bcdiv()

(PHP 4, PHP 5, PHP 7)

2个任意精度的数字除法计算

说明

bcdiv(string $left_operand,string $right_operand[,int $scale= int]): string

左操作数除以右操作数

参数

$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。

返回值

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

范例

bcdiv()示例

<?php
echo bcdiv('105', '6.55957', 3);  // 16.007
?>

参见

• bcmul()2个任意精度数字乘法计算

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