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On Thursday, April 10, 2003, at 04:40 AM, Michael Burschik wrote:
In addition to vector-unzip, SRFI-43 defines several "common unzippers", but fails to specify how their names relate to vector-unzip's argument n. As faras I can tell from the reference implementation, the following holds:(vector-unzipn vec) == (vector-unzip vec (- n 1)). If this is true, however,then the reference implementation incorrectly defines vector-unzip5 as (vector-unzip vec 5).
I've added specification for how the N in VECTOR-UNZIPn relates to how it
unzips. And actually, the statement: (vector-unzipN vec) == (vector-unzip vec (- N 1))is false. If you notice in the reference implementation, plain VECTOR-UNZIP already subtracts one from N to get the highest index to get a value from --
(define (vector-unzip vec i) (let loop ((vecs '()) (i (- i 1))) ;; ^^^^^^^^^^^ (if (negative? i) (apply values vecs) (loop (cons (vector-map (cut vector-ref <> i) vec)) vecs) (- i 1)))))Therefore, VECTOR-UNZIP1 would start getting stuff at index -1, but that's negative, so VECTOR-UNZIP1 would always return zero values. That isn't exactly
what you'd want.
Regards Michael Burschik