From: daniel@...42.com Date: 2020-03-09T14:06:19+00:00 Subject: [ruby-core:97421] [Ruby master Misc#16678] Array#values_at has unintuitive behavior when supplied a range starting with negative index Issue #16678 has been updated by Dan0042 (Daniel DeLorme). Negative indices have always meant "offset from the end" in ruby. So if you take a negative index and add the size of the array you get the "normal index" and then I think you'll see everything is pretty intuitive. ```ruby a = (1..5).to_a # get all values from a[-4] (a[1]) to a[3] a.values_at(-4..3) #=> [2, 3, 4] a.values_at(1..3) #=> [2, 3, 4] # get all values from a[-1] (a[4]) to a[3] a.values_at(-1..3) #=> [] a.values_at(4..3) #=> [] #range start > range end = empty range, therefore empty array ``` But I think this is slightly inconsistent: ```ruby (4..6).map{ a[_1] } #=> [5, nil, nil] a.values_at(4..6) #=> [5, nil, nil] (-7..-5).map{ a[_1] } #=> [nil, nil, 1] a.values_at(-7..-5) #=> RangeError (-7..-5 out of range), should be [nil, nil, 1] imho ``` ---------------------------------------- Misc #16678: Array#values_at has unintuitive behavior when supplied a range starting with negative index https://bugs.ruby-lang.org/issues/16678#change-84554 * Author: prajjwal (Prajjwal Singh) * Status: Open * Priority: Normal ---------------------------------------- Consider the following: ``` ruby # frozen_string_literal: true a = (1..5).to_a p a.values_at(3..5) # => [4, 5, nil] p a.values_at(-1..3) # => [] ``` When the range begins with a negative `(-1, 0, 1, 2, 3)`, it returns an empty array, which surprised me because I was expecting `[1, 2, 3, 4]`. The argument for this is that it cold be confusing to allow this because the index `-1` could refer to the last argument and it would be unintuitive to return an array `[5, 1, 2, 3, 4]` with jumbled values. The argument against it is that it makes perfect sense to account for this case and return `[nil, 1, 2, 3, 4]`. Opening a dialog to see what others think of this. -- https://bugs.ruby-lang.org/ Unsubscribe: