Source: https://github.com/Slicer/Slicer/pull/430#issuecomment-162657193

From Csaba:

When adding utilities to vtkAddon, it would be nice if you could check https://github.com/SlicerRt/SlicerRT/blob/master/SlicerRtCommon/SlicerRtCommon.h, there are many similar utility functions there that can be useful.

From Andras:

I will send another pull request with the fuzzy compare added to vtkAddon. I'm not sure where to add it in vtkAddon though. Should I create a vtkAddonMath class and make it a static method of that?

OK, I'll add a vtkAddonMatrix4x4 class, derived from vtkMatrix4x4 (similarly to how we did it for vtkOrientedGridTransform and vtkOrientedBSplineTransform)

From Isaiah:

(replacing inline transform handling with GetTransformBetweenTransformables could probably cut 5% of lines from Slicer base)

From Csaba

GetTransformBetweenTransformables
DoVolumeLatticesMatch
AreExtentsEqual
IsEqual(const vtkMatrix4x4& lhs, const vtkMatrix4x4& rhs)
Maybe the one with the templated vectors too.
Also there are a few about colors, but I don't think they'd belong in vtkAddon.
While we're at it, there are a few similar transforms in
https://github.com/SlicerRt/SlicerRT/blob/master/SegmentationCore/vtkOrientedImageDataResample.h
like
TransformExtent
AreEqualWithTolerance
IsTransformLinear