(PHP 4, PHP 5, PHP 7)
bcdiv — 2个任意精度的数字除法计算
$left_operand
, string $right_operand
[, int $scale = int
] ) : string
左操作数除以右操作数
left_operand左操作数，字符串类型
right_operand右操作数，字符串类型
scale此可选参数用于设置结果中小数点后的小数位数。也可通过使用 bcscale() 来设置全局默认的小数位数，用于所有函数。
返回结果为字符串类型的结果，如果右操作数是0结果为null
Example #1 bcdiv() 示例
<?php
echo bcdiv('105', '6.55957', 3); // 16.007
?>
The custom bcdiv function listed at the top of this page produces very different results from bcdiv, as it rounds instead of truncating the result. Consider the following:
<?php
function bcdiv_cust( $first, $second, $scale = 0 )
{
$res = $first / $second;
return round( $res, $scale );
}
echo bcdiv('1','2','0') . " vs. " bcdiv_cust('1','2','0'); // prints '0 vs. 1'
?>
Perhaps some one can find useful this function to compute the modular inverse of a integer (extended euclidean algorithm):
function invmod($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;
<?php
//converting in to required precision of decimal points
$result= bcdiv(89.99999999997,2.57865741235478,2);
echo "$result"; // 34.90 result with 2 decimal points
?>
Decimal to binary conversion, using BC Math.
Note: this function is VERY slow if the decimal number is too big!
<?
function bc_decbin($dec_str) {
if (strlen($dec_str)>0) {
$bin_str = '';
do {
if (((int)$dec_str[strlen($dec_str)-1] % 2) === 0)
$bin_str .= '0';
else
$bin_str .= '1';
$dec_str = bcdiv($dec_str, '2');
} while ($dec_str!='0');
return strrev($bin_str);
}
else
return null;
}
?>
-----
Cristian
www.CodeFlower.com