Re: [PHP-GENERAL] Powers Gone Wrong?

Hi Jonathan,

There is no exponentiation operator in PHP.  To raise one number to the 
power of another, you must use either the pow function.

The >> and << operators are used for bitwise shift.

HTH,

Zak

At 09:13 PM 6/2/00 +0100, Jonathan Wright \(DjNA\) wrote:
>Hiya,
>
>I'm a bit of a newbie to PHP (although I know quite a bit of Perl), and I
>wrote some code to test out Powers (<<). It all seams to be working fine,
>until it gets to 2^0 (two to the power zero). It should be 1 and it's giving
>me 0.
>
>Written into the code is a tester, for converting a number to binary. It's a
>prototype for a selection I'm writing. Depending on what someone what's they
>add up all of the numbers of the options, and this will decode them. If you
>call powers.php?power=5, bit 2 and bit 0 should show positive, so selection
>1 and 4 will run. If you call 6, bit 2 and 1 should show positive, but bit 0
>does as well, as it's coming out 0.
>
>This is my fault, or a possible bug? I think I've got it right. All the
>other powers (bit 8 = 256, bit 16 = 65,536) seam correct, but why 0?
>
>Thanks.
>
>---powers.php----------------------------------
>
>
><?php
>
>$binary="";
>
>for ($i=16; $i>=0; $i--)
>   { echo "2<<".$i." = ".(2 << ($i-1))."\n   bit ".$i;
>       if (($power-(2 << ($i-1))) >= 0)
>         { $power -= (2 << ($i-1));
>           $binary .= "1";
>          echo " -> Positive\n"; }
>       else
>         { echo " -> Negative\n";
>           $binary .= "0";  }
>   }
>echo "Binary : ".$binary."\n\n\n";
>
>?>
>----------------------------------------------- Give it a go. I can't see 
>the problem, unless it's my understanding ;-) Thanks again. - - - - - - - 
>- - - - - - - - - - - - - Jonathan Wright [DjNA] [email protected] 
>www.djna.fsnet.co.uk ICQ [21961373] -- PHP General Mailing List 
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