From: ruby-core@...
Date: 2014-11-19T17:54:29+00:00
Subject: [ruby-core:66363] [ruby-trunk - Feature #10445] [Feedback] [PATCH	3/3] Extend Matrix#[]

Issue #10445 has been updated by Marc-Andre Lafortune.

Status changed from Open to Feedback

I understand the idea, but I'm not convinced.

Currently, [] is a simple access to the elements of a matrix. This proposal makes it more complex and changes completely the type of return depending on the arguments. The main question is: when would someone want to extract a minor from a matrix and much prefer calling `[]` instead of the clearer and explicit `minor`?

I feel like we should favor explicitness in this case.

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Feature #10445: [PATCH 3/3] Extend Matrix#[]
https://bugs.ruby-lang.org/issues/10445#change-50014

* Author: gogo tanaka
* Status: Feedback
* Priority: Normal
* Assignee: Marc-Andre Lafortune
* Category: lib
* Target version: 
----------------------------------------
I've made patches which Matrix#[] returns new vector if either arguments is range, 
and returns new matrix, if both arguments are range. 

Like below.

```ruby
# matrix[row, column]          -> obj        or nil
# matrix[row, col_range]       -> new_vector or nil
# matrix[row_range, column]    -> new_vector or nil
# matrix[row_range, col_range] -> new_matrix or nil

Matrix.diagonal(9, 5, -3)[1, 1]
  => 5

Matrix.diagonal(9, 5, -3)[1, 0..1]
  => Vector[0, 5]

Matrix.diagonal(9, 5, -3)[0..1, 0]
  => Vector[9, 0]

Matrix.diagonal(9, 5, -3)[0..1, 0..1]
  => Matrix[[9, 0], [0, 5]]
```

I'm not sure `matrix[row, col_range] ` should return `vector` or `matrix`
But from my view, it's fine.

I'm not in a hurry. Take your time.

---Files--------------------------------
add_test.patch (1.05 KB)
implement_matrix.rb.patch (1.96 KB)
update_NEWS.patch (825 Bytes)


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