[ruby-core:100471] [Ruby master Feature#17277] Make Enumerator#with_index yield row and col indices for Matrix

[ruby-core:100471] [Ruby master Feature#17277] Make Enumerator#with_index yield row and col indices for Matrix

[grzegorz.jakubiak]

Issue #17277 has been reported by greggzst (Grzegorz Jakubiak).

----------------------------------------
Feature #17277: Make Enumerator#with_index yield row and col indices for Matrix
https://bugs.ruby-lang.org/issues/17277

* Author: greggzst (Grzegorz Jakubiak)
* Status: Open
* Priority: Normal
----------------------------------------
Currently this code seems to be counting index based on the internal array of arrays and it's not correct for the matrix which should return row and col indices

```
Matrix[[0,2,3,4], [6,7,8,9], [1,4,5,8]].each.with_index { |e, index| print "#{index} " } ; puts
0 1 2 3 4 5 6 7 8 9 10 11 
=> nil
```

I'm aware of the fact that you could do following and you get the correct results:

```
Matrix[[0,2,3,4], [6,7,8,9], [1,4,5,8]].each_with_index { |e, row, col| print "[#{row}, #{col}] " } ; puts
[0, 0] [0, 1] [0, 2] [0, 3] [1, 0] [1, 1] [1, 2] [1, 3] [2, 0] [2, 1] [2, 2] [2, 3] 
=> nil
```

You can even chain `each_with_index` with other enumerators and access indices within them e.g.
```
Matrix[[0,2,3,4], [6,7,8,9], [1,4,5,8]].each_with_index.filter_map { |e, row, col| [row, col] if e % 4 == 0}
=> [[0, 0], [0, 3], [1, 2], [2, 1], [2, 3]]
```

However, I feel we should override `with_index` for Matrix so it returns row and col indices.



-- 
https://bugs.ruby-lang.org/

[ruby-core:100472] [Ruby master Feature#17277] Make Enumerator#with_index yield row and col indices for Matrix

[marcandre-ruby-core]

Issue #17277 has been updated by marcandre (Marc-Andre Lafortune).


What about chained enumerators?

```ruby
matrix.each(:diagonal).each_const(2).with_index do |elem, ?|
```

It's not clear to me how that could be implemented efficiently, do you have an idea?

Finally, what is the use case?

I would rather add `map_with_index`....

----------------------------------------
Feature #17277: Make Enumerator#with_index yield row and col indices for Matrix
https://bugs.ruby-lang.org/issues/17277#change-88091

* Author: greggzst (Grzegorz Jakubiak)
* Status: Open
* Priority: Normal
----------------------------------------
Currently this code seems to be counting index based on the internal array of arrays and it's not correct for the matrix which should return row and col indices

```
Matrix[[0,2,3,4], [6,7,8,9], [1,4,5,8]].each.with_index { |e, index| print "#{index} " } ; puts
0 1 2 3 4 5 6 7 8 9 10 11 
=> nil
```

I'm aware of the fact that you could do following and you get the correct results:

```
Matrix[[0,2,3,4], [6,7,8,9], [1,4,5,8]].each_with_index { |e, row, col| print "[#{row}, #{col}] " } ; puts
[0, 0] [0, 1] [0, 2] [0, 3] [1, 0] [1, 1] [1, 2] [1, 3] [2, 0] [2, 1] [2, 2] [2, 3] 
=> nil
```

You can even chain `each_with_index` with other enumerators and access indices within them e.g.
```
Matrix[[0,2,3,4], [6,7,8,9], [1,4,5,8]].each_with_index.filter_map { |e, row, col| [row, col] if e % 4 == 0}
=> [[0, 0], [0, 3], [1, 2], [2, 1], [2, 3]]
```

However, I feel we should override `with_index` for Matrix so it returns row and col indices.



-- 
https://bugs.ruby-lang.org/

[ruby-core:100473] [Ruby master Feature#17277] Make Enumerator#with_index yield row and col indices for Matrix

[grzegorz.jakubiak]

Issue #17277 has been updated by greggzst (Grzegorz Jakubiak).


