Hi,
Probably due to all operations not being in-place, chaining operations on
bignums is very costful.
for example, using bitwise-bit-field[1] on bignums is atrocious.
I also tried
(define (reverse-bits n)
(for/fold ([reversed 0])
([i (in-range (integer-length n))])
(bitwise-ior (bitwise-arithmetic-shift-left reversed 1)
(or (and (bitwise-bit-set? n i) 1) 0))))
but it's not much better. Having in-place operations would help
(define (reverse-bits n)
(for/fold ([reversed 0])
([i (in-range (integer-length n))])
(bitwise-arithmetic-shift-left! reversed 1)
(bitwise-ior! reversed (or (and (bitwise-bit-set? n i) 1) 0))))
What do you think?
[1]
https://github.com/racket/r6rs/blob/master/r6rs-lib/rnrs/arithmetic/bitwise-6.rkt#L89
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