bitwise function needed

[sfullman]

Hi There,

I DID do some searching but bitwise operations are still new to me and didn't find anything out.

Doubles are 1,2,4,8,16,32,64, etc. - these are the binary 0 and 1 places. That much I understand.

So, here is a function I'd like to write elegantly,

function bitwise_op($body, $place, $op='write'){
//function here, $op can also be 'read' - see below

}

some examples:

bitwise_op(7, 2); //returns 7 since 2 is already there
bitwise_op(5, 2); //returns 7 because 2 was added to 1+4
bitwise_op(7,-2); //returns 5 because the 2 was present and was subtracted
bitwise_op(5,-2); //returns 5 because the 2 was NOT present and couldn't be subtracted
bitwise_op(15,4, 'read'); //returns true because 4 is in 1+2+4+8
bitwise_op(30,1, 'read'); //returns false because 1 is not in 2+4+8+16

This is probably very easy - and I'd be glad to work with hints, thanks.

Samuel

[laserlight]

You can consider:

<?php
function bitwise_read($body, $place) {
	return ($body & $place) != 0;
}

function bitwise_write($body, $place) {
	if ($place < 0) {
		return ($body & abs($place)) ? ($body + $place) : $body;
	} else {
		return ($body & $place) ? $body : ($body + $place);
	}
}

echo bitwise_write(7, 2) . "<br />\n";
echo bitwise_write(5, 2) . "<br />\n";
echo bitwise_write(7, -2) . "<br />\n";
echo bitwise_write(5, -2) . "<br />\n";
echo (bitwise_read(15, 4) ? "true" : "false") . "<br />\n";
echo (bitwise_read(30, 1) ? "true" : "false") . "<br />\n";
?>

Read the PHP Manual on the bitwise operators.

[sfullman]

Thanks laserlight, and I wanted to comment that it works as a javscript function also, just remove the $ from the vars and change abs() to Math.abs().