# Question about op. overloading **URL:** \ **Category:** Ruby\ **Created:** [December 3, 2008, 9:55am UTC](https://www.ruby-forum.com/t/question-about-op-overloading/154725 "2008-12-03T09:55:11Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![maartenm](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/5e9695/32.png) [@maartenm](https://www.ruby-forum.com/u/maartenm)\ **Post date:** [December 3, 2008, 9:55am UTC](https://www.ruby-forum.com/t/question-about-op-overloading/154725/1 "2008-12-03T09:55:11Z")
I have: class Sudoku def @rows[r][c] end def set(r,c,a) @rows[r][c]=a end end Now, how can I define a []= operator instead of the awkward set(r,c,a) ? I want to be able to do sudoku[2,3]=candidate or even sudoku[2][3] = candidate and sudoku[3] = row Are these things possible? How, I could not find the information. (I’m just learning, for educational reasons I don’t want to extend the Matrix class) ---
**Author:** ![maartenm](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/5e9695/32.png) [@maartenm](https://www.ruby-forum.com/u/maartenm)\ **Post date:** [December 3, 2008, 10:10am UTC](https://www.ruby-forum.com/t/question-about-op-overloading/154725/2 "2008-12-03T10:10:48Z")
Jesús Gabriel y Galán wrote: > Hope this helps, > > Jesus. So simple, I should have known. 🙂 Thank you! – Maarten ---
**Author:** ![maartenm](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/5e9695/32.png) [@maartenm](https://www.ruby-forum.com/u/maartenm)\ **Post date:** [December 3, 2008, 10:20am UTC](https://www.ruby-forum.com/t/question-about-op-overloading/154725/3 "2008-12-03T10:20:19Z")
What about sudoku[r][c]= a though? Is that possible? I thought I’d be able to fluke it by overloading [] to return an array. But how do I pass parameters inside the bracket? And how woudl I get puts sudoku[][3] to return the third column? ---
**Author:** ![maartenm](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/5e9695/32.png) [@maartenm](https://www.ruby-forum.com/u/maartenm)\ **Post date:** [December 3, 2008, 11:26am UTC](https://www.ruby-forum.com/t/question-about-op-overloading/154725/4 "2008-12-03T11:26:29Z")
2008/12/3 Maarten M. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): > What about > sudoku[r][c]= a > though? > > Is that possible? I thought I’d be able to fluke it by overloading [] to > return an array. But how do I pass parameters inside the bracket? You do not need an array but rather a proxy: class X ColProxy = Struct.new :owner, :column do def owner.matrix[[column, row]] end ``` def []=(row,val) owner.matrix[[column, row]] = val end ``` end attr\_reader :matrix def initialize @matrix = {} end def ColProxy.new(self, column) end end irb(main):026:0\> x = X.new =\> #\ irb(main):027:0\> x[1][2] = 3 =\> 3 irb(main):028:0\> x[1][2] =\> 3 irb(main):029:0\> x =\> #\3}\> > And how woudl I get > > puts sudoku[][3] > > to return the third column? You can do it similarly. Just make the argument for X#[] optional and return another proxy. I would really rather go with the other approach to stuff all coordinates in a single pair of brackets and or provide additional methods. Kind regards robert ---
**Author:** ![maartenm](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/5e9695/32.png) [@maartenm](https://www.ruby-forum.com/u/maartenm)\ **Post date:** [December 3, 2008, 12:20pm UTC](https://www.ruby-forum.com/t/question-about-op-overloading/154725/5 "2008-12-03T12:20:22Z")
Maarten M. wrote: > What about > sudoku[r][c]= a > though? > > Is that possible? Simpler would be if you use sudoku[r,c] = a Just define your []= method to take 3 arguments. > And how woudl I get > > puts sudoku[][3] > > to return the third column? Again, your [] method can take 2 arguments. sudoku[nil,c] could be used to give the column. But I think a separate method for this makes more sense: sudoku.col© ---
**Author:** ![maartenm](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/5e9695/32.png) [@maartenm](https://www.ruby-forum.com/u/maartenm)\ **Post date:** [December 3, 2008, 10:07am UTC](https://www.ruby-forum.com/t/question-about-op-overloading/154725/6 "2008-12-03T10:07:48Z")
On Wed, Dec 3, 2008 at 9:49 AM, Maarten M. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > end > Are these things possible? How, I could not find the information. > A []= operator is possible. It’s syntactic sugar for a method named > “[]=” > and at least two parameters: what’s inside the brackets and the > “assigned” value. An example: irb(main):001:0\> class A irb(main):002:1\> def []= (a,b) irb(main):003:2\> @x[a] = b irb(main):004:2\> end irb(main):005:1\> attr\_reader :x irb(main):006:1\> def initialize irb(main):007:2\> @x = {} irb(main):008:2\> end irb(main):009:1\> end =\> nil irb(main):010:0\> a = A.new =\> #\ irb(main):011:0\> a[:a] = :b =\> :b irb(main):012:0\> a =\> #\:b}\> If you add more parameters to the method, you can use more “keys” inside the brackets: irb(main):013:0\> class A irb(main):014:1\> def []= (a,b,c) irb(main):015:2\> puts a,b,c irb(main):016:2\> end irb(main):017:1\> end =\> nil irb(main):018:0\> a = A.new =\> #\ irb(main):019:0\> a[:a,:b] = :c a b c =\> :c Hope this helps, Jesus. ---
**Author:** ![maartenm](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/5e9695/32.png) [@maartenm](https://www.ruby-forum.com/u/maartenm)\ **Post date:** [December 3, 2008, 12:22pm UTC](https://www.ruby-forum.com/t/question-about-op-overloading/154725/7 "2008-12-03T12:22:52Z")
Brian C. wrote: > But I think a separate method for this makes more sense: sudoku.col© Yeah that’s what I did eventually. To be honest I could’ve found all this stuff myself, I was confused by the output ruby gave me and didn’t realize I just needed an extra parameter. Sorry and thanks to everyone.