[PHP-BUG] Req #76578 [NEW]: ** operator and negative base

From:             amenshchikov at gmail dot com
Operating system: Debian 9
PHP version:      7.2.7
Package:          PHP Language Specification
Bug Type:         Feature/Change Request
Bug description:** operator and negative base

Description:
------------
---
From manual page: http://www.php.net/language.operators.arithmetic
---
When I try to raise number -9 to the power of 0.5 (take a root of even
degree), I have -3 as result. But I think that NaN should be a more
correct in this case.

Test script:
---------------
echo -9**0.5;

Expected result:
----------------
NAN

Actual result:
--------------
-3

-- 
Edit bug report at https://bugs.php.net/bug.php?id=76578&edit=1
-- 
Try a snapshot (PHP 5.4):   https://bugs.php.net/fix.php?id=76578&r=trysnapshot54
Try a snapshot (PHP 5.5):   https://bugs.php.net/fix.php?id=76578&r=trysnapshot55
Try a snapshot (trunk):     https://bugs.php.net/fix.php?id=76578&r=trysnapshottrunk
Fixed in SVN:               https://bugs.php.net/fix.php?id=76578&r=fixed
Fixed in release:           https://bugs.php.net/fix.php?id=76578&r=alreadyfixed
Need backtrace:             https://bugs.php.net/fix.php?id=76578&r=needtrace
Need Reproduce Script:      https://bugs.php.net/fix.php?id=76578&r=needscript
Try newer version:          https://bugs.php.net/fix.php?id=76578&r=oldversion
Not developer issue:        https://bugs.php.net/fix.php?id=76578&r=support
Expected behavior:          https://bugs.php.net/fix.php?id=76578&r=notwrong
Not enough info:            https://bugs.php.net/fix.php?id=76578&r=notenoughinfo
Submitted twice:            https://bugs.php.net/fix.php?id=76578&r=submittedtwice
register_globals:           https://bugs.php.net/fix.php?id=76578&r=globals
PHP 4 support discontinued: https://bugs.php.net/fix.php?id=76578&r=php4
Daylight Savings:           https://bugs.php.net/fix.php?id=76578&r=dst
IIS Stability:              https://bugs.php.net/fix.php?id=76578&r=isapi
Install GNU Sed:            https://bugs.php.net/fix.php?id=76578&r=gnused
Floating point limitations: https://bugs.php.net/fix.php?id=76578&r=float
No Zend Extensions:         https://bugs.php.net/fix.php?id=76578&r=nozend
MySQL Configuration Error:  https://bugs.php.net/fix.php?id=76578&r=mysqlcfg