Definition: | atom x3 = and_bits(atom x1, atom x2) |
Description: |
Perform the logical AND operation on corresponding bits in x1 and x2. A bit in x3 will be 1 only if the corresponding bits in x1 and x2 are both 1. Commonly used to test bit settings in a bit-field (see example 1). |
Comments: |
This function may be applied to an atom or sq_and_bits() to all elements of a
sequence. The rules for sequence operations apply.
The arguments must be representable as 32-bit numbers, either signed or unsigned. If you intend to manipulate full 32-bit values, you should declare your variables as atom, rather than integer. The integer type is limited to 31-bits. Results are treated as signed numbers. They will be negative when the highest-order bit is 1. Caution: many cryptographic functions and the like require unsigned 32-bit integers, especially when bit-shifting. Sometimes a poke4() followed by a peek4u() might help. To understand the binary representation of a number you should display it in hexadecimal notation. Use the %x format of printf(). |
Example 1: |
if and_bits(flags,XPAD) then width-=XPADDING end if -- apply width padding |
Example 2: |
a = and_bits(#0F0F0000, #12345678) -- a is #02040000 |
Example 3: |
s = sq_and_bits(#FF, {#123456, #876543, #2211}) -- s is {#56, #43, #11} |
Example 4: |
a = and_bits(#FFFFFFFF, #FFFFFFFF) -- a is -1 -- Note that #FFFFFFFF is a positive number, -- but the result of a bitwise logical operation is interpreted -- as a signed 32-bit number, so it is negative. |
See Also: | or_bits, xor_bits, not_bits, int_to_bits |