CLHS: Function LOGAND, LOGANDC1, LOGANDC2...

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Function LOGAND, LOGANDC1, LOGANDC2, LOGEQV, LOGIOR, LOGNAND, LOGNOR, LOGNOT, LOGORC1, LOGORC2, LOGXOR

Syntax:

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:

integers---integers.

integer---an integer.

integer-1---an integer.

integer-2---an integer.

result-integer---an integer.

Description:

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.

Examples:

     (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:

boole

Notes:

`(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))

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