SymfonyWorld Online 2022 Winter Edition

# BCMath Arbitrary Precision Mathematics

• Introduction
• Installing/Configuring
• Predefined Constants
• BC Math Functions
• 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

### User Contributed Notes 6 notes

56
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.
21
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:
<?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;
}
?>
18
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:

<?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
?>
-12
Artur Kuritsyn
4 years ago
Useful function for bcround

function getBcRound(\$number, \$precision = 0)
{
\$precision = (\$precision < 0)
? 0
: (int) \$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)
}

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));
-21
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.
-14
Anonymous
4 years ago
Useful function for bcround

function getBcRound(\$number, \$precision = 0)
{
\$precision = (\$precision < 0)
? 0
: (int) \$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)
}

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));