What is bcmath php extension?

BCMath Arbitrary Precision Mathematics

• Introduction
• Installing/Configuring
  • Requirements
  • Installation
  • Runtime Configuration
  • Resource Types
• Predefined Constants
• BC Math Functions
  • bcadd — Add two arbitrary precision numbers
  • bccomp — Compare two arbitrary precision numbers
  • bcdiv — Divide two arbitrary precision numbers
  • bcmod — Get modulus of an arbitrary precision number
  • bcmul — Multiply two arbitrary precision numbers
  • bcpow — Raise an arbitrary precision number to another
  • bcpowmod — Raise an arbitrary precision number to another, reduced by a specified modulus
  • bcscale — Set or get default scale parameter for all bc math functions
  • bcsqrt — Get the square root of an arbitrary precision number
  • bcsub — Subtract one arbitrary precision number from another

Hayley Watson ¶

6 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.

volek at adamv dot cz ¶

7 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:
/**
* 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 (

ClaudiuS ¶

9 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:

/* 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

Artur Kuritsyn ¶

5 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));

George Lund ¶

8 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.

Anonymous ¶

5 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));