Bug #9499: The Vector.cross_product function returns the opposite vector of the expected result

• Status: Closed
• Assignee: marcandre (Marc-Andre Lafortune)
• Target version: -
• ruby -v: ruby 2.1.0dev (2013-09-22) [i386-mingw32]
• Backport: 1.9.3: DONTNEED, 2.0.0: DONTNEED, 2.1: DONE

[dodo (Deyan Hadzhiev)]

The member function of class Vector returns the opposite vector of the expected result. The function calculates the resulting vector as if the cross_product is v X self instead of self X v. Just to be sure I tried running the exact example from the 2.1.0 documentation, where is specified:
Vector[1, 0, 0].cross_product Vector[0, 1, 0] => Vector[0, 0, 1]
The documentation is right, but running the example produces Vector[0, 0, -1].
The fix is just to swap the two arguments of the '-' operator.
The implementation is in matrix.rb line:1764

[nagachika (Tomoyuki Chikanaga)]

• Status changed from Open to Assigned
• Assignee set to marcandre (Marc-Andre Lafortune)
• Backport changed from 1.9.3: UNKNOWN, 2.0.0: UNKNOWN, 2.1: UNKNOWN to 1.9.3: DONTNEED, 2.0.0: DONTNEED, 2.1: REQUIRED

[nagachika (Tomoyuki Chikanaga)]

• Status changed from Assigned to Closed
• % Done changed from 0 to 100

Applied in changeset ruby-21:r46789.

---

merge revision(s) r46780: [Backport #9499]

* lib/matrix.rb: Fix sign for cross_product [#9499]

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 1.9.3: DONTNEED, 2.0.0: DONTNEED, 2.1: REQUIRED to 1.9.3: DONTNEED, 2.0.0: DONTNEED, 2.1: DONE

backported at r46789.