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comp.lang.ruby

Matrix-element extractor -- How to define it

RichardOnRails

5/3/2008 8:04:00 PM

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
6 Answers

Daniel Finnie

5/4/2008 1:06:00 AM

0

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.o...

Dan

On Sat, May 3, 2008 at 4:05 PM, RichardOnRails
<RichardDummyMailbox58407@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
>
>

RichardOnRails

5/4/2008 8:39:00 PM

0

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.o...
>
> 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

RichardOnRails

5/4/2008 8:43:00 PM

0

On May 4, 4:38 pm, RichardOnRails
<RichardDummyMailbox58...@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.o...
>
> > 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

I should have mentioned that I used "alias old_[] [] " in the context
of "Matrix < Array", so there's no wonder it didn't work. Sorry about
that omission.

Daniel Finnie

5/4/2008 9:45:00 PM

0

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.o...
> >
> > 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
>
>
>

RichardOnRails

5/5/2008 3:37:00 AM

0

On May 4, 5:44 pm, Daniel Finnie <d...@danfinnie.com> wrote:
> 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
>
> <RichardDummyMailbox58...@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.o...
>
> > > 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

Hi Daniel,

Thanks for your additional response.

> misguided

No problem! I misguide myself all the time :-) Any, it's history.

I've got two questions about my current version of your code, which
works fine BTW.

1. Where is the get method come from. I looked in Ruby RDoc and (i)
see no get method for Array, nor (ii) any related get method on the
Methods section of the RDoc. I'd really like a pointer to it's
documentation. It certainly is useful in this context.

2. As I mentioned, I switched from "old_[](*args)" in the else
clause to "super *args". which works fine for the most part. I works
fine, too, except I want to substitute "raise 'invalid data'" or
something more descriptive. Unfortunately, when I do that I get a
syntax error.

If you have the time, I'd love to get your take on these issues.
Code and output is below for your convenience.

Best wishes,
Richard

class Matrix < Array
def [] *args
if (args.length == 2) && args[0].is_a?(Integer) && args[1].is_a?
(Integer)
get(*args)
else
super *args
end
end
end

m = Matrix[ [10,20,30], [40,50,60], [70,80,90] ];
puts m [0] [1] # 20
puts m [2] [0] # 70
puts m[1] # 40
# 50
# 60

# This displayed nicely in my browser (Firefox 2.0). I hope it does
in yours!

smorgas

10/29/2009 3:58:00 AM

0

On Wed, 28 Oct 2009 16:45:11 -0700, Klaus Schadenfreude
<klausschadenfreude@yahoo.com> wrote:

>Didn't think you could support your lie

Loonytarian

Even sounds hilarious

Snicker