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bcpowmod

(PHP 5)

bcpowmod -- Raise an arbitrary precision number to another, reduced by a specified modulus

说明

string bcpowmod ( string left_operand, string right_operand, string modulus [, int scale] )

Use the fast-exponentiation method to raise left_operand to the power right_operand with respect to the modulus modulus.

参数

left_operand: The left operand, as a string.
right_operand: The right operand, as a string.
modulus: The modulus, 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().

返回值

Returns the result as a string, or NULL if modulus is 0.

注释

注意: Because this method uses the modulus operation, non-natural numbers may give unexpected results. A natural number is any positive non-zero integer.

范例

The following two statements are functionally identical. The bcpowmod() version however, executes in less time and can accept larger parameters.

<?php
$a = bcpowmod($x, $y, $mod);

$b = bcmod(bcpow($x, $y), $mod);

// $a and $b are equal to each other.

?>

参见

bcpow()

bcmod()

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