factorial()
Syntax:
string factorial ( n [, k] )
Arguments:
| string | n | a positive integer of arbitrary digit length or zero; must be passed as a string
for values beyond the capacity of numeric types
| | string | k | a positive integer of arbitrary digit length or zero less than or equal to n;
must be passed as a string for values beyond the capacity of numeric types; optional argument
|
Description:
This function will calculate the factorial n! of a positive integer or zero. Will also calculate the
logical simplification of the equation n!/k! if k is specified in the second argument. Uses the math
functions of the BC math library extension: arguments must be passed as strings, for values beyond the
capacity of numeric types, and the function always returns a string, but it can handle virtually any size
string.
Source:
<?php
/* calculates n!/k! */
function factorial($n,$k='1'){
/* cast args as string types */
$n = (string) $n;
$k = (string) $k;
/* multiply iteratively */
$result = '1';
$k = bcadd($k,'1');
for($xth=$k;bccomp($xth,$n)<1;$xth=bcadd($xth,'1')){
$result = bcmul($result,$xth);
}
return $result; // string
}
/*
* Copyright 2001 David Altherr;
* altherda@email.uc.edu
* www.davidaltherr.net
*
* Free for use under MIT open source public license
*/
?>
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