On Mon, Jun 6, 2011 at 17:45, Robby Findler <ro...@eecs.northwestern.edu> wrote: > On Mon, Jun 6, 2011 at 8:24 AM, Erich Rast <er...@snafu.de> wrote: >> I had something similar in mind but was wondering about the >> space-efficiency of a vector of booleans. Does the compiler represent >> this as a memory area where each boolean corresponds to a single bit? > > It does not. The simplest way to do something like that in Racket is > to use an exact integer to represent your set and use the bitwise > operations to adjust the set (if the set has 30 or fewer members (62 > on a 64 bit build) then there won't be any allocation for new sets).
Attached there is an implementation of compact boolean vectors that I used in a program of mine. This was good enough for my needs and I have not tried alternative implementations. Note that in this implementation there's no guarantee that (= (boolean-vector-length (make-boolean-vector n)) n) but only that (>= (boolean-vector-length (make-boolean-vector n)) n) Suggestions for improvements, of course, are welcome. Cheers P.
boolean-vectors.rkt
Description: Binary data
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