Re^2: Bitwise and operator question

Replies are listed 'Best First'.
Re^3: Bitwise and operator question by FunkyMonk (Bishop) on Aug 09, 2007 at 14:55 UTC
Because... `Decimal Binary 123 01111011 4 00000100 ======== 00000000 when ANDed together` [download] The answer comes from ANDing the bits in the columns together. Bit 2 (third from the right) has a decimal value of 4 (because 2² = 4). Is that any clearer?	[reply] [d/l]
Re^3: Bitwise and operator question by mr_mischief (Monsignor) on Aug 09, 2007 at 15:12 UTC
Because it's a bitwise AND. `123 = 1111011 4 = 0000100 ^` [download] The operator '&' returns a value where each bit of one value is is ANDed against each bit of the other value. The marked digit is 1 for the value 4, and 0 for value 123. The rest of the digits are 1 for value 123 and 0 for 4. When you do an AND of each bit in this case, there are no bits which are 1 in both values. That's why you get a value with no bits set to 1, which is 0. It'll help if you stop thinking of '&' and '\|' as mathematical operators and thinking of them as boolean logical tests against vectors of bits, which is essentially what they are. From perlop: Bitwise And Binary "&" returns its operands ANDed together bit by bit. (See also "Integer Arithmetic" and "Bitwise String Operators".) Note that "&" has lower priority than relational operators, so for example the brackets are essential in a test like `print "Even\n" if ($x & 1) == 0;` [download] Bitwise Or and Exclusive Or Binary "\|" returns its operands ORed together bit by bit. (See also "Integer Arithmetic" and "Bitwise String Operators".) Binary "^" returns its operands XORed together bit by bit. (See also "Integer Arithmetic" and "Bitwise String Operators".) Note that "\|" and "^" have lower priority than relational operators, so for example the brackets are essential in a test like `print "false\n" if (8 \| 2) != 10;`	[reply] [d/l] [select]