From: Joel Pearson <lists@...>
Date: 2013-02-15T07:50:59+09:00
Subject: Re: Select "columns" from multidimensional array?

Interesting Matrix build. It's giving me a bit of a headache just trying 
to figure out the links involved.

So MatrixPart defines the methods and the "parent" matrix (held as an 
instance variable); and row and column both use these methods and both 
access the variable which points to the matrix they're part of.

The rows and columns can be selected based on given headers, and each 
will reference the other... and this is where my head explodes:

def index( row, col )
  @row_headers.index( row ) * @col_headers.size + @col_headers.index( 
col )
end

It takes a bit of getting used to, but thanks to Ruby's flexible array 
class adding nil values automatically when you specify an index higher 
than the upper boundary, that works.

I guess with a bit more poking and prodding I could figure out how to 
append, insert, and delete rows and columns. After all, it's only a math 
problem in the end. All the interconnected references (especially the 
layered yields) still make my head spin though :)

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