I also noticed when combining `each_with_index` with `inject` it passes `element, row_index and col_index` as one argument to the block

```ruby
Matrix[[1,2,4,5],[7,8,9,2]].each_with_index.inject({}) { |acc, e, row, col| puts "#{acc}, #{e}, #{row}, #{col}"; acc[[e[1],e[2]]] = e[0]; acc } 
{}, [1, 0, 0], , 
{[0, 0]=>1}, [2, 0, 1], , 
{[0, 0]=>1, [0, 1]=>2}, [4, 0, 2], , 
{[0, 0]=>1, [0, 1]=>2, [0, 2]=>4}, [5, 0, 3], , 
{[0, 0]=>1, [0, 1]=>2, [0, 2]=>4, [0, 3]=>5}, [7, 1, 0], , 
{[0, 0]=>1, [0, 1]=>2, [0, 2]=>4, [0, 3]=>5, [1, 0]=>7}, [8, 1, 1], , 
{[0, 0]=>1, [0, 1]=>2, [0, 2]=>4, [0, 3]=>5, [1, 0]=>7, [1, 1]=>8}, [9, 1, 2], , 
{[0, 0]=>1, [0, 1]=>2, [0, 2]=>4, [0, 3]=>5, [1, 0]=>7, [1, 1]=>8, [1, 2]=>9}, [2, 1, 3], , 
=> {[0, 0]=>1, [0, 1]=>2, [0, 2]=>4, [0, 3]=>5, [1, 0]=>7, [1, 1]=>8, [1, 2]=>9, [1, 3]=>2}
```

marcandre (Marc-Andre Lafortune) wrote in #note-1:
> What about chained enumerators?
> 
> ```ruby
> matrix.each(:diagonal).each_const(2).with_index do |elem, ?|
> ```
> 
> It's not clear to me how that could be implemented efficiently, do you have an idea?

I tried with refinement for Enumerator in Matrix and use `each_with_index` to yield `row` and `col` index but couldn't get it working...

> Finally, what is the use case?

I would like to access matrix indices in enumerable methods to perform some operations based on them. 


> I would rather add `map_with_index`....

I guess this would be helpful but I think it doesn't give enough flexibility because if you want to use `with_index` in `select` you don't need the `map` part and so on






----------------------------------------
Feature #17277: Make Enumerator#with_index yield row and col indices for Matrix
https://bugs.ruby-lang.org/issues/17277#change-88092

* Author: greggzst (Grzegorz Jakubiak)
* Status: Open
* Priority: Normal
----------------------------------------
Currently this code seems to be counting index based on the internal array of arrays and it's not correct for the matrix which should return row and col indices

```
Matrix[[0,2,3,4], [6,7,8,9], [1,4,5,8]].each.with_index { |e, index| print "#{index} " } ; puts
0 1 2 3 4 5 6 7 8 9 10 11 
=> nil
```

I'm aware of the fact that you could do following and you get the correct results:

```
Matrix[[0,2,3,4], [6,7,8,9], [1,4,5,8]].each_with_index { |e, row, col| print "[#{row}, #{col}] " } ; puts
[0, 0] [0, 1] [0, 2] [0, 3] [1, 0] [1, 1] [1, 2] [1, 3] [2, 0] [2, 1] [2, 2] [2, 3] 
=> nil
```

You can even chain `each_with_index` with other enumerators and access indices within them e.g.
```
Matrix[[0,2,3,4], [6,7,8,9], [1,4,5,8]].each_with_index.filter_map { |e, row, col| [row, col] if e % 4 == 0}
=> [[0, 0], [0, 3], [1, 2], [2, 1], [2, 3]]
```

However, I feel we should override `with_index` for Matrix so it returns row and col indices.



-- 
https://bugs.ruby-lang.org/

[ruby-core:100492] [Ruby master Feature#17277] Make Enumerator#with_index yield row and col indices for Matrix

[nobu]

Issue #17277 has been updated by nobu (Nobuyoshi Nakada).

