;;;
;;; logical.scm - logical (bitwise) operations.  to be autoloaded.
;;;  
;;;   Copyright (c) 2000-2011  Shiro Kawai  <shiro@acm.org>
;;;   
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;;;   are met:
;;;   
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;;;  
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;;;      documentation and/or other materials provided with the distribution.
;;;  
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;;;      software without specific prior written permission.
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(select-module gauche)

;; SLIB compatible interface.

(define (logtest . args)  ;; can be optimized for two-arg case
  (not (zero? (apply logand args))))

(define (logbit? index n)
  (not (zero? (logand n (ash 1 index)))))

(define (copy-bit index from bit)
  (if bit
      (logior (ash 1 index) from)
      (logand (lognot (ash 1 index)) from)))

(define (bit-field n start end)
  (check-arg integer? start)
  (check-arg integer? end)
  (if (< start end)
      (let ((mask (- (ash 1 (- end start)) 1)))
        (logand (ash n (- start)) mask))
      0))

(define (copy-bit-field to start end from)
  (check-arg integer? start)
  (check-arg integer? end)
  (if (< start end)
      (let ((mask (- (ash 1 (- end start)) 1)))
        (logior (logand to (lognot (ash mask start)))
                (ash (logand from mask) start)))
      from))

