bcmul
<?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));
}
?>
bcpow
(PHP 4, PHP 5)
bcpow — Raise an arbitrary precision number to another
Descrierea
string bcpow
( string $left_operand
, string $right_operand
[, int $scale
] )
Raise left_operand to the power right_operand.
Parametri
- left_operand
-
The left operand, as a string.
- right_operand
-
The right operand, as a string.
- scale
-
Acest parametru opțional este utilizat pentru a stabili numărul cifrelor după virgulă din rezultat. De asemenea puteți să stabiliți parametrul global scale pentru toate funcțiile utilizând bcscale().
Valorile întoarse
Returns the result as a string.
Exemple
Example #1 bcpow() example
<?php
echo bcpow('4.2', '3', 2); // 74.08
?>
Note
Notă:
bcpow() may return a result with fewer digits after the decimal point than the scale parameter would indicate. This only occurs when the result doesn't require all of the precision allowed by the scale. For example:
Example #2 bcpow() scale example
<?php
echo bcpow('5', '2', 2); // prints "25", not "25.00"
?>
Vedeți de asemenea
- bcpowmod() - Raise an arbitrary precision number to another, reduced by a specified modulus
- bcsqrt() - Get the square root of an arbitrary precision number
add a note
User Contributed Notes
bcpow
thomas at tgohome dot com
13-Jul-2009 12:19
11-Feb-2005 01:58
Well, if bcpow has limits, then this should work:
<?php
function bcpow_($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)
09-Aug-2004 05:42
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