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PHP - Manual: BC Math

来源：网络转载　浏览：30627次　时间：2024-06-30
简介 » « 数学扩展
  • PHP 手册
  • 函数参考
  • 数学扩展

BCMath 任意精度数学

  • 简介
  • 安装／配置
    • 需求
    • 安装
    • 运行时配置
    • 资源类型
  • 预定义常量
  • BC 数学 函数
    • bcadd — 两个任意精度数字的加法计算
    • bccomp — 比较两个任意精度的数字
    • bcdiv — 两个任意精度的数字除法计算
    • bcmod — 任意精度数字取模
    • bcmul — 两个任意精度数字乘法计算
    • bcpow — 任意精度数字的乘方
    • bcpowmod — Raise an arbitrary precision number to another, reduced by a specified modulus
    • bcscale — 设置/获取所有 bc math 函数的默认小数点保留位数
    • bcsqrt — 任意精度数字的二次方根
    • bcsub — 两个任意精度数字的减法
add a note

User Contributed Notes 6 notes

up down 56 Hayley Watson6 years ago This extension is an interface to the GNU implementation as a library of the Basic Calculator utility by Philip Nelson; hence the name. up down 21 volek at adamv dot cz7 years ago Note that when you use implementation of factorial that ClaudiuS made, you get results even if you try to calculate factorial of number that you normally can't, e.g. 2.5, -2, etc. Here is safer implementation:
<?php
/**
* Calculates a factorial of given number.
* @param string|int $num
* @throws InvalidArgumentException
* @return string
*/
function bcfact($num)
{
    if (!filter_var($num, FILTER_VALIDATE_INT) || $num <= 0) {
        throw new InvalidArgumentException(sprintf('Argument must be natural number, "%s" given.', $num));
    }

    for ($result = '1'; $num > 0; $num--) {
        $result = bcmul($result, $num);
    }

    return $result;
}
?> up down 18 ClaudiuS9 years ago Needed to compute some permutations and found the BC extension great but poor on functions, so untill this gets implemented here's the factorial function:

<?php
/* BC FACTORIAL
* n! = n * (n-1) * (n-2) .. 1 [eg. 5! = 5 * 4 * 3 * 2 * 1 = 120]
*/
function bcfact($n){
    $factorial=$n;
    while (--$n>1) $factorial=bcmul($factorial,$n);
    return $factorial;
}

print bcfact(50);
//30414093201713378043612608166064768844377641568960512000000000000
?> up down -12 Artur Kuritsyn4 years ago Useful function for bcround

    function getBcRound($number, $precision = 0)
    {
        $precision = ($precision < 0)
                   ? 0
                   : (int) $precision;
        if (strcmp(bcadd($number, '0', $precision), bcadd($number, '0', $precision+1)) == 0) {
            return bcadd($number, '0', $precision);
        }
        if (getBcPresion($number) - $precision > 1) {
            $number = getBcRound($number, $precision + 1);
        }
        $t = '0.' . str_repeat('0', $precision) . '5';
        return $number < 0
               ? bcsub($number, $t, $precision)
               : bcadd($number, $t, $precision);
    }
   
    function getBcPresion($number) {
        $dotPosition = strpos($number, '.');
        if ($dotPosition === false) {
            return 0;
        }
        return strlen($number) - strpos($number, '.') - 1;
    }
   
