Bug #119710 column value unexpectedly change ,after changing atan2 function

• Submitted: 17 Jan 8:16
• Modified: 19 Jan 8:03
• Reporter: Aaditya Dubey
• Status: Not a Bug
• Category: MySQL Server: Optimizer
• Severity: S3 (Non-critical)
• Version: 8.0.x, 8.4.x
• OS: Any
• CPU Architecture: Any

[17 Jan 8:16] Aaditya Dubey

Description:
for the atan2 function,after changing atan2(y,x) to -atan(-y,x),the value should be the same ,but for the -0,+0value,there is a bug.

How to repeat:
mysql> select atan2(-0,-1);
+-------------------+
| atan2(-0,-1)      |
+-------------------+
| 3.141592653589793 |
+-------------------+
1 row in set (0.01 sec)
mysql> select -atan2(0,-1);
+--------------------+
| -atan2(0,-1)       |
+--------------------+
| -3.141592653589793 |
+--------------------+
1 row in set (0.00 sec)

[19 Jan 8:03] Roy Lyseng

Thank you for the bug report.
However, this is not a bug.
+0 and -1 are identical values, hence atan2(-0,-1) and atan2(0,-1) should have identical results.