Matrix-element extractor -- How to define it

[RichardOnRails]

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

 

[Daniel Finnie]

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

 

[RichardOnRails]

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

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:

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]

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

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]

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

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

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:

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]

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

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
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

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