added bit-vector <-> {string,list} operations
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@ -27,24 +27,27 @@
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(fxvector-set! words q (- (expt 2 r) 1)))
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(bit-vector words size word-size))
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(define (bit-vector* . init-bits)
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(define bv (make-bit-vector (length init-bits)))
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(for ([i (in-naturals)]
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[b (in-list init-bits)])
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(bit-vector-set! bv i b))
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bv)
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(define bit-vector*
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(let ([bit-vector
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(lambda init-bits
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(list->bit-vector init-bits))])
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bit-vector))
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(define (bit-vector-ref bv n
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[default (bad-index-error 'bit-vector-ref n)])
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(define not-given (gensym))
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(define (bit-vector-ref bv n [default not-given])
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(unless (exact-nonnegative-integer? n)
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(raise-type-error 'bit-vector-ref "exact nonnegative integer" n))
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(cond
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[(>= n (bit-vector-size bv))
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(if (procedure? default)
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(default)
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default)]
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[else
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(unsafe-bit-vector-ref bv n)]))
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(raise-argument-error 'bit-vector-ref "exact-nonnegative-integer?" n))
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(cond [(< n (bit-vector-size bv))
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(unsafe-bit-vector-ref bv n)]
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[else
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(cond [(eq? default not-given)
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(raise-range-error 'bit-vector-ref
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"bit-vector"
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"" n bv 0 (sub1 (bit-vector-size bv)))]
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[(procedure? default)
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(default)]
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[else default])]))
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(define (unsafe-bit-vector-ref bv n)
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(define-values (wi bi) (quotient/remainder n bits-in-a-word))
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@ -97,6 +100,37 @@
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(for/sum ([fx (in-fxvector (bit-vector-words bv))])
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(fxpopcount fx)))
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(define (bit-vector->list bv)
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(define len (bit-vector-size bv))
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(let loop ([i 0])
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(cond [(< i len)
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(cons (unsafe-bit-vector-ref bv i)
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(loop (add1 i)))]
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[else null])))
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(define (list->bit-vector init-bits)
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(define len (length init-bits))
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(define bv (make-bit-vector len))
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(for ([i (in-range len)]
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[b (in-list init-bits)])
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(bit-vector-set! bv i b))
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bv)
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(define (bit-vector->string bv)
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(let* ([l (bit-vector-size bv)]
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[s (make-string l)])
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(for ([i (in-range l)])
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(string-set! s i (if (unsafe-bit-vector-ref bv i) #\1 #\0)))
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s))
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(define (string->bit-vector s)
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(let* ([bv (make-bit-vector (string-length s) #f)])
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(for ([i (in-range (string-length s))])
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(when (eqv? (string-ref s i) #\1)
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(bit-vector-set! bv i #t)))
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bv))
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(define-vector-wraps "bit-vector"
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bit-vector? bit-vector-length bit-vector-ref bit-vector-set! make-bit-vector
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unsafe-bit-vector-ref bit-vector-set! bit-vector-length
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@ -171,6 +205,14 @@
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(-> bit-vector? any)]
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(rename bit-vector-copy*
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bit-vector-copy
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(-> bit-vector? bit-vector?)))
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(-> bit-vector? bit-vector?))
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[bit-vector->list
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(-> bit-vector? (listof boolean?))]
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[list->bit-vector
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(-> (listof boolean?) bit-vector?)]
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[bit-vector->string
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(-> bit-vector? string?)]
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[string->bit-vector
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(-> (and/c string? #rx"^[01]*$") bit-vector?)])
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(provide in-bit-vector for/bit-vector for*/bit-vector)
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@ -32,17 +32,19 @@ Creates a new bit-vector of size @racket[size]. All elements
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are initialized to @racket[fill].
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@examples[#:eval the-eval
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(define bv (make-bit-vector 3))
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(bit-vector-ref bv 1)]
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(bit-vector-ref (make-bit-vector 3) 2)
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(bit-vector-ref (make-bit-vector 3 #t) 2)
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]
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}
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@defproc[(bit-vector [elem boolean?] ...)
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bit-vector?]{
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Creates a new bit-vector containing each @racket[elem] in order.
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@examples[#:eval the-eval
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(define bv (bit-vector #f #t #f))
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(bit-vector-ref bv 1)]
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(bit-vector-ref (bit-vector #f #t #f) 1)
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]
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}
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@defproc[(bit-vector? [v any/c]) boolean?]{
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@ -56,8 +58,13 @@ Returns @racket[#t] if @racket[v] is a bit-vector, @racket[#f] otherwise.
