#35319 [NEW]: modulo operator is not coherent with mathematical definition

From: ian at euona dot com Operating system: Win XP PHP version: 5.0.5 PHP Bug Type: Math related Bug description: modulo operator is not coherent with mathematical definition Description: ------------ This is the same problem as stated in reports 20365 and 29822. This is indeed not bogus, PHP, C and Javascript are NOT producing the mathematical correct result. Per definition modulus arithmetics create a ring structure containing the values [0,1,...,(n-1)]. THERE ARE NO NEGATIVE NUMBERS! The current behavior is not intuitive and basically incorrect. An integer typecast is not the same as floor. This is a big problem when shifting table fields (e.g. weekdays). Take a look at spreadsheet software. //This is the way % should behave function math_mod($a,$n){$n=abs($n);if($n===0){return NULL;}return $a-$n*floor($a/$n);} //this function emulates ($a%$n) function php_mod($a,$n){return $a-$n*(int)($a/$n);} Reproduce code: --------------- echo -5%7 , ' ', fmod(-5,7),' ', 1%0,' ', 3%-2; Expected result: ---------------- 2 2 NULL 1 Actual result: -------------- -5 -5 NULL 1 -- Edit bug report at http://bugs.php.net/?id=35319&edit=1 -- Try a CVS snapshot (php4): http://bugs.php.net/fix.php?id=35319&r=trysnapshot4 Try a CVS snapshot (php5.0): http://bugs.php.net/fix.php?id=35319&r=trysnapshot50 Try a CVS snapshot (php5.1): http://bugs.php.net/fix.php?id=35319&r=trysnapshot51 Fixed in CVS: http://bugs.php.net/fix.php?id=35319&r=fixedcvs Fixed in release: http://bugs.php.net/fix.php?id=35319&r=alreadyfixed Need backtrace: http://bugs.php.net/fix.php?id=35319&r=needtrace Need Reproduce Script: http://bugs.php.net/fix.php?id=35319&r=needscript Try newer version: http://bugs.php.net/fix.php?id=35319&r=oldversion Not developer issue: http://bugs.php.net/fix.php?id=35319&r=support Expected behavior: http://bugs.php.net/fix.php?id=35319&r=notwrong Not enough info: http://bugs.php.net/fix.php?id=35319&r=notenoughinfo Submitted twice: http://bugs.php.net/fix.php?id=35319&r=submittedtwice register_globals: http://bugs.php.net/fix.php?id=35319&r=globals PHP 3 support discontinued: http://bugs.php.net/fix.php?id=35319&r=php3 Daylight Savings: http://bugs.php.net/fix.php?id=35319&r=dst IIS Stability: http://bugs.php.net/fix.php?id=35319&r=isapi Install GNU Sed: http://bugs.php.net/fix.php?id=35319&r=gnused Floating point limitations: http://bugs.php.net/fix.php?id=35319&r=float No Zend Extensions: http://bugs.php.net/fix.php?id=35319&r=nozend MySQL Configuration Error: http://bugs.php.net/fix.php?id=35319&r=mysqlcfg