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# bcpowmod

(PHP 5)

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

## Description

string bcpowmod ( string x, string y, string modulus [, int scale] )

Use the fast-exponentiation method to raise x to the power y with respect to the modulus modulus. The optional scale can be used to set the number of digits after the decimal place in the result.

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

## 範例

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. ?>`

## 參考

bcpow() and bcmod().

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