Bug #18994: Range#last(n) returns empty for single-element Integer Range

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: ruby 3.1.2p20 (2022-04-12 revision 4491bb740a) [x86_64-darwin20]
• Backport: 2.7: WONTFIX, 3.0: REQUIRED, 3.1: DONE

[masasakano (Masa Sakano)]

Range#last(n) with a single-element of Integer returns an empty Array. It should return a one-element Array.

Interestingly, when the element is a String, last(n) returns a one-element Array, expectedly.

I have checked the behaviour with some selected past versions of Ruby. In up to Ruby-2.6.5, it worked correctly. In Ruby-2.7.0, it doesn't. Nor in Ruby-3, including the current version (Ruby-3.1.2).

The following demonstrates the behaviour (Ruby-3.1.2; same in Ruby-2.7.0). Only the first one does not work in the way it should.

(8..8).last(1)        # => []  (!!) (should be: [8])
(8..8).to_a.last(1)   # => [8]
(8..8).first(1)       # => [8]
(?a..?a).last(1)      #=> ["a"]
(?a..?a).to_a.last(1) #=> ["a"]
(?a..?a).first(1)     #=> ["a"]

[byroot (Jean Boussier)]

• Backport changed from 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN to 2.7: WONTFIX, 3.0: REQUIRED, 3.1: REQUIRED

Thanks, I have a patch for it: https://github.com/ruby/ruby/pull/6324

[byroot (Jean Boussier)]

• Status changed from Open to Closed

Applied in changeset git|bbe5ec78463f8d6ef2e1a3571f17357a3d9ec8e4.

---

rb_int_range_last: properly handle non-exclusive range

[Bug #18994]

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 2.7: WONTFIX, 3.0: REQUIRED, 3.1: REQUIRED to 2.7: WONTFIX, 3.0: REQUIRED, 3.1: DONE

ruby_3_1 941c888b041decb45034572d766120f9be34986e merged revision(s) bbe5ec78463f8d6ef2e1a3571f17357a3d9ec8e4.