Re: how to introduce reference objects into ruby

In Ruby, there's the []= and [] operators which you can define together.
The []= can play both the role of subscripting and assignment without
needing any intermediate references. Also, Ruby's subscript operator can

take any number of arguments. The right-handed value is always the last
in 
the list of args.

class MyMatrix
  ...
  def []=(i,j,value)
    @rows[i][j]=value
    @columns[i][j]=value
  end
end

mm=MyMatrix.new
mm[3,5] = 42

Indeed, the only drawback is that I have to keep the row and column-wise
elements synchronized, e.g., after an addition or something. For a
matrix with equal row and column sizes, this would mean a duplication of
the needed operations if a reference object existed. But when row "i" is
much longer than column "j", I would rather only lookup and modify the
element (i,j) via the columns, since the Hash llokup for the row will
take much longer.

Greetings,
Geert.