# 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

67
Hayley Watson
8 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.`
22
8 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;}?>`
16
ClaudiuS
10 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?>`
-8
Artur Kuritsyn
6 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));`
-22
George Lund
9 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
6 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));`