[HARLEQUIN][Common Lisp HyperSpec (TM)] [Previous][Up][Next]



logand &rest integers => result-integer

logandc1 integer-1 integer-2 => result-integer

logandc2 integer-1 integer-2 => result-integer

logeqv &rest integers => result-integer

logior &rest integers => result-integer

lognand integer-1 integer-2 => result-integer

lognor integer-1 integer-2 => result-integer

lognot integer => result-integer

logorc1 integer-1 integer-2 => result-integer

logorc2 integer-1 integer-2 => result-integer

logxor &rest integers => result-integer

Arguments and Values:


integer---an integer.

integer-1---an integer.

integer-2---an integer.

result-integer---an integer.


The functions logandc1, logandc2, logand, logeqv, logior, lognand, lognor, lognot, logorc1, logorc2, and logxor perform bit-wise logical operations on their arguments, that are treated as if they were binary.

The next figure lists the meaning of each of the functions. Where an `identity' is shown, it indicates the value yielded by the function when no arguments are supplied.

Function  Identity  Operation performed                         
logandc1  ---       and complement of integer-1 with integer-2  
logandc2  ---       and integer-1 with complement of integer-2  
logand    -1        and                                         
logeqv    -1        equivalence (exclusive nor)                 
logior    0         inclusive or                                
lognand   ---       complement of integer-1 and integer-2       
lognor    ---       complement of integer-1 or integer-2        
lognot    ---       complement                                  
logorc1   ---       or complement of integer-1 with integer-2   
logorc2   ---       or integer-1 with complement of integer-2   
logxor    0         exclusive or                                

Figure 12-18. Bit-wise Logical Operations on Integers

Negative integers are treated as if they were in two's-complement notation.


 (logior 1 2 4 8) =>  15
 (logxor 1 3 7 15) =>  10
 (logeqv) =>  -1
 (logand 16 31) =>  16
 (lognot 0) =>  -1
 (lognot 1) =>  -2
 (lognot -1) =>  0
 (lognot (1+ (lognot 1000))) =>  999

;;; In the following example, m is a mask.  For each bit in
;;; the mask that is a 1, the corresponding bits in x and y are
;;; exchanged.  For each bit in the mask that is a 0, the 
;;; corresponding bits of x and y are left unchanged.
 (flet ((show (m x y)
          (format t "~%m = #o~6,'0O~%x = #o~6,'0O~%y = #o~6,'0O~%"
                  m x y)))
   (let ((m #o007750)
         (x #o452576)
         (y #o317407))
     (show m x y)
     (let ((z (logand (logxor x y) m)))
       (setq x (logxor z x))
       (setq y (logxor z y))
       (show m x y))))
>>  m = #o007750
>>  x = #o452576
>>  y = #o317407
>>  m = #o007750
>>  x = #o457426
>>  y = #o312557
=>  NIL

Side Effects: None.

Affected By: None.

Exceptional Situations:

Should signal type-error if any argument is not an integer.

See Also:



(logbitp k -1) returns true for all values of k.

Because the following functions are not associative, they take exactly two arguments rather than any number of arguments.

 (lognand n1 n2) ==  (lognot (logand n1 n2))
 (lognor n1 n2) ==  (lognot (logior n1 n2))
 (logandc1 n1 n2) ==  (logand (lognot n1) n2)
 (logandc2 n1 n2) ==  (logand n1 (lognot n2))
 (logiorc1 n1 n2) ==  (logior (lognot n1) n2)
 (logiorc2 n1 n2) ==  (logior n1 (lognot n2))
 (logbitp j (lognot x)) ==  (not (logbitp j x))

[Starting Points][Contents][Index][Symbols][Glossary][Issues]
Copyright 1996, The Harlequin Group Limited. All Rights Reserved.