Raise an arbitrary precision number to another, reduced by a specified modulus (original) (raw)
bcpowmod
(PHP 5, PHP 7)
bcpowmod — Raise an arbitrary precision number to another, reduced by a specified modulus
Description
bcpowmod ( string $base , string $exponent , string $modulus [, int $scale = 0 ] ) : string
Parameters
base
The base, as an integral string (i.e. the scale has to be zero).
exponent
The exponent, as an non-negative, integral string (i.e. the scale has to be zero).
modulus
The modulus, as an integral string (i.e. the scale has to be zero).
scale
This optional parameter is used to set the number of digits after the decimal place in the result. If omitted, it will default to the scale set globally with the bcscale() function, or fallback to 0 if this has not been set.
Return Values
Returns the result as a string, or FALSE if modulus is 0 or exponent is negative.
Notes
Note:
Because this method uses the modulus operation, numbers which are not positive integers may give unexpected results.
Examples
The following two statements are functionally identical. Thebcpowmod() version however, executes in less time and can accept larger parameters.
<?php <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>a</mi><mo>=</mo><mi>b</mi><mi>c</mi><mi>p</mi><mi>o</mi><mi>w</mi><mi>m</mi><mi>o</mi><mi>d</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">a = bcpowmod(</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.4306em;"></span><span class="mord mathnormal">a</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">b</span><span class="mord mathnormal">c</span><span class="mord mathnormal">p</span><span class="mord mathnormal">o</span><span class="mord mathnormal" style="margin-right:0.02691em;">w</span><span class="mord mathnormal">m</span><span class="mord mathnormal">o</span><span class="mord mathnormal">d</span><span class="mopen">(</span></span></span></span>x, <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>y</mi><mo separator="true">,</mo></mrow><annotation encoding="application/x-tex">y, </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.625em;vertical-align:-0.1944em;"></span><span class="mord mathnormal" style="margin-right:0.03588em;">y</span><span class="mpunct">,</span></span></span></span>mod);$b = bcmod(bcpow($x, <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>y</mi><mo stretchy="false">)</mo><mo separator="true">,</mo></mrow><annotation encoding="application/x-tex">y), </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal" style="margin-right:0.03588em;">y</span><span class="mclose">)</span><span class="mpunct">,</span></span></span></span>mod);// <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>a</mi><mi>a</mi><mi>n</mi><mi>d</mi></mrow><annotation encoding="application/x-tex">a and </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6944em;"></span><span class="mord mathnormal">aan</span><span class="mord mathnormal">d</span></span></span></span>b are equal to each other.?>