Yuichi Nishiwaki
commit
5323149faf
|
|
@ -0,0 +1,182 @@
|
|||
(define-library (srfi 60)
|
||||
(import (scheme base)
|
||||
(srfi 1))
|
||||
|
||||
;; # Bitwise Operations
|
||||
(define (logand . args)
|
||||
(letrec ((lgand
|
||||
(lambda (x y)
|
||||
(if (or (zero? x) (zero? y))
|
||||
0
|
||||
(+ (* (lgand (floor/ x 2) (floor/ y 2)) 2)
|
||||
(if (or (even? x) (even? y)) 0 1))))))
|
||||
(fold lgand -1 args)))
|
||||
|
||||
(define bitwise-and logand)
|
||||
|
||||
(define (logior . args)
|
||||
(letrec ((lgior
|
||||
(lambda (x y)
|
||||
(cond
|
||||
((= x y) x)
|
||||
((zero? x) y)
|
||||
((zero? y) x)
|
||||
(else
|
||||
(+ (* (lgior (truncate-quotient x 2)
|
||||
(truncate-quotient y 2))
|
||||
2)
|
||||
(if (and (even? x) (even? y)) 0 1)))))))
|
||||
(fold lgior 0 args)))
|
||||
|
||||
(define bitwise-ior logior)
|
||||
|
||||
(define (logxor . args)
|
||||
(letrec ((lgxor
|
||||
(lambda (x y)
|
||||
(cond
|
||||
((zero? x) y)
|
||||
((zero? y) x)
|
||||
(else
|
||||
(+ (* (lgxor (floor/ x 2) (floor/ y 2)) 2)
|
||||
(if (even? x)
|
||||
(if (even? y) 0 1)
|
||||
(if (even? y) 1 0))))))))
|
||||
(fold lgxor 0 args)))
|
||||
|
||||
(define bitwise-xor logxor)
|
||||
|
||||
(define (lognot n)
|
||||
(- -1 n))
|
||||
|
||||
(define bitwise-not lognot)
|
||||
|
||||
(define (bitwise-if mask n0 n1)
|
||||
(logior (logand mask n0)
|
||||
(logand (lognot mask) n1)))
|
||||
|
||||
(define bitwise-merge bitwise-if)
|
||||
|
||||
(define (logtest j k)
|
||||
(not (zero? (logand j k))))
|
||||
|
||||
(define any-bits-set? logtest)
|
||||
|
||||
;; # Integer Properties
|
||||
(define (logcount n)
|
||||
(letrec ((lgcnt
|
||||
(lambda (n)
|
||||
(if (zero? n) 0
|
||||
(+ (lgcnt (floor/ n 2))
|
||||
(if (even? n) 0 1))))))
|
||||
(if (negative? n)
|
||||
(lgcnt (lognot n))
|
||||
(lgcnt n))))
|
||||
|
||||
(define bit-count logcount)
|
||||
|
||||
(define (integer-length n)
|
||||
(let loop ((n n) (count 0))
|
||||
(if (zero? n)
|
||||
count
|
||||
(loop (floor/ n 2) (+ count 1)))))
|
||||
|
||||
(define (log2-binary-factors n)
|
||||
(+ -1 (integer-length (logand n (- n)))))
|
||||
|
||||
(define first-set-bit log2-binary-factors)
|
||||
|
||||
;; # Bit Within Word
|
||||
(define (logbit? index n)
|
||||
(logtest (expt 2 index) n))
|
||||
|
||||
(define bit-set? logbit?)
|
||||
|
||||
(define (copy-bit index from bit)
|
||||
(if bit
|
||||
(logior from (expt 2 index))
|
||||
(logand from (lognot (expt 2 index)))))
|
||||
|
||||
|
||||
;; # Field of Bits
|
||||
(define (ash n count)
|
||||
(if (negative? count)
|
||||
(let ((k (expt 2 (- count))))
|
||||
(if (negative? n)
|
||||
(+ -1 (truncate-quotient (+ 1 n) k))
|
||||
(truncate-quotient n k)))
|
||||
(* (expt 2 count) n)))
|
||||
|
||||
(define arithmetic-shift ash)
|
||||
|
||||
(define (bit-field n start end)
|
||||
(logand (lognot (ash -1 (- end start)))
|
||||
(ash n (- start))))
|
||||
|
||||
(define (copy-bit-field to from start end)
|
||||
(bitwise-if (ash (lognot (ash -1 (- end start))) start)
|
||||
(ash from start)
|
||||
to))
|
||||
|
||||
(define (rotate-bit-field n count start end)
|
||||
(let* ((width (- start end))
|
||||
(count (floor-remainder count width))
|
||||
(mask (lognot (ash -1 width)))
|
||||
(zn (logand mask (ash n (- start)))))
|
||||
(logior (ash (logior (logand mask (ash zn count))
|
||||
(ash zn (- count width)))
|
||||
start)
|
||||
(logand (lognot (ash mask start)) n))))
|
||||
|
||||
(define (reverse-bit-field n start end)
|
||||
(letrec ((bit-reverse
|
||||
(lambda (k n)
|
||||
(let loop ((m (if (negative? n) (lognot n) n))
|
||||
(k (- k 1))
|
||||
(rvs 0))
|
||||
(if (negative? k)
|
||||
(if (negative? n) (lognot rvs) rvs)
|
||||
(loop (ash m -1)
|
||||
(- k 1)
|
||||
(logior (ash rvs 1) (logand 1 m))))))))
|
||||
(let* ((width (- start end))
|
||||
(mask (lognot (ash -1 width)))
|
||||
(zn (logand mask (ash n (- start)))))
|
||||
(logior (ash (bit-reverse width zn) start)
|
||||
(logand (lognot (ash mask start)) n)))))
|
||||
|
||||
;; Bits as Booleans
|
||||
(define (integer->list k . len)
|
||||
(let ((len (if (null? len) (integer-length k) len)))
|
||||
(let loop ((k k) (len len) (acc '()))
|
||||
(if (or (zero? k) (zero? len))
|
||||
acc
|
||||
(loop (floor/ k 2) (- len 1) (cons (if (even? k) #f #t) acc))))))
|
||||
|
||||
(define (list->integer lst)
|
||||
(let loop ((lst lst) (acc 0))
|
||||
(if (null? lst)
|
||||
acc
|
||||
(loop (cdr lst) (+ (* acc 2) (if (car lst) 1 0))))))
|
||||
|
||||
(define (booleans->integer . args)
|
||||
(list->integer args))
|
||||
|
||||
(export logand bitwise-and
|
||||
logior bitwise-ior
|
||||
logxor bitwise-xor
|
||||
lognot bitwise-not
|
||||
bitwise-if bitwise-merge
|
||||
logtest any-bits-set?
|
||||
logcount bit-count
|
||||
integer-length
|
||||
log2-binary-factors first-set-bit
|
||||
logbit? bit-set?
|
||||
copy-bit
|
||||
bit-field
|
||||
copy-bit-field
|
||||
ash arithmetic-shift
|
||||
rotate-bit-field
|
||||
reverse-bit-field
|
||||
integer->list
|
||||
list->integer
|
||||
booleans->integer))
|
||||
Loading…
Reference in New Issue