Caché ObjectScript Reference
$ZBOOLEAN


Bitwise logical operation function.
Synopsis
$ZBOOLEAN(arg1,arg2,bit_op)
$ZB(arg1,arg2,bit_op)
Parameters
$ZBOOLEAN performs the bitwise logical operation specified by
bit_op on two arguments,
arg1 and
arg2.
$ZBOOLEAN returns the results of the bitwise combination of
arg1 and
arg2, as specified by the
bit_op value. You can view the results using the
ZZDUMP command.
$ZBOOLEAN performs its operations on either character strings or numbers. For character strings, it performs logical AND and OR operations on each character in the string. For numbers, it performs a logical AND and OR operation on the entire number as a unit. To force the evaluation of a numeric string as a number, preface the string with a plus sign (+).
Note:
$ZBOOLEAN does not support Unicode characters with a value larger than ASCII 255. To apply
$ZBOOLEAN to a string of 16bit Unicode characters, you must first use
$ZWUNPACK, followed by
$ZBOOLEAN, followed by
$ZWPACK.
$ZBOOLEAN and
$BITLOGIC use different data formats. The results of one cannot be used as input to the other.
The bitwise operations includes 16 possible Boolean combinations of
arg1 and
arg2. The following table lists these combinations.
Where:
& is logical AND
! is logical OR
~ is logical NOT
^ is exclusive OR

An integer. A positive or negative whole decimal number of up to 18 digits. No characters other than the numbers 0–9 and, optionally, one or more leading plus and minus signs are permitted. Leading zeros are ignored.

A string. Enclosed in quotation marks, a string of any length with any contents is permitted. Note that the string “123” and the integer 123 are not the same. A null string is permitted, but if
arg2 is the null string,
$ZBOOLEAN always returns the value of
arg1, regardless of the
bit_op value.

A signed string. A string preceded by a plus or minus sign is parsed as an integer, regardless of the string’s contents. Signed strings are subject to the same length restriction as integers. A signed null string is equivalent to zero.
It is strongly recommended that
arg1 and
arg2 either both resolve to an integer or both resolve to a string. Generally,
arg1 and
arg2 should be the same data type; combining an integer and a string in a
$ZBOOLEAN operation does not give a useful result in most cases.
Parameters
arg1
The first argument in the bitwise logical expression. For strings, the length of the returned value is always the same as the length of this argument.
arg2
The second argument in the bitwise logical expression.
bit_op
The bitwise logical operation to be performed, specified as a numeric code from 0 to 15, inclusive. Because this code is handled as a bit mask, a value of 16=0, 17=1, 18=2, etc.
The
bit_op values 0 and 15 return a constant value, but they also evaluate the arguments. If
arg1 is an integer (or signed string),
bit_op 0 returns 0, and
bit_op 15 returns –1 (the one’s complement of 0.) If
arg1 is a string,
bit_op 0 returns a low value (hex 00) for each character in
arg1, and
bit_op 15 returns a high value (hex FF) for each character in
arg1. If
arg2 is the null string (""), both operations return the literal value of
arg1.
The
bit_op values 3, 5, 10 and 12 perform a logical operation on only one of the arguments, but they evaluate both arguments.

bit_op=3 always returns the value of
arg1, regardless of the value of
arg2.

bit_op=5 returns the value of
arg2 when the two arguments have the same data type. However if one argument is a string and the other argument is an integer (or signed string) results are unpredictable. If
arg2 is the null string
$ZBOOLEAN always returns the literal value of
arg1.

bit_op=10 returns the one’s complement value of
arg2 if both arguments are integers. If
arg1 is a string, the operation returns a high order character for each character in
arg1.. If
arg2 is a string, and
arg1 is an integer, the bitwise operation is performed on the
arg2 string. If
arg2 is the null string
$ZBOOLEAN always returns the literal value of
arg1.

bit_op=12 returns the one’s complement value of
arg1 if it is an integer (or signed string), for any value of
arg2 except the null string. If
arg1 is a string, the operation returns the one’s complement (as a hex value) of each character in
arg1. If
arg2 is the null string
$ZBOOLEAN always returns the literal value of
arg1.
The following three examples all illustrate the same AND operation. These examples AND the ASCII values of lowercase letters with the ASCII value of the underscore character, resulting in the ASCII values of the corresponding uppercase letters.
WRITE $ZBOOLEAN("abcd","_",1)
displays ABCD.
The lowercase "a" = [01100001] (ASCII decimal 97)
The underscore character "_" = [01011111] (ASCII decimal 95)
The uppercase "A" = [01000001] (ASCII decimal 65)
The following example performs the same AND operation as the previous example, but uses the ASCII decimal values of the arguments. The function $ASCII("a") returns the decimal value 97 for the first argument:
WRITE $ZBOOLEAN($ASCII("a"),95,1)
displays 65.
The following example performs the same AND operation, using a $CHAR value as the second argument:
WRITE $ZBOOLEAN("a",$CHAR(95),1)
displays A.
The following examples illustrate logical OR:
displays 1.
displays 1.
displays 3.
displays 2.
displays 3.
The following logical OR examples demonstrate the difference between string comparisons and number comparisons:
WRITE $ZBOOLEAN(64,255,7)
compares the two values as numbers and displays 255.
WRITE $ZBOOLEAN("64","255",7)
compares the two values as strings and displays 65.
WRITE $ZBOOLEAN(+"64",+"255",7)
the plus signs force the comparison of the two values as numbers, and displays 255.
The following examples illustrate exclusive OR:
displays 1.
displays 0.
displays 3.
displays 0.
displays 1.
WRITE $ZBOOLEAN(64,255,6)
displays 191.
The following example shows a 4byte entity with all bytes set to 1:
displays 1.
The following example will set x to 3 bytes with all bits set to 1:
SET x=$ZBOOLEAN("abc",0,15)
WRITE !,$LENGTH(x)
WRITE !,$ASCII(x,1)," ",$ASCII(x,2)," ",$ASCII(x,3)
The first WRITE displays 3; the second WRITE displays 255 255 255.
Integer Processing
Before
$ZBOOLEAN performs the bitwise operation, it interprets each numeric value as either an 8byte or a 4byte signed binary value, depending on size.
$ZBOOLEAN always interprets a numeric value as a series of bytes. The boolean operation uses these bytes as a string argument. The result type is the same as the type of
arg1.
If either
arg1 or
arg2 is numeric and cannot be represented as an 8byte signed integer (larger than 18 decimal digits), a <FUNCTION> error results. If both
arg1 and
arg2 are numeric and one of them requires 8 bytes to be represented, then both values are interpreted as 8byte binary values.
After the previous transformations are complete, the given Boolean combination is applied bit by bit to
arg1 and
arg2 to yield the result. The result returned is always the same length as
arg1 (after the above transformations of numeric data). If the length of
arg2 is less than the length of
arg1, then
arg2 is repeatedly combined with successive substrings of
arg1 in left to right fashion.
$ZBOOLEAN always interprets the numeric value as a series of bytes in littleendian order, with the loworder byte first, no matter what the native byte order of your machine is.
There are four possible states of any two bits being compared from within arg1 and arg2. The Boolean operation generates a true result (=1) if and only if bit_op has the bit mask shown in the table.
EQV and IMP Logical Operators
$ZBOOLEAN indirectly supports EQV and IMP logical operators. These logical operators are defined as follows:
See Also
Copyright © 19972019 InterSystems Corporation, Cambridge, MA