I just read that this is no longer a place for Racket discussions, so I'm moving the question to https://racket.discourse.group/
sobota, 5 kwietnia 2025 o 11:53:06 UTC+2 [email protected] napisał(a): > I've had an idea to implement a #lang that would provide some syntactic > extensions akin to those provided by the Kawa Scheme, particularly with > regard to the usage of a colon. > > In particular, in Kawa: > - the sequence "x:" will be read as a keyword equivalent to #:x > - the sequence "a:b" will be read as ($lookup$ a `b) > - likewise, the sequence "a:b:c" will be read as ($lookup$ ($lookup$ a `b) > `c) and so on > - if two colons appear in a row, as in, say "a::b", they will be treated > as a separate token, i.e. > > (call-with-input-string "a::b" read) > will return the symbol a > > and > (call-with-input-string "(a::b)" read) > will return the list of three tokens, (a :: b) > > Kawa treats each pair of colons as a separate token, so > > (call-with-input-string "(:::::::)" read) > returns the list (:: :: :: :) > but I would actually prefer to treat a sequence of two or more colons as a > single token. > > In either case, I wonder if someone could guide me how to do this, > preferably using Racket's internal machinery that's already out there. > > I found that atoms in Racket are being read by the > "read-symbol-or-number?" procedure from expander/read/symbol-or-number.rkt, > but I don't think it is sufficiently tweakable - in particular because if I > read a colon, I might have to unread it if I can peek another colon. > > Is there any simple way out of this situation, or do I have to actually > implement a Lisp reader from scratch? (I'd be OK with that, because I > already wrote a reader in Kawa that I think I could adapt, but then I'd > probably have some questions about dealing with syntax objects. The > alternative would be to modify Racket's sources to make the reader API more > flexible, e.g. allowing to parameterize expander's "read" with the > "read-symbol-or-number" function, which I think would be more in the spirit > of Racket, but it would probably also take more time to downstream) > > Thanks in advance, > Panicz > -- This group is deprecated and retained as an archive. Racket discussions have moved to the Racket Discourse at https://racket.discourse.group/ . --- 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]. --- 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 visit https://groups.google.com/d/msgid/racket-users/be221cb3-3054-4c94-8c13-855a22b96e59n%40googlegroups.com.
