Poking around in the the SketchUp Program Files folder it appears that the RubyStdLib folder contains all of the standard library classes. Is there any particular way that these files should be loaded or included?
If I was to load the matrix.rb file I would need to specify the path which would be OS dependent and SU version dependent, for example on Windows:
C:\Program Files\SketchUp\SketchUp 2017\Tools\RubyStdLib
what would this be on a Mac?