    var_dump(getBcRound('3', 0) == number_format('3', 0));
    var_dump(getBcRound('3.4', 0) == number_format('3.4', 0));
    var_dump(getBcRound('3.56', 0) == number_format('3.6', 0));
    var_dump(getBcRound('1.95583', 2) == number_format('1.95583', 2));
    var_dump(getBcRound('5.045', 2) == number_format('5.045', 2));
    var_dump(getBcRound('5.055', 2) == number_format('5.055', 2));
    var_dump(getBcRound('9.999', 2) == number_format('9.999', 2));
    var_dump(getBcRound('5.0445', 5) == number_format('5.044500', 5));
    var_dump(getBcRound('5.0445', 4) == number_format('5.04450', 4));
    var_dump(getBcRound('5.0445', 3) == number_format('5.0445', 3));
    var_dump(getBcRound('5.0445', 2) == number_format('5.045', 2));
    var_dump(getBcRound('5.0445', 1) == number_format('5.05', 1));
    var_dump(getBcRound('5.0445', 0) == number_format('5.0', 0));//
    var_dump(getBcRound('5.04455', 2) == number_format('5.045', 2));
    var_dump(getBcRound('99.999', 2) == number_format('100.000', 2));
    var_dump(getBcRound('99.999') == number_format('99.999', 0));
    var_dump(getBcRound('99.999', 'a') == number_format('99.999', 0));
    var_dump(getBcRound('99.999', -1.5) == number_format('99.999', 0));
    var_dump(getBcRound('-0.00001', 2) == number_format('-0.000', 2));
    var_dump(getBcRound('-0.0000', 2) == number_format('0', 2));
    var_dump(getBcRound('-4.44455', 2) == number_format('-4.445', 2));
    var_dump(getBcRound('-4.44555', 0) == number_format('-4.5', 0));
    var_dump(getBcRound('-4.444444444444444444444444444444444444444444445', 0) == number_format('-4.5', 0)); up down -21 George Lund8 years ago It's worth noting that this library is named very wrongly.

It may be called 'Binary Calculator', but what you're getting is a decimal calculator that can represent base-10 fractions accurately. up down -14 Anonymous4 years ago Useful function for bcround

    function getBcRound($number, $precision = 0)
    {
        $precision = ($precision < 0)
                   ? 0
                   : (int) $precision;
        if (strcmp(bcadd($number, '0', $precision), bcadd($number, '0', $precision+1)) == 0) {
            return bcadd($number, '0', $precision);
        }
        if (getBcPresion($number) - $precision > 1) {
            $number = getBcRound($number, $precision + 1);
        }
        $t = '0.' . str_repeat('0', $precision) . '5';
        return $number < 0
               ? bcsub($number, $t, $precision)
               : bcadd($number, $t, $precision);
    }
   
    function getBcPresion($number) {
        $dotPosition = strpos($number, '.');
        if ($dotPosition === false) {
            return 0;
        }
        return strlen($number) - strpos($number, '.') - 1;
    }
   
    var_dump(getBcRound('3', 0) == number_format('3', 0));
    var_dump(getBcRound('3.4', 0) == number_format('3.4', 0));
    var_dump(getBcRound('3.56', 0) == number_format('3.6', 0));
    var_dump(getBcRound('1.95583', 2) == number_format('1.95583', 2));
    var_dump(getBcRound('5.045', 2) == number_format('5.045', 2));
    var_dump(getBcRound('5.055', 2) == number_format('5.055', 2));
    var_dump(getBcRound('9.999', 2) == number_format('9.999', 2));
    var_dump(getBcRound('5.0445', 5) == number_format('5.044500', 5));
    var_dump(getBcRound('5.0445', 4) == number_format('5.04450', 4));
    var_dump(getBcRound('5.0445', 3) == number_format('5.0445', 3));
    var_dump(getBcRound('5.0445', 2) == number_format('5.045', 2));
    var_dump(getBcRound('5.0445', 1) == number_format('5.05', 1));
    var_dump(getBcRound('5.0445', 0) == number_format('5.0', 0));//
    var_dump(getBcRound('5.04455', 2) == number_format('5.045', 2));
    var_dump(getBcRound('99.999', 2) == number_format('100.000', 2));
    var_dump(getBcRound('99.999') == number_format('99.999', 0));
    var_dump(getBcRound('99.999', 'a') == number_format('99.999', 0));
    var_dump(getBcRound('99.999', -1.5) == number_format('99.999', 0));
    var_dump(getBcRound('-0.00001', 2) == number_format('-0.000', 2));
    var_dump(getBcRound('-0.0000', 2) == number_format('0', 2));
    var_dump(getBcRound('-4.44455', 2) == number_format('-4.445', 2));
    var_dump(getBcRound('-4.44555', 0) == number_format('-4.5', 0));
    var_dump(getBcRound('-4.444444444444444444444444444444444444444444445', 0) == number_format('-4.5', 0)); add a note

官方地址：https://www.php.net/manual/en/book.bc.php

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