Re: bit wise math? Is there a function to easily return the bits?

["Richard Lynch" <ceo@xxxxxxxxx>]

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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