bcpowmod
These functions DO NOT round off your values. No arbitrary precision libraries do it this way. It stops calculating after reaching scale of decimal places, which mean that your value is cut off after scale number of digits, not rounded. To do the rounding use something like this:
<?php
function bcround($number, $scale=0) {
$fix = "5";
for ($i=0;$i<$scale;$i++) $fix="0$fix";
$number = bcadd($number, "0.$fix", $scale+1);
return bcdiv($number, "1.0", $scale);
}
?>
bcscale
(PHP 4, PHP 5)
bcscale — 모든 bc 수치계산 함수의 scale 매개변수의 기본값을 설정한다
설명
string bcscale
( int $scale
)
이 함수는 scale 매개변수를 명시하지 않은 모든 bc 수치계산 함수의 의 scale 매개변수의 기본값을 설정한다.
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User Contributed Notesbcscale
mwgamera at gmail dot com
05-Dec-2007 06:45
05-Dec-2007 06:45
invincible at limitedintelligence dot com
08-Feb-2006 03:50
08-Feb-2006 03:50
If you don't set the default scale, be careful when you're chaining together several BC math functions - since by default, these functions will round off your values, losing accuracy very quickly:
<?php
$a = 1.234
$b = 2.345
$c = 7.890
$ab = bcmul($a,$b); // 2
$abc = bcmul($ab,$c);
echo $abc; // 15
?>
... compare with the answer you get when you use more decimal places:
<?php
$a = 1.234
$b = 2.345
$c = 7.890
bcscale(15);
$ab = bcmul($a,$b); // 2.893730
$abc = bcmul($ab,$c);
echo $abc; // 22.83152970
?>