) (in-dict spec)]) >> > (pred? (dict-ref h k))))) >> >> The macro is merely a syntactic transformation to 1 line of code that >> implements >> the functionality of the contract at run-time. >> Is there some reason to avoid macros in this particular case? > > There's rarely any problem with macros that only provide syntactic sugar. > > The issues wrt contracts are how heavy are the dictionary functions. The FOR > loop is concerning because the check time is proportional to the size of the > dictionary [again recalling that contracts live on in release code]. > > For performance it would be better to enforce the predicate on values as they > are entered, and then assume anything already in the dictionary is correct. > It is sensible to provide a function that validates the whole dictionary, but > I would make it something the programmer has to invoke deliberately rather > than a contract to be enforced at (even just 1st in module) mention of the > dictionary. > > YMMV, > George > > -- > 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]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/racket-users/95997336-33d4-5c5b-b329-9ea691fe59ef%40comcast.net. -- 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]. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/E9A25DEF-7B1B-426C-AFAD-319C5C2E9757%40williamjbowman.com.
