Hi all,
I'd love any comments on the following as a general technique for
"hash-consing" - that is, making (equal?) imply (eq?). (Corollary: two
canonicalized values will be (eq?) iff they are (equal?).)
Is it worth considering this as something to push into the C runtime for
speed?
#lang racket/base
(provide canonicalize)
(require ffi/unsafe/atomic)
(define canonical-values (make-weak-hash))
(define (canonicalize val)
(start-atomic)
(define b (hash-ref canonical-values
val
(lambda ()
(hash-set! canonical-values
val
(make-weak-box val))
#f)))
(end-atomic)
(if b (weak-box-value b) val))
See also
https://gist.github.com/tonyg/86d0052c9c28431e1546#file-hashcons-rkt-L9-L17,
where I have test cases demonstrating simple uses of canonicalize and
its interactions with the garbage collector.
Regards,
Tony
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