bcpow

(PHP 4, PHP 5, PHP 7)

bcpowRaise an arbitrary precision number to another

Опис

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

Raise left_operand to the power right_operand.

Параметри

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().

Значення, що повертаються

Returns the result as a string.

Приклади

Приклад #1 bcpow() example

<?php

echo bcpow('4.2''3'2); // 74.08

?>

Примітки

Зауваження:

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:

Приклад #2 bcpow() scale example

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

Прогляньте Також

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

add a note add a note

User Contributed Notes 3 notes

up
-2
thomas at tgohome dot com
12 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));
}


?>
up
-2
Anonymous
17 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.
up
-2
Michael Bailey (jinxidoru at byu dot net)
17 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
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