From: Daniel Finnie <dan@...>
Date: 2008-05-05T06:44:54+09:00
Subject: Re: Matrix-element extractor -- How to define it

Hi again,

I'm glad super worked out for you.  That's the "right way" to do it
for inheritance.

I have a feeling I may have misguided you with the "alias old_[] []"
line.  It should probably be something like "alias old_brackets []" as
I doubt that old_[] is a valid method name (I just checked and it
isn't, to be sure).

Dan

On Sun, May 4, 2008 at 4:40 PM, RichardOnRails
<RichardDummyMailbox58407@uscomputergurus.com> wrote:
> On May 3, 9:06 pm, Daniel Finnie <d...@danfinnie.com> wrote:
>  > Hi,
>  >
>  > You do this:
>  > class Array
>  >   alias old_[] []
>  >   def [] *args
>  >     if *args.length == 2 && args[0].is_a? Integer && args[1].is_a? Integer
>  >       get(*args)
>  >     else
>  >       old_[](*args)
>  >   end
>  > end
>  >
>  > Of course, this would remove some of the functionality of an Array for
>  > every Array, not just matricies.  Consider making a subclass of Array
>  > like this:
>  > class Matrix < Array
>  >   ...
>  > end
>  >
>  > Now you can modify Matrix at will without affecting Array.
>  >
>  > If you are creating a Matrix for purely pragmatic reasons (i.e., not
>  > as an excercise) then there is an excellent Matrix class in the Ruby
>  > standard library:http://ruby-doc.org/stdlib/
>  >
>  > Dan
>  >
>  > On Sat, May 3, 2008 at 4:05 PM, RichardOnRails
>  >
>
> > <RichardDummyMailbox58...@uscomputergurus.com> wrote:
>  > > Hi,
>  >
>  > >  I defined and populated a 9x9 matrix (Array of Arrays) of strings, m
>  >
>  > >  I defined an element-extractor:
>  >
>  > >  class Array
>  > >         def get(i,j)
>  > >                 line =self[i-1]
>  > >                 char = line[j-1]
>  > >         end
>  > >  end
>  >
>  > >  To get the first element of the second row, I used the following,
>  > >  which worked fine:
>  >
>  > >  m.get(2,1)
>  >
>  > >  I'd like to write merely m(2,1).  How can I do that simply?
>  >
>  > >  Thanks in Advance,
>  > >  Richard
>
>  Hi Daniel,
>
>  Thanks for the "kick start" and the Matrix class.  I got the latter
>  working,  but I'm going to "roll my own" because I want a Sudoku
>  solver that works the way I do manually.  I know there's a free solver
>  written in VisualProlog, but like Frank Sinatra, "I'll do it my
>  way" :-)
>
>  >     alias old_[] []
>
>  I'm running ruby 1.8.6 (2007-09-24 patchlevel 111) [i386-mswin32].  It
>  barfed on "old_", so I substituted:
>     else
>       super(*args)
>  which worked fine.
>
>  Best wishes,
>  Richard
>
>
>