bcpow

(PHP 4, PHP 5, PHP 7)

bcpow — Raise an arbitrary precision number to another

Description

string bcpow ( string $left_operand , string $right_operand [, int $scale = 0 ] )

Raise left_operand to the power right_operand.

Parameters

left_operand: The left operand, as a string.
right_operand: The right operand, as a string.
scale: This optional parameter is used to set the number of digits after the decimal place in the result. If omitted, it will default to the scale set globally with the bcscale() function, or fallback to 0 if this has not been set.

Return Values

Returns the result as a string.

Examples

Example #1 bcpow() example


<?php

echo bcpow('4.2', '3', 2); // 74.08

?>

Notes

Note:
bcpow() may return a result with fewer digits after the decimal point than the scale parameter would indicate. This only occurs when the result doesn't require all of the precision allowed by the scale. For example:

Example #2 bcpow() scale example

<?php echo bcpow('5', '2', 2); // prints "25", not "25.00" ?>

User Contributed Notes

thomas at tgohome dot com

6 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));

}





?>

Anonymous

11 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.

Michael Bailey (jinxidoru at byu dot net)