Assignee set to marcandre (Marc-Andre Lafortune)
Status changed from Open to Assigned

----------------------------------------
Feature #17277: Make Enumerator#with_index yield row and col indices for Matrix
https://bugs.ruby-lang.org/issues/17277#change-88111

* Author: greggzst (Grzegorz Jakubiak)
* Status: Assigned
* Priority: Normal
* Assignee: marcandre (Marc-Andre Lafortune)
----------------------------------------
Currently this code seems to be counting index based on the internal array of arrays and it's not correct for the matrix which should return row and col indices

```
Matrix[[0,2,3,4], [6,7,8,9], [1,4,5,8]].each.with_index { |e, index| print "#{index} " } ; puts
0 1 2 3 4 5 6 7 8 9 10 11 
=> nil
```

I'm aware of the fact that you could do following and you get the correct results:

```
Matrix[[0,2,3,4], [6,7,8,9], [1,4,5,8]].each_with_index { |e, row, col| print "[#{row}, #{col}] " } ; puts
[0, 0] [0, 1] [0, 2] [0, 3] [1, 0] [1, 1] [1, 2] [1, 3] [2, 0] [2, 1] [2, 2] [2, 3] 
=> nil
```

You can even chain `each_with_index` with other enumerators and access indices within them e.g.
```
Matrix[[0,2,3,4], [6,7,8,9], [1,4,5,8]].each_with_index.filter_map { |e, row, col| [row, col] if e % 4 == 0}
=> [[0, 0], [0, 3], [1, 2], [2, 1], [2, 3]]
```

However, I feel we should override `with_index` for Matrix so it returns row and col indices.



-- 
https://bugs.ruby-lang.org/

[ruby-core:100493] [Ruby master Feature#17277] Make Enumerator#with_index yield row and col indices for Matrix

[grzegorz.jakubiak]

Issue #17277 has been updated by greggzst (Grzegorz Jakubiak).


greggzst (Grzegorz Jakubiak) wrote in #note-2:
> I also noticed when combining `each_with_index` with `inject` it passes `element, row_index and col_index` as one argument to the block
> 
> ```ruby
> Matrix[[1,2,4,5],[7,8,9,2]].each_with_index.inject({}) { |acc, e, row, col| puts "#{acc}, #{e}, #{row}, #{col}"; acc[[e[1],e[2]]] = e[0]; acc } 
> {}, [1, 0, 0], , 
> {[0, 0]=>1}, [2, 0, 1], , 
> {[0, 0]=>1, [0, 1]=>2}, [4, 0, 2], , 
> {[0, 0]=>1, [0, 1]=>2, [0, 2]=>4}, [5, 0, 3], , 
> {[0, 0]=>1, [0, 1]=>2, [0, 2]=>4, [0, 3]=>5}, [7, 1, 0], , 
> {[0, 0]=>1, [0, 1]=>2, [0, 2]=>4, [0, 3]=>5, [1, 0]=>7}, [8, 1, 1], , 
> {[0, 0]=>1, [0, 1]=>2, [0, 2]=>4, [0, 3]=>5, [1, 0]=>7, [1, 1]=>8}, [9, 1, 2], , 
> {[0, 0]=>1, [0, 1]=>2, [0, 2]=>4, [0, 3]=>5, [1, 0]=>7, [1, 1]=>8, [1, 2]=>9}, [2, 1, 3], , 
> => {[0, 0]=>1, [0, 1]=>2, [0, 2]=>4, [0, 3]=>5, [1, 0]=>7, [1, 1]=>8, [1, 2]=>9, [1, 3]=>2}
> ```
> 

My bad I just figured out that's a case for `inject` so it shouldn't be considered in this discussion. 