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any/c]{
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Returns the element at index @racket[index], if @racket[index] is less
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than @racket[(bit-vector-length gv)]. Otherwise, @racket[default] is
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than @racket[(bit-vector-length bv)]. Otherwise, @racket[default] is
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invoked if it is a procedure, returned otherwise.
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@examples[#:eval the-eval
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(bit-vector-ref (bit-vector #f #t) 1)
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(bit-vector-ref (bit-vector #f #t) 5 'not-there)
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]
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}
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@defproc[(bit-vector-set!
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@ -68,9 +75,13 @@ invoked if it is a procedure, returned otherwise.
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void?]{
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Sets the value at index @racket[index] to be @racket[value].
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@examples[#:eval the-eval
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(define bv (bit-vector #f #t #f))
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(bit-vector-ref bv 1)]
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(define bv (bit-vector #f #t))
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(bit-vector-ref bv 0)
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(bit-vector-set! bv 0 #t)
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(bit-vector-ref bv 0)
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]
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}
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@defproc[(bit-vector-length [bv bit-vector?])
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@ -83,6 +94,7 @@ Returns the number of items in the bit-vector @racket[bv].
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exact-nonnegative-integer?]{
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Returns the number of set bits in the bit-vector @racket[bv].
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@examples[#:eval the-eval
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(bit-vector-popcount (bit-vector #f #t #t))]
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}
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@ -103,10 +115,9 @@ to @racket[end] (exclusive).
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Returns a sequence whose elements are the elements of the bit-vector
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@racket[bv]. Mutation of @racket[bv] while the sequence is running
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changes the elements produced by the sequence. To obtain a sequence
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from a snapshot of @racket[gv], use @racket[(in-vector
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from a snapshot of @racket[bv], use @racket[(in-bit-vector
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(bit-vector-copy bv))] instead.
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@examples[#:eval the-eval
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(define bv (bit-vector #f #t #f))
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(for/list ([x (in-bit-vector bv)]) x)]
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@ -133,11 +144,13 @@ the value of @racket[fill-expr], which defaults to @racket[#f] (i.e.,
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the default argument of @racket[make-bit-vector]).
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@examples[#:eval the-eval
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(define (to-list bv) (for/list ([x bv]) x))
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(to-list (for/bit-vector ([i '(1 2 3)]) (odd? i)))
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(to-list (for/bit-vector #:length 2 ([i '(1 2 3)]) (odd? i)))
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(to-list (for/bit-vector #:length 4 ([i '(1 2 3)]) (odd? i)))
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(to-list
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(bit-vector->list
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(for/bit-vector ([i '(1 2 3)]) (odd? i)))
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(bit-vector->list
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(for/bit-vector #:length 2 ([i '(1 2 3)]) (odd? i)))
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(bit-vector->list
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(for/bit-vector #:length 4 ([i '(1 2 3)]) (odd? i)))
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(bit-vector->list
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(for/bit-vector #:length 4 #:fill #t ([i '(1 2 3)]) (odd? i)))
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]
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@ -152,4 +165,20 @@ mutate a shared bit-vector.}
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Like @racket[for/bit-vector] but with the implicit nesting of @racket[for*].
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}
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@deftogether[[
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@defproc[(bit-vector->list [bv bit-vector?]) (listof boolean?)]
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@defproc[(list->bit-vector [bits (listof boolean?)]) bit-vector?]
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@defproc[(bit-vector->string [bv bit-vector?]) (and/c string? #rx"^[01]*$")]
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@defproc[(string->bit-vector [s (and/c string? #rx"^[01]*$")]) bit-vector?]
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]]{
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Converts between bit-vectors and their representations as lists and
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strings.
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@examples[#:eval the-eval
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(bit-vector->list (string->bit-vector "100111"))
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(bit-vector->string (list->bit-vector '(#t #f #t #t)))
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]
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}
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@close-eval[the-eval]
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@ -114,3 +114,13 @@
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(for ([ws (in-list '(8 30 62))])
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(for ([i (in-range 10)])
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(test (* ws 10))))))
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(test-case "bit-vector string->list"
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(let ([bitstrings '("0" "1" "10" "11" "1010110011100011110000")])
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(for ([s (in-list bitstrings)])
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(check-equal? (bit-vector->string (string->bit-vector s)) s)
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(let ([bitlist (for/list ([c (in-string s)]) (eqv? c #\1))])
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(check-equal? (bit-vector->list (string->bit-vector s))
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bitlist)
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(check-equal? (string->bit-vector s)
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(list->bit-vector bitlist))))))
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