----- Original Message -----
From: "Satyam" <Satyam@xxxxxxxxxxxxx>
<pre><?php
$n = 7;
for ($i = 1; $i< $n;$i <<=1) if ($i & $n) $a[] = $i;
// put it in an array or do whatever, $i contains the parts.
Sorry, the above fails for numbers which are powers of two, it should have
been:
for ($i = 1; $i <= $n;$i <<=1) if ($i & $n) echo "$i<br />";
(Notice less than or equal in the while part)
Satyam
var_dump($a);
?>
</pre>
----- Original Message -----
From: "Richard Lynch" <ceo@xxxxxxxxx>
To: "Jon Anderson" <jon@xxxxxxxxxxxxxxxxxx>
Cc: "blackwater dev" <blackwaterdev@xxxxxxxxx>;
<php-general@xxxxxxxxxxxxx>
Sent: Friday, January 26, 2007 12:29 AM
Subject: Re: bit wise math? Is there a function to easily return the
bits?
On Thu, January 25, 2007 1:34 pm, Jon Anderson wrote:
function bits($num) {
$bit_array = str_split(strrev(decbin(intval($num))));
$val_array = array();
foreach ($bit_array as $pow => $bit) {
if ($val = $bit * pow(2,$pow))
$val_array[] = $val;
}
return($val_array);
}
(I wanted to see if I could write it in few LOC.) I wonder if there's
a
faster way...
//these might be marginally faster...
function bits($num){
$bits = array();
$bin = decbin(intval($num));
$v = 1;
for ($b = strlen($bin) - 1; $b >= 0; $b--){
if ($bin[$b] === '1') $bits[] = $v;
$v = $v * 2;
}
return $bits;
}
function bits($num){
$num = (int) $num;
$v = 1;
$bits = array();
while ($v <= $num){
if ($v & $num) $bits[] = $v;
$v = $v * 2;
}
return $bits;
}
I suspect there is a much faster way, somewhere, somehow...
jon
blackwater dev wrote:
Is there a php function I can call to pass in a number and get the
values
returned?
For example, pass in 7 and get 1,2,4 ?
Thanks!
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Know what I want?
I want you to buy a CD from some starving artist.
http://cdbaby.com/browse/from/lynch
Yeah, I get a buck. So?
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