如何ceil,floor和round bcmath数字?

时间:2009-10-29 09:53:30

标签: php rounding floor bcmath ceil

我需要模仿bcmath数字上的ceil()floor()round()函数的确切功能I've already found a very similar question但不幸的是{{ 3}}因为缺少对负数的支持而且缺少round()函数的精度参数

我想知道是否有人能够为这个问题提出一个相当简短而优雅的解决方案。

感谢所有输入,谢谢!

6 个答案:

答案 0 :(得分:27)

经过一夜失败试图解决这个问题后,我相信我找到了一个相当简单的解决方案,这里是:

function bcceil($number)
{
    if (strpos($number, '.') !== false) {
        if (preg_match("~\.[0]+$~", $number)) return bcround($number, 0);
        if ($number[0] != '-') return bcadd($number, 1, 0);
        return bcsub($number, 0, 0);
    }
    return $number;
}

function bcfloor($number)
{
    if (strpos($number, '.') !== false) {
        if (preg_match("~\.[0]+$~", $number)) return bcround($number, 0);
        if ($number[0] != '-') return bcadd($number, 0, 0);
        return bcsub($number, 1, 0);
    }
    return $number;
}

function bcround($number, $precision = 0)
{
    if (strpos($number, '.') !== false) {
        if ($number[0] != '-') return bcadd($number, '0.' . str_repeat('0', $precision) . '5', $precision);
        return bcsub($number, '0.' . str_repeat('0', $precision) . '5', $precision);
    }
    return $number;
}

我想我没有错过任何东西,如果有人能发现任何错误,请告诉我。以下是一些测试:

assert(bcceil('4') == ceil('4')); // true
assert(bcceil('4.3') == ceil('4.3')); // true
assert(bcceil('9.999') == ceil('9.999')); // true
assert(bcceil('-3.14') == ceil('-3.14')); // true

assert(bcfloor('4') == floor('4')); // true
assert(bcfloor('4.3') == floor('4.3')); // true
assert(bcfloor('9.999') == floor('9.999')); // true
assert(bcfloor('-3.14') == floor('-3.14')); // true

assert(bcround('3', 0) == number_format('3', 0)); // true
assert(bcround('3.4', 0) == number_format('3.4', 0)); // true
assert(bcround('3.5', 0) == number_format('3.5', 0)); // true
assert(bcround('3.6', 0) == number_format('3.6', 0)); // true
assert(bcround('1.95583', 2) == number_format('1.95583', 2)); // true
assert(bcround('5.045', 2) == number_format('5.045', 2)); // true
assert(bcround('5.055', 2) == number_format('5.055', 2)); // true
assert(bcround('9.999', 2) == number_format('9.999', 2)); // true

答案 1 :(得分:2)

这些是支持舍入的负数和精度参数的。

function bcceil($val) {
    if (($pos = strpos($val, '.')) !== false) {
        if ($val[$pos+1] != 0 && $val[0] != '-')
            return bcadd(substr($val, 0, $pos), 1, 0);
        else
            return substr($val, 0, $pos);
    }
    return $val;
}

function bcfloor($val) {
    if (($pos = strpos($val, '.')) !== false) {
        if ($val[$pos+1] != 0 && $val[0] == '-')
            return bcsub(substr($val, 0, $pos), 1, 0);
        else
            return substr($val, 0, $pos);
    }
    return $val;
}

function bcround($val, $precision = 0) {
    if (($pos = strpos($val, '.')) !== false) {
        if ($precision > 0) {
            $int = substr($val, 0, $pos);
            $pos2 = ++$pos+$precision;
            if ($pos2 < strlen($val)) {
                $val2 = sprintf('%s.%s', substr($val, $pos, $pos2-$pos), substr($val, $pos2));
                $val2 = $val2[0] >= 5 ? bcceil($val2) : bcfloor($val2);
                if (strlen($val2) > $precision)
                    return bcadd($int, $val[0] == '-' ? -1 : 1, 0);
                else
                    return sprintf('%s.%s', $int, rtrim($val2, '0'));
            }
            return $val;
        } else {
            if ($val[$pos+1] >= 5)
                return ($val[0] == '-' ? bcfloor($val) : bcceil($val));
            else
                return ($val[0] == '-' ? bcceil($val) : bcfloor($val));
        }
    }
    return $val;
}