Anyways it'd be good to have `with_index` chained to whatever enumerator returning Matrix indices

----------------------------------------
Feature #17277: Make Enumerator#with_index yield row and col indices for Matrix
https://bugs.ruby-lang.org/issues/17277#change-88112

* Author: greggzst (Grzegorz Jakubiak)
* Status: Assigned
* Priority: Normal
* Assignee: marcandre (Marc-Andre Lafortune)
----------------------------------------
Currently this code seems to be counting index based on the internal array of arrays and it's not correct for the matrix which should return row and col indices

```
Matrix[[0,2,3,4], [6,7,8,9], [1,4,5,8]].each.with_index { |e, index| print "#{index} " } ; puts
0 1 2 3 4 5 6 7 8 9 10 11 
=> nil
```

I'm aware of the fact that you could do following and you get the correct results:

```
Matrix[[0,2,3,4], [6,7,8,9], [1,4,5,8]].each_with_index { |e, row, col| print "[#{row}, #{col}] " } ; puts
[0, 0] [0, 1] [0, 2] [0, 3] [1, 0] [1, 1] [1, 2] [1, 3] [2, 0] [2, 1] [2, 2] [2, 3] 
=> nil
```

You can even chain `each_with_index` with other enumerators and access indices within them e.g.
```
Matrix[[0,2,3,4], [6,7,8,9], [1,4,5,8]].each_with_index.filter_map { |e, row, col| [row, col] if e % 4 == 0}
=> [[0, 0], [0, 3], [1, 2], [2, 1], [2, 3]]
```

However, I feel we should override `with_index` for Matrix so it returns row and col indices.



-- 
https://bugs.ruby-lang.org/

[ruby-core:100507] [Ruby master Feature#17277] Make Enumerator#with_index yield row and col indices for Matrix

[sawadatsuyoshi]

Issue #17277 has been updated by sawa (Tsuyoshi Sawada).


I think the current behaviour is natural. You cannot play around with `with_index` since its receiver is `Enumerator`, not `Matrix`, and the information as a matrix is already gone.

You can retrieve the row and column indices easily from the flattened indices:

```ruby
m.each.with_index{|e, index| p index.divmod(m.column_size)}
[0, 0]
[0, 1]
[0, 2]
[0, 3]
[1, 0]
[1, 1]
[1, 2]
[1, 3]
[2, 0]
[2, 1]
[2, 2]
[2, 3]
```


----------------------------------------
Feature #17277: Make Enumerator#with_index yield row and col indices for Matrix
https://bugs.ruby-lang.org/issues/17277#change-88130

* Author: greggzst (Grzegorz Jakubiak)
* Status: Assigned
* Priority: Normal
* Assignee: marcandre (Marc-Andre Lafortune)
----------------------------------------
Given a matrix:

```ruby
matrix = Matrix[[0,2,3,4], [6,7,8,9], [1,4,5,8]]
```

You could get the row and col indices of a matrix using `Matrix#each_with_index`:

```ruby
matrix
.each_with_index { |e, row, col| p [row, col] }
[0, 0]
[0, 1]
[0, 2]
[0, 3]
[1, 0]
[1, 1]
[1, 2]
[1, 3]
[2, 0]
[2, 1]
[2, 2]
[2, 3] 
```

You can chain it with other enumerators and access indices within them:

```ruby
matrix
.each_with_index
.filter_map { |e, row, col| [row, col] if e % 4 == 0}
# => [[0, 0], [0, 3], [1, 2], [2, 1], [2, 3]]
```

Meanwhile, `with_index` after `Matrix#each` returns flattened indices, not row or column indices, which does not look right:

```ruby
matrix
.each.with_index { |e, index| p index }
0
1
2
3
4
5
6
7
8
9
10
11
```

I feel we should override `with_index` for `Matrix` so it returns row and column indices.



