bcpow

(PHP 4, PHP 5)

bcpow — Effettua l'elevamento a potenza

Descrizione

string bcpow ( string $x , string $y [, int $precisione ] )

Eleva x alla potenza y. Il parametro opzionale precisione può essere usato per impostare il numero di cifre dopo il punto decimale nel risultato.

Esempi

Example #1 bcpow() example


<?php

echo bcpow(4.2, 3, 2); // 74.08

?>

Vedere anche:

bcpowmod() e bcsqrt().

bcpowmod

bcmul

[edit] Last updated: Fri, 17 May 2013

add a note User Contributed Notes bcpow - [3 notes]

down

thomas at tgohome dot com ¶

3 years ago


<?php





bcscale(100);





/*


 * Computes the natural logarithm using a series.


 * @author Thomas Oldbury.


 * @license Public domain.


 */


function bcln($a, $iter = 10)


{


    $result = "0.0";


    


    for($i = 0; $i < $iter; $i++)


    {


        $pow = (1 + (2 * $i));


        $mul = bcdiv("1.0", $pow);


        $fraction = bcmul($mul, bcpow(bcsub($a, "1.0") / bcadd($a, "1.0"), $pow));


        $result = bcadd($fraction, $result);


    }


    


    return bcmul("2.0", $result);


}





/*


 * Computes the base2 log using baseN log.


 * @note Requires above functions.


 * @author Thomas Oldbury.


 * @license Public domain.


 */


function bclog2($a, $iter = 10)


{


    return bcdiv(bcln($a, $iter), bcln("2", $iter));


}





/*


 * Computes the base10 log using baseN log.


 * @note Requires above functions.


 * @author Thomas Oldbury.


 * @license Public domain.


 */


function bclog10($a, $iter = 10)


{


    return bcdiv(bcln($a, $iter), bcln("10", $iter));


}








?>

down

Michael Bailey (jinxidoru at byu dot net) ¶

8 years ago


bcpow() only supports exponents less than or equal to 2^31-1.  Also, bcpow() does not support decimal numbers.  If you have scale set to 0, then the exponent is converted to an interger; otherwise an error is generated.



--

Michael Bailey

http://www.jinxidoru.com

down

Anonymous ¶

8 years ago


Well, if bcpow has limits, then this should work:

<?php

function bcpow_($num, $power) {

    $awnser = "1";

    while ($power) {

        $awnser = bcmul($awnser, $num, 100);

        $power = bcsub($power, "1");

    }

    return rtrim($awnser, '0.');

}

?>

Just that $power cannot have decimal digits in it.

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