International PHP Conference Berlin 2025

BCMath Arbitrary Precision Mathematics

  • Introduction
  • Installing/Configuring
  • BC Math Functions
    • bcadd — Add two arbitrary precision numbers
    • bcceil — Round up arbitrary precision number
    • bccomp — Compare two arbitrary precision numbers
    • bcdiv — Divide two arbitrary precision numbers
    • bcdivmod — Get the quotient and modulus of an arbitrary precision number
    • bcfloor — Round down arbitrary precision number
    • 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
    • bcround — Round arbitrary precision number
    • 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
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User Contributed Notes 3 notes

up
77
Hayley Watson
9 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.
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26
volek at adamv dot cz
9 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
18
ClaudiuS
11 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
?>
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