bcdiv
(PHP 4, PHP 5)
bcdiv — Divide two arbitrary precision numbers
Описание
string bcdiv
( string $left_operand
, string $right_operand
[, int $scale
] )
Divides the left_operand by the right_operand .
Список параметров
- left_operand
-
The left operand, as a string.
- right_operand
-
The right operand, as a string.
- scale
-
This optional parameter is used to set the number of digits after the decimal place in the result. You can also set the global default scale for all functions by using bcscale().
Возвращаемые значения
Returns the result of the division as a string, or NULL if right_operand is 0.
Примеры
Пример #1 bcdiv() example
<?php
echo bcdiv('105', '6.55957', 3); // 16.007
?>
Коментарии
Perhaps some one can find useful this function to compute the modular inverse of a integer (extended euclidean algorithm):
function invmod($a,$b) {
$n=$b;
$x=0; $lx=1; $y=1; $ly=0;
while ($b) {
$t=$b;
$q=bcdiv($a,$b,0);
$b=bcmod($a,$b);
$a=$t;
$t=$x; $x=bcsub($lx,bcmod(bcmul($q,$x),$n)); $lx=$t;
$t=$y; $y=bcsub($ly,bcmod(bcmul($q,$y),$n)); $ly=$t;
}
if (bccomp($lx,0) == -1)
$lx=bcadd($lx,$n);
return $lx;
}
// verify
$n="2447995268898324993537772139997802321";
$t="64941057316178801556773346239351236811";
$m="123456789";
$i=invmod($t,$n);
// (t*m)*inv(t) is m
echo bcmod(bcmul(bcmod(bcmul($t,$m),$n),$i),$n) == $m;