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bcpow

(PHP 4, PHP 5)

bcpowRaise an arbitrary precision number to another

Описание

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

Raise left_operand to the power right_operand .

Список параметров

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. You can also set the global default scale for all functions by using bcscale().

Возвращаемые значения

Returns the result as a string.

Примеры

Пример #1 bcpow() example

<?php

echo bcpow('4.2''3'2); // 74.08

?>

Смотрите также

  • bcpowmod() - Raise an arbitrary precision number to another, reduced by a specified modulus
  • bcsqrt() - Get the square root of an arbitrary precision number


User Contributed Notes
bcpow
thomas at tgohome dot com
13-Jul-2009 07:19
<?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));
}


?>
11-Feb-2005 09:58
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)
10-Aug-2004 12:42
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
 

 
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