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BCMath Arbitrary Precision Mathematics
Introduction
For arbitrary precision mathematics PHP offers BCMath which
supports numbers of any size and precision up to 2147483647 (or 0x7FFFFFFF) decimal digits,
if there is sufficient memory, represented as strings.
Valid (aka. well-formed) BCMath numbers are strings which match the regular expression
/^[+-]?[0-9]*(\.[0-9]*)?$/.
Caution
Passing values of type float to a BCMath function which expects
a string as operand may not have the desired effect due to the
way PHP converts float values to string, namely
that the string may be in exponential notation (which is not
supported by BCMath), and that, prior to PHP 8.0.0, the decimal separator is locale dependent
(while BCMath always expects a decimal point).
<?php
$num1 = 0; // (string) 0 => '0'
$num2 = -0.000005; // (string) -0.000005 => '-5.05E-6'
echo bcadd($num1, $num2, 6); // => '0.000000'
setlocale(LC_NUMERIC, 'de_DE'); // uses a decimal comma
$num2 = 1.2; // (string) 1.2 => '1,2'
echo bcsub($num1, $num2, 1); // => '0.0'
?>
- 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
- BcMath\Number — The BcMath\Number class
Hayley Watson ¶11 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 ¶11 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 $result;
}
?>
ClaudiuS ¶13 years ago
Needed to compute some permutations and found the BC extension great but poor on functions, so untill this gets implemented here's the factorial function:
<?php
/* BC FACTORIAL
* n! = n * (n-1) * (n-2) .. 1 [eg. 5! = 5 * 4 * 3 * 2 * 1 = 120]
*/
function bcfact($n){
$factorial=$n;
while (--$n>1) $factorial=bcmul($factorial,$n);
return $factorial;
}
print bcfact(50);
//30414093201713378043612608166064768844377641568960512000000000000
?>