php教程

BCMath 任意精度数学

User Contributed Notes

Artur Kuritsyn 18-Sep-2017 11:59
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));
Anonymous 18-Sep-2017 11:58
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));
Hayley Watson 26-Oct-2015 01:30
This extension is an interface to the GNU implementation as a library of the Basic Calculator utility by Philip Nelson; hence the name.
volek at adamv dot cz 15-Jan-2015 01:44
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;
}
?>
George Lund 20-May-2014 12:48
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.
ClaudiuS 19-Feb-2013 02:25
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
?>

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