-- 
https://bugs.ruby-lang.org/

[ruby-core:100666] [Ruby master Feature#17277] Make Enumerator#with_index yield row and col indices for Matrix

[grzegorz.jakubiak]

Issue #17277 has been updated by greggzst (Grzegorz Jakubiak).


sawa (Tsuyoshi Sawada) wrote in #note-7:
> I think the current behaviour is natural. You cannot play around with `with_index` since its receiver is `Enumerator`, not `Matrix`, and the information as a matrix is already gone.
> 
> You can retrieve the row and column indices easily from the flattened indices:
> 
> ```ruby
> matrix.each.with_index{|e, index| p index.divmod(matrix.column_size)}
> [0, 0]
> [0, 1]
> [0, 2]
> [0, 3]
> [1, 0]
> [1, 1]
> [1, 2]
> [1, 3]
> [2, 0]
> [2, 1]
> [2, 2]
> [2, 3]
> ```

I get that but it means performing divmod calculation every time one needs to work row and col indices out. Couldn’t we maybe return a subclass of Enumerator that implements proper with_index for Matrix?



----------------------------------------
Feature #17277: Make Enumerator#with_index yield row and col indices for Matrix
https://bugs.ruby-lang.org/issues/17277#change-88307

* Author: greggzst (Grzegorz Jakubiak)
* Status: Assigned
* Priority: Normal
* Assignee: marcandre (Marc-Andre Lafortune)
----------------------------------------
Given a matrix:

```ruby
matrix = Matrix[[0,2,3,4], [6,7,8,9], [1,4,5,8]]
```

You could get the row and col indices of a matrix using `Matrix#each_with_index`:

```ruby
matrix
.each_with_index { |e, row, col| p [row, col] }
[0, 0]
[0, 1]
[0, 2]
[0, 3]
[1, 0]
[1, 1]
[1, 2]
[1, 3]
[2, 0]
[2, 1]
[2, 2]
[2, 3] 
```

You can chain it with other enumerators and access indices within them:

```ruby
matrix
.each_with_index
.filter_map { |e, row, col| [row, col] if e % 4 == 0}
# => [[0, 0], [0, 3], [1, 2], [2, 1], [2, 3]]
```

Meanwhile, `with_index` after `Matrix#each` returns flattened indices, not row or column indices, which does not look right:

```ruby
matrix
.each.with_index { |e, index| p index }
0
1
2
3
4
5
6
7
8
9
10
11
```

I feel we should override `with_index` for `Matrix` so it returns row and column indices.



-- 
https://bugs.ruby-lang.org/

[ruby-core:101467] [Ruby master Feature#17277] Make Enumerator#with_index yield row and col indices for Matrix

[marcandre-ruby-core]

Issue #17277 has been updated by marcandre (Marc-Andre Lafortune).

Status changed from Assigned to Closed

Closing for lack of a viable solution

----------------------------------------
Feature #17277: Make Enumerator#with_index yield row and col indices for Matrix
https://bugs.ruby-lang.org/issues/17277#change-89242

* Author: greggzst (Grzegorz Jakubiak)
* Status: Closed
* Priority: Normal
* Assignee: marcandre (Marc-Andre Lafortune)
----------------------------------------
Given a matrix:

```ruby
matrix = Matrix[[0,2,3,4], [6,7,8,9], [1,4,5,8]]
```

You could get the row and col indices of a matrix using `Matrix#each_with_index`:

```ruby
matrix
.each_with_index { |e, row, col| p [row, col] }
[0, 0]
[0, 1]
[0, 2]
[0, 3]
[1, 0]
[1, 1]
[1, 2]
[1, 3]
[2, 0]
[2, 1]
[2, 2]
[2, 3] 
```

You can chain it with other enumerators and access indices within them:

```ruby
matrix
.each_with_index
.filter_map { |e, row, col| [row, col] if e % 4 == 0}
# => [[0, 0], [0, 3], [1, 2], [2, 1], [2, 3]]
```

Meanwhile, `with_index` after `Matrix#each` returns flattened indices, not row or column indices, which does not look right:

```ruby
matrix
.each.with_index { |e, index| p index }
0
1
2
3
4
5
6
7
8
9
10
11
```

I feel we should override `with_index` for `Matrix` so it returns row and column indices.



-- 
https://bugs.ruby-lang.org/