bug on bc math? View as Markdown

Hi:

I'd like mark this as a doc problem, see the comment of the bcmatch lib:

/* The multiply routine. N2 times N1 is put int PROD with the scale of
the result being MIN(N2 scale+N1 scale, MAX (SCALE, N2 scale, N1 scale)).
*/
void bc_multiply (bc_num n1, bc_num n2, bc_num *prod, int scale TSRMLS_DC)

and

• Here is the full add routine that takes care of negative numbers.
  N1 is added to N2 and the result placed into RESULT. SCALE_MIN
  is the minimum scale for the result. */

void bc_add (n1, n2, result, scale_min)

thanks
Hi:
but on the hand, we may also consider this as a bug, behavior not
act like the doc said :)

any IMO, fixing this, we should add some logic in PHP side, like
before returning value to user .

the code will look like(for bc_multiply):

if (result->n_scale < scale ) {
result->n_value = erealloc($result->n_value, scale);

   memset(result->n_result + result->n_scale, '0', scale - result->n_scale);

   result->n_scale = scale;

}

this will be a little ugly, since it alter the bc_num struct which
should only inside bc lib, what do you think?

thanks

Hi,

before raising a bug I was wondering if anyone noticed this odd behavior in
BC math functions ?

Actual

php -r "echo bcmul('1.1', '9.0', 5);" ==> 9.90
php -r "bcscale(5); echo bcmul('1.1', '9.0');" ==> 9.90
php -r "bcscale(5); echo bcadd('8.9', '1.0');" ==> 9.90000

Expected

php -r "echo bcmul('1.1', '9.0', 5);" ==> 9.90000
php -r "bcscale(5); echo bcmul('1.1', '9.0');" ==> 9.90000
php -r "bcscale(5); echo bcadd('8.9', '1.0');" ==> 9.90000

Seen on 5.3 and 5.4.

Looking at
http://git.php.net/?p=php-src.git;a=history;f=ext/bcmath/bcmath.c;h=5dfafa8bd8dbc1703af2ea4452ac2b05b765a619;hb=HEADI
couldn't see any recent change related to this bug.

Thank you

--
Laruence Xinchen Hui
http://www.laruence.com/

--
Laruence Xinchen Hui
http://www.laruence.com/