(PHP 4, PHP 5, PHP 7, PHP 8)
bcpow — Raise an arbitrary precision number to another
Raise num to the power
exponent.
numThe base, as a string.
exponent
The exponent, as a string. If the exponent is non-integral, it is truncated.
The valid range of the exponent is platform specific, but is at least
-2147483648 to 2147483647.
scaleНеобов'язковий параметр,
яким вказується кількість знаків після крапки в результаті. Якщо опущено,
застосовується межа, що встановлена глобально функцією
bcscale(), або ж 0, якщо межа ще не
встановлена.
Returns the result as a string.
| Версія | Опис |
|---|---|
| 7.3.0 | bcpow() now returns numbers with the requested scale. Formerly, the returned numbers may have omitted trailing decimal zeroes. |
Приклад #1 bcpow() example
<?php
echo bcpow('4.2', '3', 2); // 74.08
?>Зауваження:
Before PHP 7.3.0 bcpow() may return a result with fewer digits after the decimal point than the
scaleparameter would indicate. This only occurs when the result doesn't require all of the precision allowed by thescale. For example:Приклад #2 bcpow() scale example
<?php
echo bcpow('5', '2', 2); // prints "25", not "25.00"
?>
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<?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));
}
?>