From: "alexeymuranov (Alexey Muranov)" <redmine@...>
Date: 2012-08-15T16:09:33+09:00
Subject: [ruby-core:47206] [ruby-trunk - Feature #6852] [].transpose should behave specially


Issue #6852 has been updated by alexeymuranov (Alexey Muranov).


marcandre (Marc-Andre Lafortune) wrote:
> HI,
> 
> alexeymuranov (Alexey Muranov) wrote:
> > marcandre (Marc-Andre Lafortune) wrote:
> > > 
> > > The later would fail for an empty set of exams and grades
> > 
> > I didn't understand this sentence.
> 
> The example using `each_with_index` will work even for empty arrays. The "equivalent" example with transpose currently works with empty arrays but would not if `transpose` returned `nil` or raised an error on [[], []]. It would make "equivalent" code behave differently in that case, and I feel that it wouldn't be more useful.

Ok, thanks, i've understood.
----------------------------------------
Feature #6852: [].transpose should behave specially
https://bugs.ruby-lang.org/issues/6852#change-28885

Author: boris_stitnicky (Boris Stitnicky)
Status: Rejected
Priority: Normal
Assignee: 
Category: core
Target version: 2.0.0


p = [1, 2, 3]
q = [4, 5, 6]
[p, q].transpose
# => [[1, 4], [2, 5], [3, 6]]
As expected, 2 x 3 vector was converted into 3 x 2.

[p].transpose
# => [[1], [2], [3]]
As expected, 1 x 3 => 3 x 1.

[].transpose
# => []
Unexpected, 0 x 3 did not become 3 x 0: [[], [], []]

In other words, when [] is the receiver, transpose has no way to know
what kind of ** 2 dimensional ** object is it - whether 0 x 3, 0 x 4, 0 x 1
or perhaps 0 x 0. #transpose should not assume it is 0 x 0. It should raise,
or warn, or complain, or require argument for this case, in short, it should
behave differently than today.


-- 
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