As a partial answer to your question, syntax objects internally have lots of caches that are most definitely mutable, but I don't think that there is any way you can observe the mutation without getting out a stopwatch.
Robby On Thu, Aug 7, 2014 at 8:44 PM, Alexander D. Knauth <alexan...@knauth.org> wrote: > > On Aug 7, 2014, at 8:53 PM, Matthias Felleisen <matth...@ccs.neu.edu> wrote: > > > Here are some examples: > > (equal? #'(lambda (x) x) #'(lambda (x) x)) > > #f > > > For these the source locations would still be different. > > (define so #'(lambda (x) x)) > (equal? so so) > > #t > > > For these they are eq?. > > > > Does equal? simply use eq? for syntax objects? > This example says probably, or am I still missing something? > (define stx #'(lambda (x) x)) > (equal? stx (datum->syntax stx (syntax-e stx) stx stx stx)) > > Are syntax objects mutable? If so, how would you define a function like eq? > say syntax-eq? without using the built-in equality? > > Are syntax objects immutable? Why should they be immutable? How does equal? > work on such structures normally? > > > I was under the impression that syntax objects were immutable, but I don’t > really know. > And anyway, for mutable vectors, strings, byte-strings, and structs, equal? > still checks each element. > > See HtDP on extensional and intensional equality. — Matthias > > > Where? I have read a lot of HtDP, and looked at it again just now, but I > don’t remember anything about this, and couldn’t find anything either. > In the BSL docs for eq? and eqv? it mentions extensional and intensional, > but doesn’t explain anything. > In Realm of Racket there was a bit about that, but that doesn’t really tell > me anything about syntax objects. > > > On Aug 7, 2014, at 5:58 PM, Alexander D. Knauth wrote: > > How does equal? determine whether two syntax objects are equal? > > Does it simply use eq?, or does it check the syntax-e, lexical context, > srcloc and properties? > > > > ____________________ > Racket Users list: > http://lists.racket-lang.org/users > > > > > ____________________ > Racket Users list: > http://lists.racket-lang.org/users > ____________________ Racket Users list: http://lists.racket-lang.org/users