答案 2 :(得分:1)

function bcnegative($n)
{
    return strpos($n, '-') === 0; // Is the number less than 0?
}

function bcceil($n)
{
    return bcnegative($n) ? '-' . bcfloor(substr($n, 1))
                          : bcadd(strtok($n, '.'), strtok('.') != 0);
}

function bcfloor($n)
{
    return bcnegative($n) ? '-' . bcceil(substr($n, 1)) : strtok($n, '.');
}

function bcround($n, $p = 0)
{
    $e = bcpow(10, $p + 1);
    return bcdiv(bcadd(bcmul($n, $e, 0), bcnegative($n) ? -5 : 5), $e, $p);
}

答案 3 :(得分:0)

我选择 Alix Axel 的变体进行四舍五入,因为它是最快的,因为它只使用加法和减法,不使用乘法和除法。为了在开始时以负精度舍入,我使用了标准函数:

sprintf('%.0F', round($result, $operand_value))

但我遇到了 here 所描述的问题。所以我扩展了这个变体以获得负精度:

function bcround($number, $precision)
{
    if($precision >= 0)
    {
        if (strpos($number, '.') !== false)
        {
            if ($number[0] != '-')
                return bcadd($number, '0.' . str_repeat('0', $precision) . '5', $precision);
            return bcsub($number, '0.' . str_repeat('0', $precision) . '5', $precision);
        }
        return $number;
    }
    else
    {
        $mod = bcmod($number, bcpow(10, -$precision));
        $sub = bcsub($number, $mod);
        if($mod[0] != '-')
        {
            $add = $mod[0] >= 5 ? bcpow(10, strlen($mod)) : 0;
        }
        else
        {
            $add = $mod[1] >= 5 ? '-'.bcpow(10, strlen($mod)-1) : 0;
        }
        return bcadd($sub, $add);
    }
}

通过递归的更优雅和更短的选择:

function bcround($number, $precision)
{
    if($precision >= 0)
    {
        if (strpos($number, '.') !== false)
        {
            if ($number[0] != '-')
                return bcadd($number, '0.' . str_repeat('0', $precision) . '5', $precision);
            return bcsub($number, '0.' . str_repeat('0', $precision) . '5', $precision);
        }
        return $number;
    }
    else
    {       
        $pow = bcpow(10, -$precision);
        return bcmul(bcround(bcdiv($number, $pow, -$precision), 0), $pow);
    }
}

但它较慢,因为它使用两个运算(除法和乘法),而不是在第一种情况下找到除法的余数 (mod) 的一个运算。速度测试证实了这一点:

第一个变体。总迭代次数:10000。持续时间:0.24502515792847 秒。

第二个变体。总迭代次数:10000。持续时间:0.35303497314453 秒。

答案 4 :(得分:-1)

仅使用bcmath函数来做到这一点:

function bcceil($number, $precision = 0) {
    $delta = bcdiv('9', bcpow(10, $precision + 1), $precision + 1);
    $number = bcadd($number, $delta, $precision + 1);
    $number = bcadd($number, '0', $precision);
    return $number;
}

function bcfloor($number, $precision = 0) {
    $number = bcadd($number, '0', $precision);
    return $number;
}

用于测试:

$numbers = [
    '1', '1.1', '1.4', '1.5', '1.9',
    '1.01', '1.09', '1.10', '1.19', '1.90', '1.99',
    '2'
];

foreach ($numbers as $n) {
    printf("%s (ceil)--> %s\n", $n, bcceil($n, 1));
}

printf("\n");

foreach ($numbers as $n) {
    printf("%s (floor)--> %s\n", $n, bcfloor($n, 1));
}

测试结果:

1 (ceil)--> 1.0
1.1 (ceil)--> 1.1
1.4 (ceil)--> 1.4
1.5 (ceil)--> 1.5
1.9 (ceil)--> 1.9
1.01 (ceil)--> 1.1
1.09 (ceil)--> 1.1
1.10 (ceil)--> 1.1
1.19 (ceil)--> 1.2
1.90 (ceil)--> 1.9
1.99 (ceil)--> 2.0
2 (ceil)--> 2.0

1 (floor)--> 1.0
1.1 (floor)--> 1.1
1.4 (floor)--> 1.4
1.5 (floor)--> 1.5
1.9 (floor)--> 1.9
1.01 (floor)--> 1.0
1.09 (floor)--> 1.0
1.10 (floor)--> 1.1
1.19 (floor)--> 1.1
1.90 (floor)--> 1.9
1.99 (floor)--> 1.9
2 (floor)--> 2.0

答案 5 :(得分:-2)

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));