From: Robert Klemme <shortcutter@...>
Date: 2013-02-18T06:28:33+09:00
Subject: Re: Select "columns" from multidimensional array?

On Sun, Feb 17, 2013 at 9:14 PM, Joel Pearson <lists@ruby-forum.com> wrote:
> I've attached my attempt at converting your code to suit mine (hope you
> don't mind the plagarism :p )

No, it's not a doctoral thesis. :-)  (allusion to German politics)

> I have a list of some of my plans to add functionality at the top, and
> I've rewritten your test at the bottom to suit the new options.
>
> I'd be interested to know whether there are any things I'm doing
> drastically wrong... I think the rows? and columns? might be able to be
> done more succinctly, for example.

First of all their names seem weird.  Methods with a question mark at
the end are usually intended to be used in a boolean context.  But
rows? and columns? return the row and column counts.  Plus, they do
not gracefully deal with an empty Matrix.  I guess for everyday use it
will be more efficient to store max values in two members because you
will need them often for iteration.

Method #array could use Columns's #map method. If you rewrite
iteration methods like this

  def each_row
    return to_enum(:each_row) unless block_given?

    (1..rows?).each do |idx|
      yield row( idx )
    end
    self
  end

Then you can even do

  def array
    each_row.map do |row|
      row.to_a
    end
  end

And I would consider changing []= to actually remove the entry if the
value is nil.  (Excel does it differently, I believe. It will not
reduce the area it considers "used" when emptying the last cell in the
last column or row.)

Ah, and I would add a validity check for addresses - otherwise one can
get any String into the Hash as key - even things which are not valid
addresses.

But generally I think you get the hang of it.

Kind regards

robert


-- 
remember.guy do |as, often| as.you_can - without end
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