gmp_fact

(PHP 4 >= 4.0.4, PHP 5, PHP 7)

gmp_fact — Factorial

说明

gmp_fact ( mixed $a ) : GMP

Calculates factorial (a!) of a.

参数

a

The factorial number.

可以是一个 GMP 数据 resouce，或一个可以转换为数值的字符串。

返回值

GMP 数值资源.

范例

Example #1 gmp_fact() example

<?php
$fact1 = gmp_fact(5); // 5 * 4 * 3 * 2 * 1
echo gmp_strval($fact1) . "\n";

$fact2 = gmp_fact(50); // 50 * 49 * 48, ... etc
echo gmp_strval($fact2) . "\n";
?>

以上例程会输出：

120
30414093201713378043612608166064768844377641568960512000000000000

User Contributed Notes

raholl 01-Oct-2018 04:01
I was expecting gmp_fact() is more effective than doing a while loop, but measurements show opposite:

<?php
$cislo = 112;
$fact = $cislo;
$ffact = 1;
$mt = microtime();
while($fact >= 1)
{
    $ffact = $fact * $ffact;
    $fact--;
}
$md=number_format(microtime()-$mt, 6);
echo "<h1>LOOP ($md):</h1>";
echo $ffact;

$mt = microtime();
$vec = gmp_fact($cislo);
$md=number_format(microtime()-$mt, 6);
echo "<h1>GMP FACT ($md):</h1>";
echo $vec;
exit();
?>

WILL OUTPUT:

LOOP (0.000022s):
1.9745068572211E+182

GMP FACT (0.000132s):
1.9745068572211E+182

Result is 0.000022s loop, and 0.000132s gmp_fact()
raholl 01-Oct-2018 03:59
I was expecting gmp_fact() is more effective than doing a while loop, but measurements show opposite:

<?php
$cislo = 112;
$fact = $cislo;
$ffact = 1;
$mt = microtime();
while($fact >= 1)
{
    $ffact = $fact * $ffact;
    $fact--;
}
$md=number_format(microtime()-$mt, 6);
echo "<h1>LOOP ($md):</h1>";
echo $ffact;

$mt = microtime();
$vec = gmp_fact($cislo);
$md=number_format(microtime()-$mt, 6);
echo "<h1>GMP FACT ($md):</h1>";
echo $vec;
exit();
?>

WILL OUTPUT:

LOOP (0.000022s):
1.9745068572211E+182

GMP FACT (0.000132s):
1.9745068572211E+182

Result is 0.000022s loop, and 0.000132s gmp_fact()