问题
I need to mimic the exact functionality of the ceil(), floor() and round() functions on bcmath numbers, I've already found a very similar question but unfortunately the answer provided isn't good enough for me since it lacks support for negative numbers and the precision argument for the round() function is missing.
I was wondering if anyone can come up with a rather short and elegant solution to this problem.
All input is appreciated, thanks!
回答1:
After a night lost trying to solve this problem I believe I've found a rather simple solution, here it is:
function bcceil($number)
{
if (strpos($number, '.') !== false) {
if (preg_match("~\.[0]+$~", $number)) return bcround($number, 0);
if ($number[0] != '-') return bcadd($number, 1, 0);
return bcsub($number, 0, 0);
}
return $number;
}
function bcfloor($number)
{
if (strpos($number, '.') !== false) {
if (preg_match("~\.[0]+$~", $number)) return bcround($number, 0);
if ($number[0] != '-') return bcadd($number, 0, 0);
return bcsub($number, 1, 0);
}
return $number;
}
function bcround($number, $precision = 0)
{
if (strpos($number, '.') !== false) {
if ($number[0] != '-') return bcadd($number, '0.' . str_repeat('0', $precision) . '5', $precision);
return bcsub($number, '0.' . str_repeat('0', $precision) . '5', $precision);
}
return $number;
}
I think I didn't miss anything, if someone can spot any bug please let me know. Here are some tests:
assert(bcceil('4') == ceil('4')); // true
assert(bcceil('4.3') == ceil('4.3')); // true
assert(bcceil('9.999') == ceil('9.999')); // true
assert(bcceil('-3.14') == ceil('-3.14')); // true
assert(bcfloor('4') == floor('4')); // true
assert(bcfloor('4.3') == floor('4.3')); // true
assert(bcfloor('9.999') == floor('9.999')); // true
assert(bcfloor('-3.14') == floor('-3.14')); // true
assert(bcround('3', 0) == number_format('3', 0)); // true
assert(bcround('3.4', 0) == number_format('3.4', 0)); // true
assert(bcround('3.5', 0) == number_format('3.5', 0)); // true
assert(bcround('3.6', 0) == number_format('3.6', 0)); // true
assert(bcround('1.95583', 2) == number_format('1.95583', 2)); // true
assert(bcround('5.045', 2) == number_format('5.045', 2)); // true
assert(bcround('5.055', 2) == number_format('5.055', 2)); // true
assert(bcround('9.999', 2) == number_format('9.999', 2)); // true
回答2:
function bcnegative($n)
{
return strpos($n, '-') === 0; // Is the number less than 0?
}
function bcceil($n)
{
return bcnegative($n) ? (($v = bcfloor(substr($n, 1))) ? "-$v" : $v)
: bcadd(strtok($n, '.'), strtok('.') != 0);
}
function bcfloor($n)
{
return bcnegative($n) ? '-' . bcceil(substr($n, 1)) : strtok($n, '.');
}
function bcround($n, $p = 0)
{
$e = bcpow(10, $p + 1);
return bcdiv(bcadd(bcmul($n, $e, 0), bcnegative($n) ? -5 : 5), $e, $p);
}
回答3:
Here's ones that support negative numbers and precision argument for rounding.
function bcceil($val) {
if (($pos = strpos($val, '.')) !== false) {
if ($val[$pos+1] != 0 && $val[0] != '-')
return bcadd(substr($val, 0, $pos), 1, 0);
else
return substr($val, 0, $pos);
}
return $val;
}
function bcfloor($val) {
if (($pos = strpos($val, '.')) !== false) {
if ($val[$pos+1] != 0 && $val[0] == '-')
return bcsub(substr($val, 0, $pos), 1, 0);
else
return substr($val, 0, $pos);
}
return $val;
}
function bcround($val, $precision = 0) {
if (($pos = strpos($val, '.')) !== false) {
if ($precision > 0) {
$int = substr($val, 0, $pos);
$pos2 = ++$pos+$precision;
if ($pos2 < strlen($val)) {
$val2 = sprintf('%s.%s', substr($val, $pos, $pos2-$pos), substr($val, $pos2));
$val2 = $val2[0] >= 5 ? bcceil($val2) : bcfloor($val2);
if (strlen($val2) > $precision)
return bcadd($int, $val[0] == '-' ? -1 : 1, 0);
else
return sprintf('%s.%s', $int, rtrim($val2, '0'));
}
return $val;
} else {
if ($val[$pos+1] >= 5)
return ($val[0] == '-' ? bcfloor($val) : bcceil($val));
else
return ($val[0] == '-' ? bcceil($val) : bcfloor($val));
}
}
return $val;
}
回答4:
Only use bcmath functions to do that:
function bcceil($number, $precision = 0) {
$delta = bcdiv('9', bcpow(10, $precision + 1), $precision + 1);
$number = bcadd($number, $delta, $precision + 1);
$number = bcadd($number, '0', $precision);
return $number;
}
function bcfloor($number, $precision = 0) {
$number = bcadd($number, '0', $precision);
return $number;
}
For test:
$numbers = [
'1', '1.1', '1.4', '1.5', '1.9',
'1.01', '1.09', '1.10', '1.19', '1.90', '1.99',
'2'
];
foreach ($numbers as $n) {
printf("%s (ceil)--> %s\n", $n, bcceil($n, 1));
}
printf("\n");
foreach ($numbers as $n) {
printf("%s (floor)--> %s\n", $n, bcfloor($n, 1));
}
And the test results:
1 (ceil)--> 1.0
1.1 (ceil)--> 1.1
1.4 (ceil)--> 1.4
1.5 (ceil)--> 1.5
1.9 (ceil)--> 1.9
1.01 (ceil)--> 1.1
1.09 (ceil)--> 1.1
1.10 (ceil)--> 1.1
1.19 (ceil)--> 1.2
1.90 (ceil)--> 1.9
1.99 (ceil)--> 2.0
2 (ceil)--> 2.0
1 (floor)--> 1.0
1.1 (floor)--> 1.1
1.4 (floor)--> 1.4
1.5 (floor)--> 1.5
1.9 (floor)--> 1.9
1.01 (floor)--> 1.0
1.09 (floor)--> 1.0
1.10 (floor)--> 1.1
1.19 (floor)--> 1.1
1.90 (floor)--> 1.9
1.99 (floor)--> 1.9
2 (floor)--> 2.0
回答5:
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));
来源：https://stackoverflow.com/questions/1642614/how-to-ceil-floor-and-round-bcmath-numbers